First Post, First adventure working on one, some fuel related issues I need help on.

[Peno67]

Hello all. First time poster. A friend of mine has a shop and works on cars moonlighting. One of his customers picked up a Delorean at an auction that wanted it gone through as it has been sitting for some time. We pulled all the old fuel out, changed filters, plugs, etc. Long and short this car has been butchered. We do have a manual. I won't go into all the crap that we found like a fuel pump that is obviously not original installed.

What we are experiencing is the car is running very rich at idle, rough idle with an occasional throaty backfire that appears to be coming from the RH side of the engine exhaust (looking from back of engine). We verified each cylinder is firing and set the timing. Attempted to set fuel mixture using dwell meter. It will not move off of a solid 40 although we had the 02 sensor disconnected as I misread the manual I believe. I think this should only be disconnected if one has the tools to set the CO2. Also noted that the part (sorry I don't remember the correct terminology) that has the two vacuum hose going to it that controls vacuum advance has been bypassed mainly I believe because one of the wire terminals is broke off. As the car warms up it seems to get a little better but it is still rough.

One question I have is related to the three brass fittings on the top front of the engine. As I read the two most forward are bank air adjustments. Manual is somewhat misguided in that in one section it states that any adjustment wont have an effect due to electronic control and then another section states not to mess with them. Unfortunately we did. I set down last night and studied the manual in peace to get a better understanding of things. I wanted to confirm the most aft fitting will adjust engine rpm.

I guess what I am looking for is where to start and what to check. Never really messed with a beast like this. It is very obvious it is running rich as it will burn your eye balls out. The first time I played with the mixture screw just forward of the injector manifold, to get it to smooth out I had to crank it in considerably which caused the converter to glow red hot so we backed it out until it killed the engine and then turned it just enough to keep it running. Have been checking posts out on here to help our cause.

Any input is appreciated.

[Bitsyncmaster]

You can not adjust idle RPM if your idle system is working. That RPM is preset to 775 RPM.

The three brass screws should be closed. (lightly seat them clockwise).

Mixture adjustment needs to be adjusted with a dwell meter if the lambda system is working. If you just set it for best idle, you will be running very rich.

[David T]

Because the car was "sitting" for a long time it will have a lot of fuel system problems. Among them will be injectors that don't spray properly and a stuck fuel plunger. If it runs at all it will run very rich and cr-ppy. To fix the stuck plunger you take the mixture unit off and forceably remove the plunger very carefully without damaging or scratching it and then clean with Acetone so it can slide smoothly in and out of the mixture unit. For the injectors you need to have them cleaned in an injector cleaner/tester. Often they can be cleaned up but not always, you may have to replace some or all of them. The O2 sensor will probably have to be replaced if it is even hooked up. Many times it is disconnected. If the car has anywhere near 30,000 miles on it or more you probably need to check the valve clearances. To attempt to adjust the duty cycle for the Lambda system you will need a full-blown tune-up so the motor is OK to tune. You cannot "adjust" the motor to run well. It has to run well BEFORE you adjust the mixture. If the tamper plug is still there the mixture is probably very close to where it needs to be so don't touch it. If the plug is removed you could be WAY off, that adjustment is VERY sensitive, a tiny amount makes a large difference. The part with the broken terminal is the vacuum advance solenoid and should be replaced. Refer to the vacuum diagram on the engine cover.

[Jonathan]

Not sure which manual you have, but the workshop manual can be downloaded here: http://dmctalk.org/showthread.php?2866-Searchable-Workshop-Technical-Bulletins-and-Volvo-Engine-Manuals

In it, you'll find a good write-up as well as several illustrations of those brass screws you mentioned on around page D:01:03. This is in the fuel and emissions section and it explains what those screws are meant to do and also what they no longer do as part of the PRV set-up in the DeLorean. All three snug closed is best.

As Dave mentioned, you need to get the idle system components working as intended and this will mean returning any hacked up wiring or features back to design. We can speculate what to do to correct a problem with a certain component bypassed or disconnected, but the real solution is to get it set-up the way it was meant to be. That'll include the vacuum advance solenoid's electrical and vacuum lines.

Take some photos of the top of your engine as well as the fuse and relay area behind the passenger seat and the group here can help get you started sorting things out on your car.

[Peno67]

Thanks for the input. My next thought was to get the injectors out and see what we have. I work at a commercial aircraft repair shop and have some possible solutions to clear up the injectors if there is a problem as we clean and flow test nozzles out of turbine engines. A quick question in the meantime. I had taken a couple of pictures going to connectors which are going no where. Are these test ports? 5483354834

[Peno67]

One more question, The mixture screw has been tampered with. Is there a good starting point to begin with as I have no idea how far off the thing is?

