Fuel shut off valve

Discussion in 'Ask An Owner Operator' started by aphauling, Mar 12, 2020.

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  1. Mar 12, 2020 #1
    aphauling

    aphauling Bobtail Member

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    I have a 1991 peterbilt 378 with a Detroit 12.7 60 series, where is the fuel shut off solenoid?
     
    aphauling, Mar 12, 2020
    aphauling, Mar 12, 2020
    #1
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  3. Mar 13, 2020 #2
    HopeOverMope

    HopeOverMope Road Train Member

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    By or on the fuel pump I would imagine?... I don’t know for sure on your particular setup. It should have a single wire with an eye on it that’s bolted to a post.
     
    HopeOverMope, Mar 13, 2020
    HopeOverMope, Mar 13, 2020
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  4. Mar 13, 2020 #3
    Rideandrepair

    Rideandrepair Road Train Member

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    I don’t know if there’s one at all. Manual fuel pump, mounted on compressor. Lines from tank, shutoff valves. That’s all I know of.
     
    Rideandrepair, Mar 13, 2020
    Rideandrepair, Mar 13, 2020
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  5. Mar 13, 2020 #4
    aphauling

    aphauling Bobtail Member

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    I’m not finding one. This engine has a DDEC II ECM in having a fueling problem trying to rule out the ecm. Already changed pump and filters. Checking lines now
     
    aphauling, Mar 13, 2020
    aphauling, Mar 13, 2020
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  7. Mar 13, 2020 #5
    Rideandrepair

    Rideandrepair Road Train Member

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    Fuel pump runs off compressor, pumps as long as it’s turning. What’s it doing? No fuel ? No ecm power? Got dash lights,check engine, etc. with key in “ on” position? I think you have the old bottom draw tanks, with cross over line on bottom. Right? Or new style, with shut offs on top? Pete’s might not have them on top, not sure. Maybe a line is sucking air, or swelled up inside, restricting flow? Tank blocked with debris? Lost prime? What’s the problem?
     
    Rideandrepair, Mar 13, 2020
    Rideandrepair, Mar 13, 2020
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  8. Mar 13, 2020 #6
    AModelCat

    AModelCat Road Train Member

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    Electronic unit injectors. Shutting off signal to the injectors is the fuel shutoff.

    I'm not a Detroit guy but typically an ECM needs to see constant power, keyed power, ground. Will also need to see engine RPM/position in order to tell the injectors when to fire. If your fuel pressure to the head is good, I'd move along to the electronic side of the system.

    @swaan knows these Detroits very well. Hopefully he can give ya some good advice.
     
    AModelCat, Mar 13, 2020
    AModelCat, Mar 13, 2020
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  9. Mar 13, 2020 #7
    aphauling

    aphauling Bobtail Member

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    It started running weak, not bad but would have to drop a couple extra gears when loaded on hills that I wouldn’t normally have to. Took it to a local guy to have it scanned because my normal guy that comes out has the flu. When he tried to scan it there was no power to the diagnostic port. Brought it back, traced wires, found a relay in the dash. Pulled the relay to check connections and put it back in and then I had power to the port. Next day went back to the local guy and he wound up not being there. It did not run good there and back. Checked power to the port when I got it back home and still had it. My normal guy come out 4 days after that tried to scan it and no power. Tried the relay again and put a new one in, still no power. Tried to crank it now it won’t crank. Checked fuel pressure to the secondary fuel filter and it is 75 psi while running on either. Trying to take off line from secondary fuel filter to the back of the engine to check for any blockage or bad places in the line. It’s in a very bad place so haven’t gotten it off yet but working on it. I’m thinking it’s the ecm but trying to rule out everything else before I drop $2,000
     
    aphauling, Mar 13, 2020
    aphauling, Mar 13, 2020
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  10. Mar 13, 2020 #8
    baha

    baha Road Train Member

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    If you have not changed fuel filters do that 1st and dump whats in them in a bucket to see if there is water or dirt in them, That is right they only run if power is going thru key, but some people have put a cut/off plumed into fuel line to the fairly cheap direct drive fuel pump as a anti/theft?
     
    Last edited: Mar 13, 2020
    baha, Mar 13, 2020
    baha, Mar 13, 2020
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  11. Mar 13, 2020 #9
    Rideandrepair

    Rideandrepair Road Train Member

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    I doubt it’s the ecm. Just guessing, maybe a bad trs or srs timing sensor. They’re both located behind the compressor. Sometimes the connection on the bottom one gets cruddy Replacing both when 1 is bad is usually done. Cost about $65-90 each. If it’s not the problem, you can keep the old ones as spares. When they go bad, Truck won’t start, no codes. If it were still running, I would suspect a bad injector or harness. But I’ve heard of the sensors causing rough running symptoms, before going bad.
     
    Rideandrepair, Mar 13, 2020
    Rideandrepair, Mar 13, 2020
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  12. Mar 13, 2020 #10
    AModelCat

    AModelCat Road Train Member

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    If its not cranking check your batteries and battery cables.
     
    AModelCat, Mar 13, 2020
    AModelCat, Mar 13, 2020
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