1976 Coupe Deville 500ci 4 bbl engine won't run
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500, 472, 425, 368 Discussion, 1976 Coupe Deville 500ci 4 bbl engine won't run in Cadillac Engine Technical Discussion; I have a 1976 Coupe Deville with a 500ci and 4 bbl carb. I went out yesterday to run an ...
  1. #1
    Raybo is offline Cadillac Owners Member
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    1976 Coupe Deville 500ci 4 bbl engine won't run

    I have a 1976 Coupe Deville with a 500ci and 4 bbl carb. I went out yesterday to run an errand and the car wouldn't start, after sitting overnight, but was running fine when it was last turned off. I tried everything regarding the accelerator pedal, pushing all the way down and slowly releasing it, pushing the pedal halfway and holding it, pumping the pedal, etc., still wouldn't start. It's turning over great just won't start. I primed the carb with starting fluid and it starts but dies immediately. The fuel gauge says I have 1/8 of a tank of gas.

    Could the fuel pump have gone bad just sitting there overnight? Could the fuel filter have clogged just sitting there overnight? I suppose I could go get some more gas and try that but really think there is gas in the tank, and the car is sitting fairly level.

    I even tried starting fluid, with my wife cranking the engine and me spaying the fluid, same as before it starts and then dies, I tried shooting another spray into the carb as it started dying but that seemed to choke it completely and it died anyway.

    Where is the fuel pump on this thing anyway? In the tank, I assume? Great! And I suppose there is no access hole in the trunk to get to it without dropping the tank?

    Is the fuel filter in the line connection at the front of the carb?

    Thanks guys, I really am not very good at working on cars, it always seems that nothing ever goes the way it should when I'm working on one - LOL.

    Any help will be greatly appreciated!!

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  3. #2
    chrisntam is offline Cadillac Owners Fanatic
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    Re: 1976 Coupe Deville 500ci 4 bbl engine won't run

    Well, it sounds like you have spark, so that's good. It does sound like a lack of fuel issue as the starting fluid starts to start the car. Take the air cleaner off and move the throttle linkage from closed to open while you look down in the carb. You should see two squirts of fuel from the accelerator pump of the carb each time you pump the accelerator. If you have fuel squirting, then the pump should be ok. If no fuel in the carb, then suspect the fuel pump. The pump should be on the engine on the drivers side towards the front of the engine. Lay down in front of the car on the drivers side, look for a metal line screwed into the bottom of the pump (going to the carb) and two rubber lines coming from the tank. You can also follow the incoming fuel line from the carb and trace it to see where it leads. It will go to the pump. If you have an externally mounted pump (I think you do) you can check the pump by removing the incoming fuel line (from the tank) and hooking up a vacuum gauge to the incoming port. Crank the engine over with the vac gauge connected to the larger hose nipple, the vacuum gauge should show vacuum being pulled, indicating suction in the tank. If nothing registers on the vac gauge, then the pump is bad. Pump is held on by two bolts to the engine, fairly easy to replace. Look on you tube for a tutorial. Be sure that when you disconnect the incoming fuel line you have a 3/8" bolt ready to go in it to block fuel from coming out. If no fuel comes out, then maybe it's out of gas. Normally, a plugged fuel filter will allow the car to start, but it won't allow enough fuel to flow and run very well. You can always get a gas can and put 5 gallons in the tank to rule out it being out of gas.........

    I think the fuel pump is on the engine, I think the fuel injected engines had the pump in the tank. Maybe one of the many people who have viewed this, but not responded can chime in.

    Not sure where the fuel filter is located, it may be in the fuel pump or could be in the inlet of the carb. Someone who owns a '76 should know, I have a '70.

  4. #3
    the APEMAN is offline Cadillac Owners Fanatic
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    Re: 1976 Coupe Deville 500ci 4 bbl engine won't run

    Sounds like the filter is clogged or fuel gauge is lying.

    Filter is right in the carbonator where the fuel inlet is. You need a 5/8th line wretch and a 1" implement of destruction to get to it. look at some Rottenchester carbonator videos for better details.

    Fuel pump is on engine. Sometimes there's an extra filter in there : )

  5. #4
    Raybo is offline Cadillac Owners Member
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    Re: 1976 Coupe Deville 500ci 4 bbl engine won't run

    I appreciate the replies! I found the fuel pump, where "Chrisntam" said it would be, and the manual said the filter is in the carb inlet. So, before tackling either of those I walked up to the nearest convenience store and bought some gas, walked back (pretty tough at 66 years old and 100 degrees outside - LOL) and poured it in the tank. Then I used a bit of gas to prime the carb and BINGO, it started and ran normally.

    I should have suspected the 38 year old fuel gauge, first. Anyway, I have a full tank of gas now and damn sure won't ever let it get below 1/4 tank again!

    Next, the exhaust manifold leak at the rear of the passenger side manifold. I have been afraid to mess with it because I know some of the bolts will break off, as they have been there 78K miles, and 6 years of sitting in a field without being driven. Need to get t fixed though, because it makes a heck of a racket when accelerating. Just fixed the power brakes, bought power booster and then master cylinder (booster turned out to be good but master cylinder wasn't). Fixed a multitude of lights, this thing has them everywhere! Put on 4 new tires and finally got it inspected and tagged, and on the road. The mileage is original, and the car is now a 3 owner. Straight body, of course the plastic bumper fillers are completely gone, why in the world Cadillac ever put that crap on such an expensive car is a puzzle. Will order aftermarket pieces soon. The interior was redone by the PO and it still looks new. So, other than the plastic pieces, some weatherstripping, slight hood and trunk adjustments, and peeling clear coat, this thing is in pretty good shape.

    Once again, thank you for the responses!!

    Ray

  6. #5
    chrisntam is offline Cadillac Owners Fanatic
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    Re: 1976 Coupe Deville 500ci 4 bbl engine won't run

    Puttin' gas in it is much easier than changing the fuel pump! Good job for checking that first! And thanks for letting us know how it turned out.

  7. #6
    Raybo is offline Cadillac Owners Member
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    Re: 1976 Coupe Deville 500ci 4 bbl engine won't run

    No problem. I'll try to post more as time goes by. On fixed income so money is tight, will take some time to get it the way I want it.

    Thanks again!

  8. #7
    the APEMAN is offline Cadillac Owners Fanatic
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    Re: 1976 Coupe Deville 500ci 4 bbl engine won't run

    The exhaust manifold bolt job is usually very painful. Sorry.

    Glad you got her running without wasting any time changing good parts.

  9. #8
    BRUCE ROE is offline Cadillac Owners Fanatic
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    Re: 1976 Coupe Deville 500ci 4 bbl engine won't run

    Quote Originally Posted by Raybo View Post
    No problem. I'll try to post more as time goes by. On fixed income
    so money is tight, will take some time to get it the way I want it.
    The gauge might be reading high, because of a poor ground to the tank unit. Look for a black
    wire from there to the frame. These tend to keep getting worse; often can be fixed without
    removing the tank. Bruce Roe

  10. #9
    Raybo is offline Cadillac Owners Member
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    Re: 1976 Coupe Deville 500ci 4 bbl engine won't run

    Thanks Bruce Roe, I'll check that out!

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