Fuel Distributor Rebuild

[Bitsyncmaster]

This FD would not produce equal amounts of fuel doing the six bottle test with the air plate pressed all the way down. It would get better (more equal) only pressing that air plate half way down.

Pulling the FD apart there is a little contamination in most fuel chamber areas (on the walls) but it does not look like that would have caused the problem. The diaphragm plate looked very good with no damage (other than where I damaged it separating the FD halves.

Inspecting I do think there is enough contamination inside a few of the ports where the injector lines connect. But the fuel would be flowing out of those ports. So are those silver barrels under each of those ports filters? And are they removable?

Also not sure if I should pull that large center barel to clean and inspect where the plunger fits into. By the way the plunger does move freely. It drops out under it's own weight.

[Bitsyncmaster]

I inspected the very small slits because that would determine the amount of fuel to each injector according to the location of the plunger. They all looked clean to me. So all I can think of is the "filters" are not matched (dirty) which may change the fuel volume.

FYI:
This FD came apart pretty easy. The T27 bolts holding it together did not seem corroded. And it does not look like there was any sealer joining the two halves. I know it's recommended to use the Permatax shellac sealer but I wonder why the factory can do it without sealer.

[OverlandMan]

You have my attention on this thread. Be curious to know how this turns out for you.

[David T]

You have my attention on this thread. Be curious to know how this turns out for you.

The fuel distributor is not the only thing that affects the volume of fuel coming out of each injector. The injectors also have something to do with it. The proper way to test is with the injectors on and then measure what comes out and you are correct, they should all be very close. The metal gasket seals the two halves together and once used, like a head gasket, it is not supposed to be reused. The way to reuse it is to smear some RTV on both sides. A little bit goes a long way. Be sure you have NO leaks once you get it back together.

[DMCVegas]

The fuel distributor is not the only thing that affects the volume of fuel coming out of each injector. The injectors also have something to do with it. The proper way to test is with the injectors on and then measure what comes out and you are correct, they should all be very close.

That was exactly what I came to say. Each injector nozzle meters the amount of fuel that passes through based upon how far it can open. But how far it opens really depends upon the strength of that internal spring. A weaker spring that puts up less resistance will open farther upon the same amount of fuel pressure that is acting upon it compared to one with a stronger spring. As a result it will flow more fuel and cause the cylinder to run richer. If an Injector requires extra pressure, you might have debris inside affecting the spring's travel. And unless I'm mistaken, this can also throw the balance of the other ports off too. Only a problem though if you start tinkering with the CO mixture screw (or the individual ports on the non-DeLorean Fuel Distributors like this one). If you just replace the bad injector, everything goes back to normal since everything else was already in spec.

This is precisely why you have to use the Injector Tester on each nozzle. As you pump fluid into the injector, and the pressure goes up, you need to check and see what the exact PSI reading is when the injector first starts to crack. Weak springs that crack out of spec means that the injector is bad and needs to be replaced. The sonic cleaning procedure that DAP does will work at breaking down dirt and lacquer, but those damaging forces are also being used on the rest of the injector as well. There is a reason that the required method to clean the injectors is simply to pump solvents through the injectors. Unlike BOSCH Diesel Injectors, Petrol/Gasoline Injectors that are hydraulically powered are NOT serviceable.

What should have been done before dismantling the distributor was this:


Measure flow rates from each Injector off of the Fuel Distributor into Graduated Cylinders.
If the flow rates do not match (10% variation I believe?), switch injectors between fuel lines to see if the problem follows the individual injectors, or the fuel line(s).
If the problem follows the injectors, bench test them with the Injector Tester. If it doesn't, proceed to Step 6.
Discard and replace with new ones any Injectors the open under too low PSI.
For Injectors that require extra pressure to open, pump solvents through the injectors several times to clean them. For those that fail to open, discard and replace with new Injectors.
Once the injectors are sorted, measure flow rates again. If flow rates issue persists, move the injector hoses to new ports on the Fuel Distributor to see if the problem follows the hoses. If it does, replace hoses.
If the problem is coming from the Fuel Distributor port, THEN investigate further. Ideally bench test and pump solvents through FD to clean it.
If the issue is still no resolved, inspect the plunger, and for NON-DeLorean Fuel Distributors with individual ports, proceed to adjust to match fuel flow rates. For Stock DMC Distributors, replace or rebuild if qualified.

