Fuel distributor locking up after the engine warms up??

[RamblinDMC]

Hi everyone,

Today I believe I have narrowed down a hot start issue to the fuel distributor. As far as the fuel system, I've replaced the WUR, accumulator, fuel pump, main pressure valve o rings, cleaned the injectors, and installed new spark plugs. When I do a cold start, my car will start up just fine, even after a week of sitting. It runs/idles smoothly and revs very responsively. However if I let it sit for longer than 30 minutes or so, and try to start it again, it just turns over and maybe sputters weakly once or twice.
To check for issues I started by disconnecting the fuel input hose from the distributor and bridging over the RPM relay to make sure my fuel pump is working. It pumps just fine.
Next I pulled one of the fuel injector lines and stuck it in a jar. I then ran the fuel pump/pressed on the air metering plate and nothing came out of the injector. Even if the injector is removed from the hose, still nothing comes out.
Then I tried to blow some compressed air into the fuel input port and I could hear the plunger move. It made a slight creaking noise. The air metering plate also felt like it had pressure behind it as well.
Then I tried to run fuel through the distributor again, the injector sprayed for about a second and stopped.

I'm thinking the plunger inside the fuel distributor is stuck.
Tomorrow I'm going to try this same procedure again to see if the injector will continually spray when the engine is completely cooled off.

Do these distributors have a history of seizing up when the engine gets warm?

What are my options to repair this? I'm aware I can send it off for repair, however, I've seen rebuilt kits online and I've ready repair guides. I looks feasible.
Also, how much should the air metering plate move when the throttle is turned?

Thanks!
Jayce

[sdg3205]

Weird. I've never heard of this as a hot start issue. Did you verify with k-jet gauges that you loose rest pressure?

I had a seemingly incurable hot start issue on a project car once and the problem was astounding. You know those o-rings on the PPR plunger we are told can be problematic? Well mine were fine BUT there is a tiny o-ring on the butt end of the plunger shaft you can't see. Mine was toast and this caused a hot start issue. Just a thought.

[RamblinDMC]

I have a k-jet gauge set and my car doesn't lose rest pressure, even after a week of sitting. I did also replace the PPR plunger o-rings. The fuel distributor just won't output any fuel when it gets warm apparently. I'm thinking the internal plunger is getting stuck.



Weird. I've never heard of this as a hot start issue. Did you verify with k-jet gauges that you loose rest pressure?

I had a seemingly incurable hot start issue on a project car once and the problem was astounding. You know those o-rings on the PPR plunger we are told can be problematic? Well mine were fine BUT there is a tiny o-ring on the butt end of the plunger shaft you can't see. Mine was toast and this caused a hot start issue. Just a thought.

[David T]

I have a k-jet gauge set and my car doesn't lose rest pressure, even after a week of sitting. I did also replace the PPR plunger o-rings. The fuel distributor just won't output any fuel when it gets warm apparently. I'm thinking the internal plunger is getting stuck.

If the internal plunger is getting stuck a simple test would be to get the motor hot, remove the air cleaner and press on the air sensor plate. If it won't move the plunger is stuck. If the problem is not rest pressure that would imply it is not a fuel system problem. Try the plug swap. Unusual to have a plunger stick on a car that runs well when cold. Usually happens on a car that hasn't run in a LONG time.

[PJ Grady Inc.]

Hi everyone,

Today I believe I have narrowed down a hot start issue to the fuel distributor. As far as the fuel system, I've replaced the WUR, accumulator, fuel pump, main pressure valve o rings, cleaned the injectors, and installed new spark plugs. When I do a cold start, my car will start up just fine, even after a week of sitting. It runs/idles smoothly and revs very responsively. However if I let it sit for longer than 30 minutes or so, and try to start it again, it just turns over and maybe sputters weakly once or twice.
To check for issues I started by disconnecting the fuel input hose from the distributor and bridging over the RPM relay to make sure my fuel pump is working. It pumps just fine.
Next I pulled one of the fuel injector lines and stuck it in a jar. I then ran the fuel pump/pressed on the air metering plate and nothing came out of the injector. Even if the injector is removed from the hose, still nothing comes out.
Then I tried to blow some compressed air into the fuel input port and I could hear the plunger move. It made a slight creaking noise. The air metering plate also felt like it had pressure behind it as well.
Then I tried to run fuel through the distributor again, the injector sprayed for about a second and stopped.

