1996 Oldsmobile Cutlass Supreme doesn’t hold fuel pressure

oldsmobile
cutlasssupreme

#1

My vehicle doesn’t hold fuel pressure when I turn it off.i checked it with a gauge.it has a new fuel pump but that didn’t help.if the engine is warm you have to crank it to start it.if it sit over nite and is cold it starts up normal.


#2

Leaky fuel injectors


#3

Thanks I thought that might be it or maybe fuel pressure regulator


#4

Start the engine and let it idle for a minute.

Shut the engine off, and remove the vacuum hose to the fuel pressure regulator.

If gas leaks from this connection, the fuel pressure regulator diaphragm is ruptured.

Tester


#5

If you do the key dance you may be able to live with it happily: turn key to On/Run (not all the way to Start.) Wait 2-5 seconds for the fuel pump to run. You may hear it. It will turn off. Turn the key to Off then back to On/Run and let the fuel pump run for the few seconds before it turns off. Each cycle of the key dance you are bringing fuel and fuel pressure up to the engine. When you finally turn the key to Start, the engine will fire right up and run because it has enough fuel and fuel pressure to start and run.


#6

I presume you mean when the engine is warm started you have to crank it for quite some time before it catches and runs, but left overnight on the next morning’s cold start, it cranks & starts up almost immediately. If its leaky injectors, they’d have to leak quickly at first, then stop leaking altogether, which I presume is a possibility. Leaky injectors aren’t a very common complaint we get here though. A fuel pressure test could confirm/disprove leaky injectors , but you can probably tell I’m doubting that idea. I’m thinking you may have some problem which is causing it to run too lean, such as air leaking into the engine somewhere. This would cause hot starting problems b/c on hot starts the computer doesn’t inject as much gasoline as on cold starts. If this air leak idea is correct, the engine computer could compensate after the engine starts running using the o2 sensor, but a fuel trim test would show it was running overly lean, esp at idle and low rpms.


#7

George,

You do realize that the O2 sensors don’t come into play until the engine reaches operating temperature, and the computer goes into the closed loop mode?

Tester


#8

That’s why with an engine air leak it doesn’t start properly on warm starts. But does on cold starts


#9

Then if that were the case, wouldn’t the Check Engine light be on reporting a lean condition from an O2 sensor?

Tester


#10

I’d expect at least a lean code pending probably. Whether the CEL would have turned on depends on the specific algorithm the manufacturer implements. OP, is your check engine light on? As I mentioned above, a fuel trim measurement is the best way to make a lean/rich determination, not necessary to depend on the check engine light.

If the problem is the fuel pressure leaking down when the engine is off, why is the starting problem worse on warm starts than cold starts? Presumably the engine has been off longer for cold starts, so the pressure should have leaked down even further.