[Bitsyncmaster]

I found a much better PDF that helps give more info for rebuilding. The photos of the parts do look just like the FD I now have apart. Note the little filters he pulled out. Not sure if I want to pull them out on this FD.

[Ron]

And unless I'm mistaken, this can also throw the balance of the other ports off too.
The pressure to each injector is maintained by the Pressure Differential Valves which these are a part of....

Dave, the plate is more than a gasket. These too serve a purpose in pressure differential (diaphram (s)). Hold the plate at an angle to a bright light and look for dimples matching where the 6 tubes rest. If you see any, they are one source of the difference in pressure/flow.

IMHO, you should have checked (and set after rebuilding) the pressure/flow of the FD w/o injectors on this type of FD (adjustable)....Since the injectors are supposed to open at the exact same time & pressure, what would be the use of having an adjustable FD (or shims for the non-adjustable) otherwise.

EDIT: There should be new screens in the kit. (They are filtering ont the way out for some weird reason...same with WUR...at mercy of hose quality...)

[Slammer]

Some info here (http://www.cis-jetronic.com/public_doc/07.3-0997-06.pdf)
I have a stuck plunger, but another FD on the way. Anyhow I may have to look into rebuilding one.

[Bitsyncmaster]

By the way, all the adjustable adjustments on this FD do is change the volume of that upper chamber of each port a very little. So with that adjustment screw in it displaces a little less volume. That screw can not touch the diaphragm or have any fuel flow holes. You probably don't get much adjustment range.

I also have a granite surface block to replace the glass plate suggested in the .PDF. Most all machine shops have these for measuring and surfacing to perfection.

Yes that diaphragm is not working like a gasket, it's movement opens and closes the ports to the injectors.

The rebuild kit just contains the diaphragm and O-rings. I bet if your careful, all you would need is the O-rings which should cost $10.

[OverlandMan]

The fuel distributor is not the only thing that affects the volume of fuel coming out of each injector. The injectors also have something to do with it. The proper way to test is with the injectors on and then measure what comes out and you are correct, they should all be very close. The metal gasket seals the two halves together and once used, like a head gasket, it is not supposed to be reused. The way to reuse it is to smear some RTV on both sides. A little bit goes a long way. Be sure you have NO leaks once you get it back together.

Not sure why you quoted me... I'm not arguing with you on your point. I just commented that I'd like to see how this works for Dave.

[DMCVegas]

The pressure to each injector is maintained by the Pressure Differential Valves which these are a part of....

Ah yes, you're right! There is still a spring inside of the Primary Pressure Regulator that would either bleed off the difference in excess pressure from a clogged injector, OR would close in order to compensate for the loss in fuel pressure from an injector with a weak spring. In either case, this would still maintain the proper operating pressures in the remaining upper and lower chambers of the Fuel Distributor.

So minor correction there (thank you, Ron!), but I'll stand by everything else.

For everyone reading this out of curiosity to learn more about your fuel injection system, it seems complicated, I know. But don't worry. This is where K-Jetronic trades off physical labor for mental labor for problem solving.

[Bitsyncmaster]

Some info here (http://www.cis-jetronic.com/public_doc/07.3-0997-06.pdf)
I have a stuck plunger, but another FD on the way. Anyhow I may have to look into rebuilding one.

Thanks. That rebuild info shows some of the parts are the same but it defiantly has a different way to adjust flow amounts. It also looks like that FD is used on a non-adjustable mixture screw because the plunger is shimmed.

