425 Stalls Uphill

[Mojochiken]

79 coupe deville stalls when going uphill, I give it gas but then the engine dies down, I give it more gas and she starts to go, and then stalls. Also has some problems when backing-up, sometimes she stalls. Its not the cat, so I'm thinking fuel filter, anyways the cars at the shop. What do you guys think?

[EDITHMAE]

Fuel Filter Or Kink In The Fuel Line Or Faulty Fuel Pump...just Guessing For Fun....good Luck

[bryan1970]

might be a float problem in the carb. or it could be a bad cap and rotor i have seen them soo bad that when almsot any kind of load it out on the engine the spark jumps to various posts inside the cap.

those are just a few guesses. let us know what the shop finds when you hear from them.

[The Ape Man]

Sounds like fuel delivery. Could be any of the stuff already mentioned. Here is one problem which drove me to completely tear my Cadillac apart 23 years ago. It had a recent fuel pump too:
One curve ball on these cars can be the fuel pump. Sometimes a valve gets stuck open within the pump itself. This then dumps most of the fuel pressure back to the tank via the small return line. Symptom will be the car always idles fine and can also take off under full power for several seconds then the engine drops out like someone turned the ignition off. Car will also die when going uphill. If you put it in neutral and allow it to idle for 20 seconds the power will then come back. The test for this it to pinch the small fuel return line closed at the fuel pump's outlet then test drive. Be careful of how you pinch the line as there isn't a lot of room and the steering linkage can interfere with your pinching device while on a test drive. If your fuel lines are old and crusty then pinching them can cause a leak in the future.

[Mojochiken]

Thanks for all your good advice, but like I said the shop has it now and if they cant figure it out I will tell them about the pintching of the return fuel line. Plus, you described the symptom to a tee.

mojo

[The Ape Man]

Make sure that the shop isn't learning on your vehicle. This can get pretty expensive.

[xxn3kr0h34rt]

Originally Posted by The Ape Man

Sounds like fuel delivery. Could be any of the stuff already mentioned. Here is one problem which drove me to completely tear my Cadillac apart 23 years ago. It had a recent fuel pump too:
One curve ball on these cars can be the fuel pump. Sometimes a valve gets stuck open within the pump itself. This then dumps most of the fuel pressure back to the tank via the small return line. Symptom will be the car always idles fine and can also take off under full power for several seconds then the engine drops out like someone turned the ignition off. Car will also die when going uphill. If you put it in neutral and allow it to idle for 20 seconds the power will then come back. The test for this it to pinch the small fuel return line closed at the fuel pump's outlet then test drive. Be careful of how you pinch the line as there isn't a lot of room and the steering linkage can interfere with your pinching device while on a test drive. If your fuel lines are old and crusty then pinching them can cause a leak in the future.

would an aftermarket fuel pump from a Cadillac vendor have these same problems?

[76 Eldo]

I know this is an old post, but did the shop fix it and how? I am having similar problems with my '76 Eldo.

Thanks.

[deVille33]

Rust fuel lines can also give you these symptoms.

[Scraped Knuckles]

It's an old post but others probably have had the same problem so I'll post this. Buy a cheap vacuum-fuel pressure tester from the parts store. The engine vacuum test can tell you if it's a plugged cat. or exhaust, late ignition timing, sticking valves or other problems. And by testing fuel pressure and flow rate you'll know if you need new lines or pump. But most likely it's the Quadrajet carb. Remove the stock fuel filter which clogs up easily and replace it with an inline filter( if you cut the fuel line a few inches away from the carb. it will be easier to remove the old filter. And the new filter can be installed where you cut the line) . Try holding the choke open by tying it, or even by putting a screw driver down the carb. , take it for a test drive and you'll see it stopped stalling up hill. It's better to buy a new carb. either Q-jet, Holley, or Edelbrock unless you have the Rochester Carbs book and some experience. A hand held vacuum pump can be used to test the choke pull off (as well as the EGR valve and the vacuum advance canister on the distributor), and new electric choke coils aren't expensive. But the old Q-jets have a habbit of leaking internally and emissions carbs have sealed mixture screws which make it hard to fix with out removing and rebuilding it. Some mid 70's to early 80's Q-jets were known to have porous castings which would leak and aren't rebuildable and the computer controlled Q-jets are junk.