I'm thinking the plunger inside the fuel distributor is stuck.
Tomorrow I'm going to try this same procedure again to see if the injector will continually spray when the engine is completely cooled off.

Do these distributors have a history of seizing up when the engine gets warm?

What are my options to repair this? I'm aware I can send it off for repair, however, I've seen rebuilt kits online and I've ready repair guides. I looks feasible.
Also, how much should the air metering plate move when the throttle is turned?

Thanks!
Jayce
No there is no history of seizing when warm only when the fuel turns sour. The air sensor flap should open slightly and oscillate when cranking. Have you tampered with your fuel mixture? If so you may just have it set too lean. Remove one injector from the head (I'd suggest the #6) and hold it over a container to catch fuel. Have someone crank the motor while you check for a light fan shaped spray of fuel from the injector. If there is no fuel spray when cranking turn the CO adjustment screw clockwise until fuel just starts to spray and you are back in the ballpark!
Rob

[RamblinDMC]

So today I removed the fuel distributor and found that the plunger did have a bit of rust on the bottom and a bit of gummy old fuel. Those kept it from moving smoothly. After cleaning the rust and gummy fuel off, the engine is running like a champ now! Actually better than it ever has. I have also found that my injectors aren't spraying as well as they should. Also ran across a disconnected electrical plug and a vacuum line. I'll post pics in a bit. Also found out that my thermostat is bad. Gonna replace that, the otterstat, some coolant hoses and clean out the radiator next. Maybe I'll clean the injectors too.

[Ron]

Sounds like you'll be in high cotton shortly!

[RamblinDMC]

So I found three interesting things behind the engine that don't really make any sense. One is a small plastic tube. It's kinda like a WD-40 straw. Seems like its part of the harness. What is this thing?
Found a disconnected vacuum line and electrical plug. Where do these go?

http://images.tapatalk-cdn.com/15/10/11/70e01408914e564da9971ced6afd5ebb.jpg

http://images.tapatalk-cdn.com/15/10/11/1b56bc30e1550f9504145ead28dd8dea.jpg

http://images.tapatalk-cdn.com/15/10/11/78006ad4cb4332f9ebb18c7982c2eb08.jpg



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[sdg3205]

The "straw" is likely the vacuum line to your heater valve

The harness does nothing.

The hose looks like it ought to be one of the two vacuum lines to the advance solenoid right there next to it. Do you have a vacuum diagram under the engine cover?

[RamblinDMC]

Ok great thanks. Where is the heater valve? My vacuum diagram is missing I found one online. It looked like the vacuum advance solenoid does have both hoses connected.

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[Bitsyncmaster]

That connector with the orange and purple wires did connect to the diagnostic connector. You just use the orange wire to test dwell on the + side of your dwell meter. Use engine block for the - side of your dwell meter.

[David T]

Sounds like you are resurrecting this car. It would make sense now that the plunger is gunked up and cleaning it fixed this problem. Also sounds like this car was meddled with and you have a lot of work to do. If the plunger was stuck it is a good bet all of the injectors will need to be cleaned to get the motor to run well. Have you cleaned out the gas tank yet?

[RamblinDMC]

Yes the first thing i did to the car was cleaned out the gas tank. It was filthy. What's the best way to clean injectors yourself without sending them out for cleaning?

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[DMCVegas]

Yes the first thing i did to the car was cleaned out the gas tank. It was filthy. What's the best way to clean injectors yourself without sending them out for cleaning?

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Usually it's easier to find a BOSCH Service Center, and have them clean them.