[SamHill]

"First, thou shalt acquire six glass jars..."

[Peno67]

Yep, out of the gate going to check valve clearance and injector pattern for a start. i do believe the Lamba system is at least somewhat operational as one can feel the vibrations with key on not running.

[Bitsyncmaster]

Yep, out of the gate going to check valve clearance and injector pattern for a start. i do believe the Lamba system is at least somewhat operational as one can feel the vibrations with key on not running.

With stock wiring, the lambda system only gets power when the engine is running. What you hear is probably the idle motor which will hum with just the key on. The frequency valve (FV) is on the passenger side valve cover. The FV is what will buzz when the lambda system is running.

[Jonathan]

Thanks for the input. My next thought was to get the injectors out and see what we have. I work at a commercial aircraft repair shop and have some possible solutions to clear up the injectors if there is a problem as we clean and flow test nozzles out of turbine engines. A quick question in the meantime. I had taken a couple of pictures going to connectors which are going no where. Are these test ports? 5483354834

Someone just recently asked the same thing about those unused connectors. The comment was that they are only used on automatic transmission cars. I'm not 100% convinced about that, but haven't been out to my own car to look for myself. I'd like to tell you one way or the other, but don't know for certain so will wait until someone else chimes in.

I would suggest confirming your ballast resistor is wired up as it should be. Something doesn't look quite right with the connections on the right side, but can't see well enough in the photo to confirm. The right side of the resistor is meant to have a double tab thingy on the top right portion that allows you to connect two of those wires to the one place. Then one on the lower right and one on the upper left. And nothing connected on the lower left. See drawing in this thread:

http://dmctalk.org/showthread.php?40-All-Wiring-Schematics&p=66530&viewfull=1#post66530

(Which is a great thread to start reading through and doing some comparisons. The entire colour wiring diagram for the car is in there as well as the bulkhead connections, fuse and relay area and many simplified diagrams breaking down smaller circuits in an easy to see schematic. Well worth looking through if you haven't already).

[David T]

One more question, The mixture screw has been tampered with. Is there a good starting point to begin with as I have no idea how far off the thing is?

Assuming the injectors are working (opening) at the correct pressure, you turn the mixture till they shut off and then turn it till they *just* start to crack open. This doesn't work with dirty injectors or a stuck fuel plunger so trying to adjust things when they aren't working properly won't get you anywhere. My guess is the mixture adjustment isn't that bad unless you already messed with it. You are running over-rich because the fuel plunger is stuck. The air sensor plate is mechanically balanced against the fuel plunger. As the plate goes down it pushes the fuel plunger up. If the plunger is dirty and sticks it won't come back down when the air sensor is released. When you have fuel pressure do you feel ANY resistance when you press on the air sensor plate? If not, that plunger is stuck and/or you have no fuel pressure in the metering unit. Once you get the plunger unstuck you need to get the injectors cleaned and tested. If you have a Volvo dealer nearby they may have an cleaner/tester. Or you can send them out.

[Peno67]

Some pics as requested5483654837548385483954840

[Peno67]

I have been doing some more book study and may have discovered part of the butcher job that may be a big problem. 2. I don't remember seeing a shielded wire on the O2 sensor and the sensor would appear to be replaced. Correct me if I am wrong but the shield is suppose to go to the ECU pin 2. Not sure how much this would play into problems.

[Chris 16409]

Just an observation, you have the "adjustable" fuel distributor. For the most part, the original fuel distributors do not have the adjustment screws around the edge. I've heard that some car may have been delivered with the adjustable type, but usually that part indicates it has been replaced.

[Bitsyncmaster]

A few more notes:

Looks like the fan fail jumpers have been hardwired.
Looks like you have one of "John's" later RPM relays. He now drills holes in the case
The fuse block has been rotated. Probably just the clips that hold it down have broken.
Your "light relay" has the jumper so the AC panel only lights when lights are on.

You should still concentrate on getting the engine running correctly. Seeing the wiring has rework just may inform you the PO may have done some changes that may effect some engine components.

[Jonathan]

Some pics as requested5483654837548385483954840

A couple of the fuses look to be the incorrect size for the location. Compare them to this schematic. Inspect the wiring and/or circuit to see if there was some reason why a higher/lower/other rated fuse was used, but intend on getting them back to what was designed.

http://dmctalk.org/showthread.php?40-All-Wiring-Schematics&p=7640&viewfull=1#post7640

I assume you have the air filter housing and just took it off while you troubleshoot and took photos?

