Start problem with 91 GTA

[Ozpont]

Hi guys... somebody with an electrical brain out there.. .???
I also have a 1991 GTA 5.7lt auto.. its been a perfect vehicle but last week..the cars suddenly developed a starting fault... it just decided to not start...a few times.. now will not start at all...
It has no Pulse to the injectors.. check the Coil and its ok.. wiring around the dissy is ok..
... could it be the anti-theft module....

Car decided not to work simply at a gas station.. just pulled up.. it was fine.. then got in to start off again.. and nothing.. turns over.. but will not start..... .. then about 5-10 minutes later it started.. I did pull the hose off the throttle body at first.. just pulled it off toto check the butterflys were opening etc..
Car started.. then drove the car about 100 miles.. no problem.. but then did not want to restart again.. .. it took 3 goes.. then went . so I took it straight home..about another 100 miles back etc..
Then when turned off at home.. it did not want to start and has NOT since..
I have changed keys.. two others and had the keys checked . .they were all consistant.

.. any ideas..??? before we look to the anti-theft module....???
thankyou

(PS.. car has 20,000 miles on it original)

 

[WS6]

It reads like a classic VATS failure, but the engine cranking over does not quite fit the symptom. If the key fails the VATS module it should not ground the starter enable relay or allow the ECM to fire the injectors. But you say it cranks with no injector pulse. So I would guess that the VATS module is not sending the signal to the ECM that this is a valid key,but it passes the key to ground the starter enable relay. I'm thinking this because of the time in between successful start ups is 5 minutes or so. Which is how the system works...once failed, even the correctly read key won't start the car for 4+ minutes.

Or...the ECM is the problem and is not firing the injectors,period. But that doesn't explain why it'll run indefinetly once started. I would think it would stall or something.

I'd drop the ECM down and reset both those chips and give it whirl.

But I'd also be on the phone to a chip burner to have a custom chip burnt with VATS disabled!



...

 

[V6TA-MI]

If memry serves a '91 is a speed denity deal right? if not the best thing to do is go thru the factory manual diagnostic chart. otherwish yer just throwing money at electrical parts.
My guess would be Crank sensor... or maybe ECM

Glenn

 

[WS6]

Yes, 90-92's are speed density systems, but the Gen I SBC'c have no crank sensors like the DIS ignitions of the LC2's. They are traditional small cap HEI's with pole piece and pick up coil in the distributor.

 

[V6TA-MI]

Yes, 90-92's are speed density systems, but the Gen I SBC'c have no crank sensors like the DIS ignitions of the LC2's. They are traditional small cap HEI's with pole piece and pick up coil in the distributor.

Ah, right,

Glenn