[Bitsyncmaster]

I looked very closely at those filters from the injector side ports out in the sun light. It looks like one of them is dirty where as the other ones are shiny. But that filter is on the outlet side of the fuel flowing into the the injector lines. The owner I'm rebuilding this for also commented on cleaning the banjo bolts with a Q-tip that one was very dirty.

So I guess I will need to pull that filter and see how dirty it is on the other side.

[Ron]

So minor correction there (thank you, Ron!), but I'll stand by everything else.

+1 !


Dave, remove all of them and soak in acetone. etc -- you'll be surprised how much comes off, regardless of how they look...

Use Indian Head or Wolf Head shellac, Silicon based stuff sux, imho. You can apply it more liberal than you might think -- just don't get it in the tiny hole and follow torque spec!

[Bitsyncmaster]

It's funny they don't include those filters, from what I see they are really micro screen that hardly will let light show through. But it makes sense that a partial plugged filter would cause the trouble. Remember I said the flow rates were worse with the air plate fully pressed and got better with the lower rate flow testing.

I pulled the housing where the plunger goes to look at that screen and it looks clean on the outside. So how did that one injector side filter get dirty?

[Bitsyncmaster]

I pulled one of the filters and it looks clean but it's a very fine screen. I found a place that sells filters and I ordered some but not sure if they are the correct size. The filter I pulled is 0.210" OD which would be 5.33 mm. The universal BOSCH basket filter shows 6 mm. I will see when they get here if they will fit.

http://injector-rehab.com/shop/Injector-Filters/

[Ron]

Dave, fwiw, I was skimming through a Bosch manual and noticed it says the springs exert 1.0 bar pressure each...another source for the different flows you are seeing (not my first guess though... ;-)

[Bitsyncmaster]

Dave, fwiw, I was skimming through a Bosch manual and noticed it says the springs exert 1.0 bar pressure each...another source for the different flows you are seeing (not my first guess though... ;-)

Thanks. I don't think those filter baskets I found are going to fit this FD. Those are really for injectors. I would have thought there would be some standard size for all the filter baskets but I guess not.

At least we are learning things about the FD.

Do our injectors have a removable filter basket on the end? I never thought to look.

[Bitsyncmaster]

Here is a photo of the filter baskets just to show you how small they are. Only dirt I see it inside the basket, so it had to get in there when the banjo bolts were removed.

The screw I used to remove them has an OD of 0.138" (thread OD). Has 20 TPI. I grabbed the top with a pair of large wire cutters and the high center of the FD used as a fulcrum. Then tapped on those wire cutter handles with a hammer. I put the screw in 3 turns which worked fine on all six baskets.

[Bitsyncmaster]

Here is a photo of the worst accumulation of "dirt" I found. This dirt must have formed from the gas since the filters in the FD would not allow that to enter.

[Bitsyncmaster]

My Dremel with some small wire brushes did a good job cleaning up all the inside surfaces. Not going to paint the outside so that will only get cleaned with a solvent soft brush soaking. I would not use a wire brush if you have an aluminum FD but the cast iron FD is very good with it.

[Ron]

I would not use a wire brush if you have an aluminum FDWhich reminds me- Alloy Adjustable Rebuild (http://dmctalk.org/showthread.php?352-K-Jetronic-System&p=185099&viewfull=1#post185099)

[Bitsyncmaster]

No need to wet sand. Just takes a few strokes on 400 grit paper. It's ready to assemble. I didn't really spot any obvious problems. But at least we know it's clean and with new O-rings and new diaphragm.

[Ron]

No need to wet sand. Just takes a few strokes on 400 grit paper. It's ready to assemble. I didn't really spot any obvious problems. But at least we know it's clean and with new O-rings and new diaphragm.I'm sure you would, but just in case, please record and post flow results.

[Bitsyncmaster]

I'm sure you would, but just in case, please record and post flow results.

My friend lives 2.5 hours away so I'm just shipping the FD back in the mail. His problem is that it hunts badly and will not hold the mixture (dwell) setting. We will see if those problems get cured or not first.