Does your car have an automatic transmission? I would assume it does as you have both of the WOT (wide open throttle, or full throttle) microswitchess connected. At least the wiring connectors I can see in the photo lying above the W-pipe show that (they are the white and black connectors that look a bit like Tetris puzzle pieces when you separate them). The idea with those WOT switches is that when you put the accelerator to the floor, the throttle cable pulls on the throttle spool and rotates it around the entire way it will go. At that limit, it has a metal nub that presses on the metal flap of the lower WOT microswitch. The other side of that metal flap then presses in a little plunger that is supposed to tell the engine to give it more gas. Kind of like if you are trying to pass someone out on the highway and need a little more oomph. When you let off the gas pedal, the throttle spool rotates back away from the flap and the plunger then releases. It is supposed to release anyway. Those little plungers can get stuck with grime or they can also get pinched if the securing screws are too tight. On the automatics, there is a second switch mounted right on top of the bottom switch and is to "kickdown" the automatic transmission from 3rd to 2nd (or 2nd to 1st) while you stand on the gas. That upper switch uses the same metal flap and operates the same way (and can fail the same way). If those switches are for whatever reason stuck/shorted into telling the engine you've got the accelerator floored, it will be trying to add extra gas into the mix. It's another thing to test and troubleshoot while you're at it.

Speaking of the O2 sensor (not the shielding wire you mentioned, I'll let someone else comment on that), you should also be able to see what is referred to as the O2 sensor reference ground wire while you have the air filter housing off. It goes right into the block in the front passenger corner and may be using a threaded hole on the side slightly. It should be easy to identify because the portion of the ground wire that is screwed into the block is a solid red colour. It then has a black quick connector on the end and then the other end of that ground wire is what goes to the ECU and O2 sensor to provide the reference ground. Confirm it is in place and making a good connection.

[David T]

I have been doing some more book study and may have discovered part of the butcher job that may be a big problem. 2. I don't remember seeing a shielded wire on the O2 sensor and the sensor would appear to be replaced. Correct me if I am wrong but the shield is suppose to go to the ECU pin 2. Not sure how much this would play into problems.

The O2 sensor doesn't have a shielded wire on it. If the motor has been running over-rich that sensor is probably contaminated anyway. In your other pictures it appears this car has been "hacked up" and will require a lot of work to undo all of the hacks. Could be a part of why it isn't running right. A bad running (or non-functional) Lambda system won't, by itself, make the motor run rich. What often happens is when it isn't running right the owner (or his mechanic) will try to compensate by adjusting the mixture screw to compensate for the failure of the Lambda system. The mixture screw is supposed to be set to the lean side of the mixture and it is the Lambda system's job to add just enough fuel to get to the perfect A/F ratio. The O2 sensor monitors the exhaust and tells the Lambda ECU to open and close the frequency valve, modulating the amount of added fuel (very simplistic explanation of the Lambda system). Again I think you are overlooking the problem is a stuck fuel plunger in the mixture unit. Adjusting the mixture screw won't (can't) do anything if the plunger is stuck.

[lazabby]

Where are you located? Perhaps a local Delorean owner can come by and help.

[Peno67]

As stated I am going to start with plunger and valve clearance. If anything it is one less item that could be in question. This is an automatic and has the microswitched on the throttle mechanism.

[Bitsyncmaster]

After the engine has sat overnight, you should have no rest pressure so you can just see it that air plate will bounce. Just tap it with your finger and if it almost bounces your FD plunger is probably fine.

You can also test your rest pressure for how long it holds. After running the engine that air plate takes some force to press down. Don't press it down but just tap it with your finger to see if you still have rest pressure. Most cars will hold rest pressure for a few hours or longer. If not, you probably need to change the fuel accumulator. This is assuming your mixture is not set so rich that the injectors are leaking fuel with the engine stopped.

[Peno67]

Today we pulled the fuel manifold/intake top off a d verified plunger was fine. A couple of I interesting finds such as an o-ring laying in the intake. The other thing and I am not sure of its purposes was a nut and washer that goes over the plunger housing with the nut being loose. Tightened it up. A bit concerned with this. Curious if there are any parts break down on this. I was also surprised when pulling the makeshift plug where you adjust the mixture at how much rougher the anti e runs although it is a source of major vacuum leak. Anyways it was fun playing around with the guts of the plunger setup. Probably won't mess with until next weekend. Going to dive into nozzles and valve clearance. By the way, is it possible for the cold start to dump fuel after start or would this not be likely?

[Rich]

By the way, is it possible for the cold start to dump fuel after start or would this not be likely?

