intermittent "hard start" when car at operating temp
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Northstar Engines and System Technical Discussion Discussion, intermittent "hard start" when car at operating temp in Cadillac Engine Technical Discussion; History: had the car for 2.5 years. 107K miles 98 Eldo Touring, relatively trouble free. The ongoing problem: Intermittently (about ...
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    mtflight's Avatar
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    intermittent "hard start" when car at operating temp

    History:
    had the car for 2.5 years. 107K miles 98 Eldo Touring, relatively trouble free.
    The ongoing problem:

    Intermittently (about 10-20% of the time) for the last year and a half I would have a difficult hot start, what I mean is let's say I go to the grocery store after work.... when I come back 45 mintues later and I crank the car, it does not ignite unless I hold for a few seconds longer.
    This would be a symptom caused by the FPR, fuel pressure regulator--but I have pulled the line off the FPR nipple when the car is running and it's dry. I've also tried putting a vacuum on the nipple both with the car off and on and get no fuel coming out, and no loss of vacuum...so thherefore, I have not replaced it (yet).

    Recent New Variation To the problem
    For the last month I have had a new symptom, presenting itself at the same time the hard hot start occurs (i.e., not in the morning when the car is cold, as then it fires up like it's brand new, but only when the car has been operating and is parked for a few minutes to an hour and even then it does not happen ALL the time).

    The new symptom is... as it does not start while I hold it in the start position... it eventually fires up (then runs fine) along with the Check engine light

    I pull the codes while the car is on and I get 3

    DTC B1910 CURRENT:
    Generator L-Terminal Open Circuit
    Circuit Description

    This test is performed with the ignition switch in RUN, the engine speed less than 400 RPM, and the vehicle diagnosic system not activated. This DTC indicates an open circuit in the Generator L-Terminal feedback circuit. The generator grounds CKT 225 when the engine speed is less than 400 RPM and the ignition switch is in RUN.
    DTC Will Set When:

    Then IPC measures engine speed less than 400 RPM and determines that the L-Terminal circuit is open by sensing a high voltage condition at terminal A9.
    DTC P1375 CURRENT:
    IC 24X Reference Circuit High Voltage
    Circuit Description

    This diagnostic test checks for 24X signal at a logic high condition. The fault could be induced by the failure of either Crankshaft Position A or B Sensor input signal to the Ignition Control Module. Under such a condition, the Ignition Control Module would force the 24X signal high. This DTC will also set if the 24X signal is shorted to voltage externally. If either condition is met DTC P1375 is set.
    Conditions for Running the DTC
    • DTC P1376 is not set.
    • Engine speed greater than 496 RPM.
    • At least 7 CAM pulses received since key ON.

    Conditions for Setting the DTC

    24X signal voltage is high and no 24X reference pulses have been received during the last 8 4X reference pulses.
    DTC P1350 CURRENT:
    Ignition Control System

    Circuit Description
    Under normal system operation when the key is turned ON and until engine RPM is high enough for the PCM to control spark, the PCM will open the bypass circuit (CKT 424) to the Ignition Control Module, the IC module will then ground the Ignition Control circuit (CKT 423). This is called module mode because the IC module is controlling spark. Once the engine speed is high enough (about 65 RPM), 4X reference pulses are received and no PCM faults are detected the PCM will close the bypass line and in response the IC module will unground the IC circuit, this allows PCM control of spark. This is called the ignition control mode. This diagnostic test is used to check for faults in both the bypass circuit and the IC circuit. To check both circuits this diagnostic runs two tests, one during crank and one while running. If Ignition Control pulses are detected by the PCM on the IC line while in module mode (cranking) or if no Ignition Control pulses are detected by the PCM while in ignition control mode (running) DTC P1350 will set.
    Conditions for Running the DTC
    • Cranking Test
      • DTC P1376 not set.
      • At least 1 4X reference pulse has been received by the PCM.
    • Running Test
      • DTC P0322 and P1376 not set.
      • At least 1 4X reference pulse has been received by the PCM.

    Conditions for Setting the DTC
    • Cranking Test Ignition Control pulses are received by the PCM when cranking or running test has failed THIS ignition cycle.
    • Running Test No Ignition Control pulses are received by the PCM while engine is running.

