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Thread: Hard start cold or hot but runs good

  1. #1
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    Hard start cold or hot but runs good

    Ok, in order to get the car started and stay running, I need to get out once it catches, and play with the pressure plate to the fuel distributor and play with the throttle. After doing this for say 45 seconds some times a little longer it will stabilize and I can drive it with no issue, idles a little rich. When I get back shut the car off and try to restart and same thing, maybe slightly harder to get started. I have pulled the fuel pump and cleaned the screens, I have replaced the fuel filter. After replacing I pulled the supply line of off the feul distributor, and hot wired the fuel pump and got all the air out of the system, and had real good fuel flow. When I turn the key on I do not hear the fuel pump come on, I switched the RPM/fuel relay and still nothing. From what I have read shouldnt the pump come on initially when the key is turned on to at least charge the system? The reason for cleaning the screens and filter, is getting what I believe is the bad gas in the return line portion. I originally cleaned the tank, new fuel pump, I have since cleaned the feed line and changed the fuel filter several times. But never considered the return line. But with more than 100 miles I would think that that would be cleaned out. Its all fresh gas, even went to the gas station near me and topped it off. Is there another part of the fuel system that could have an effect on the initial fuel pump operation? Like I said once I can get it running it stays running and drives good. Just dont dare go to store and shut it off.

  2. #2
    Under Ron's watchful eye. Glory be to Ron! Michael's Avatar
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    Sounds like it might be a rest pressure problem. Possibly bad o rings in the primary pressure regulator or completely shot accumulator. Could also be a big fat intake leak, mixture out of adjustment(due to another problem).

    When you say "play with pressure plate" I am assuming you mean the metering plate.
    Last edited by Michael; 04-26-2020 at 10:19 AM.

  3. #3
    Under Ron's watchful eye. Glory be to Ron! Michael's Avatar
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    I reread your post and I would also check to see if the distributer plunger is stuck.

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    Quote Originally Posted by Michael View Post
    Sounds like it might be a rest pressure problem. Possibly bad o rings in the primary pressure regulator or completely shot accumulator. Could also be a big fat intake leak, mixture out of adjustment(due to another problem).

    When you say "play with pressure plate" I am assuming you mean the metering plate.
    Yes the metering plate, and I went out pulled the injectors out hot wired the pump and set the CO screw as close as can be done this way. And voila the car starts right up, I did check the wirs to the pump and other connections. But it starts and restarts good, just a slight hesitation on acceleration. But I am still having an issue with the screens on the fuel pump getting clogged. Is there a way to 'flush' the return lines other than running it and keep cleaning the screens? The acccumulator was/is new. But after all this would I be better off changing it out? Not a lot of fun on my back under the car. Thanks again for the feedback.

  5. #5
    Under Ron's watchful eye. Glory be to Ron! Michael's Avatar
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    If the accumulator is new forget it. It's probably good. When you say your screens are clogging up, what is that? Your fuel filter? Your fuel filter filters the fuel from the pump not the return so if it's getting visibly clogged then you might have some serious contamination in your tank, pick up screen clogged, etc.

    You can pull the pump and look into the tank, it should be fairly obvious if your tank is contaminated. If it is dirty, then I would drain and clean the tank and replace the pump and filter. I say replace the pump because if your filter is clogged as quickly as you say, then the damage to the pump may be done. It's hard to find a quality OE setup anymore, so it might be a good time to upgrade to a modern unit.

    Once the car is running well enough to go into closed loop, you can adjust your mixture. It's damn near impossible to set it without some type of reading instrument, either a dwell meter or multi meter or exhaust probe.
    Last edited by Michael; 04-26-2020 at 12:30 PM.

  6. #6
    Senior Member Bitsyncmaster's Avatar
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    Some cars will prime with an OE RPM relay and others don't. What causes the prime on OE RPM relays is it sees an ignition pulse after the power is applied to the RPM relay. It is not a designed feature in the OE RPM relays to prime the fuel system.
    Dave M vin 03572
    http://dm-eng.weebly.com/

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    Quote Originally Posted by Michael View Post
    If the accumulator is new forget it. It's probably good. When you say your screens are clogging up, what is that? Your fuel filter? Your fuel filter filters the fuel from the pump not the return so if it's getting visibly clogged then you might have some serious contamination in your tank, pick up screen clogged, etc.

    You can pull the pump and look into the tank, it should be fairly obvious if your tank is contaminated. If it is dirty, then I would drain and clean the tank and replace the pump and filter. I say replace the pump because if your filter is clogged as quickly as you say, then the damage to the pump may be done. It's hard to find a quality OE setup anymore, so it might be a good time to upgrade to a modern unit.

    Once the car is running well enough to go into closed loop, you can adjust your mixture. It's damn near impossible to set it without some type of reading instrument, either a dwell meter or multi meter or exhaust probe.
    KIMG0261.jpgKIMG0260.jpg I have attached pictures of the screens on the pump and pump housing, the return line dumps into the housing. The fuel in the tank looks good, this is a new fuel pump. And I will use the dwell meter to fine tune the CO screw. It has started easy the bunch of times I tried, and even hot it restarts with relative ease.

  8. #8
    Under Ron's watchful eye. Glory be to Ron! Michael's Avatar
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    Yeah that's not an OE pump assembly but I hope it's not too new because your strainers are picking up a lot of junk. Your tank may be dirty and dirt kills pumps. Sounds like your main problem was cured with a mixture adjustment but you need to figure out why it got so out of whack to begin with. That screw doesn't turn itself so something changed to throw the mixture out to begin with, most likely a vacuum leak but don't dismiss a fuel delivery component. You can compensate a problem with mixture but that doesn't fix it.

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    If, all of a sudden, you have cold start problems you check the cold start valve (and associated parts) and the CPR and it's hoses. If it seems to creep and get worse slowly, you may need a tune-up.
    David Teitelbaum

  10. #10
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    Quote Originally Posted by Michael View Post
    Yeah that's not an OE pump assembly but I hope it's not too new because your strainers are picking up a lot of junk. Your tank may be dirty and dirt kills pumps. Sounds like your main problem was cured with a mixture adjustment but you need to figure out why it got so out of whack to begin with. That screw doesn't turn itself so something changed to throw the mixture out to begin with, most likely a vacuum leak but don't dismiss a fuel delivery component. You can compensate a problem with mixture but that doesn't fix it.

    Thanks for the feedback, I am guilty of adjusting it, slightly without using the dwell. And now that I have the timing dialed in and will get the dwell and fine tune the CO adjustment should put me in good shape. And hopefully work through the fuel issue. Then on to getting some of the finer details worked out.

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