johnd1975

I have a very odd ongoing problem with my 1990 Vette.
It stays in the garage most the time and is driven occassionally.

1.) After driving it one day I parked it in the garage and everything
seemed fine.
a couple days later it woudln't start, battery was strong but it
would just keep turning over but never sounded like it was getting
spark or gas..My brother and I look at everything we could think of.
since I ran the battery down, I removed the battery terminals and
charged the battery, the next morning it started.

2.) Ok, I drove the car a bit and parked it again ( started the
following day no problem) but after aprking it in the garage again
and letting it sit a few days the same thing happened , would crank
over strongly but no sign of spark etc... so I removed the battery
terminals to reset the computer but this didn't seam to work...
So the next mroning I was watching Pat Gosses show , Gosses garage and
one of his callers had a similar issue and Pat told him it could be
the Anti Theft device and to try another key with the Chip in it, so i
tried one of my spare keys that were never used and the car stated
right up.. thought I found the problem but maybe I didn't. drove the
car for a while that day , parked it again in the garage.

3.) Tried starting the car a few days later, same thing sounded like
it was not getting any spark so I tried removing the battery terminals
to reset the computer etc etc. but that didn't work and neither did
the new Key with the computer chip (trie the original key as well....)
battery was fully charged....... so I did some research online and
found one place that said to try unplugging the MAP sensor
and then try starting it well I did that and it started right up,
plgged the MAP sensor back in drove it around for a bit , parked it in
the garage, tried to start it yesterday and the same thing is
happeneing,,, just turns over,,,, so I tried all the things I've
mentioned so far but this time nothing will allow me to start my
Corvette.

I believe something is arming my Anti-theft system, Do you have any
Idea what I might do to get this corrected...???? Could it be my ECM
(computer)
could it be the button with the little plunger that in the door that
makes the interior light come on and go off which also may be
connected to the Anti-theft system?

I am the second owner of this car ,it is mint condition with 60,000 miles
I've owned it since 1994 and have litterally babied it...

when the car is running it runs great....

Please direct me if you can.

johnzz4

I believe that the security doesn't even allow it to turn over (not 100% sure though).... A couple thoughts:

1) Poor connection to distributor/coil.
2) Poor connection at one of the battery posts.

tjwong

If it is the VATs system that is keeping you from starting. It would also disable the starter as well. When this happens check for spark, pull a couple wires off the top of the distributor and crank it over, you should see a decent arc from the distributor terminals. Also check the coolant temperature sensor for corrosion. If corrosion is presentl replace the sensor and its connector, you can usually get this as a package deal from the parts stores.

89vettefromhell

well i just got done recently with that same problem.. and your situation sound sjust like mine that i fixed 2 days ago... check your fuel pump relay and fuel pump.... if tis turning over and starting sometime.. then dieing later in the day ... its probably a fuel pump.. easy 30 min install if you have to get one also you might wanna grab some new battery bolts if you got the side mounts... they tend to help get better connection to battery over older ones

dlmeyers

A few points.

I suspect you are missing spark or fuel.

First, there are two aspects to the 90's VATS (Vehicle Anti Theft System), vehicle crank AND injector pulse. I recommend you get the Factory Service Manual set for the real deal but will attempt to give a very brief, general description. Another anti theft system, the Intrusion Detection System (IDS) involves door locks, horns, start enable relay, etc and is NOT part of the VATS system. This sytem checks to see how you entered the vehicle and will not allow engine crank if it thinks you broke a window.

After noting the correct resistance on the key pellet, VATS will provide a ground for the start enable relay and the engine cranks. A SECOND signal (I think it is a voltage drop) is noted by the ECM and will allow injectors pulse. It is rare for one thing being done, (engine cranking) and the ECM not receiving the GO signal from the VATS. I would consider buying a noid light, (pretty cheap), and using this test light checking injector pulse. If the injectors are being pulsed, I would then consider testing fuel pressure at the rail. If there is an injector pusle problem/fuel pressure issue, we go to other areas.

If you have a flashing noid light, good fuel pressure, I'd go spark hunting. The NAPA store may have a little gadget you can hook onto the spark plug and then hook on the plug wire. You crank the engine and check for spark showing through this little device. Again, this device is not that expensive. If no secondary spark, (or weak spark) we focus on the primary and secondary ignition system.

Again, if you have the manuals, a few small trouble shooting aids, one should be able to determine which system is not participating.

In summary, the ECM may not be pulsing the injectors due to a variety of reasons, (VATS included), there may be no fuel/fuel pressure, or a problem with the primary or secondary ignition system.

Good luck with this repair. Darn cars.

Let us know. Be glad to help.


dlmeyers 90 coupe zf6 3 speed shocks

JYAMZE

Try Rapping on the fuel tank. when you get the no start condition,
jump outta the car, open the fuel door and give it a couple of good whacks...(nothing that will damage it) then try starting it. if this solves the problem then you need to take out the fuel pump assembly and clean the contacts. the rapping is shaking up a bad connection.
This was a suggestion by the C4 GURU Gordon Kilebrew (sorry if that's spelled wrong) it might be in tech tips.

Morley

First verify that you have spark during the no start situation. Then test fuel pressure.
Next hook a noid light to one of the inector connectors (also during no start). If the noid light doesn't light up as you crank there are a couple of possibilities. 1) ignition module isn't giving the ref pulse to the ECM so it will fire the injectors. 2) the wire for the ref pulse is broken or shorted(intermittant). 3) ECM is on its way out 4) flakey connection at the injector fuses.

89vettefromhell

good call.. also turn the power on and listen to the tank and see if you can hear the pump... you should be able to... if not replace it... and i cannot stress this enough... dont just go on that though.. CHECK THE RELAY... and wires on the current pump.. could just be corroded wiress