    So again, this coincides with the hard hot start... car runs fine and will turn on fine MOST of the time. This set of codes along the with the SES light has only come on 3 times in the last month. I can delete them all after shutting the car down for a short while. Else I can only delete the B1375 and B1910 after restarting the car (it starts up right away after turning it off) as they show up as history after a short while, while the B1350 remains current until I shut the car down for a few minutes (I can delete it the next time I crank the car).

    So what is going on??? my theory is the hot start may be due to an injector or maybe the FPR, and leaving the car in the "START" mode for too long causes all the other codes to show up (as the car notices it's not starting--so it offers an explanation). HELP!!

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    misfit6794 is offline Cadillac Owners Connoisseur
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    Re: intermittent "hard start" when car at operating temp

    THe fuel pressure regulator is a very cheap part, and very easy to replace (there's a write up in tech tips section), even though you checked it, just replace it, because it really sounds like that is your issue. The only other possibility would be a leaky fuel injector.

  4. #3
    FrankT's Avatar
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    Re: intermittent "hard start" when car at operating temp

    MTFLIGHT,

    “my theory is the hot start may be due to an injector or maybe the FPR, and leaving the car in the "START" mode for too long causes all the other codes to show up” I disagree, I think the P codes are setting for a reason, like a lack of ignition pluses, if the engine is flooded because of leaking fuel injector or FPR then try starting it with the pedal to floor, this will cut off all additional fuel, (de-choke), if the engine has fuel in it and spark is present the engine will fire up right away.

    DTC P1350
    You said that P1350 remains current while the engine is running.
    • Running Test: No Ignition Control pulses are received by the PCM while engine is running. Possibly a bad ignition module, module circuit, terminal connection.
    Try this to validate your theory on the fuel system. When the no start condition is present try spraying starting fluid in the throttle body and see if it starts. If it does not start, then the DTCs are setting because incorrect ignition pluses are detected by the ECM.
    Also keep in mind that if you have one bad crank sensor the symptom will be exactly as you described a long crank, then it starts, this happens mostly after a heat soak. If the ECM is not seeing the ref pluses, then it will look at the other crank sensor and if it then sees the pluses it will fire up the engine.

    DTC P1375 CURRENT:IC 24X Reference Circuit High Voltage Possible cause is a crank sensor, this makes senses. Crank Sensor failures can be heat related, they will most likely fail when HOT.
    My suggestion: Don’t throw your money away by throwing parts at it, diagnose the DTCs first. It’s a Process of elimination.

  5. #4
    DevilleMN is offline Cadillac Owners Member
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    Re: intermittent "hard start" when car at operating temp

    My '94 C was doing trhye exact same intermitant warm/hot start. Had to wait 10 to 20 minutes and it would go. Acted as if it was flooded. Just thew opposite was the case. A lean condition was occuring due to fuel pump failing.

    1, Replaced the FPR- No difference.
    2. Checked fuel pump relay- OK.
    3. Had no codes.
    4. Replaced the fuel pump. Fixed the problem.

    Now it does not stumble a second or two after cold start. No hot start issues.

    Took the fuel pump apart and found the neg. brush spring had been over heating and lost the ability to tension the brush against the armature.

    Check for fuel pressure, cold and hot. 40 + psi.

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    mtflight's Avatar
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    Re: intermittent "hard start" when car at operating temp

    Well it happened one more time yesterday. I made some new observations. After the hard start, I can turn the car off and turn it back on without problems.


    Frank T:
    The P1350 and P1375 are only present as CURRENT if I continue the cycle (aka leave the car on after the hard start), but if I restart it right away they move to HISTORY (and I have no problem restarting, as if it were a flooding issue)

    Unfortunately both the P1350 and P1375, and B1910 are too complex for me to figure out as per the Factory Service Manual since they require using the famous Tech II to run diagnostics or voltage measurements etc. I wish they pointed to particular car components to replace, but they don't.

    So being that I have 108K miles on the FPR, I am leaning toward replacing it as a first step. I really wish some of the gurus would chime in if they have experience on this.

    I discovered that if I drive on the same cycle that I had a hard start, not only is the check engine light on, but something causes the car to not cool normally (I think maybe the voltage spike affects the fans' normal operation because my temp gauge went to the next line after the middle and the digi readout was 232--it's the second time I notice it so it's no coincidence). Restarting immediately, and clearing the PCM history codes relieves this issue...temp goes back down to 196-212 etc., So while the hard start be annoying, it is affecting critical systems too.

