1996 Formula LT1 6spd, when cold it takes about 1+ min of solid cranking to start. priming the pump (leaving key on, on then off etc) changes nothing, also putting the gas to the floor doesnt help, once started(starter fluid helps) when cold it runs fine. can turn off and will start up just fine.

other problem is once its warm, it runs perfect, can shut off and start up just fine, but if i wait 10-20 mins, its hard to start but different. it tries to start and IF i get it to start it runs like crap then it will die. almost like its running off of 2 cylinders, extremely rich, can smell it.

if i let it sit for a few more minutes itll start and stay running but like crap, till i rev it to clear out the fuel then it runs perfect, can shut it off and turn it back on fine, till i wait for a cold/wait 10-20 min hot start, i honestly dont even know where to start

the gas tank builds up pressure if thats a problem


ive been searching for months on different forums for a fix but cant find anyone that has the same problems, ive just been living with it, i work from home, and i dont have the money for a mechanic

 

Have you hooked up a fuel pressure gauge and then tried to start it? Checked for spark while cranking?

 

i dont have a fuel pressure gauge but ill borrow/buy one to check. and spark seems fine because starter fluid helps it start right up, but i can check it too

i found on another forum to check the coolant temp sensor ohms and it just keep rising untill my ohm meter cant read it. starts at like 4.5k and goes up to 19.5k, this is when engine is cold and its 55*f outside, does that mean its bad? but when i do get it running the engine runs fine which seems weird to me. its only 15 bucks so wont hurt to replace anyways

 

That is strange about the temp sensor. Here is a table of what values you should see at what temperature:

4th Gen LT1 F-body Tech Articles

Looks like if your starting value is 4.5K that's right on the money for 55 degrees. Then it goes the wrong direction and I don't know why. Are you continuing to read ohms as the engine is warming up?

 

I replaced mine just to eliminate it and it was very easy to do. Makes just one less thing to worry about and these do go bad over time for some reason.

 

i did it with engine off and cold. which makes me think it is bad since it goes that high. i bought a new one but havent installed it yet. and it holds 2.9k at room temp which is correct on the chart. im going to try to install it in the next couple days, thanks for the replies

 

You could always test the old one by putting it in boiling water and checking ohms as it heats up. But since you already have a new one might as well just install it.

 

tested the old one. at 140* it was showing ohms as if it was 95*, not sure thats enough to throw off the computer, the test i did with it in the car i guess i was doing it wrong. installed the new one. still alittle hard to start cold but im letting it cool down for 30 mins to test and see if the major problem is still there

 

that wasnt it. still same exact problem, going to test fuel pressure next.

 

Let us know what you find. For a hard start I would expect to see fuel pressure build then rapidly drop off.

 

dont have a fuel pressure gauge yet. but i did pull the vacuum off the fuel pressure regulator and i smell fuel in the vacuum line. does that mean its bad?

 

That is not a good sign. There is possible leakage past the diaphragm. If so, it will dump fuel in the closest cylinders on the RH side of the engine.

 

ah k thanks. as soon as i replace it ill report back. might be a few weeks as im low on money. thanks for all the replies

 

replaced the fpr and it wasnt it. still loosing pressure

 

I fought with the same problem. Checked for leaking injectors, FPR, sensors. Doing my fuel pump as we speak, so hopefully that fixes it. My car would take 2-4 primes to build pressure. After that it would run and hold fine. Leave it for a few min and it would drop fast.