1982 Deville check engine light
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HT4100 4.1, 4.5, 4.9 Discussion, 1982 Deville check engine light in Cadillac Engine Technical Discussion; Hello, I'm having some problems w/ my '82 ht4100 deville. The first problem is that the fuel pump connector doesn't ...
  1. #1
    Slacker is offline Cadillac Owners Fanatic
    Automobile(s): 1987 Cadillac Fleetwood Brougham
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    1982 Deville check engine light

    Hello,

    I'm having some problems w/ my '82 ht4100 deville. The first problem is that the fuel pump connector doesn't receive power when in the "on"position for that short time or when cranking or car is on. I put in a new fuel pump (old one was bad) and fuel filter. By bypassing the connector everything works and the car starts.

    The connector was working and then quit suddenly. Could this be a relay that went bad? If so, do you guys know which one it is? (They don't seem to be labeled)

    Also, when the car is on, by bypassing the fuel pump connector, I get a steady check engine light. I saw to receive codes you hold "off" and "warmer" but I'm not getting anything. (My warmer button might be on it's way out) Is there another way to get the codes? I know with my '84 chevy I can short the connector and get the codes to display via blinks of the check engine light. Does this car have something similar to that?

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  3. #2
    carnut is offline Cadillac Owners Master
    Automobile(s): 1988 Allante' (sold), 1984 Eldorado, 84 Sedan DeVille
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    Re: 1982 Deville check engine light

    where did you get another 12 volt source to power the fuel pump? the ECM provides a ground to complete the circuit to activate the pump. did this lack of voltage occur just after pump replacement or days later? need more info. 82 DeVille is rear wheel drive, correct? if so, you should be able to jumper the ALDA connector under dash by park brake assembly.

  4. #3
    Slacker is offline Cadillac Owners Fanatic
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    Re: 1982 Deville check engine light

    Quote Originally Posted by carnut View Post
    where did you get another 12 volt source to power the fuel pump? the ECM provides a ground to complete the circuit to activate the pump. did this lack of voltage occur just after pump replacement or days later? need more info. 82 DeVille is rear wheel drive, correct? if so, you should be able to jumper the ALDA connector under dash by park brake assembly.
    I sort of "macgyvered" an extra line from the battery around the car to the pump connector. The ground was to the battery and fuel tank. (Just done for testing to make sure the pump was working correctly).

    The connector on the car that supplies the power was working earlier that afternoon and then died. It seems like it's been inconsistent since I picked the car up a week ago. (Sometimes it will kick on, some times it won't...)

    And yep, the '82 is rear wheel. I'll try to jump the connector when I get home and see what error codes I have. Hopefully that will provide some more insight.

    Thanks.

  5. #4
    carnut is offline Cadillac Owners Master
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    Re: 1982 Deville check engine light

    That harness receives power thru the oil pressure sender harness. If the ECM sees no oil pressure it disconnects fuel pump power. So look at the wiring to the oil sender.

  6. #5
    Slacker is offline Cadillac Owners Fanatic
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    Re: 1982 Deville check engine light

    Yeah I was reading up on how it gets power through the oil sensor too... Wasn't the problem though. I searched up the relay / fuse diagram and noted all the ones related to fuel related items. I pulled them out and checked. I found a bad fuel pump fuse which I must have tripped in my "wire-crazy" by pass.

    Also, once I replaced that and fired the engine up, the check engine light stopped. Must have been noticing that the fuel pump wasn't getting power from traditional means.

    Thanks for the help!

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