'93 Eldorado, 4.9L - Partial Fire, No Start
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HT4100 4.1, 4.5, 4.9 Discussion, '93 Eldorado, 4.9L - Partial Fire, No Start in Cadillac Engine Technical Discussion; 1993 Eldorado, 4.9L, 200k, No Codes. My engine is in a no-start condition. When I turn the key to engage ...
  1. #1
    kdcing is offline Cadillac Owners Fanatic
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    '93 Eldorado, 4.9L - Partial Fire, No Start

    1993 Eldorado, 4.9L, 200k, No Codes.

    My engine is in a no-start condition. When I turn the key to engage the starter....the starter engages, starter/engine turns, and the engine partially fires/misfires but does not fire enough to get started (basically, the engine coughs and sputters.) When the key is placed in the "On" position, I can hear the fuel pump run....and it continues to run and run well beyond the normal 2-3 seconds of run time. I have let it go for as long as 20-30 seconds....I ended up turning the key off to prevent burning up the pump.

    Does anyone know what triggers the fuel pump to shut off w/ the key in the "On" position.....i.e. is there a fuel pressure sensor that signals the pcm to shut off the fuel pump? or is the fuel pump simply on a 2-3 second timer?

    It is extremely cold again in Chicago. My theory is that my fuel lines are frozen, thus preventing the fuel system from pressurizing...and thus preventing the pcm from shutting off the fuel pump (when the key is in the "On" position). Does this make sense? It is too cold to do any hands-on troubleshooting, so I will not be getting a fuel pressure guage on the engine until Tuesday.

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    Submariner409's Avatar
    Submariner409 is offline If it won't run, install a sound system
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    Re: '93 Eldorado, 4.9L - Partial Fire, No Start

    Actually, with key on the fuel pump primes the system, shuts down on a timer, and/or at start it runs constantly until you get to the gas station or Florida. Electric FI pumps run all the time, with the FPR constantly bypassing unused fuel to the tank.

    I have no idea of the fuel pressure regulation system on a 4.9.

    Some fuel pumps are commanded to run by an oil pressure signal. No pressure, no fuel.

  4. #3
    Ranger's Avatar
    Ranger is offline Cadillac Owners Member
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    Re: '93 Eldorado, 4.9L - Partial Fire, No Start

    Try spraying some fuel down the TB while someone cranks it. If it starts and then dies, you have a fuel supply problem.

  5. #4
    JC316 is offline Cadillac Owners Connoisseur
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    Re: '93 Eldorado, 4.9L - Partial Fire, No Start

    I agree with Ranger. You also need to get a fuel pressure gauge to see how much PSI you have at the rail.

  6. #5
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    HUF
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    Re: '93 Eldorado, 4.9L - Partial Fire, No Start

    Quote Originally Posted by kdcing View Post
    1993 Eldorado, 4.9L, 200k, No Codes.

    My engine is in a no-start condition. When I turn the key to engage the starter....the starter engages, starter/engine turns, and the engine partially fires/misfires but does not fire enough to get started (basically, the engine coughs and sputters.) When the key is placed in the "On" position, I can hear the fuel pump run....and it continues to run and run well beyond the normal 2-3 seconds of run time. I have let it go for as long as 20-30 seconds....I ended up turning the key off to prevent burning up the pump.

    Does anyone know what triggers the fuel pump to shut off w/ the key in the "On" position.....i.e. is there a fuel pressure sensor that signals the pcm to shut off the fuel pump? or is the fuel pump simply on a 2-3 second timer?

    It is extremely cold again in Chicago. My theory is that my fuel lines are frozen, thus preventing the fuel system from pressurizing...and thus preventing the pcm from shutting off the fuel pump (when the key is in the "On" position). Does this make sense? It is too cold to do any hands-on troubleshooting, so I will not be getting a fuel pressure guage on the engine until Tuesday.
    Are you sure you hear the fuel pump? There is also air copressor running for some 20 seconds to keep the rear level up. The fuel pump starts right after the ignition key is ON, but the air compressor starts a few seconds later.

  7. #6
    kdcing is offline Cadillac Owners Fanatic
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    Thread Starter

    Re: '93 Eldorado, 4.9L - Partial Fire, No Start

    Well, the fuel lines may not be frozen and the fuel pump may be acting correctly...it will run for 2-3 seconds when the key is 1st turned to "on", however, if the key is then turned to "start" and returned to "on", then the fuel pump will continue to run. I've never had the key in the "2nd" "On" position (i.e. On-Start-On) without the engine running (i.e. the engine has always started), so I guess I was looking for something obviously different/wrong when the engine did not start yesterday. The sound definitely is from the fuel pump as it has the higher pitched whine....not the lower pitched gurgle of the ELC compressor.

    In any case, I will be troubleshooting the basics (fire, fuel, air) when Mother Nature chills out....or should I say, warms up. Thanks for the assists.

  8. #7
    kdcing is offline Cadillac Owners Fanatic
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    Thread Starter

    Re: '93 Eldorado, 4.9L - Partial Fire, No Start

    ....well, she's back up and going. No troubleshooting...no parts replaced...after it finally warmed up to 17 degrees F yesterday, she fired right up. Either the fuel lines were frozen or the extreme cold from last weekend caused some other issue......which will likely return during the next sub-zero stint!

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