My junker still doesn't start up right ! If I put a fuel pressure gauge on it, I'll get 42 psi during the 2 second pump run when I turn the key on. The pressure drops to about 37-38 when the pump shuts off. When I try to crank the engine, it does not fire up. It will eventually start, but it takes a few tries. This happens every time the car has set for more than a couple of hours. It even does this if it sets for a week, so I have ruled out injector leak down. Besides, the pump holds pressure well. If I prime the plenum with a couple of squirts of fuel from a spray bottle, the car starts fine. I would hate to buy a Mustang because of this

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'89 GTA, Ported Plenum, BBK throttle body, 24lb Motorsport injectors, Jet stage 2 chip, AFPR, no cats and a Flowmaster.
'95 GMC soon to be 383 daily driver w/Howell multi-point injection conversion

 

maybe the wire for the cold start injector is off??? i dunno... i would check things like that, maybe ignition would be a good place to look too

Steve

 

Hey my man... I got a question for you. Why do you always call your car a "junker" everytime you post ? If you don't like that "junker" why not sell it to somebody that DOES ?! It looks to me that you do you like Mustangs better and dont give a **** about thirdgens. So go buy your Mustang and give the GTA to someone that car really give it some TLC.


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92 Z28 L98 350
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Ported and polished heads, ported stock TPI base, ported plenum, Comp Cams XR270HR-10 cam (lift .495/.502 duration 218/224 lobe separation 110), Edelbrock TES headers, LT4 valve springs, Crane AFPR, Flowmaster catback with LT1 style tips, MSD coil & wires...

"Take that auto, drop it in first, hold the brakes, stomp the gas and grin from ear to ear! :-)

 

Thanks for the input Steve. I actually don't have a cold start injector, and I kinda ruled out ignition because it cranks right up if I prime it. Also, I checked several plug wires at one time to verify spark while cranking. Looked pretty good. The "car" does seem to act as if needs a cold start injector, but it has no place for one, and has never had one since I have owned it.

And for you "Blade", I do like my "car", and I don't like "Mustangs". You don't know me, so don't comment on what I call my "car". This is a tech board, I asked for some technical advice, not rude replies. Keep them to yourself please.

 

89 TPI's are mass-air-flow systems, right?

It's possible on a v6 for it's MAF sensor to be busted, but not throw a code. V6's have different MAF's than v8's though. The test for a bad MAF on a v6 is to unplug the MAF and try driving the car. Is that the same for a v8?


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-Tom P (Hot rodded 1986 Firebird 2.8l) from http://www.f-body.net/mailbag/3rd/3rd_mailbag.html message boards

 

TomP, I did try that, no difference. Thanks for the suggestion though. Does anyone know if it would make a difference if I had an '88 PROM?

 

Check the TPS setting and also clean the throttle body and plenum with some throttle body cleaner.

 

Thanks, madmax, I have checked the TPS, but have really cleanded the plenum. I really haven't driven the car much since I ported the plenum. I'll clean it anyway, just to be sure.

 

Freeze,

Have you checked the injector pulses while cranking? It definitely sounds like a fuel delivery problem, especially since the manual priming gets it to fire immediately.

Incidentally, if you are using a PROM from an '88, you may have discovered the problem. The '88 TPI had a cold start valve (9th injector) and relied upon that for extra starting fuel. The '89 and later TPIs deleted the cold start valve and programmed longer pulses for the service injectors while cranking to provide the extra starting fuel. Since an '88 PROM wouldn't do that, you'd be starving for fuel on cold starts (sound familiar?).

It would have been a lot easier to diagnose earlier if you had mentioned a different PROM.

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Later,
Vader
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"Make Me Bad"
Adobe Acrobat Reader 4.0

 

Thanks for the input Vader. I didn't mention the PROM earlier, because I didn't expect it. The car used to run fine with that chip, but I had a leaking injector also. Kinda self primed the engine, and I was driving the car daily. The chip was in the car when I bought it, and I added the Jet prom, but i still use the '88 calpak because of the way Jet build their chips. I did order a new factory Mem-cal friday, so maybe that will help. I guess all my upgrades fixed a problem that actually helped the car start with the '88 chip. I'll find out soon, and let everyone know. Thanks for the help.

 

Changed the PROM, but symptoms still the same . It might start a little easier, but still takes a couple of tries. I posted another topic about start-up input. I am open for all ideas, I have alomst replaced the entire TPI system. I am planning a fuel pump replacement, although I can't find anything to tell me that I need to.

 

IAC? Vacume leaks? I guess that's where I'd start looking, find something that could change your air to fuel mixture. I guess even the EGR could do that. If all else fails, pull those injectors again, and test 'em out to make sure. I have had new parts come DOA.
Good luck
BTW, my car is similar, but I haven't tried manual priming. I jsut put a fuel pressure gage on it, and in 1/2 hour I went from 42 PSI down to 18 PSI...not good, I still have to rule out the return line, but since when I first start the car, I have to rev it, while holding the pedal constant, my rpms rise and fall. Around 3000 rpm misses become audiable, and it will not rev past 3500 until it warms up. I think I got a bad injector, or 2, or 3, but I plan on checking everything 1st
Good luck w/ yours
Corry