49er

After sitting for a day or longer, my C4 will not start when I'm cranking it normally.
If I squirt a blast of staring fluid it will fire off. Sometimes it takes several "squirt and crank" iterations to get it started.
Once started, on any given day, it will run well and start-up reliably if I turn it off.

I'd appreciate any good advice???

Hot Rod Roy

Why doesn't anybody ever ask for bad advice? There's much more of that available!!

First: Please fill out your Personal Profile. It's much easier to give advice when we're not required to be psychic, too! There's only a few of us that qualify for that title.

Second: What year Corvette are you working with?

Y-bodluvr

Could be a bad Fuel Pump Relay

49er

Why would the fuel pump relay suddenly start working after I spray starter fluid and get it to start?

Y-bodluvr

the fuel Pump Relay just sends a signal to the fuel Pump before startup if it’s BAD the car WONT start and yes you can “jump” start it with starting fluid to bypass that if it runs good after starting it’s more than likely NOT the pump or filter years ago I had the exact same issue with an 89 GTA it would only start spraying throttle body fluid in the throttle body and after an IDIOT mechanic assured me my Pump was bad and changing it well it was only a $10 Relay that was the actual problem..

Y-bodluvr

the problem may also be temperature related a bad coolant temperature sensor can also cause a cold start issue

64Scout

There is an oil pressure switch that also runs the fuel pump, it's there as a backup. A lot of people dont understand that and think it kills the engine if it loses oil pressure.

Does the engine start if you crank it a long time? What if you crank for a few seconds, stop for a few, and then crank again?

Hot Rod Roy

The relay activates the fuel pump to provide fuel pressure, before the engine starts. If the relay ( or its connector ) is bad, you won't have any fuel pressure to start the engine. When you spray starting fluid into the engine, you are providing the fuel to start the engine. After the engine is running, you don't need the relay.

If you use a jumper wire to put 12 v. on pin G of your ALDL connector, will the engine start without starting fluid? The ALDL connector is at the bottom of your instrument panel, to the right of your steering column.

Why won't you tell us what year Corvette you are working on???

Hot Rod Roy

But we've got to know the year of your car!

KyleF

Study the diagram......


Initial Prime for 2 seconds comes from the ECM, then once the the engine cranks, the relay kicks in, if the relay fails, the circuit can be completed by the oil pressure switch.

Y-bodluvr

My GTA had a brand new fuel pump AND oil pressure switch and still a NO START until the fuel pump Relay was replaced

bjankuski

That is probably because you did not crank the car long enough to build up oil pressure or the oil pressure switch also failed. If the car started with a new fuel pump relay it would eventually start with the oil pressure switch unless it also failed.

Silver85

If it's an early model you could simply have an issue with the cold start injector. The slow ECM and batch firing made for some difficulty on the early year models to get the fuel mixture rich enough to fire off in colder conditions.

Y-bodluvr

Pretty sure OP’s car is a 93 automatic

KyleF

Highly unlikely unless in a really cold environment. The 92/93 LT1 was still batch fire, so were the later TPIs. There are kits to eliminate the the 9th injector. Remember, these systems have to be built to work in South Texas and Northern Canada.

49er

Thanks all! Good info I did not know about.

Sorry...it's a 1993 Rock-Stock

I'm confused about the fuel pump relay thread. I would think the fuel pump requires power all the time the key is on, not just during starting. I'll try pin "G" this weekend.

The oil pressure interlock is something I did not know about.

Isn't there also a cold-start injector too that could be the culprit?

Hot Rod Roy

We need a '93 expert here. Is pin G correct for the '93? That's okay for the early 'vette's, but I might not be correct for the '93.

It's times like this the FSM sure comes in handy!! (Factory Service Manual)

Y-bodluvr

No the cold start or 9th injector was only on 85-88’s

49er

Thanks for the wiring diagrams. That explains a lot! The replies are also really helpful!

Yes a 93 automatic. I'm in Los Angeles, so it is not "cold". Problem occurs when it hasn't been started for say 24 hrs.

One thing that is odd...after I get it started the first time, it will re-start no problem for the rest of the day. Maybe there is residual pressure in the FI system so the prime circuit is not needed if it's only been sitting for 30 minutes? Does that make sense?

Thanks again to all for taking the time to help me out.!!!

revival1

I had this problem with 1989 with a L98. Didn't away's happen but did happen a lot. Turned out to be intake was leaking air. After it was sealed up never had the problem again