Hey guys,

I just recently got my Z (96Z 6M) and from the day I got it it had trouble starting. After it sits for any more than 30 mins it takes some cranking before it fires up. I have to crank it once for 5 secs, it usually doesn't start, but on the second try it stumbles to life. Once started the car runs great.

What could be causing this? Fuel or ignition problem? BTW I just changed the fuel filter today, and no improvement.

Thanks,
-Max

 

I would suggest doing a fuel pressure test with a fuel pressure gauge. Hard starting can be the effect of a weak fuel pump. Can you hear it turn on when you turn the key?

 

Hard starting is often a fuel issue...... Maybe a fuel filter ir an can of injector cleaner.

just a thought

 

Also, get it scanned for codes....

 

Make sure you do a few of the tests. I had the same problem for like 6 mths , took it to the dealer and they said that my pressure was low and told me I needed a new pump. So I replaced the old pump with a Walbro from racetronix . My fuel pressure didn't seem to fade away as fast when I let it sit for a bit but still faded. Now I know that it wasn't completly the fuel pump's problem. I spent $100 to have a dealer find the long cranking time and in the end the problem is still there So make sure you pinpoint the problem before blameing the pump. Might be like injectors leaking or a couple other problems. I took it to the dealers thinking they would do all the tests but they only did a pressure test. I am soooo glad I didn't let them replace my pump for $600. Also the service guys at the desk told me that the pump in my B4C was a heavy duty one and thats why it cost $ 250. As aposed to the regular one that z28's get . These service guys Don't have a clue.

 

Long cranking times are usually from fuel draining back toward the tank or fuel dripping into the intake and puddling. In either event, the fuel pressure at the fuel rail will drop off very quickly after the engine is shut off.

First check for any fuel leaks near the fuel rails and particularly around the FPR. Then pull the vac line off the FPR and see if it's wet. I would also put a vacuum source like a mityvac brake bleeder on the hose to see if it holds vacuum. If not replace it.

Now eliminate the injectors as the cause. 2 ways to do that. You could pinch the plastic line before the fuel rails on the incoming side, as you shut down the car. If the pressure still bleeds off, the injectors are the problem. I don't like this method though because you could damage the plastic lines if you're not careful.

The other way to check the injectors for leaking is to lift the fuel rails and injectors up so the nozzles are visible and turn the pump on. There is a fuel pump prime connector located near the PCM. With pressure, the leaky one(s) will be visible.

If you have eliminated the injectors and the FPR as the cause of the quick fuel pressure drop after the car is shut down. The only thing left is the fuel pump. The problem would be a sticky check ball in the stock pump.

 

Thanks for the help guys,

From what I understand this could be caused by three things, bad fuel pump, leaking injector(s), or a bad FPR. I definetely want to eliminate the injectors and the FPR before I start replacing the fuel pump. Does anybody know of a good website with detailed directions on how to properly do this (I don't want to risk breaking the fuel lines by squeezing them)?

Also, if it turns out to be the pump and I don't replace it, does the drop in fuel pressure mean the pump could break any day now? And would injector cleaner help at all if it turns out the injectors are leaking?

Thanks,
-Max

 

Don't know of any website with instructions but it's not hard either.

To test the FPR, simply put a vacuum source on the vac line. I use a mityvac brake bleeder but you could use your mouth suction. Look out if the FPR has a hole in it as you will get a mouthfull of gas. That's all you have to do for the FPR.

The injectors can be checked by simply lifting them all up by unbolting the fuel rails. just a few bolts. If you power up the fuel pump with the engine off, you will be able to see which one is leaking. Having them professionally cleaned can and usually does fix the leaking problem.

As far as the fuel draining back toward the tank caused by the check ball in the fuel pump. This won't hurt the fuel pump unless your fuel level is extremly low, but it doesn't do your starter any good. All that long cranking will take it's toll on the starter longevity.

 

Just to clarify, how do I check if the FPR works? I disconnect the vacuum tube and suck on it while the car is off. If I get a moutful of gas the FPR is bad, and if I don't the problem is elsewhere. Correct?

Thanks,
-Max

 

That is for leaks only Yes that is correct. That is not checking it's ability to regulate pressure but your problem would be due to leaking not pressure anyway.