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Thread: Uneven Injector Output ***Split from PPR Shim Source ***

  1. #1
    absotively posilutely bytes311's Avatar
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    Uneven Injector Output ***Split from PPR Shim Source ***

    On the topic of PPR shims, the PO installed a Volvo fuel distributor 0 438 100 076 on my car which I believe crosses over from a Volvo 260. Engine runs fine, but when I tried the spray test with the RPM relay jumpered, only one or two injectors spray, and both at random. I've had the injectors professionally cleaned, so I don't know if there's a difference in internal pressure between the Volvo and the DMC FD, but it appears that my PPR also only has one shim. Could that be the problem?

    20180728_180612.jpg

  2. #2
    Delorean Guru
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    There is no direct cross/over from anything to a Delorean as far as the fuel system is concerned. The part number on each part is very application specific. That said, there are other applications close enough that they will work but they were not designed to work optimally for the Delorean. It is also possible to modify parts so that they can work on a Delorean. Inside the F/D the parts have specific profiles, the springs are set to specific pressures, and the passages are drilled to certain sizes. Ideally you should strive to get the correct part if at all possible. It is getting harder and harder as the parts get older and older and the cross/overs also get older and harder to get too. Look to the Delorean vendors to get, if not the correct parts, at least parts that will work. They must have stock of parts for their service business.
    David Teitelbaum

  3. #3
    Senior Member Bitsyncmaster's Avatar
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    Quote Originally Posted by bytes311 View Post
    On the topic of PPR shims, the PO installed a Volvo fuel distributor 0 438 100 076 on my car which I believe crosses over from a Volvo 260. Engine runs fine, but when I tried the spray test with the RPM relay jumpered, only one or two injectors spray, and both at random. I've had the injectors professionally cleaned, so I don't know if there's a difference in internal pressure between the Volvo and the DMC FD, but it appears that my PPR also only has one shim. Could that be the problem?

    20180728_180612.jpg
    If your car runs fine than something is wrong with your test that only showed one or two injectors spraying. Did you press the air plate all the way down to test? If so try the test just pressing about half way down. I have see one car that had the correct FD not spray good with the plate all the way down but would do it fine at half way down.
    Dave M vin 03572
    http://dm-eng.weebly.com/

  4. #4
    absotively posilutely bytes311's Avatar
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    Thank you for your responses.

    With the air plate halfway or fully down I get the same result. For me, this was a sporadic hot start issue until I installed Bitsyncmaster's solid state RPM relay. Now that the pump auto-primes every time, it hasn't been a real issue, but I still want to address the root cause.

    I may just call around and see if any of our vendors are opened to making a FD swap.

  5. #5
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    Does the same thing happen if you swap both injectors with two that don't currently do that?

  6. #6
    Administrator Ron's Avatar
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    Quote Originally Posted by bytes311 View Post
    Thank you for your responses.

    With the air plate halfway or fully down I get the same result. For me, this was a sporadic hot start issue until I installed Bitsyncmaster's solid state RPM relay. Now that the pump auto-primes every time, it hasn't been a real issue, but I still want to address the root cause.
    $.03

    I believe what Dave was saying is that you should ignore the flow when the injectors are fully open...that basically never happens.
    The injectors should all open at the ~same time and the output of each should increase equally as the plate is moved down farther. The PPR maintains a constant pressure for the FD. The FD is responsible for maintaining equal pressure-volume to each injector. The injectors have a spring loaded valve that opens when the pressure is above ~4 Bar. So, if the injectors are not opening at the same time or not delivering the same volume of fuel as each other, suspect the FD internals, the injectors, and the injector fuel lines.

    To find the root cause try:
    Mark the order in which the injectors open. (The spec is has range of 3.5 to 4.1 Bar, so if they are really close, consider them the same.)
    Swap the feed hoses, of the first and last injector to open, at the FD end.
    If the order is the the same as before, it's not the FD. Otherwise, it is the FD.
    If the order changes, it's a hose(s) or injector(s). So swap the two feed hoses, at the injector ends.
    If the order now changes, it's the hose. Otherwise, it's the injector.

    (If you have put it all back together since posting, you might be able to show that it's the FD without involving injectors 5 & 6, a PITA to get to...)

  7. #7
    Delorean Guru
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    First things first. Check that all of the injectors have the same (and correct!) part #'s. If they were "mixed and matched" they will never spray or open equally. If they are all the same send them out to be cleaned and tested. Once you know all of the injectors are good, if you still get uneven openings and sprays you have a problem with the F/D and that should be sent out. If it isn't the correct part # you should try to get the correct one. If the injector seals are no longer rubbery but are hard, replace them while you are checking the injectors. Checking injectors using the F/D is not a good test. It is possible you have a very low primary pressure and only the injectors with the lowest opening pressure are opening. The test you should be doing is measuring the primary pressure. If it is not right none of the other parts will work right.
    David Teitelbaum

  8. #8
    absotively posilutely bytes311's Avatar
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    Thank you all for your suggestions. All of my injectors have the same part #, and I've had them cleaned professionally. I also have brand new fuel lines from DPI, so the fuel system itself is clean. I may just bite the bullet and buy the right FD for the car.

    The mechanic at the shop where I had my injectors cleaned suggested that I take a rubber mallet to the FD and knock on it a few times which I'm very reluctant to do.

  9. #9
    Senior Member Bitsyncmaster's Avatar
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    Quote Originally Posted by bytes311 View Post
    Thank you all for your suggestions. All of my injectors have the same part #, and I've had them cleaned professionally. I also have brand new fuel lines from DPI, so the fuel system itself is clean. I may just bite the bullet and buy the right FD for the car.

    The mechanic at the shop where I had my injectors cleaned suggested that I take a rubber mallet to the FD and knock on it a few times which I'm very reluctant to do.
    I'm running the same "076" FD on my car with no problems. Not saying something is not wrong with yours.
    Dave M vin 03572
    http://dm-eng.weebly.com/

  10. #10
    absotively posilutely bytes311's Avatar
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    Quote Originally Posted by Bitsyncmaster View Post
    I'm running the same "076" FD on my car with no problems. Not saying something is not wrong with yours.
    I'm going to get some kjet gauges on it. Since you have the same FD as I, do you know what the ideal primary pressure should be?

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