The purpose of the CSV is exactly that, to give a shot of fuel during cold starts. Substitute for what would've been a choke on a carbureted engine.

Section D:01:09-10 in the Workshop Manual tells about the components of the cold start circuit, including when/how they get turned on and off.

Is that what you meant by "dump fuel after start"?

[Peno67]

Yes that is what I meant and have read and understand it's operation although haventbloomed into it. What I was wondering is is there any chance it could fail in the open position or not likely?

[Bitsyncmaster]

It would be unlikely the CSV could dump fuel after the start. The CSV only gets power from the starter circuit. You can just pull the connector off the CSV (only need it for a cold start) to test the circuit. But I guess a faulty leaking CSV could be dumping some fuel but I have never heard of that happening.

[Peno67]

Thanks for clarification. Does anyone k ow where to get a parts breakdown for the fuel distributer? The washer I mentioned on the plunger slide body appears that maybe it is suppose to be a retainer to hold the plunger from falling out. It would never happen I suppose one together. Looking online it also appears this is likely a -109a distributer. Appears it is for a delorean.

[David T]

Thanks for clarification. Does anyone k ow where to get a parts breakdown for the fuel distributer? The washer I mentioned on the plunger slide body appears that maybe it is suppose to be a retainer to hold the plunger from falling out. It would never happen I suppose one together. Looking online it also appears this is likely a -109a distributer. Appears it is for a delorean.

There is no parts breakdown of the fuel distributor, it isn't supposed to be taken apart, only replaced. It is possible, since the wiring was messed with, that the CSV is running all the time. Just unplug it. BTW, what color plug is plugged into it? It is possible the plugs were swapped with the CPR and the CSV is running wild. Take a picture of the hardware and maybe we can identify it and where it goes.

[Peno67]

So today we started by checking compression to make sure no issues were deep. Then pulled fuel injectors. A couple of them had a cruddy spray pattern so we cleaned all of them. Also noted when putting plugs back in that an assumption was that the gap was correct new and this was not so. The were all about .015 gapped to much. We then did a valve adjustment. All exhaust valves were around .010 and intakes were probably in the .005 range. We remedied this. The engine now runs 100% much smoother and we were able to adjust dwell and indeed noticed the O2 sensor was working. We now have an issue in that the idle is running at 1025ish. Have completey ohmed out the idle system. One item of interest is the thermosistor is showing open between pins 9 and 11 at the ECU. We had been running the car which may have opened it although from reading in the book I don't know if it is open cold or hot. I was going to ohm out the wires but can't find where this thing lives. I fear it is under the intake? All other wires and the diode checks out. I am down to a problem with the thermosistor or possibly the idle control valve is bad. Or at least I think. Any input on why the idle is where it is?

[Ron]

Under the manifold in the coolant distribution pipe. D:05:02, Fig 38
You might want to check the connections and readings at the White 9 pin bulkhead connector first.
See .PDF file in the Resource Section HERE (http://dmctalk.org/showthread.php?40-All-Wiring-Schematics&p=52873&viewfull=1#post52873) for more info.

[Jonathan]

More info and picture of where the thermistor is located here: http://dmctalk.org/showthread.php?10336-Assorted-helpful-technical-photos&p=222057&viewfull=1#post222057

[Peno67]

My partner in crime brought the valve to work this morning. We cleaned it and hooked up to a power supply and it is working. He is going to install tonight and see what happens and will also disconnect plug if it doesn't seem to work and see if rpm increases. Confirmed that the temp switch or at least the wiring going to it is a problem although unless this is open in the cold position I wouldn't think this is causing the idle problem. Will report back more this evening.

[Peno67]

To follow on, the cleaned valve was installed. The car was started in a cold condition and the rooms would steadily fluctuate between 1000 to 2000 rpm. After warming up for a good period the rpm settled in arou d 170p. Disconnecting the onboard ECU plug resulted in the engine going to around 3000 rpm. Based on input this would seem to indicate the valve is working? If so what should we be looking at to get the rpm in check?

[David T]

Verify the throttle arm is returning ALL the way to the idle position and the throttle plates are closed. Inspect the decel valves and springs on the throttle plates to make sure they are held closed. Try to fix any vacuum leaks.

[NckT]

Check that the ecu has reference to the thermistor (engine coolant temp) resistance. Unplug the 4 wire multi plug that's on the bank of the black ecu behind the drivers seat and use a multi meter to measure the resistance between the black/light grey and the black/yellow cable. You should get a resistance to temperature ir approx 8k ohm to 14k ohm on warm engine. If you get open circuit then shove in the back of the multi plug a 10k ohm resistor so it touches the metal pins and reconnect. If this fixes the idle then you may have a bad electrical connection, usually at the church window electrical multi plugs that is located behind the coil cover at the back right of the engine.