[Ron]

My friend lives 2.5 hours away so I'm just shipping the FD back in the mail. His problem is that it hunts badly and will not hold the mixture (dwell) setting. We will see if those problems get cured or not first.In other words, your's is running fine and you aren't going to muck with it for tests...:deviltail:

[Bitsyncmaster]

In other words, your's is running fine and you aren't going to muck with it for tests...:deviltail:

Yes. It's not that much work to swap FDs twice but it's getting colder now so not much fun.

Has anyone found out if the injectors we use have those removable filter baskets? I never really looked closely into the feed end of the injector.

[Bitsyncmaster]

Well I did find what may have been a problem. There was a little "crap" on one of the spring seats that presses on the diaphragm to make the seal on each cylinder. I did not inspect those until I assembled the unit.

I used the Indian head gasket shellac for the seal on each half. I let it dry for one hour before assembly and it still remains soft but not so sticky that you will never get it apart again. I still wonder if that sealer is really necessary because it does not look like the factory build used any sealer. Since the halves are thick cast iron and perfectly flat, I would think it would seal without a sealer.

[Ron]

Has anyone found out if the injectors we use have those removable filter baskets? I never really looked closely into the feed end of the injector.
38164

[DMCMW Dave]

38164

Not removable.

[David T]

Not removable.

Although it is not removable it is overly large and should not get plugged up. If it is sludgy you can usually break it down and blow it through the injector. In my experience, the filters don't plug up so much as the spring and valve get messed up and the injector won't operate at the correct pressures anymore. The pattern usually will clean up too. If the injector won't open and close at the correct pressures you won't get the motor to run right. There is no way to reverse flow the injector either. The only method of cleaning them is the injector tester/cleaner. You can see a picture of it in the Workshop manual D:03:01 J.28876. The manual says the injectors are non-serviceable.

[Ron]

Not removable.
+1 !

He originally asked about "removable filter basket on the end"...I was pointing out that they are inside instead.
Thanks for heading off any confusion!

P.S. Just went through a set recently sent out to be cleaned this weekend....I think these things should have "Timex" stamped on them ;-)

[DMCVegas]

Not trying to throw out a "me too" post, but rather trying to clear some things up.

Only Diesel Injectors can be disassembled to clean/service/replace internals. With those you can clean them, replace springs, and swap shims to adjust the pressure in which they crack open to balance out the injectors. Diesel Injectors are two-piece that simply unscrew.

K-Jet Petrol injectors are a single, solid-piece.

http://forums.pelicanparts.com/uploads13/K+Jetronic+CIS+injector1218172791.jpg

With these injectors, the filter goes in first, and is then held in by a ring or clip of some sort to keep it up, out of the way of the valve assembly. The assembly goes in next, and it's the Valve Seat that gets pressed in, and holds the needle and spring in place.

Now I've seen various places that sell remanufactured injectors at half price as brand new ones. But I don't know exactly *how* they go about doing this. Do they actually replace the filters and springs? Or are these just injectors that go through an ultrasonic cleaning with a bit of spit and polish? The fact that no vendors offer remanufactured injectors says allot. Though who knows if that might ever change. As of right now, GB seems to be the only source for these remanufactured injectors. But even then, it's not a self-serviceable part, no.

[Ron]

Not trying to throw out a "me too" post, but rather trying to clear some things up.I hope you are underestimating the perceived value of your comments, rather than being PC, Robert :deviltail:



Now I've seen various places that sell remanufactured injectors at half price as brand new ones. But I don't know exactly *how* they go about doing this. Do they actually replace the filters and springs? Or are these just injectors that go through an ultrasonic cleaning with a bit of spit and polish?
A while back I sat down and called a lot of places because their sites were vague about the subject, if mentioned at all. The vast majority attempted to sidestep questions with a canned speech about being fully tested and guaranteed...
But one said they had a way to hold the valve open and back flush them. I'm not sure how well that would work with "nasty" ones, looking at diagrams (like your pic) and what I would expect the flow to be.
Customers who chose cleaning had good luck with ones sent out to be cleaned. I.E. The "good" ones rarely failed shortly afterwards. Later on, I tried it by rigging up spare K-Jet parts laying around and had the same luck. But, to me, it is just not worth the time and effort...you wind up with a used/mixed set, have to wait on replacements (or stock them), and worry about the one piece of trash missed letting go (at the most inopportune moment possible, of course ;-) I don't see how one could actually inspect the the job "properly".
They are not THAT expensive....



