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

  1. #11
    Senior Member
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    Quote Originally Posted by Peno67 View Post
    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.
    David Teitelbaum

  2. #12

  3. #13
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    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.

  4. #14
    Senior Member Chris 16409's Avatar
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    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.
    Chris Miles

    For Better or Worse I own a DeLorean!
    1983 Grey Manual, VIN #16409, Fresno, California

  5. #15
    Senior Member Bitsyncmaster's Avatar
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    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.
    Dave M vin 03572
    http://dm-eng.weebly.com/

  6. #16
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    Quote Originally Posted by Peno67 View Post
    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...ull=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.
    Last edited by Jonathan; 12-09-2017 at 10:10 AM.


    Sept. 81, auto, black interior

  7. #17
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    Quote Originally Posted by Peno67 View Post
    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.
    David Teitelbaum

  8. #18
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    Where are you located? Perhaps a local Delorean owner can come by and help.
    Shannon

  9. #19
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    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.

  10. #20
    Senior Member Bitsyncmaster's Avatar
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    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.
    Dave M vin 03572
    http://dm-eng.weebly.com/

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