If not then you'll have to back probe the wiring from the ecu to the device, but take note that from the throttle(closed) switch to the ecu there is an interposing diode that is in the wiring at the back of the black idle ecu towards the firewall moulded in a black plastic connector. This is to prevent back feed from another circuit that the micro switch operates, so don't bypasd/short out/ shunt this out.

Good luck

NickT

[Peno67]

Here is what I have figured out. I mentioned an oring found in the intake. Pretty sure this is for the airtube from the idle motor. Got a he'll of a vacuum leak under the intake area. Also found the cold start injector is pooched. Verified voltage and ground at the plug. Also confirmed the idle valve and ECU is operating although the thermsistor is open or at least the circuit is and will likely require a pull of the intake. Thanks for the resistor idea at the plug. Tried this just shorting a wire and after finding out restance is needed I will give this a shot. We are going to park this thing in a barn till spring as we got other work piling up as well as snow.. Thanks for all the help. I will report back

[Peno67]

Well it has taken a bit longer than spring time to get the owner to get some parts. As a follow on to above items, we pulled the intake and confirmed the thermistor was bad and replaced. Checked all related vacuum lines under the intake for any leaks. While we were in we also checked the other coolant temp sensor, replaced all the intake o-rings and gaskets and reinstalled. We also replaced the CSV and confirmed it was operating. Also replaced the vacuum advance control mounted on the firewall (forgot what this is called). Now when the engine is cold it will at least try and start but immediately dies. After a few attempts it then won't fire at all telling me the heater is working properly to prevent flooding. If once it starts we feed gas through the intake to keep it running, after it warms up this is no longer necessary and the engine runs fine albeit at around 1050 rpms. Ended up out of curiosity, pulling apart the pressure regulator and found a bit of a mess, all insulation on heater wires were gone and one wire melted in two. Confirmed the heating resistor was good and a repair was done. I will assume the only way to check this entire regulator out is with pressure gauges and adapters which I am sure we could make if required. So this entire mess has me asking more questions. First off it is apparent we have a fuel delivery issue when cold, just don' t know the cause. I am also concerned with how much the fuel air mixture was messed with. Here are some questions:

1. Is there a ground zero starting point to go with on the fuel air mixture screw. We do have a dwell meter although I wanted to know if someone can confirm something. It is an older craftsman unit that has scales for 4/6/8 cylinders. I read somewhere where one should use the 4 cylinder scale or half of the eight and I question if this is tester specific or for all? I read that another way to get a good staring point is to remove a injector and adjust the mixture screw with the engine not running until a injector starts to break open. Not sure if this is such a good idea.

2. If we crank in the fuel mixture screw clockwise enough we can get it to start cold although it sure seems like it is running rich after warmup based on our eyeballs burning out in the garage in a very short time frame. Also this increases the rpm. I wouldn't think if electronic idle system was working right that this would happen. If after it warms up I back the mixture screw out to get it down to 750 then it obviously is not going to start cold and then it runs pretty rough at the 750.

3. Would greatly appreciate some guidance on Step 1 thru Â…. on check this part of the system and then next and so on. I would like to take the logical approach to getting down to the bottom of this as we must be getting close and much has been repaired.


Any input is appreciated. If you can tolerate 3 previous pages of back and forth it may answer some questions of other items already addressed.

[82DMC12]

Peno,

Yes, the suggestion to close the mixture screw until the injectors stop, and then open it until the injectors just barely crack open, is correct to get to a baseline where the machine will idle well enough so that you can adjust the mixture with the dwell meter. As to which scale to use, sorry, it's been over a decade since I did it last time I don't remember, but my meter only has 6 cyl and 8 cyl scales. I THINK I used 8 cyl somehow...

Regarding the high idle, Have you confirmed the idle stop screw and the microswitch trip screw are not adjusted too aggressively so they are interfering with the throttle closing completely? There is also linkage between the idle spool and the throttle which can be lengthened or shortened. maybe someone adjusted that linkage so that the throttle won't close all the way. I would consider taking this whole throttle system apart, clean the spool and spring, grease the linkage, and set the stop screw and microswitch screw again so you're confident the throttle will close at idle.

[Peno67]

Thanks for the feedback. Seems like I remember reading that one can use 8 cylinder but I think you divide by 2. Maybe someone else will comment.

[Ron]

Yep, 4 cylinder or 8 cylinder / 2

More in the How To Section HERE (http://dmctalk.org/showthread.php?12909-How-To-Set-CO-Dwell).