1994 Fleetwood. Runs for 30 minutes and quits ???
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5.0 and 5.7 Discussion, 1994 Fleetwood. Runs for 30 minutes and quits ??? in Cadillac Engine Technical Discussion; I have a new fuel pump on it, fuel filter, coil pack. It acts the same way a car does ...
  1. #1
    travillac is offline Cadillac Owners Member
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    Question 1994 Fleetwood. Runs for 30 minutes and quits ???

    I have a new fuel pump on it, fuel filter, coil pack. It acts the same way a car does when the catelytic converters get stopped up, but i had them removed and that made it work for about 2 months, then it started doin the same thing again It will run PERFECT for about 20 or 30 minutes, then quits with no warning, then you gotta let it sit there for almost an hour before you can get it to go for the same length of time. I dunno what to do. Everyone's looked at it and checked all the sensors ( just about it ) someone even told me it would do that without the converters. sheesh. ( because these 94 Fleetwoods have 2 converters and 4 mufflers ) Would a bad oxygen sensor do that ? the local parts store said their machine wouldnt read codes because the engine light doesnt stay on, it only comes on the moment its gonna quit. Any advice to get my baby goin again the way it should would help. Thank ya !

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    N0DIH's Avatar
    N0DIH is online now Cadillac Owners Master
    Automobile(s): 94 Fleetwood Brougham
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    Re: 1994 Fleetwood. Runs for 30 minutes and quits ???

    Is the Fuel Pump Relay overheating? It might overheat and shut down. You can put a light across the contacts of the relay, one side is +12v, one side is going to the pump. So if the relay opens a light turns on. Simple quick and dirty. Then you can tap on it, or if you had to, you can jumper it to get it going again. That is where I would start.

    Else, I would be looking at the Optispark. If it is on the fritz ($$$$) it can be pricey to fix. Katshot recommended 140K replacement of the Opti and the water pump in his vast experience in the limo fleet for max reliability.

    As for troubleshooting the Opti, you will probably need an oscilloscope to try to see what the ECM is seeing. If it loses the cam sensor pulse, it will not know where #1 is and not run. But, once it is running, it ~shouldn't~ shut down. But if the (known issue with Opti's) optical sensor fails (overheat) it will shut down, as it will have lost all references.

    If you prove it is not fuel related (fuel pressure gauge will do it too, but harder to drive it with a gauge attached so you can read it), then I would attach the scope to the opti's "chopper wheel" 360 degree output and the 3 slot output, watch each and you can tell if it loses one when it dies and you are at cranking speeds. These 3 slots
    (10 degree opening, 20 degree and 30 degree I think) tell it where it is, #1 is at the leading edge of one, then 2 other cyls are at certain points. It doens't matter which comes up first, it can start on any of them, that is why this is such a fast starting engine. Just needs one of them to know where it is in the sequence, once started, it uses the high resolution 360 degree chopper wheel for accurate timing.

    The Opti is different than a normal distributor. It treats the engine as 8 1 cyl engines, not 1 8 cyl engine. So it can vary timing for each cyl individually. So if one cyl is knocking, then it can pull timing back on it individually. Very cool if you ask me.

    Hope that helps some!

  4. #3
    juiced94fleet is offline Cadillac Owners Member
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    Re: 1994 Fleetwood. Runs for 30 minutes and quits ???

    Sorry to hear about this, My 94 fleet was having the same exact problems, I thought I was the only one, but I changed the fuel pump and now the car doesnt run at all, It just keeps cranking, I still have to check the filter and regulator and misc other lil things, but Im sure I cant get it to run again, So frustrating, Well maybe you may have a few pointers for me, any advice will help, Thanks.

  5. #4
    ssstealth's Avatar
    ssstealth is offline Cadillac Owners Enthusiast
    Automobile(s): 06 STS-V, 94 Fleetwood TS
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    Re: 1994 Fleetwood. Runs for 30 minutes and quits ???

    Remember that you can check the codes yourself right from the dashboard. Hold the "Off" and "Warmer" buttons together for 5 seconds to enter the diagnostics mode.

    See the following link for more info...
    Fleetwood Diagnostics

  6. #5
    juiced94fleet is offline Cadillac Owners Member
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    Re: 1994 Fleetwood. Runs for 30 minutes and quits ???

    I have tried this on board code thing, I dont understand how it works, I followed all the directions and I get into test mode, but what do you do from there? Because it will come up like -38 and then directions say use fan to go up or down, so what what does this show if you can just keep going up or down from like -01 to -38, and you can just keep doing this all day manually, it doest stop on any certain codes etc, So anymore info on how to use this will help out alot, I have read and done everything it said to do, I just dont how to retreive any codes, and should it go through on its own and show the codes, Thanks.

  7. #6
    ssstealth's Avatar
    ssstealth is offline Cadillac Owners Enthusiast
    Automobile(s): 06 STS-V, 94 Fleetwood TS
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    Re: 1994 Fleetwood. Runs for 30 minutes and quits ???

    Use the link above for the detailed instructions after you get into the diagnostics mode... Good luck.

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