timonator

iTrader: (4)

Ok guys, I picked up another little project,a nice clean 91 Z28, Texas car.The problem is it doesn't want to start. When I crank it it over it will pop but doesn't want to keep running. It has about 37 psi at the rail when I turn the key on and the pump cycles. I also tried adjusting the TPS. It just doesn't want to stay running. Any ideas ?

KNBlazer

it could be your timing... it could be your plugs, coil, cap and rotor, ign module...

juanillox8

iTrader: (7)

check ur map sensor and vacuum lines

timonator

iTrader: (4)

It's only getting 32 psi at the fuel rail when I turn the key on or jump the relay. It drops immediatley. I have 12.4 v at the pump. I'm thinking the pump is weak. Any thoughts ?

timonator

iTrader: (4)

Ok,new pump puts out 40 psi ,still have the same problem. New plugs&wires good spark. Had the ignition module tested. Vacuum lines all appear good. Sometimes it will even idle for like 10-20 seconds but just doesn't want to run.

John 89 Formula

If the car was sitting for a while it could be bad gas, or the fuel filter could be clogged tight

timonator

iTrader: (4)

New fuel new filter

timonator

iTrader: (4)

Ok,so I think it's either a vats problem or a ECM problem. I got it to actually run for about three minutes today after diconnecting and reconecting the vats connector under the steering column. I'm not sure but I don't think the injectors are getting a consistent pulse. Is there any way to test this.

timonator

iTrader: (4)

I really need some solid advice with this car. When I first start it it idles for about a minute or two and then dies like someone turned the ignition off. Every time thereafter that I start it, it runs a shorter time before dying. If I try to give it throttle at all it dies. I have 40 psi at the fuel rail till it dies. I had the ignition module tested repeatedley until it was burning hot. New plugs,wires,cap& rotor. new tps, new iac, new fuel pump. I even took the intake apart to check the fp regulator which appears to be fine.Please help.
Thanks

Sprayed92

man my 92 formula did the exact same thing as you are describing when msd box and my ecm went bad. Do you have a buddy with a 90-92 thirdgen? if you do you might try swapping the ecm.

John 89 Formula

Bad map sensor?

timonator

iTrader: (4)

How do I test the MAP sensor ?

John 89 Formula

I think auto zone can test it for you, but they're cheap auto zone sells it for $40.00

b4ccamaro

I would be guessing the rubber hose between the pump and the fuel line in the tank. It wont be the VATS. If the vats was causing it, the car would never start. You may have really plugged injectors.

timonator

iTrader: (4)

Why would it be the rubber hose in the tank ?

ASE doc

I would start by monitoring spark and injector pulse while the car runs. Look for drop out when the car dies. I suspect that you have a bad pick up coil. Its the small circular coil in the distributor, above the ign module. It provides the PIP (primary ignition pulse) that is used both to generate spark and to fire injectors. When it drops out you lose both. This coil should ohm out between 500 and 1500. If not, replace it. You can test injector pulse quick and dirty with a test light back probing at the -term of the inj connector, ground clamp of test light to batt+, with the engine running, light should flash. For a better test, use a lab scope, back probing inj connector. Most lab scopes will have sample wave forms to compare. The batch fire V8 has 2 seperate injector drivers so test one inj on each bank. You can test injector impedance by accessing the injectors themselves, they should ohm at 12. Or an easy way is to go to the ECM connector and test injector banks. Impedance of each bank should be about 3 ohms ( 12 ohms / 4).

ASE doc

The MAP sensor should read about 4.5v at the middle wire of the 3 wire connector, key on engine off. At idle it should read about 1.7 - 2v, depending on idle quality. Basically it converts manifold vacuum to voltage, ranging from 4.5V at atmospheric pressure to about .5V at 28". You can bench test it with a vacuum pump. Watching data with a scan tool is the easiest way to check TPS and MAP.

timonator

iTrader: (4)

I put in a new map sensor. It didn't fix the problem.

timonator

iTrader: (4)

I swore the pickup coil was within the ohm range when I tested it before. I have an LED light thing that goes between the injector and plug to check for pulse which it appears I am not getting. It seems like the spark drops off right as it dies. I do have a good scanner if you could recommend what I should look at.

timonator

iTrader: (4)

My pickup coil is.872

John 89 Formula

Unplug the oil pressure switch and jump across it to energize the fuel pump then start the car and see if it stays running, if so replace the oil pressure switch.

timonator

iTrader: (4)

Ok, I'll try that when I get home tonight. Thanks

b4ccamaro

The rubber hose dry rots in the tank if it isn't submerged in gas. So if the car sat with a 1/4 tank or so, it cracks and just hemorrhages fuel back into the tank.

timonator

iTrader: (4)

I've pulled the pump put about 4 times trying different pumps. The rubber hose appears to be fine.

timonator

iTrader: (4)

Ok, tried jumping the wires for the oil pressure safety switch but that blew the fuse. I also tested for injector pulse with a noid light and am getting pulse right up until it dies.

timonator

iTrader: (4)

Well, I found the problem. When I unplugged #3 fuel injector and put the noid light on it, then started it it idled, didn't die,I was able to rev it up. I actually got to take the car around the block after 2 weeks of losing my mind trying to figure out what the problem was.
A big ,big thanks to everyone for helping me with my car!