1988 C4 Hard Start problem
Thread Starter
4th Gear
Joined: Mar 2023
Posts: 4
Likes: 1
1988 C4 Hard Start problem
I have a 1988 Corvette thats been having hard start issues. The starter seems good, but the car wont turn over when cold unless I give it a little bit of throttle. When its hot, it does a better job of starting. I already went ahead and replaced the spark plugs, wires, distributor cap and rotor, ignition module and coil. I also replaced the alternator, belt and tensioner. It seems I'm getting good power and spark. I replaced the throttle position sensor as well and still no luck.
I'm looking at where to start next to fix this. I've replaced the fuel filter and pump recently. I'm wondering if maybe the fuel pressure regulator could be bad? I have had a small amount of fuel come out of the throttle but I wasnt sure if that was just from the hard starts. It also smells rich and a little bit smoky when it does fire.
My other through is maybe a bad cold start injector sensor, causing the cold start to add too much fuel?
If anyone has had similar symptoms, please let me know where to start.
I'm looking at where to start next to fix this. I've replaced the fuel filter and pump recently. I'm wondering if maybe the fuel pressure regulator could be bad? I have had a small amount of fuel come out of the throttle but I wasnt sure if that was just from the hard starts. It also smells rich and a little bit smoky when it does fire.
My other through is maybe a bad cold start injector sensor, causing the cold start to add too much fuel?
If anyone has had similar symptoms, please let me know where to start.
Racer
Joined: Sep 2001
Posts: 365
Likes: 93
From: Chesterfield VA
Try either having your injectors cleaned or replace them. Could also be a pressure regulator leaking down. The car gets a prime pulse when you first turn the key but if there is no pressure in the line, then the line has to have pressure before fuel comes out that injector. You may only be getting a fraction of fuel prime on cold start up because of this vs when it’s hot and the pressure hasn’t leaked off.
Drifting
Joined: Mar 2003
Posts: 1,828
Likes: 214
From: Charlestown IN
Cruise-In V Veteran
If it's like my '85, check your fuel pressure with a tester from Harbor Freight or some where similar. Turn the key to on and if you watch the gauge, you can see if the pressure is bleeding off from a leaky injector. You can also check the injectors by using an ohm meter to see if the resistance is correct. Mine were 14.8 to 15 ohms. Also, if you turn the key on and have pressure, put 12 volts to an injector and see if the pressure drops. That will tell you if it's squirting or not. I assume you set the TPS at .5 or so volts, although that won't prevent the start.
Racer
Joined: Sep 2001
Posts: 365
Likes: 93
From: Chesterfield VA
The 85 is a little different than the 88, but by all means you can check the fuel pressure just like you said to see if it is bleeding off. The 88 uses all 8 injectors for the prime pulse on the engine where as the 85 had a cold start 9th injector. I don't recommend trying to test the injector the way you did, if you check the injector wires both will be positive until the ECM fires the injector and it will pull it to ground. The best way to check this is to pick up a set of noid lites from harbor freight and they will light up when the injector fires. The injectors used on the C4's were bad injectors to start with and they usually have a coil failure when they get hot, I would rule this issue out on a cold start. Since it starts when hot I am sure the injectors are working ok but it never hurts to check so that you can rule the issue out. If the car has done alot of sitting I am going to lean towards the pressure regulator. It is a small disk of metal on the inside that seals off the flow of fuel and with the alcohol in the fuel this can rust and not fully seat. It will cause the fuel pressure to leak down and cause the issue you are having.