The fact that no vendors offer remanufactured injectors says allot. Though who knows if that might ever change. As of right now, GB seems to be the only source for these remanufactured injectors. But even then, it's not a self-serviceable part, no.
Watch Rock Auto...I see new Bosch with exact number pop up in stock every once in a while for $35 ea (I posted a "get em' while they are hot" a few times here (with no response) several times. I got a set at $32 ea (price if buying a full set) this summer. They happen to be showing available right now for $44.99 ea.

[Bitsyncmaster]

Here is a photo from John's web page. What cleaning will remove rust?

[Ron]

Good point!
...not to mention the the surface left behind if you could.

[DMCVegas]

I hope you are underestimating the perceived value of your comments, rather than being PC, Robert :deviltail:

What can I say? I still have flashbacks to the old ways of moderation on the DML...

https://apocalypsenowpma.files.wordpress.com/2014/10/tumblr_ms40zzxbal1qfhre5o1_400_zpsa9d8a99e.gif



A while back I sat down and called a lot of places because their sites were vague about the subject, if mentioned at all. The vast majority attempted to sidestep questions with a canned speech about being fully tested and guaranteed...
But one said they had a way to hold the valve open and back flush them. I'm not sure how well that would work with "nasty" ones, looking at diagrams (like your pic) and what I would expect the flow to be.
Customers who chose cleaning had good luck with ones sent out to be cleaned. I.E. The "good" ones rarely failed shortly afterwards. Later on, I tried it by rigging up spare K-Jet parts laying around and had the same luck. But, to me, it is just not worth the time and effort...you wind up with a used/mixed set, have to wait on replacements (or stock them), and worry about the one piece of trash missed letting go (at the most inopportune moment possible, of course ;-) I don't see how one could actually inspect the the job "properly".
They are not THAT expensive....

Exactly! That's my whole worry about this is the "good enough" attitude about refurbishing the parts, and then just relying upon warranty for the rest.

If I were to do a (somewhat) quick and dirty method here, what I'd probably do first would be to pump acid (hydrofluoric or phosphorous?) through the injectors. That would in theory get rid of the rust scale, and maybe some varnish. Though who knows if it might not also pit things and cause a bad seal or compromise the filter. Best I could figure to get the nozzle to stick open would be to wedge it open while under pressure. Then back flow the acid through the injector. Once that's done, pumps some solvents or distillates through it to clean the acid out and remaining varnish, and then some light oil to prevent rust for storage.

Of course that's assuming that whomever is servicing these injectors even cares that much about a job well done. What worries me about the "back flush" method there is damaging the valve seat by wedging it open and it never properly sealing ever again because the valve and the seat have been scored.

The only viable option that I can actual see to rebuild one of these fuel injectors would be to use an induction coil. Hit the coil on the tip to heat it up, and we should be able to cause the lip around the Valve Seat to expand enough to pull/drill the entire valve assembly out. Then move the coil up the injector body. The what appears to be brass ring that holds the filter basket in should heat at a much slower rate. Puncture the basket with a tool that has at least 3 clips to press down on the basket rim to push that ring out as you pull. The induction coil should heat the metal to expand it enough to clear it out. Then you would just clean up the injector housing, and reassemble with new parts.

The problem with this however is:

We don't even have a source for replacement filter baskets and valve assemblies.
If the internals of the injector housing are too far damaged, we've wasted our time.
Tooling for this rig would not be cheap to come by, and on a small scale may not be economical compared to just buying new injectors all together.





