I have a 89 iroc z28 with the 5.7 tpi. the problem i am having is when i shut the car off i can't start it right up for a couple of minutes. I am getting good spark, 48 lbs to the rail but the pulse to the injector is pulsing but is very dim. I have changed everything i can think of and more to fix this but can't find anything. even had it put on a computer with no luck.
when the car starts it fires right up and runs good but when i shut it off it won't start right back up. Any thing anyone can think of (probably already did it) please let me know.

 

whoops, I just re-read the post.... I dunno

 

Starter heat soak maybe?

 

has a brand new starter

 

what kind ofsound does it make when you try to start it? does it even turn over?

if it's a slow whine sound then it's heatsoak.

 

Just because it has a new starter doesn't mean that it isn't heat soaking. The problme isn't the starter, but where it's located. If it picks up enough heat from the headers it can basically lock itself up solid. It won't turn again until it has a chance to cool off.

How old is the battery? How many CCAs? Are you still using the stock solenoid? Has the battery been relocated? Does the car have headers?

I used to have the exact same problem. I switched to a remote Ford style solenoid and mounted an Optima in the trunk. I changed all my battery cables and grounds to 1/0 gauge cable. I also wrapped the starter with a heat reflective blanket. Haven't had a reoccurance since.

 

Yes the car has headers. But its not the problem i replaced the starter a week ago. As soon as i started it upafter replacing the starter i let it run for 30 seconds then shut it off and it did it then also. Somethimes i can let the car sit for 2 or 3 hours and it still does it. But its cranking very good when it not starting. Again getting 49 to the rail, very good spark at the coil and #8, getting pulse to injectior but very faint. Everything with the fuel seems to be fine. When the car startes it starts right up and runs perfect it's just when i shut it off and try to start it right back up is when it happens hot or cold. battery is less then 1 year alt is about 9 or so months old.

 

It's a wiring problem, the wiring is getting heat soaked and causing high resistance (dim pulsing noid light).

 

hey this is worth a try,carfully look at your wires running from your coil to your modual. could be a broken wire.

 

So it spins up and cranks over fine but just won't start?

I agree that it's probably a wiring problem. Could also be ECM or injector related. You can get your injectors cleaned for $10 each. Probably not a bad idea, especially if they are old.

 

car does start

 

I'm confused. What exactly is the problem?

 

injector relay maybe

 

[QUOTE]Originally posted by JerseyIrocZ
[B]I have a 89 iroc z28 with the 5.7 tpi. the problem i am having is when i shut the car off i can't start it right up for a couple of minutes....

I had the same problem with my 87 Z28. It had a LB9 in it that I replaced with the L98 (5.7L TPI engine). I retraced my wiring, the voltage supply to the fuel injectors, and replaced fuel pump/oil pressure switch and fuel pump relay. None of these worked. I eventually replaced the battery with one that has 1000 CCA and my problem is no where near as bad. A friend of mine with an 90 Mustang GT was having the same problem, his fuel pump went out and after replacing it, the problem was solved. My fuel pump is a little weak, but I am going to nurse it along until it goes (hopefully in the driveway).

 

On my 89 formula I have the same problem. It can sit for as little as 5 minutes and it will start, always starts on the turn of the key the first time. I have noticed that the delay seems to be shorter when the battery is fully charged. I had to replace the battery when I first got the car, and essentially the problem went away... until the battery got run down from the car sitting for a while. Fuel pressure is great, I replaced the distributor, but haven't yet determined the best way to test the voltage to the injectors - anyone know the best way?

Oh, and the starter cranks strong until the battery starts to weaken.

 

Use a test light to check the electrical current at each injector connection, the pulse is to fast for a multimeter. If the light comes on while you are cranking the engine over, you are getting voltage to the injector. You can use a multimeter to check the resistance between the terminals on the injectors themselves, if memory serves me right they should be between 14 to 16 ohms.

 

i had a problem similar to this with my 87 formula 350 bird. turned out the altenator was weak....not completely dead but getting close and the modulator was bad. it would choose when it wanted to give spark and when it didnt. i would check your modulator. hope it helps.

 

so it cranks fine but won't start when its hot?????

 

Kidcamarosc,

Mine will start when hot and after it has sat for a while, but it takes several tries it doesn't fire right off like it does when the cold start injector is active under engine temps of 100 degrees.

 

id maybe let it get warm, shut it off and let it sit for a couple minutes then pull the vacuum line of the fuel pressure regulator and see if there is gas leaking out mybe it has a hole in the diaphram.

 

Thanks, I'll give it a try!