    Back to the "flood" hypothesis:
    It won't give any problems during a quick stop and turn off, but rather if you turn the car off and come back to it 20 minutes later up to 2 hrs later. With a full cool-down there are no issues starting (as I mentioned before car starts like new every morning).

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    fubar569 is offline Cadillac Owners Fanatic
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    Re: intermittent "hard start" when car at operating temp

    Quote Originally Posted by mtflight View Post
    Well it happened one more time yesterday. I made some new observations. After the hard start, I can turn the car off and turn it back on without problems.


    Frank T:
    The P1350 and P1375 are only present as CURRENT if I continue the cycle (aka leave the car on after the hard start), but if I restart it right away they move to HISTORY (and I have no problem restarting, as if it were a flooding issue)

    Unfortunately both the P1350 and P1375, and B1910 are too complex for me to figure out as per the Factory Service Manual since they require using the famous Tech II to run diagnostics or voltage measurements etc. I wish they pointed to particular car components to replace, but they don't.

    So being that I have 108K miles on the FPR, I am leaning toward replacing it as a first step. I really wish some of the gurus would chime in if they have experience on this.

    I discovered that if I drive on the same cycle that I had a hard start, not only is the check engine light on, but something causes the car to not cool normally (I think maybe the voltage spike affects the fans' normal operation because my temp gauge went to the next line after the middle and the digi readout was 232--it's the second time I notice it so it's no coincidence). Restarting immediately, and clearing the PCM history codes relieves this issue...temp goes back down to 196-212 etc., So while the hard start be annoying, it is affecting critical systems too.

    Back to the "flood" hypothesis:
    It won't give any problems during a quick stop and turn off, but rather if you turn the car off and come back to it 20 minutes later up to 2 hrs later. With a full cool-down there are no issues starting (as I mentioned before car starts like new every morning).


    i really don't think the FPR is going to have much to do with this...you simply have at least 2 ignition related codes that BOTH require some sort of input from the Crank sensors to function properly. As stated, sensor failure can manifest itself in a number of ways including heat...

    I would replace both A and B crank sensors with NEW components, and since the FPR is so cheap so it at the same time for extra insurance...while doing so get yourself a fuel pressure gauge and see what your FP is actually coming in at...

    the first code...that worries me...doesnt generator usually refer to alternator usually? although that would make no sense here...

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    Re: intermittent "hard start" when car at operating temp

    [quote=mtflight;1233877]
    Frank T:
    The P1350 and P1375 are only present as CURRENT if I continue the cycle (aka leave the car on after the hard start), but if I restart it right away they move to HISTORY (and I have no problem restarting, as if it were a flooding issue)
    quote]

    mtflight,
    Now that you started a new thread I'm a little confused to as to which one to post to.

    The codes are moving to history because the problem with the crank pluses disappears. So, then codes P1350 and P1375 run and pass, thus, they are now history codes. I am sticking with my orginal advice, sounds like crank sensors.

    If it was flooded, then why would these two codes run and fail consistenly?

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    mtflight's Avatar
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    Re: intermittent "hard start" when car at operating temp

    Quote Originally Posted by FrankT View Post
    mtflight,
    Now that you started a new thread I'm a little confused to as to which one to post to.

    The codes are moving to history because the problem with the crank pluses disappears. So, then codes P1350 and P1375 run and pass, thus, they are now history codes. I am sticking with my orginal advice, sounds like crank sensors.

    If it was flooded, then why would these two codes run and fail consistenly?
    Post to this one.

    The bizarre part is that once the car finally starts, codes are current, then I turn off and restart and they're history and I have no problems restarting.

    How much are the crank position sensors? They are behind the radiator, above the oil filter adapter somewhere, correct? I can't even see them... I can't imagine how to get in there. I saw they're only held in place by a couple of screws--Braille method?

    The B1910 appears at the same time, but becomes history sooner.

    EDIT: I had the hard start issue every now and then for the last couple of years, when car was hot...(so for a while I suspected the FPR) but back then it was without any codes. If I didn't hold the start position long enough, I may ocasionally get a backfire... so I decided to just hold it in the start position and thus the codes started coming. I looked up the sensors--they're about $32 without shipping at Rock Auto... not bad. I'll have to check to see if they come with the O-ring, which I suspect they should.

    Keep the ideas coming--I appreciate them!

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    Re: intermittent "hard start" when car at operating temp

    CKP sensors are indeed above the oil filter adapter. One bolt on each I believe (maybe 2). Remove the plastic air damn from under the car and go up from underneath. Remove the oil filter adapter first. It's still gonna be tight.

