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Thread: Bosch CIS fuel pressure gauge

  1. #21
    DMC Midwest - 815.459.6439 DMCMW Dave's Avatar
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    Quote Originally Posted by Rich View Post
    Before ordering any parts be sure that the hoses that feed the warmup regulator are all solid. No splits, no cracks? Use an inspection mirror to verify, assuming you can't smoke test them.

    A very small split/leak in the hose at a tee leading to the rear fitting on the WUR was causing a stumble during cold acceleration on ours at one point a few years back. After spotting that split I replaced the hose. Solid ever since and still on the original WUR.
    That won't impact the static pressure though, and his is too high when cold. Still a good thing to check if you have a car that falls on its face when cold.
    Dave S
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  2. #22
    Senior Member skill's Avatar
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    I had a similar issue on a different car. The idle was up and down and everywhere. Cause; High carbon build up internal. I switched out the spark plugs, cleaned (decarbonized) out the plenum, replaced gaskets as necessary and replaced the fuel injectors (and cleaned them one-by-one). It corrected the issue. If someone could tell me, where on the PRV would it have carbon (gunk) build up on this engine?
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  3. #23
    Senior Member Trstno1's Avatar
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    Quote Originally Posted by skill View Post
    I had a similar issue on a different car. The idle was up and down and everywhere. Cause; High carbon build up internal. I switched out the spark plugs, cleaned (decarbonized) out the plenum, replaced gaskets as necessary and replaced the fuel injectors (and cleaned them one-by-one). It corrected the issue. If someone could tell me, where on the PRV would it have carbon (gunk) build up on this engine?
    What is the plenum?
    You can't buy happiness, but you can buy a DeLorean and that's sort of the same thing....

  4. #24
    DMC Midwest - 815.459.6439 DMCMW Dave's Avatar
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    Quote Originally Posted by Trstno1 View Post
    What is the plenum?
    Intake manifold. I've seen some pretty gunky buildup on DeLorean valves, which is what he's talking about. Not enough to cause a (proven) running issue though. The DMC intake will get dirty but I've never seen any build-up.

    This has become a huge issue on modern direct-injection cars as there is no fuel wash on the back of the intake valves. Not so much of a problem since CIS sprays fuel all the time!
    Dave S
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  5. #25
    '82 T3 Turbo FABombjoy's Avatar
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    Quote Originally Posted by MikeWard View Post
    For testing the control pressure from cold, the CPR (or WUR as it is sometimes referred to) should be tested with the electrical plug disconnected and the vacuum pipes removed
    Yes, this is critical, and reading back through the thread I'm not sure if this was part of the testing that the OP performed:

    Quote Originally Posted by D:02:01
    3. Control Pressure "WARM" (Regulator temp above 40c)

    a. Test with Intake manifold vacuum disconnected from control pressure regulator: 3.4-3.8 Bar
    b. Connect vacuum pump to vacuum port on control pressure regulator which contains the delay valve: 1 .4-1.8 Bar
    Vacuum Setting Value: 450-550 mbar (13.3-16.2 in Hg)
    Quote Originally Posted by DMCMW Dave View Post
    That won't impact the static pressure though, and his is too high when cold. Still a good thing to check if you have a car that falls on its face when cold.
    If only the upper chamber sees vacuum wouldn't this be the result? Seems like this could be related to the vac plumbing still. VDV backwards or blocked?

    I know that if the lower chamber develops a leak you'll get a huge lean spike on throttle.
    Luke S :: 10270 :: 1982 Grey 5-Speed :: Single T3 .60/.48 Watercooled :: Borla Exhaust :: MSD Ignition :: MS3X In Process :: DevilsOwn Methanol Injection

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  6. #26
    Senior Member Trstno1's Avatar
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    Quote Originally Posted by FABombjoy View Post
    Yes, this is critical, and reading back through the thread I'm not sure if this was part of the testing that the OP performed:




    If only the upper chamber sees vacuum wouldn't this be the result? Seems like this could be related to the vac plumbing still. VDV backwards or blocked?

