OK when it is COLD my 'Vette starts just fine a little loapy mabey but it picks right up. If it is HOT it starts fine too.BUT if it has been warmed up and sits for a while it wont start for about 20-30 sec of turning over where do I start................

 

Start by finding the fuel pump relay and checking it.
If you have no capability for checking it, replace it.
Since it's an intermittent problem, go ahead and replace it as it is the most likely candidate.

It's up on the firewall between the power brake booster and the distributor.

 

do you hear the fuel pump prime in those situations? (should occur for 2 or 3 seconds after you turn the key)

 

My thought is leaky injectors flooding the motor. Cold it either evaporates or helps in starting the motor. Hot it may also burn off or not have enough time to "leak" down before you start it again..

 

I'm NOT saying anyone else is wrong.

The oil pressure switch bypasses the fuel pump relay once oil pressure builds.
It seems since the delay in starting is timed just about right to allow the engine to pump up the oil pressure and bypass the pump relay this seems to be the best place to start.

Good idea to listen for the pump but I've never been able to hear the pump prime on either my '91 or my '84. Maybe there's something wrong with them where I can't hear it but they run good.

Relays CAN & DO make connection sometimes and sometimes they don't. Particularly when they get old and have switched a few thousand times. Like any electro/mechanical device, they don't have an infinite lifespan.

To do this right, go get a fuel pressure gauge and connect it to the schraeder valve and see if it pumps up when you turn on the switch and when it doesn't start.
If it doesn't probably the relay is bad or possibly the fuel pump is bad, or the connections on the pump is bad or there is a intermittent connection somewhere in the wiring.

Again, my best idea if you aren't really into the technical end of these things would be to change the fuel pump relay.
I have found a few of them bad that caused this symptom.

If you want to become an ace Corvette technical guy, I'd start by getting the FSM for this particular year model, a fuel pressure gauge, a scanner, a secondary voltage tester, an injector test box, sensor testers,spare ECM's, on and on.
If you just want to fix just this one, try the fuel pump relay.

JMHO and everyone else's advice here is good too.

 

Thanks Guys I will probably just replace it as I am starting to go over evrything slowly. I already got FSM (pelinemnary white one) and am starting my tool and testing collection. This forum has helped alot by just reading through the posts. My only wish and suggestion is if the forum were broken down by years as I did not know till I bought it the differences in the 90's C-4's and that the 93-94 had opti issues. But I got an oil leak to chase down and suspect it is going to require more help from you all and the dreaded pump/opti swap when I try to fix the drip.

 

In my experience this is always caused by a leaking injector. When the car sits after been run, the fuel pressure in the rail slowly empties through the leaking injector. Thats why when u try and start it, it has to get through all that fuel 1st.

 

If it smells like gas and blows alot of black smoke out the back when it cranks up the SupaVette is probably right.

A fuel pressure leakdown test would be the definitive answer on that and that's a very easy test.
And then comes the hard part...identifying which one is bad if you suspect there's a leaky one..

I've seen several peple replace all the injectors trying to fix this when it wasn't the injectors at all. (and they have brought them to me afterwards to fix)

We can speculate all day but that's not going to fix it.

Good luck with it.

 

Well I am going to do the test got a gauge know to clamp each line after pressurizing the system to tell which it may be injector or check valve but my bet is relay I am an electrician and have relays stick at work all the time they are only good for so many cycles or the contacts wear out. Only$9 and seems to be good preventive maintenence. But if it is injectors ya gotta do what ya gotta do. I gotta can of Chevron injector cleaner in it now gonna hope but gotta get rid of this white stuff layin around all over the place. It would not hurt if the Sub-Zero wind chills went with it;-)

 

Uh-Oh, I "almost" forgot about this one.....

There is a check valve back with the pump... it 'could' be bad and allow fuel to drain back to the tank but I doubt this is the problem.
Your fuel pump will re-pressurize the fuel rail in about 2 seconds after the key is turned on.
That is if all is working correctly.

I'd think you'd have the symptom after the car has been sitting for a few hours rather than after it has warmed up but you never know.

Good luck with it.
Jim

PS: Go to WallyWorld and get some B12 Chemtool and put it in your gas. It's a pretty good cleaner and will help clean the deposits off the back of your intake valves as well.

 

Well did the fuel pressure test today(first day above freezing since my last) although the pressure DID NOT come up by just turning the key on a slight kick on of the starter gave me 45lbs. immediately. It held for about 5 min so I went to put the cover back up after changing the relay and checked it about 5-10min later it was at 20lbs so yeah something is leaking. could not find a place to pinch the lines to eliminate the check valve but since when it does start it seems flooded(have to rev it to stabilize idle after rumbling start) my bet is leaky injector or 2.Now what is the best way to get them checked and repaired. At 155k I would think the injectors might need a little pep me up. If I start it back up after only a min or 2 it fires up like a new car.

 

anyone got suggestions?

 

Exactly how mine acted, turned out to be leaking injectors, originals BTW.

 

:agree:

What you describe are exact tell-tale symptoms of leaky injectors, which (I think it's safe to say) will occur to every L98 during their lifetime