Hello,

My Father has a 1996 LT4 Corvette with 64,000 miles on it. It had been parked for three years but had been started every once in a while. My Father decided to start driving it...he put about 70 miles on it (not at one time). He stopped one day to get gas and when he cranked the car it popped once and it started but was running backwards for a few seconds before it died. Now everytime he tries to crank the car it kicks back (he can see the fan blade try to turn counter clockwise) on the first crank and will not start. He has since changed the distributor on it but still has the same problem. Every mechanic he has talked to is stumped by the problem. He has some guys looking at it but they want to strip the motor down and look at the timing chain. My Father is trying to get opinions on this first because of the cost of stripping the motor down. Anyone have any ideas?

Thanks,
Trever

 

If it's an LT4, that means it has an optispark on the front of the motor, not a distributor like on the gen 1 sbc. If he did change the optispark, he needs to check the wires and make sure they are connected in the right order. It is very easy to screw this up on that motor. You need to check the fuel pressure, there is a fitting on the passenger side fuel rail to do this. Should be around 40 psi when the key is turned on. Make sure you can hear the fuel pump run for a few seconds when the key is turned on. If that's fine, move on to checking all the ignition components, plugs, wires, etc.

 

The fan is electric.

Changed the distributor?

The symptoms would indicate a failed OptiSpark likely from sitting and collecting dust/condensation inside. They are fragile at best. IF that was replaced, then there are wires to be repaired.

3 yrs in Storage....storage is the technical word for mice nesting and munching on wire insulation and other misc tasty plastics. All you need do is find them. I';ve seen ants stuffed inside a relay that they caused to short out.

Fix/service all grounds, not talking battery cables either.

Visually inspect every inch of wire harness that can be seen.Look for/at damaged insulation and signs of damage/wear/injury to the harness.

Do a real fuel pressure test, with leakdown times and ohm all 8 injectors. Then test pressure regulator diaphram for leaking into the plenum via vac lines.

A car thats sat for that long even with a start up (which don;t count for much) collects trouble as time does not stop degrading rubber, plastics, lubricants,fuels etc,.
when its been properly stored problems will appear. When just parked,...they are assured.

Best advice, go find a real Corvette mechanic. There are so many possible issues with this car.
The typical shop hand (tech, circumcised, asm,gm, whatever) is'nt going to know or understand the idiosyncrasys of a C4. Those guys are getting far and few between. Most of the ones that are available are sitting in here at night...in our rocking chairs...
Todays techs want to apply todays technology to a car that was not based on that...so they rarely diagnose more than flat tires from the 80s & 90s.

BTW...it kicks back because the timing is way far advanced at start up...something that should NOT be happening with an opti system.

 

Suspect the opti spark ignition system.

 

It would be unusual for a timing chain to fail on a LTX engine. I agree with the others here--it sounds like a opti distributor problem. I'd guess the dist. wasn't installed correctly-EXCEPT the problem was there before and after. Have any of the "stumped" mechanics scanned for codes ? Optis can fail and set codes, but not always.

 

Thanks for the feedback everyone...I have passed the info on to my Father. I will post what the results end up being for his problem.

-Trever

 

There seems to be some missing info here. So, the car had been sitting for three years. Started "every once in a while"...weekly, bi-weekly, monthly, twice a year, once a year, once or twice all together? How was the car "parked"? In a garage, storage unit, outside?

He put 70 miles on it recently. What system checks were done on first start up, or did he just start it and go? How did it run during these 70 miles? Was it running on the gas that was in the tank for three years? Was this the first time he put fuel in it since he started driving it again?

My first suspicion is that there may have been sediment in fuel tank that got stirred when new gas was put in and fouled the pump and/or the filter. Check fuel pressure. Secondly, there may be varnish on the injectors, but since it ran for 70 miles they're probably okay. I suspect sediment based upon the trouble starting immediately after fill up. I would check that first along with connections, grounds, vacuum lines, etc.

By fan blade, do you mean the one on the alternator?

Was the optispark replaced before or after this particular incident? If so, was the timing chain checked? Were new plugs and wires installed? Or at least the old ones checked? How about the crank position sensor?

What does the OBDII say? Any codes?

BTW, I have an LT4 and cannot resist driving it for three days, much less three years.

 

Thanks for the questions...here are the answers:

Q: Started "every once in a while"...weekly, bi-weekly, monthly, twice a year, once a year, once or twice all together?
A: Once or twice a year.

Q: How was the car "parked"?
A: Outside, partly on a cement driveway. No cover.

Q: What system checks were done on first start up, or did he just start it and go?
A: Fresh fuel, new battery, Fuel additive. No check engine lights so he drove it.

Q: Was it running on the gas that was in the tank for three years?
A: A little was in it but he added fresh fuel and fuel additive before driving it.

Q: Was this the first time he put fuel in it since he started driving it again?
A: It was on empty, he added fresh fuel from a gas can. This particular time was the second time at the gas pump. He drove the car for a week or so putting 70 miles on it.

Q: By fan blade, do you mean the one on the alternator?
A: I misspoke about the fan blade, he told me he was looking at the alternator and saw it turn counter clockwise "back lash" (his words).

Q: Was the optispark replaced before or after this particular incident?
A: After the problem.

Q: If so, was the timing chain checked?
A: No, it was not checked before or after the problem.

Q: Were new plugs and wires installed?
A: No

Q: Or at least the old ones checked?
A: The plugs were a little blackish but the car ran fine up until he stopped for gas.

Q:How about the crank position sensor?
A: He replaced it after the problem.

Q: What does the OBDII say? Any codes?
A: He said the guys that are looking at the car could not check the codes. He said that they said they couldn't read the codes. The computer would not let them in.

Thanks,
Trever

 

Q:How about the crank position sensor?
A: He replaced it after the problem.

Q: What does the OBDII say? Any codes?
A: He said the guys that are looking at the car could not check the codes. He said that they said they couldn't read the codes. The computer would not let them in.

The crank position sensor was for OBDII missfire detection on '96 and up ONLY--it has nothing to do with starting or how the engine runs. Your father needs to find a "mechanic" with a OBDII scanner and check for codes.