I posted a while ago about this but I didn't have as much background as I do now about it.

http://web.camaross.com/forums/showthread.php?t=306416

Anywho, went to the track this weekend and had mediocre performance in good weather (12.2-12.3 @ 109/110) with some great 60' times (best of 1.63)

Several times through the night my car would not start, it would crank, but wouldn't start. After a few minutes I would come back and it would start up, but I'd have to hold the gas down for about 30 seconds at about 3 or 4k rpm for the car to level out and stay on without dying. Thinking it was the battery I didn't give it much thought.

Next day on my way to another destination I stopped for some grub and sure enough the problem happened again. Car started up, idle fluctuated up and down, then just died. Would do this several times, then just crank and not start. After about 10 minutes I was able to get it to start and kept my foot down on the gas to keep it from dying.

Everytime the car does this it seems to be OK afterwards and drive pretty much fine. It might be down a bit in power, but maybe that's just me?

Finally today leaving the hotel from our trip, the car did the same thing again. This time, the battery gave up the ghost 100%. Had the car towed and the battery replaced with a brand new one. Car them seemed ok, cranked probably 10 times in a row with no problem. Stopped at a rest stop, and it happened again. So it's not the battery (alternator also tested fine).

Sorry to be longwinded but it's the best way I can get this problem explained. When just cruising along around 50-80, the car will also seem to sorta vibrate every few seconds.. but it doesn't feel like a typical miss.

Hope this is enough info, but I would really like to not start throwing parts at the car chasing a ghost. I can't get the problem to be consistant either, so it's hard to diagnose. Opti? Fuel pump?

Opti is stock with 86k miles, so is the fuel pump.

 

To help narrow down some ideas. Did you unscrew the cover off the shrader valve and see if fuel was coming into the lines? Take something small like a nail or key or something and push the button in it. If air comes in it's likely your fuel pump is going. If you get fuel, it's likely it is not. You might want to try it several times, especially when your having the starting issues. It may be sparatic as it's going out. I had a similar problem where I'd crank the car and never get a fire(after my dumb **** ran out of gas). Ended up frying the pump. If your running those times and with almost 90k on the stock pump it's possible it's slowly dying on you.

 

Some folks have mentioned the fuel pump, a local buddy of mine and someone in the last thread (even with lacking info). I was hoping it'd be the opti since it's easy to swap out.. buuut.

I've gone outside since I got home and probably started the car 10 times in a row without a hitch. It only seems to do it during inconvenient times like when in a parking lot, gas station, or 200 miles away from home.

Hopefully I'll catch it and be able to perform some tests. I'm going to rent a fuel pressure gauge tomorrow and see what kinda readings I get. Anyone know what the readings should be before starting (ignition on) and during idle?

The schraeder valve test.. try that with the car running, correct?

 

Javi

If you want to check the schaeder valve cycle the key a few times and leave it turned on but not running. There should be enough pressure when you push on the valve to let some come out. It kinda sounds like opti to me. My car did almost the exact same thing when the opti went out. Ussually from what I have seen If it is the fuel pump the car will act up once it gets hot. If you need any help with anything let me know I am just down the road, or hit me up on pbfbody. On my fuel pressure gauge in the car my fuel pressure with the key on is ussually 42ish, once it idles maybe 38.

 

cool, thanks for the info there man.. at least I've got some stuff to look into.

I'll let ya know on the forums if I need a hand with it

 

ugh.. started up fine again this morning....

any other angles to look at would be appreciated.

 

check fuel pressure.. my z is been doing the same yours is for about 3 weeks now, it will start up fine and run ok smoke the tires and all but i hooked a gauge up and i only have 25psi.. im like you i would be away from home or any help and the car would run like crap or not start so i would check fuel pressure and see where it's at. i cannot see it being your opti if you can start it up and it runs fine and then the next 10th time it doesnt...

 

good info there my_iroc....

question, even when the car was running fine, was the fuel pressure low like you just said?

I'm just hoping it's one or the other and I can diagnose it correctly.. fixing the problem doesn't phase me, it's just throwing parts at the car that I want to avoid!

 

at 25 psi the car would run normal i had my pressure drop to 18-20 and thats when it wouldn't start and when it did it would stumble or hesistate, it even sounded like i had a huge cam in the car at one point.. i did about every test you could do on the fuel system and refered to 5 boards for info because i didn't want to throw parts at my car.. but if it's a problem with the fuel system it can be the regulator or the pump..

heres what i did--- i pulled the vacuum line off the regulator and saw that the pressure didn't change at all so then i hooked up a vacuum pump to the regulator and applied 25 inchs of vacuum and pressure went up to about 30, just to be sure it was the pump i changed the regulator with a known good one from my 95Z and pressure was the same, i also checked to see what the voltage was at the relay and then the pump connector and found that i was getting anywhere from 13.7-13.9 at the pump so i know it wasent a voltage problem. I also cleaned all the grounds that control the fuel pump curcuit and still had 30 psi, i even went to the fuel pump prime connector under the hood applied voltage to the pump and nothing for about 3 min the pressure stayed and then out of no where the pressure shot up to about 45psi so after talking to some co workers and consulting a "tech 2" we found that the pump was in need of replacement and in the computers history we found that there was a lean mixture code which leads us to believe that this problem has been around for awhile and is now starting to get worse. I ordered a new racetronix pump and when it gets here problem should be solved and im looking forward to see how much the rear tires can go up in smoke with 43-45psi of fuel pressure.. also like i said earlier if you have fuel problems there will be something in the history or a code for lean mixture i kept getting p0300 and p420 which i was told was caused by the crappy fuel pressure sorry for the long post but just trying to help..

 

Yea man, hoook up a fuel pressure guage to the schrader and route it somewhere so you can close the hood.. Then drive it and see if maybe you can get that problem to happen.. Sounds like the opti. if it were the plugs the problem would most likely be there ALL the time. The opti is the only thing I can think of in the car that likes to "mess" with you. lol.

 

my iroc -> thanks again for the input, long posts are much appreciated in this case, trust me I'll be sure to report my findings.

 

Don't forget to email support@racetronix.com for the instructions.

 

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Thank You