Watch Rock Auto...I see new Bosch with exact number pop up in stock every once in a while for $35 ea (I posted a "get em' while they are hot" a few times here (with no response) several times. I got a set at $32 ea (price if buying a full set) this summer. They happen to be showing available right now for $44.99 ea.

I hear you. Every once in a while someone pipes up about not having proper PRV camshaft tools, and I'll dig up links to eBay auctions where someone has either pieces or even an entire set, and no one really cares.

[Bitsyncmaster]

Get some 30 AWG wire wrap wire and that is small enough to hold the valve open. That's what I tried a long time ago.

[DMCVegas]

Get some 30 AWG wire wrap wire and that is small enough to hold the valve open. That's what I tried a long time ago.

Hopefully it wouldn't be as bad with the soft insulator, but still what about damage to the valve and valve seat? Did they still crack within spec with no leaks at rest pressures?

[Bitsyncmaster]

Hopefully it wouldn't be as bad with the soft insulator, but still what about damage to the valve and valve seat? Did they still crack within spec with no leaks at rest pressures?

You use the wire only. It is copper so its soft enough not to damage the steel valve. I never tested them with a bench test.

[DMCVegas]

You use the wire only. It is copper so its soft enough not to damage the steel valve. I never tested them with a bench test.

Gotcha. Bench testing injectors though is absolutely paramount. Here is an example of a hand operated one:

http://www.peachparts.com/shopforum/attachments/general-information/60936d1226706069-how-build-diesel-injector-pop-tester-poptester.jpg

Given the fitting sizes on the tube, as well as the pressure gauge, this one is for Diesel. But for Petrol, all one needs to do is to change the fittings and swap the gauge over to a 100 PSI unit. You can also get pneumatically driven ones as well. But getting back to the point here, bench testing the injectors accomplishes 4 big tasks:

Checking Spray Pattern.
Cleaning Injectors.
Ensuring proper Spring functionaliy by Verifying the Minimal Opening Pressure.
Balancing the Fuel Injection System for a properly running engine.


The First is a given of course. You *can* of course do the same thing on the engine, or on a bench jig with the air mixture unit, but this is actually far easier and much quicker.
The Second is important because you can spray through some harsh solvents or distillates through the injectors for an intense cleaning without worrying about rotting the rubber in the fuel injection system, or contaminating the catalytic converter, or the O2 Sensor.
The Third is cruicial because you need to ensure that the springs are functioning for two big reasons:

Injectors themselves do NOT measure fuel flow. They are dependant upon line pressures. If they open too early, that cylinder will run too rich which can lead to a whole host of other problems.
If the Spring inside the injector is bad, it also may fail to maintain proper rest pressure. This means that you can have a "Hot Start" issue that is not related to the Check Valve or Accumulator.

The Fourth and final item is of course all-inclusive of the previous items. As stated we need properly functioning injectors to atomize fuel, help deliver the proper amount of fuel, and to help the engine start up and also run without any problems.


Remember before when I had said that my troubleshooting steps would have involved metering fuel from each injector into a graduated cylinder, and then swapping hoses with ports on the Fuel Distributor? This is why. If the problem is following an injector, I would just remove all injectors and bench test them. If 1,2,3,5, & 6 are all operating within spec, then I'm just going to dump #4 and replace it and verify the repair. BOOM! The entire system is fixed. This is also where the Fuel Pressure Gauge comes in handy. Hot Start Issue? See if it's on the Supply side, or the Delivery side. Delivery? Replace the PPR Seals. Still got a problem? Test those injectors and replace what is bad. BOOM! Problem solved. Best of all? Lets say you have a properly tuned engine that was working just fine. And THEN say you had a problem with the PPR, or an injector, right? Just replace the bad part and it's done! Everything falls back within spec and doesn't have to be tuned! You're good to go.