    I know that if the lower chamber develops a leak you'll get a huge lean spike on throttle.
    I did unplug the WUR when cold start tested and still recievied 40 psi control pressure upon startup. I was curious about the vacuum as well. I did replace all of the lines when I had the manifold off, but I checked them 3-4 times for correctness prior to putting it all back together. I gues the large unknown is just how the vacuum solinoid and vacuum delay should be working. Should I be able to blow through the vacuum delay valve? I have verified it to be oriented the right way with the white side facing the front of the car.
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  7. #27
    '82 T3 Turbo FABombjoy's Avatar
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    Quote Originally Posted by Trstno1 View Post
    I did unplug the WUR when cold start tested and still recievied 40 psi control pressure upon startup.
    Unplugged... the power? The vacuum?

    The electrical is for the heater on the bimetallic arm and it's effects are slow. You want it disconnected during a cold test so the CP doesn't start slowly creeping upwards during the test.

    With vac removed, if you have high cold and good hot (also high) then could be a clogged filter screen?

    I have mercilessly dinked around with my WUR but I've not had to troubleshoot much in the realm of non-user induced faults. But based on how it works, errant vacuum signals could have significant effects on control pressure. Taking measurements with vac disconnected can at least cut the troubleshooting tree in half.

    Vac solenoid is for ignition advance. If you hook the lines up backwards your car will hold revs for no good reason.

    Testing the delay valve is easy:
    http://www.justanswer.com/uploads/Au...ons_930001.pdf
    "Spark delay valve" or VDV is the type we have, not the two-way type.
    Luke S :: 10270 :: 1982 Grey 5-Speed :: Single T3 .60/.48 Watercooled :: Borla Exhaust :: MSD Ignition :: MS3X In Process :: DevilsOwn Methanol Injection

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  8. #28
    Senior Member Bitsyncmaster's Avatar
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    Quote Originally Posted by FABombjoy View Post
    I know that if the lower chamber develops a leak you'll get a huge lean spike on throttle.
    You always get a lean spike on all engines with a throttle punch. The throttle plates open to let in air and before the fuel can react it will spike lean. I've recorded AFR from my wideband and you can always see on the plots when the throttle was opened. It will go rich when it's shut.
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  9. #29
    '82 T3 Turbo FABombjoy's Avatar
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    Quote Originally Posted by Bitsyncmaster View Post
    You always get a lean spike on all engines with a throttle punch.
    I did write that funny, really is should read: If you have a vac leak to the lower chamber your AFRs will go continuous > 18:1 on throttle, making the car nearly undriveable until the vacuum control valve switches off the vacuum (and switches on the vac distributor advance).

    When I opened up the cover on the WUR adjustment screw to adjust control pressure, I forgot to seal the hole. My car would start fine, idle fine, and drive terribly for the first 2 minutes of warmup. A penny and high-temp silicone seals the hole perfectly
    Luke S :: 10270 :: 1982 Grey 5-Speed :: Single T3 .60/.48 Watercooled :: Borla Exhaust :: MSD Ignition :: MS3X In Process :: DevilsOwn Methanol Injection

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  10. #30
    Senior Member Trstno1's Avatar
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    Quote Originally Posted by FABombjoy View Post
    Unplugged... the power? The vacuum?

    The electrical is for the heater on the bimetallic arm and it's effects are slow. You want it disconnected during a cold test so the CP doesn't start slowly creeping upwards during the test.

    With vac removed, if you have high cold and good hot (also high) then could be a clogged filter screen?

    I have mercilessly dinked around with my WUR but I've not had to troubleshoot much in the realm of non-user induced faults. But based on how it works, errant vacuum signals could have significant effects on control pressure. Taking measurements with vac disconnected can at least cut the troubleshooting tree in half.

    Vac solenoid is for ignition advance. If you hook the lines up backwards your car will hold revs for no good reason.

    Testing the delay valve is easy:
    http://www.justanswer.com/uploads/Au...ons_930001.pdf
    "Spark delay valve" or VDV is the type we have, not the two-way type.

    I know I unplugged the electrical portion of the WUR, Though I am now questioning if I pulled the vacuum hose off too. I'll have to hook up the pressure gauge again and disconnect everything from the WUR and cold start it just to make sure the pressure is still high. I would rather it be a mistake in testing than my wallet being $200 lighter.....

    If I confirm I still have 40 psi cold starting control pressure, I replace the WUR Correct? If I have normal cold starting psi without anything connected then it safe to assume have something wonky going on with the vacuum system right?
    You can't buy happiness, but you can buy a DeLorean and that's sort of the same thing....

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