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Thread: Bosch CIS fuel pressure gauge

  1. #11
    DMC Midwest - 815.459.6439 DMCMW Dave's Avatar
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    Quote Originally Posted by Trstno1 View Post
    The control pressure shown in the video was a cold start.

    What would it mean if the control pressure starts so high? It seems after a cold start its immediately at 40 psi and gradually increases to a little over 50 psi before it stabilizes.
    .
    How cold? If "overnight Alaska" cold, that is way to high to start with. Dave M is right - should start at more like 20 psi. If overnight in a 80F degree heated garage, it's probably OK. That can really only be a bad regulator, only way to tell for sure is swap it. Too bad, because it appears to have the right pressure as soon as it warms up. Strange failure mode. More typical of a bad regulator is a 70psi reading all the time.
    Dave S
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  2. #12
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    Quote Originally Posted by Trstno1 View Post
    Ok so I competed some tests this morning. Please tell me what you think.

    Primary pressure is 5 bar
    I would add some a shim or two to it, to put it back to the book values - would aim for 5.2 to 5.3 bar.

    Adjustment shims are available from the Eurotec club for this purpose if required, as mentioned in this topic here: http://dmctalk.org/showthread.php?12...egulator-Shims


    Quote Originally Posted by Trstno1 View Post
    Control pressure starts at 40 psi and slowly stabilizes up to 50 psi or 3.5 bar - the blip of the throttle when cold takes the pressure down to 40 psi and it slowly increases to 50 psi again. Once the car is warm blipping the throttle does nothing to the control pressure, it stays steady at 50 psi. Am I correct in saying the WUR appears to be working, but slowly....is that normal?
    Per your video, at the rate the control pressure rose up to 3.5 bar, I assume you had the electrical plug connected to it?

    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.

    Use a thermometer to measure the temperature of the CPR casing, and reference this to the temp/pressure chart in the manual as the engine warms up:
    cpr temp to pressure.JPG
    Attached Images
    Last edited by MikeWard; 03-07-2016 at 10:22 AM. Reason: Additional info added

  3. #13
    Senior Member Trstno1's Avatar
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    Quote Originally Posted by DMCMW Dave View Post
    How cold? If "overnight Alaska" cold, that is way to high to start with. Dave M is right - should start at more like 20 psi. If overnight in a 80F degree heated garage, it's probably OK. That can really only be a bad regulator, only way to tell for sure is swap it. Too bad, because it appears to have the right pressure as soon as it warms up. Strange failure mode. More typical of a bad regulator is a 70psi reading all the time.
    I have the heat up in the garage since I've been working on the car. I think it's set at 65 degrees.

    And did you mean it would be a bad warm up regulator or primary pressure regulator? Also, what do you think the consequences of such a high cold start control pressure would be? Does it really hurt anything?
    Last edited by Trstno1; 03-07-2016 at 11:08 AM.
    You can't buy happiness, but you can buy a DeLorean and that's sort of the same thing....

  4. #14
    Admins Never Retire Ron's Avatar
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    Just in case, it seems you are missing the idea behind the WUR/CPR... if the WUR (and thus engine) is cold, it will lower the control pressure to enrich the fuel and then lean it out to normal operating pressure (50 psi)/fuel ratio as the engine warms up.
    If it has been in a heated area, it would start control pressure at a higher rate than 20 psi ie expected/'normal'.

    FWIW:
    -Mine at 55 F, will start off at ~24 psi and go to the 50 psi quickly ( < minute or so, iirc).
    -I would expect it to start at the 40 psi, if it were ~85 F and go to 50 psi within a few seconds.
    -Having sat in a heated area at the 65 F overnight, I'd expect it to start at ~26 F....that be the case, yours is a little off but it's not that critical, as long as it hits and holds 50 psi when fully warm.
    -Again, the engine must not run for hours, preferably sat over night (internal cylinder temp is what matters most, not ambient air), you have one very short time period to check it...

    FWIW- I would not mess with the Primary Pressure with it being at 5.0 bar because it is within the "checking value" specs given in the manual at D:02:01 of 4.9-5.5 Bar (71-79psi)....(don't see 0.1 psi off of "setting value" as the problem)

    P.S. Dave was saying the CPR;WUR could be bad, not PPR.

    P.P.S. IMHO, once you run it around a little with some cleaner in it and fresh plugs, I'd bet the only problem you have (expect possibly a bad WUR, which I would not bet on yet) would be to only see a hunting problem during warm up, which is typical IF your injectors are not flowing exactly the same AT IDLE and/or ALL settings etc correct before adjusting the CO (Dwell) LAST. They are just particularly fussy when cold.

    Hope this helps.....
    Last edited by Ron; 03-07-2016 at 02:11 PM.

  5. #15
    DMC Midwest - 815.459.6439 DMCMW Dave's Avatar
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    Quote Originally Posted by Trstno1 View Post
    I have the heat up in the garage since I've been working on the car. I think it's set at 65 degrees.

    And did you mean it would be a bad warm up regulator or primary pressure regulator? Also, what do you think the consequences of such a high cold start control pressure would be? Does it really hurt anything?
    Warmup regulator. And if you can live with awful performance until warm-up, it's not hurting anything given the pressures you are seeing. It's just way too lean for a few minutes and will be hard to get moving, i.e. will tend to stall when you let out the clutch (or put in drive). It will be a lot worse if you happen to park the car out in the real cold, maybe even hard to start (seems like you may be seeing that problem, although it would be more of a start/die/stare/die a few times and then it would run.

    For future reference, if the pressure were to stabilize too high, you would need to fix it for sure.
    Dave S
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  6. #16
    Senior Member Trstno1's Avatar
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    Yes! thank you very much!


