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91 Z - 305 TPI Won't Start

Old 11-26-2018, 09:42 AM
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91 Z - 305 TPI Won't Start

I have been looking around and haven't found a similar post, sorry if this is an answered question. My 91 Z 305TPI was running great until one day I felt it stumble a little, felt like losing fuel, and then it died. Battery was great, cranked fast but nothing happening. Got it home, fired right up ran great for a minute or two and died, same thing. Tried it again yesterday, started, ran real rough but smoothed out ran for a couple minutes then I shut it off and on restart ran for a couple seconds and died then same thing. After that, it sputters a little on first crank and then nothing. I am getting no codes, the SES light comes on like it should. New gas (was driving it every day)
I was figuring fuel pump or spark but put a gage on it and got 40+ psi that held 10 minutes or so, and getting good spark through the plug wires. I am not really sure how to test the injector pulse, should I unplug the connector and then check for voltage at each terminal? I have new injectors that I was figuring on installing but want to ask before I do that and have something else be wrong.
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Old 11-27-2018, 10:03 PM
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Re: 91 Z - 305 TPI Won't Start

You could hook any 12v light to each fuel injector connector, turn the key and watch it pulse. I use, i believe its a 9004 headlight.
It might be an ignition module problem. I've never seen the issue myself but I hear that symptoms are similar to yours.
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Old 11-28-2018, 06:58 AM
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Re: 91 Z - 305 TPI Won't Start

That series likely used Multec injectors, a known weak spot. Each injector should be tested for coil resistance. Expect to read a minimum 12Ω cold.
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Old 11-28-2018, 09:38 AM
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Car: 1991 Z-28
Engine: 305 TPI
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Re: 91 Z - 305 TPI Won't Start

Thanks, I do have a new set of injectors and was preparing to replace them anyway.
I think the originals are still in the car, and it sat for 10 years before I got it and figured they may be "tired" but never checked them.
I did check number 1 injector wiring last night and was getting 12 volts on both sides of the connector with the ignition on.
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Old 12-02-2018, 03:54 PM
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Car: 1992 Pontiac Trans Am GTA
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Re: 91 Z - 305 TPI Won't Start

Will the engine fire and run if you press and hold (don't pump) the accelerator while cranking the engine?

Does the engine start while cold? Will it start while hot?
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Old 12-03-2018, 07:18 AM
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Re: 91 Z - 305 TPI Won't Start

I did try throttle open, partially open, pumping, no change, now the car won't run really long enough to warm up.
I purchased a noid light, and the pass side bank were much dimmer than the drivers side, drivers were strong and bright, passengers were really dim.
I decided to jump in and replace the injectors as they look like originals, (grey bodies) I figure that can't hurt and I had them anyway.
I took it all apart yesterday and as long as I can get everything back together I will keep my fingers crossed that these were the problem.
Can anyone look at the attached picture, will I have any issue using the yellow injectors with no provision for the retaining clip the grey ones had?
(Sorry this picture is so big)
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Old 12-03-2018, 10:01 AM
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Re: 91 Z - 305 TPI Won't Start

no you will not have any problems. The pressure from the fuel rail is what holds them in place.
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Old 12-07-2018, 03:57 PM
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Re: 91 Z - 305 TPI Won't Start

Any luck?
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Old 12-08-2018, 06:28 AM
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Re: 91 Z - 305 TPI Won't Start

Just getting everything put back together, hopefully this afternoon I will be able to give it a try. Fingers crossed.
Thanks
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Old 12-09-2018, 08:58 AM
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Car: 1991 Z-28
Engine: 305 TPI
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Re: 91 Z - 305 TPI Won't Start

Update, new injectors are in and all is well, car runs great and no leaks!
Although there is a lot on the top of the motor, this was really pretty straight forward.
I wound up removing the alternator to remove the fuel lines, and once I figured out the right length of extensions and ratchets to get to all the runner bolts it was really pretty straight forward.
Thanks for the feedback!
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Old 12-09-2018, 05:35 PM
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Re: 91 Z - 305 TPI Won't Start

Hmm, interesting. This is the first that I've ever heard of a fuel-injected engine failing to run due to failure of multiple injectors.
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Old 12-09-2018, 06:47 PM
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Re: 91 Z - 305 TPI Won't Start

Originally Posted by Yeret View Post
Hmm, interesting. This is the first that I've ever heard of a fuel-injected engine failing to run due to failure of multiple injectors.
shorted out coils shuts off the injector driver. Unfortunately a common issue with multec injectors.
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Old 12-10-2018, 06:09 AM
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Car: 1991 Z-28
Engine: 305 TPI
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Re: 91 Z - 305 TPI Won't Start

Made it to work this morning car seems to be running great.
Hope there are no other issues lurking that the injectors didn't;t cure.
That's what AAA is for HAHA.
Thanks again for the comments and advise!
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