Need help! Having starting problems with my 84 Coupe DeVille
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HT4100 4.1, 4.5, 4.9 Discussion, Need help! Having starting problems with my 84 Coupe DeVille in Cadillac Engine Technical Discussion; So recently bought a 84 Coupe DeVille with the HT4100. Motor turns but will not fire. Replaced the plugs, plug ...
  1. #1
    jollygreen is offline Cadillac Owners Member
    Join Date
    Aug 2014
    Posts
    7
    So recently bought a 84 Coupe DeVille with the HT4100. Motor turns but will not fire. Replaced the plugs, plug wires, fuel filter, fuel pump, fuel strainer, battery, starter and did oil change. Still will not fire. Double checked all the replaced parts everything checks out. Checked the throttle body to see if it was supplying gas, no gas. Butterfly opens and closes fine no gas from the injectors. Pulled the fuel lines at the throttle body. One was dry the other had fuel in it. So my questions are, could it be the throttle body has gone bad or are the injectors bad?

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  3. #2
    carnut is offline Cadillac Owners Master
    Automobile(s): 1988 Allante' (sold), 1984 Eldorado, 84 Sedan DeVille
    Join Date
    Feb 2003
    Location
    california
    Age
    67
    Posts
    5,770

    Re: Need help! Having starting problems with my 84 Coupe DeVille

    You need to screw a fuel pressure tester onto the schrader valve just in front of the throttle body. Crank the engine over and write down the fuel pressure reading and report back. Should be around 9 to 12 lb. if memory serves. How much gas is in the tank? I presume you looked at and/ or replaced the injector fuses. This engine also would shut down the fuel pump if it saw no oil pressure. The sender above the oil filter adapter has more than one wire. Check them for being disconnected, broken burnt up. They can get too close to the exh. manifold and melt. With someone listening at the fuel filler and you turning the key to run, they should hear the pump buzz for a few seconds, is that happening? Did you buy it as a non running car?

  4. #3
    jollygreen is offline Cadillac Owners Member
    Join Date
    Aug 2014
    Posts
    7
    I did buy the car non running. I bought it from my cousin. It sat for several years neglected. Story is it ran like a charm when it was parked. Cranked several times over a 2 year span then cousin moved outta town left car at his mom's. Still ran like a charm. Sat and sat. Saw it bought it tuned the key motor turned no fire.

    Ran a couple test after replacing the fuel pump, it does make the buzzing noise for a sec after you turn the key. Haven't ran a fuel pressure test yet since dropping the tank and replacing the pump, strainer, and filter. Probably should do that.

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