    Quote Originally Posted by Ron View Post
    Just in case, it seems you are missing the idea behind the WUR/CPR... if the WUR (and thus engine) is cold, it will lower the control pressure to enrich the fuel and then lean it out to normal operating pressure (50 psi)/fuel ratio as the engine warms up.
    If it has been in a heated area, it would start control pressure at a higher rate than 20 psi ie expected/'normal'.

    FWIW:
    -Mine at 55 F, will start off at ~24 psi and go to the 50 psi quickly ( < minute or so, iirc).
    -I would expect it to start at the 40 psi, if it were ~85 F and go to 50 psi within a few seconds.
    -Having sat in a heated area at the 65 F overnight, I'd expect it to start at ~26 F....that be the case, yours is a little off but it's not that critical, as long as it hits and holds 50 psi when fully warm.
    -Again, the engine must not run for hours, preferably sat over night (internal cylinder temp is what matters most, not ambient air), you have one very short time period to check it...

    FWIW- I would not mess with the Primary Pressure with it being at 5.0 bar because it is within the "checking value" specs given in the manual at D:02:01 of 4.9-5.5 Bar (71-79psi)....(don't see 0.1 psi off of "setting value" as the problem)

    P.S. Dave was saying the CPR;WUR could be bad, not PPR.

    P.P.S. IMHO, once you run it around a little with some cleaner in it and fresh plugs, I'd bet the only problem you have (expect possibly a bad WUR, which I would not bet on yet) would be to only see a hunting problem during warm up, which is typical IF your injectors are not flowing exactly the same AT IDLE and/or ALL settings etc correct before adjusting the CO (Dwell) LAST. They are just particularly fussy when cold.

    Hope this helps.....
    You can't buy happiness, but you can buy a DeLorean and that's sort of the same thing....

  7. #17
    Senior Member Trstno1's Avatar
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    I really appreciate the information. I will order a new WUR tomorrow and recheck the control pressure after the install. Would this also potentially be the reason I crank so much prior to the car cold starting? Thanks very much for all the help!



    Quote Originally Posted by DMCMW Dave View Post
    Warmup regulator. And if you can live with awful performance until warm-up, it's not hurting anything given the pressures you are seeing. It's just way too lean for a few minutes and will be hard to get moving, i.e. will tend to stall when you let out the clutch (or put in drive). It will be a lot worse if you happen to park the car out in the real cold, maybe even hard to start (seems like you may be seeing that problem, although it would be more of a start/die/stare/die a few times and then it would run.

    For future reference, if the pressure were to stabilize too high, you would need to fix it for sure.
    Last edited by Trstno1; 03-07-2016 at 03:02 PM.
    You can't buy happiness, but you can buy a DeLorean and that's sort of the same thing....

  8. #18
    DMC Midwest - 815.459.6439 DMCMW Dave's Avatar
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    Quote Originally Posted by Trstno1 View Post
    I really appreciate the information. I will order a new WUR tomorrow and recheck the control pressure after the install. Would this also potentially be the reason I crank so much prior to the car cold starting? Thanks very much for all the help!
    Probably not. You need to check the cold start valve to see if it sprays when engine is cold. They rarely fail but the thermo-time switch, or bad wiring, will cause that.

    If the valve isn't spraying, do the "plug swap" or "hot wire inside" to force it, and see if it works.

    Plug Swap - connect the gray warmup regulator plug to the blue injector. This will fire the injector as long as the engine is running, so you need to disconnect it ASAP when it starts or it will flood. This also tends to wear out the connectors.

    "hot wire inside" - Locate the unused relay socket at the back of the electrical compartment. Usually white but sometimes black. Jumper the white-red to the blue-black. This will fire the injector as long as the engine is cranking. Will be great when cold, will flood it when hot so don't just leave the jumper in place. DO NOT CONNECT ANYTHING TO THE BLACK (ground) wire or you will melt things. Some folks wire this as a push-button to avoid replacing the thermotime switch.
    Dave S
    DMC Midwest - retired but helping
    dswingle@DeLorean.com

  9. #19
    Senior Member Trstno1's Avatar
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    Quote Originally Posted by DMCMW Dave View Post
    Probably not. You need to check the cold start valve to see if it sprays when engine is cold. They rarely fail but the thermo-time switch, or bad wiring, will cause that.

    If the valve isn't spraying, do the "plug swap" or "hot wire inside" to force it, and see if it works.

    Plug Swap - connect the gray warmup regulator plug to the blue injector. This will fire the injector as long as the engine is running, so you need to disconnect it ASAP when it starts or it will flood. This also tends to wear out the connectors.

    "hot wire inside" - Locate the unused relay socket at the back of the electrical compartment. Usually white but sometimes black. Jumper the white-red to the blue-black. This will fire the injector as long as the engine is cranking. Will be great when cold, will flood it when hot so don't just leave the jumper in place. DO NOT CONNECT ANYTHING TO THE BLACK (ground) wire or you will melt things. Some folks wire this as a push-button to avoid replacing the thermotime switch.

    Ok, the cold start valve tests good. So I guess the long cranking on cold start would mean faulty thermotime switch or bad wiring. What am I looking for to test the thermotime switch electrically?
    Also, I just want to confirm before ordering a new WUR that the lower control pressure on cold start up closer to spec than the one I have now will make the engine run better until it warms up? It seems to run good when warm, just kinda funky when cold.
    You can't buy happiness, but you can buy a DeLorean and that's sort of the same thing....

  10. #20
    Senior Member Rich's Avatar
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    Quote Originally Posted by Trstno1 View Post
    It seems to run good when warm, just kinda funky when cold.
    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.
    March '81, 5-speed, black interior

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