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Discussion Starter #1
Hello! Sometimes when I go to start my 96 Caprice, it takes a few seconds of cranking then starts, but runs horrible until I tap the gas, then it runs fine for the rest of the trip. When it starts, it reminds me of when a high compression 60s car diesels when you shut it off.
It only started doing this a few days ago, and did it twice on my last trip.
Any ideas on what this could be?
 

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Given those miles, to reduce the 'possibles' from a few dozen down to something workable what diagnosis have you already done yourself?

Otherwise:
Define this 'sometimes' thing. More often when cold than hot? More often when hot than cold?
Have you done any basic fuel pressure checks?
How many years since the opti was tuned up? Or replaced? Has it recently been touched?
 

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Discussion Starter #3
It does it more often when cold but is still intermittent.
I have not done a fuel pressure check yet, but plan to this weekend.
I took the opti off to inspect/clean it about 1k ago.

Could it be the tps? When I got the car the tps was bad, and it was hard to start similarly to what its doing now.
Its runs great though not at all like it did with a bad tps.
 

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It does it more often when cold but is still intermittent.
Maybe tired old fuel pump after gradual leakdown and taking it's sweet time to build pressure. Or humidity on antique crappy spark wires. Or maybe not.
I have not done a fuel pressure check yet, but plan to this weekend.
Will go a long way in narrowing down things.
I took the opti off to inspect/clean it about 1k ago.
New parts? Properly blueprinted when re-assembled?

Could it be the tps? When I got the car the tps was bad, and it was hard to start similarly to what its doing now.
Its runs great though not at all like it did with a bad tps.
TPS, IAC, MAF, MAP, .... A million things individually cause hard start, or collectively after time. I'd search on here and/or google every one of them, and attend ALL adjustment procedures and reg. maint. stuff possible (EGR check, hose vacuum leak(s), new plugs, wires, IC/ICM volt. checks, gumout over the intake) without buying too many parts just to throw at it.
Your symptoms also could be just a mouse nest in the airbox or a tank of bad gas. Maybe you're a maint. fanatic or just dam lucky, but Ima thinking more connected to that 264k thing.
 

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Discussion Starter #5
Sorry for the late response, been a little busy lately.
The fuel pressure at idle tested 36 psi. And fuel pressure when priming was at 46psi, then dropped almost imediately after the fuel pump shut off. I don't think it's supposed to do that, any ideas?

Using this new found knowledge, I turned the car on and quickly cranked it before the pressure dropped, and it started much quicker than normal.
 

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I stole this snip with tests which may point to either FPR or worn FP check valve. With your numbers it does not sound like FPR, but do the "pull the vac line off" check to make sure. 1.Having it only hard start (after a while), 2.starts fast just after turning off, and 3. no sputters when driving, points to the back of the car.

[stole]
typical tests for the FPR is to attach a pressure gauge to the injectors fuel rail at the schrader valve. Check the pressure with key on, engine off. (43 psi approx) Turn the engine on and let it come to idle. Fuel pressure should be lower (5 lbs ? have to look it up) Remove the vaccum tube from the back of the FPR and the fuel pressure should go up to around the 43 psi again.

If the fuel pressure doesn't change after removing vaccum tube, or gas comes out of the back of the regulator, the regulator is bad. If the fuel pressure is very high, the fuel pressure regulator could be bad. If the pressure is low, it could be the FPR, a clogged fuel filter, or failing fuel pump. The fuel filter is easy to change and its cheap. I am not sure about the best way to diagonse the fuel pump without removing it.

Is your car not starting after it has sat awhile but starts when you have driven it recently? Does it start with a full tank of gas but not a partialy empty tank? If the check valve in the fuel pump assembly is failing, the pump will lose its prime and take awhile to reprime the pump. If you can get the fuel pressure gauge to sit up on the windsheild where you can see it inside the car you can observe the fuel pressure when you turn on the ignition switch but not start the car. You should have full pressure as soon as you turn on the key. If you don't, try turning the key off, then on again. The pump runs a few seconds each time you turn the key on so it should prime the pump. /[stole]
 

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Discussion Starter #7
My FPR tested good and had no fuel in the vacuum line. It has trouble starting if its been sitting for more then a few mins, and starts pretty consistently regardless of fuel level.
 

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What is your battery voltage at start up when sitting overnight?
 
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