Carburetors are Checkers, and Fuel Injection is Chess. With Fuel Injection (be it Mechanical or Electronic) you don't have to constantly rebuilt everything. Just replace what individual components are bad. That is the reward for using your brain: less physical labor and cheaper repair prices.

[David T]

Gotcha. Bench testing injectors though is absolutely paramount. Here is an example of a hand operated one:

http://www.peachparts.com/shopforum/attachments/general-information/60936d1226706069-how-build-diesel-injector-pop-tester-poptester.jpg

Given the fitting sizes on the tube, as well as the pressure gauge, this one is for Diesel. But for Petrol, all one needs to do is to change the fittings and swap the gauge over to a 100 PSI unit. You can also get pneumatically driven ones as well. But getting back to the point here, bench testing the injectors accomplishes 4 big tasks:

Checking Spray Pattern.
Cleaning Injectors.
Ensuring proper Spring functionaliy by Verifying the Minimal Opening Pressure.
Balancing the Fuel Injection System for a properly running engine.


The First is a given of course. You *can* of course do the same thing on the engine, or on a bench jig with the air mixture unit, but this is actually far easier and much quicker.
The Second is important because you can spray through some harsh solvents or distillates through the injectors for an intense cleaning without worrying about rotting the rubber in the fuel injection system, or contaminating the catalytic converter, or the O2 Sensor.
The Third is cruicial because you need to ensure that the springs are functioning for two big reasons:

Injectors themselves do NOT measure fuel flow. They are dependant upon line pressures. If they open too early, that cylinder will run too rich which can lead to a whole host of other problems.
If the Spring inside the injector is bad, it also may fail to maintain proper rest pressure. This means that you can have a "Hot Start" issue that is not related to the Check Valve or Accumulator.

The Fourth and final item is of course all-inclusive of the previous items. As stated we need properly functioning injectors to atomize fuel, help deliver the proper amount of fuel, and to help the engine start up and also run without any problems.


Remember before when I had said that my troubleshooting steps would have involved metering fuel from each injector into a graduated cylinder, and then swapping hoses with ports on the Fuel Distributor? This is why. If the problem is following an injector, I would just remove all injectors and bench test them. If 1,2,3,5, & 6 are all operating within spec, then I'm just going to dump #4 and replace it and verify the repair. BOOM! The entire system is fixed. This is also where the Fuel Pressure Gauge comes in handy. Hot Start Issue? See if it's on the Supply side, or the Delivery side. Delivery? Replace the PPR Seals. Still got a problem? Test those injectors and replace what is bad. BOOM! Problem solved. Best of all? Lets say you have a properly tuned engine that was working just fine. And THEN say you had a problem with the PPR, or an injector, right? Just replace the bad part and it's done! Everything falls back within spec and doesn't have to be tuned! You're good to go.

Carburetors are Checkers, and Fuel Injection is Chess. With Fuel Injection (be it Mechanical or Electronic) you don't have to constantly rebuilt everything. Just replace what individual components are bad. That is the reward for using your brain: less physical labor and cheaper repair prices.

This is some "Rube Goldberg" set-up! Using a small bottle jack! The proper tester/cleaner allows you to "shock" or shake loose the injector by hitting the handle hard and fast to clean the valve seat. You are supposed to use Paint Thinner because it is the same viscosity as gasoline and not as flammable. In my experience you don't have to get the injectors perfect, just close so the motor will run smoothly. Once the car gets driven regularly (or at least it isn't sitting anymore with stale fuel) you add a can of Techron to a full tank of fuel and it will clean the injectors some more. The injectors seem to work just fine if the car gets used. Letting the car sit and the fuel going bad is deadly to the injectors.

[Bitsyncmaster]

Now what kind of setup could we use to test a fuel distributor. I guess it would be nice to have a spare top half of the manifold so it would hold the plunger at the correct position and you could move the plunger a calibrated amount. Would also guess a fuel pump and accumulator so the pressures are smooth.

If I ever do another FD rebuild, I want to try without using any sealer like the factory does. So you would want a quick test to verify no leaks at least.

