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Thread: $0D 16197427 Fuel Pump run time?

  1. #1
    EFI GearHead ! EagleMark's Avatar
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    $0D 16197427 Fuel Pump run time?

    On a 16197427 $0D stock truck. Has had MPFI PCM and memcal mod done. WIth key on engine off, What would make fuel pump on time change from 2 seconds to 15+ seconds? Does fuel pump run constant in LHM?

    1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
    1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
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  2. #2
    Fuel Injected! JeepsAndGuns's Avatar
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    0x4958, max time for fuel pump running with no DRP
    BJYL stock is 10 seconds, as with most other $0D V8 bins I have seen. I tested it on mine and I turn the key on, and fuel pump runs for ~10 seconds.
    Most $0E bins I looked at were 3 seconds. I think I raised it on my old 0E bin to make the fuel pump prime a little longer as I had a pump that the check valve in it that didnt work that great and would bleed off when it was off.

    In my many mistakes and blunders in my tuning, it does seem like I remember that when the 7427 was in LHM the pump would run constantly when the key would turned on. I have forgotten to put my chip back in a few times in the past, and figured it out when the pump wouldnt shut off, and I couldnt get ALDL connection. Only started the engine once when I did this. Found out real quick something was wrong, as the IAC also peggs wide open....lol
    79 Jeep Cherokee, AMC 401, T-18 manual trans, hydroboost, 16197427 MPFI system---the toy

    93 Jeep YJ Wrangler, 4.0L, 5 speed, 8.8 rear, homebrew hub conversion and big brakes, hydroboost, 2.5in OME lift, 31x10.50's---the daily driver

    99 Jeep WJ Grand Cherokee limited, 4.0L, auto, 2wd, leather and power everything, 99% stock---the long distance highway ride.

  3. #3
    EFI GearHead ! EagleMark's Avatar
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    Cool thanks! That was it, 10 seconds and I am used to 2, so I thought there was an issue.

    1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
    1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
    -= =-

  4. #4
    Fuel Injected! JeepsAndGuns's Avatar
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    Wonder why they went from 2 seconds in $42, to 10 seconds in $0D, but then 3 in $0E?
    Seems odd.
    79 Jeep Cherokee, AMC 401, T-18 manual trans, hydroboost, 16197427 MPFI system---the toy

    93 Jeep YJ Wrangler, 4.0L, 5 speed, 8.8 rear, homebrew hub conversion and big brakes, hydroboost, 2.5in OME lift, 31x10.50's---the daily driver

    99 Jeep WJ Grand Cherokee limited, 4.0L, auto, 2wd, leather and power everything, 99% stock---the long distance highway ride.

  5. #5
    Fuel Injected!
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    Would it have anything to do with the hot fuel handling? $42 was running the hot fuel module in some setups, not sure about the other two. I've wondered why GM wasted the money on the hot fuel module when I figured the ECM could have handled the same task.
    "Frankentruck" is a "1985" K5, TPI 350 '165/6E (Vortec Heads, SDPC2000 base, roller cam, headers), 32 Spline SM465, 205 w/VSS, 10b/14SF, 3.42's and 33" tires. Soon to be boxed frame, '87 sheetmetal, and TPI w/ '727

  6. #6
    EFI GearHead ! EagleMark's Avatar
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    This is the fuel pump runtime if you turn key on and don't start engine. The hot fuel thing your talking about on HD trucks lets the fuel pump run 20 seconds after shutdown to cool TBI, avoid vapor lock was theory... it's a little gray box if you ever find one in a harness.

    1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
    1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
    -= =-

  7. #7
    Fuel Injected!
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    Right, but couldn't they do the same thing on startup? I suppose that would require to the driver to be smart (and GM probably learned that lesson with the diesel Olds 350) but since the pump is in the tank, running it prior to start should solve vapor lock, just have to put enough fuel through the lines to cool them and fill things back up, right?
    "Frankentruck" is a "1985" K5, TPI 350 '165/6E (Vortec Heads, SDPC2000 base, roller cam, headers), 32 Spline SM465, 205 w/VSS, 10b/14SF, 3.42's and 33" tires. Soon to be boxed frame, '87 sheetmetal, and TPI w/ '727

  8. #8
    EFI GearHead ! EagleMark's Avatar
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    Right, but like you said it's up to driver. Not many would slow down turning key on and waiting for fuel flow, it's straight to crank. Which is another strange reason why this on time would even change at all? For 99.9% of drivers it could be on forever, or off forever till DRP... it's only purpose is a diagnostic test to me?

    I'm not sure that 20 second after engine off would really help? So what 20 seconds on a hot truck motor pulling a load, then it sits off and frys, so how would that help? If a hot engine was started again within half hour in desert it would still be way hot... they found it needed for something?

    1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
    1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
    -= =-

  9. #9
    Fuel Injected!
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    Veering off topic, but I noticed (in our cool climate, on a 454)) that the TBI gets INCREDIBLY hot, although this is with an aluminum intake. It was hot enough a few minutes after shut down to vaporize fuel that dripped onto the TBI to intake bolts. I was very surprised that they got that hot. Maybe circulating fuel 20 seconds is enough to take enough heat out of the aluminum. Even after sitting for a day, the TBI still had fuel pressure in it when I went to take the regulator back off, so I assume it makes some difference.

    When he didn't have the module hooked up he didn't notice problems, but again, this isn't in a very hot climate either.

    Substituted a nut for the thin shim I had already tried in the FPR, BLM's better get driven down this time. :)
    "Frankentruck" is a "1985" K5, TPI 350 '165/6E (Vortec Heads, SDPC2000 base, roller cam, headers), 32 Spline SM465, 205 w/VSS, 10b/14SF, 3.42's and 33" tires. Soon to be boxed frame, '87 sheetmetal, and TPI w/ '727

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