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    Talking Re: intermittent "hard start" when car at operating temp

    Quote Originally Posted by mtflight View Post

    The bizarre part is that once the car finally starts, codes are current, then I turn off and restart and they're history and I have no problems restarting.

    How much are the crank position sensors? They are behind the radiator, above the oil filter adapter somewhere, correct? I can't even see them... I can't imagine how to get in there. I saw they're only held in place by a couple of screws--Braille method?

    The B1910 appears at the same time, but becomes history sooner.

    EDIT: I had the hard start issue every now and then for the last couple of years, when car was hot...(so for a while I suspected the FPR) but back then it was without any codes. If I didn't hold the start position long enough, I may ocasionally get a backfire... so I decided to just hold it in the start position and thus the codes started coming. I looked up the sensors--they're about $32 without shipping at Rock Auto... not bad. I'll have to check to see if they come with the O-ring, which I suspect they should.

    Keep the ideas coming--I appreciate them!
    mtflight,
    I don't think think its bizzare that the codes are going in history, you are performing a PCM reset when you key down and restart. On that second key cycle the problem is not current because the car starts normally, thus, its history.

    I'm stumped why B1910 is showing up. This DTC indicates an open circuit in the Generator L-Terminal feedback circuit. This might be a seperate problem. How old is the battery? Are you getting the Not Charging message or battery lamp at the same time? Maybe the excessive cranking is bringing down the system voltage. At any rate for now, I would go after the "P" codes, worry about B1910 later if it retruns.

    If you didn't have the P codes, I would agree with your FPR diag. Have you checked the vacumm line to the FPR for fuel?

    If I do a quick key on and start on my 99STS I get the ocassional backfire thro the intake too. I think it maybe a normal querk in the N*.

    One more thing you might wana try, if you're handy with a DMM, follow the service information for P1375 the only time it requires a scan tool is when retriving and clearing DTCs, use your dash for this.
    These kind of problems are not an easy task via posting.
    Good luck, Frank

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    mtflight's Avatar
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    Re: intermittent "hard start" when car at operating temp

    Thanks the B1950 is under the IPC (instrument panel cluster), and indeed, after the "hard start" if I don't restart right away (aka keep going on the same cycle) the tachometer will not work (aka RPMs). A test which I do not want to do, but may be smart is to deliberately leave the starter in the on position for a little longer than usual--to see if the electronics go haywire--that may not prove anything though.

    Both the Generator and the battery are less than a year old. The actual codes started appearing a month ago.

    Update: I got under the car to look for the Crank position sensors. The bottom one is so gummed up I could not even find it. I replaced my oil pressure sensor a while back because it was leaking. I think it used to splash on the Crank position sensor.

    This crank position sensor is so difficult to access that I could not even get my hand in there to unplug it and clean its contact. I sprayed some electronic contact cleaner (solvent that is electronics safe) and I could finally see it. I did a few hot starts and had no issues. I hope the problem is that simple (intermittent contact at the sensor plug).

    If I have to replace it, the problem is not so much the oil filter adapter as is the engine mount bracket that is right under it (and the oil pressure sensor which I had to install using "the Braille method" as well due to the bracket. It's sandwiched between the exhaust manifold and the engine mount bracket :-S .

    Thanks for all your help--keep the suggestions coming!

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    CPA-ESQ. is offline Cadillac Owners Member
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    Re: intermittent "hard start" when car at operating temp

    Hi guys:

    I wanted to bump this to see if you think that I should replace my FPR (fuel pressure regulator)

    Again - about 20-30% of the time the car is hard to start - cranks and cranks and cranks until it finally starts.

    This could be hot or cold (cold being garage kept)

    96 STS

    I changed the battery over the weekend - and it still does it.

    Where is the write up on how to find / replace the FPR? I tried to find it.

    Thanks

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    Re: intermittent "hard start" when car at operating temp

    Don't change the FPR till you check it. The tutorial for checking and replacing it are in the Tech Tips section.

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    Re: intermittent "hard start" when car at operating temp

    Fund it in the help section

    http://www.cadillacforums.com/forums...-pressure.html



    Oh - well.. I'll read a bit more tomorrow and see how I could check it... unless someone wants to post a good way to check this

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    Re: intermittent "hard start" when car at operating temp

    That is the way to check it. Quick and simple. Just pull the vacuum line while idling and look for fuel as described.

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