But... If you like, you can easily build the part yourself:
http://www.peachparts.com/shopforum/general-information/224334-how-build-diesel-injector-pop-tester.html

Or you could buy one ready made:
https://mercedessource.com/store/cis-gas-fuel-injector-spray-pattern-tester-and-nozzle-cleaner

The only difference between a Diesel and a Gasoline/Petrol injector tester are really just the fittings and the PSI Gauges. Once you're done you could either start charging a couple bucks for the service, or just simply be the hero of all your fellow DeLorean owners and help them out with the communal tool during your local tech days.

[SS Spoiler]

I had a bad miss so I took out all the injectors and dropped them
into a can of injector cleaner for a week to soak. Put them back
in and the miss was gone. Did that 16 years ago, haven't touched
them since.....worth a shot

[RamblinDMC]

I had a bad miss so I took out all the injectors and dropped them
into a can of injector cleaner for a week to soak. Put them back
in and the miss was gone. Did that 16 years ago, haven't touched
them since.....worth a shot
Ok thanks, I'll give that a try. Suppose I could do that and then blow them out with an air hose.

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[Bitsyncmaster]

Usually it's easier to find a BOSCH Service Center, and have them clean them.

But... If you like, you can easily build the part yourself:
http://www.peachparts.com/shopforum/general-information/224334-how-build-diesel-injector-pop-tester.html

Or you could buy one ready made:
https://mercedessource.com/store/cis-gas-fuel-injector-spray-pattern-tester-and-nozzle-cleaner

The only difference between a Diesel and a Gasoline/Petrol injector tester are really just the fittings and the PSI Gauges. Once you're done you could either start charging a couple bucks for the service, or just simply be the hero of all your fellow DeLorean owners and help them out with the communal tool during your local tech days.

Those testers/cleaners are pretty cool. I would think you could get a higher cleaner flow rate by designing a unit with a tank of cleaner and that tank is pressurized via your air compressor. I wish there was a way to back flow clean them but unless you can hold the valve in the injector open, no way.

[Slammer]

Any advise on getting the plunger unstuck? Without dismantling the distributor.
Mine is not moving at all.

[DMCVegas]

Those testers/cleaners are pretty cool. I would think you could get a higher cleaner flow rate by designing a unit with a tank of cleaner and that tank is pressurized via your air compressor. I wish there was a way to back flow clean them but unless you can hold the valve in the injector open, no way.

You can purchase pneumatically powered ones, absolutely. In fact, if you're looking to make as multi-purpose of a tool as possible, that would be the way to go. You can adjust the line pressure on the injectors by adusting the pressure regulator from the compressor feed. The end connectors are completely interchangeable too.

So you have one tool where you using various adapters you could crank the solvent pressure up to 74 PSI, and blow out your CIS injectors. Then you could swap adapters, lower pressure to the mid 30's, and then either clean EFI Injectors one at a a time, OR just connect the line to the Schrader valve on your EFI Manifold and clean both your injectors as well as your combustion chambers.

I've also seen pictures where the Mercedes and Porsche mechanics pull the entire K-Jetronic system off of the engine, and have a jig they place everything onto where they can just pump solvent through and clean out the CPR, Frequency Valve, and Distributor simultaneously as well. Of course the other part of this too is that on those more fancy CIS systems, they also have the ability to adjust flow to the individual ports, so those rigs have another purpose for fine-tuning as well. I suppose you could do this on the car and also get the combustion chambers if you really wanted to...

Depending upon which kit you buy with what adapters it has included, it might run you between $125 to $400. But the good news is it's a multi-purpose tool that will work on ALL of your cars and trucks.

[RamblinDMC]

So today, after letting my car sit for a day, my car started cold on the first crank! Additionally, after running for about 30 mins, I shut it off for about 5 minutes and it started again on the first crank. Looks like the fuel problems have been solved! I'm really glad I didn't send off my fuel distributor for rebuild when it was just a sticky plunger.

[RamblinDMC]

Any advise on getting the plunger unstuck? Without dismantling the distributor.
Mine is not moving at all.

You don't actually have to dismantle the distributor itself. You just have to remove it from the air metering unit. Remove all of the fuel hoses and the three screws on top and it will lift off. Then you can access the plunger for cleaning. It will slide out of the underside of the distributor. Be very careful with it. Don't use sand paper and scratch it up. That'll ruin it.