Cat 3126 B won't start ****HELP***

Discussion in 'Trucks [ Eighteen Wheelers ]' started by rpsunrise, Nov 29, 2009.

  1. rpsunrise

    rpsunrise Bobtail Member

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    Nov 29, 2009
    Albany NY
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    Hello and please help:

    I have a 1999 Cat 3126B in my motor home which was running great until we got home from a long trip. After about 2 weeks of being idle, it would turn over but did not fire. I did not change any filters so they should be filled with fuel. No white smoke out of the exhaust when being turned over so I suspected the injector actuator solenoid valve was bad and replaced it. At the same time I changed the oil and replaced the filter so that is clean. I questioned if the manifold pre-heater was working and the relay was corroated so when I tried to loosen the connectors one broke so I put a new relay on which seams to be working (12 volts to it and resistance across the pre-heater.

    It will start with some short blasts of either (I know, not recommended) and run fine after starting. When it was running after starting with either I filled it with fuel and brought it back home. Next day it would not start again. I’m wondering if I have a faulty fuel check valve and where it/they (supply and/or return) are? This engine has a small primer on the water separator filter but none on the engine and seconddary filter. Also where is the fuel transfer pump (near the HPOP)?

    Any suggestions you may have would be greatly appreciated. My local (30 miles away) Cat dealer will not come down to run the codes and I hesitate using either to start it again.

    Thanks
    Bob
     
  2. Coal Bucket

    Coal Bucket Light Load Member

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    Nov 15, 2008
    Charm City
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    Think i'd start there... good luck
     
  3. DDS

    DDS Medium Load Member

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    May 20, 2008
    Toronto
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    You need to check it for faults in the ecm, An weak engine speed timing sensors can cause this problem but without checking for faults, guessing costs money,
     
  4. Coal Bucket

    Coal Bucket Light Load Member

    179
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    Nov 15, 2008
    Charm City
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    i missed the part about their being codes..... good catch dds
     
  5. Jas

    Jas Medium Load Member

    What are the fault codes?
    Turn the ignition on.
    Turn the cruise control off.
    Hold down the cruise set button.
    The check engine light will flash.
    Count the flashes, they will be two digit numbers, eg. 6 flashes then a pause then 3 flashes would be code 63. there may be several codes, it will flash them all one after another. You usually need to go through this process several times to make sure your getting the codes correct.

    Does it start by itself once it has warmed up?

    Really need to check the HEUI oil pressure while cranking, if it has an internal oil leak or a worn HEUI pump it wont get enough oil pressure to fire the injectors when cranking.
     
    rpsunrise Thanks this.
  6. rpsunrise

    rpsunrise Bobtail Member

    8
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    Nov 29, 2009
    Albany NY
    0
    Thanks for your replies:

    I ran the codes as Jas suggested and came up with 87 and 34 in that order. I think the 34 relates to the intake manifold air temp which I thought might be one of my problems and giving me trouble starting. Might also explain why it didn't explode when I used either the last time I was able to start it. I took off the air filter boot that connects to the manifold where the heater is and used a laser thermostat during the preheat cycle and nothing happened, stayed at 47 deg F outside and inside.

    Going to pick up a new one shortly, one of my cheaper parts at $120.

    I did try to preheat the chamber where the heater is with a heat gun but it just cranked and no pop.

    Still thinking I might have more than one problem like a leaking check valve.

    Your thoughts are appreciated.

    Bob
     
  7. rpsunrise

    rpsunrise Bobtail Member

    8
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    Nov 29, 2009
    Albany NY
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    PS: I have an HPOP that activates the injectors. Is that similar to a HEUI?

    Side note; The RV was running flawless all year (a first) and even when we were in Cedar Rapids Iowa volunteering to rebuild homes after last years flood and temperatures were in the 30's. Got home and parked it in the driveway and that's where it died. Hay, it could have died in New Mexico so count my blessings.
     
  8. rpsunrise

    rpsunrise Bobtail Member

    8
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    Nov 29, 2009
    Albany NY
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    PSS: I was wrong, code 34 is secondary speed sensor and I think I have to remove the air compressor to get at it.

    Preheater was bad anyway so not a big deal but not looking forward to replacing the sensor in that tight area.:biggrin_25513:
     
  9. DDS

    DDS Medium Load Member

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    May 20, 2008
    Toronto
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    The speed sensor is your problem, You can change it without removing the air compressor. You have to pry the bracket up on the one your removing, that will let you remove one at a time leaving the bracket only on the upper sensor. Pop the botton one off the new one and install it in one at a time. You will need to break the tie straps off the brackets this will allow you to pull enough harness out from behind the compressor to disconnect the plugs. Note undo only one sensor at a time and replaced, this will help prevent the wiring harness from falling behind the compressor, Big pain to get back up. Changed over a 100 up here like that, never had to remove the compressor.
     
    rpsunrise Thanks this.
  10. rpsunrise

    rpsunrise Bobtail Member

    8
    0
    Nov 29, 2009
    Albany NY
    0
    DDS Thanks:

    It would appear that the sensors are directly under the fuel transfer pump from the picture Cat sent me. Just got the parts (sensors and O rings) but haven't crawled under the RV yet.

    Do you loosen the old sensor bracket bolt and then bend the fingers of the bracket to get the old sensor out, install the new sensor then bend the fingers back down? I see how they will pop out of the new bracket and they have different numbers on each sensor so I'm sure they have to go in as they are on the bracket. You make is sound easy, how are my knuckles going to look when I'm done?:biggrin_2552:

    Thanks again, hope that's the problem.
    Bob
     
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