I also don't think you need a rebuild kit. I did not find any bad O-rings and the diaphragm would have been fine now that I know to remove the center housing first. That housing with it's six O-rings are what hold the halves together. Of course if the diaphragm is damaged then you have to buy one of the expensive rebuild kits.

[DMCVegas]

This is some "Rube Goldberg" set-up! Using a small bottle jack!

Nope. The tool isn't really available any longer. If they do pop-up, they got for top-dollar. I've seen the "Official" Ferrari ones (which are BOSCH units that have just been repackaged in a box with a prancing pony) go for about $500-$800. The conversion of a bottle jack is a well documented, and accepted procedure to build your own Injector Tester. And it is a conversion because there is some re-routing of hydraulic passages involved. You can easily and cheaply build one yourself, or places will indeed sell you you pre-made and ready to go.

Here is the more traditional BOSCH-type design:
http://www.ultimategarage.com/shop/part.php?products_id=5359

And here is the far more economical converted bottle jack setup:
https://mercedessource.com/store/cis-gas-fuel-injector-spray-pattern-tester-and-nozzle-cleaner



The proper tester/cleaner allows you to "shock" or shake loose the injector by hitting the handle hard and fast to clean the valve seat. You are supposed to use Paint Thinner because it is the same viscosity as gasoline and not as flammable. In my experience you don't have to get the injectors perfect, just close so the motor will run smoothly.

Depends upon what you view as "perfect". They don't have to all crack at exactly the same PSI, or flow precisely the same amount of fuel. But you do need to ensure that they're operating within spec. Proper metering of fuel relies upon the injectors, the fuel distributor, the primary pressure regulator, the control pressure regulator, and the fuel pump. Those items do have to be in tune with one another to work properly. Otherwise we'll be chasing phantoms all over the place. Like I said earlier, if you've got an injector with a weak spring that doesn't hold rest pressure, it's going to bleed off fuel and pressure from the Fuel Distributor. Which then looks like the common faulty Accumulator or Check Valve on the Fuel Pump. Then we're off chasing the wrong thing, and spending money and time on things we don't need.

Now I'm not a professional mechanic, but this guy is, and he says the exact same thing:
https://www.youtube.com/watch?v=pOZRHt-GkHY



Now what kind of setup could we use to test a fuel distributor. I guess it would be nice to have a spare top half of the manifold so it would hold the plunger at the correct position and you could move the plunger a calibrated amount. Would also guess a fuel pump and accumulator so the pressures are smooth.

I've posted this video before, but here it is again: https://www.youtube.com/watch?v=1-PuxKL3ieY

As you can see, this setup uses a jig to hold everything in place, but this is still something that you can easily do. As demonstrated by this: https://www.youtube.com/watch?v=qWCLwznFJ14


Remove the Air Cleaner Assembly.
Pull out all 6 CIS Injectors.
Unbolt the Cold Start Valve.
Unbolt the Frequency Valve.
Unbolt the Control Pressure/Warm Up Regulator.
Disconnect the Supply and Return Lines from the Fuel Distributor.
Disconnect the Air Mixture Unit from the feed to the Throttle Assembly.
Unbolt the Idle Speed Motor, and Pull out the Auxiliary Air Tube.
Remove the remaining two screws on the brackets suspending the Air Mixture Unit, and pull it out.


Once you had it on the bench, you'd need a spare fuel pump & filter, as well as the feed and return hoses for your bench tank, and to assemble the PPR again for full flow testing. Plus install the Tester Gauge, and if need be a 12V source too in order to heat up the WUR for normal operation and/or testing. Unless of course you just want to get a spare K-Jetronic Air Mixture Unit and spare hoses to just build a permanent test rig. But why bother unless you start repairing/testing Fuel Distributors en masse?

[Rich_NYS]

Great thread Dave, very interesting stuff to see here!

[SupercoolBill]

Just read all of this.
Very enlightening. I will be reading it again.

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