When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
I recently acquired a 86 c4 Corvette, but it has a fuel issue. The fuel pump has been replaced and the tank cleaned. Distributor has been rebuilt and Throttle body as well. It keeps loading up the cylinders and back firing like it's getting to much fuel. Next thing to be replaced is the fuel pressure regulator. Not sure if it will fix it. Does anyone have any tips or have encountered this issue and solved it?
have you ran a fuel pressure diagnostics before saying you have a fuel pressure issue? if the fuel pressure appears to be OK, i'd suspect maybe a timing issue. don't randomly start replacing parts, e.g. pressure regulator, w/o proper troubleshooting. do you have a FSM?
Fuel Pressure Regulator could be shot, you could have a leaking injector, could be a ignition issue causing a short loss of spark - or timing could be off...
Suggestions:
Check Fuel Pressure (including leak down rate after pump is switched off).
Check Ignition Timing.
Pull the Plugs and see if any smell like gasoline.
I recently acquired a 86 c4 Corvette, but it has a fuel issue. The fuel pump has been replaced and the tank cleaned. Distributor has been rebuilt and Throttle body as well. It keeps loading up the cylinders and back firing like it's getting to much fuel. Next thing to be replaced is the fuel pressure regulator. Not sure if it will fix it. Does anyone have any tips or have encountered this issue and solved it?
Hook up a gauge to the fuel rail and find out what the pressure is when you turn it on without cranking. Turn key off and see if it holds pressure and for how long. If all this is good, it might be the injectors. Which ones do they look like?
When I first picked up my project 89, I had a similar issue. I bought at FP gauge and performed the leak down test and found one of the original multecs was leaking ever so slightly. Then I also ohmd all of the injectors to make sure they had proper resistance, one of them did not. Replaced all of them with new Bosch D3 and that never happened again. I'd start with FP, leak down test, and check injector resistance.
When I first picked up my project 89, I had a similar issue. I bought at FP gauge and performed the leak down test and found one of the original multecs was leaking ever so slightly. Then I also ohmd all of the injectors to make sure they had proper resistance, one of them did not. Replaced all of them with new Bosch D3 and that never happened again. I'd start with FP, leak down test, and check injector resistance.
Even if it wasn't leaking, I'd ditch the Multecs just because something better is out there. I don't want to have to only patronize gas stations with pure gas. In my home area, I'd have to go 20 minutes out of the way or somehow get to the airfield (which I have never tried) to get to their gas. The ethanol will eat the windings and screw up the injector sooner or later. Now I can pump up anywhere I wish.
Even if it wasn't leaking, I'd ditch the Multecs just because something better is out there. I don't want to have to only patronize gas stations with pure gas. In my home area, I'd have to go 20 minutes out of the way or somehow get to the airfield (which I have never tried) to get to their gas. The ethanol will eat the windings and screw up the injector sooner or later. Now I can pump up anywhere I wish.
Agreed my friend. If the OP wants to make this a regularly driven vehicle, switching to new style injectors is a must. For a couple hundred bucks and an afternoon of elbow grease, the swap is actually quite easy
Agreed my friend. If the OP wants to make this a regularly driven vehicle, switching to new style injectors is a must. For a couple hundred bucks and an afternoon of elbow grease, the swap is actually quite easy
Just thought of it. I'd also have FIC service the cold start injector while it is being done
OP still hasn't stated fuel pressure...or what "too much pressure" is....can't believe the number of people changing parts without knowing fuel pressure.....these cars should have come with a gauge....it's just the very 1st thing you need to know.....
OP still hasn't stated fuel pressure...or what "too much pressure" is....can't believe the number of people changing parts without knowing fuel pressure.....these cars should have come with a gauge....it's just the very 1st thing you need to know.....
If he has Multecs, they need to be placed in the appropriate location. Trash bin. If not, I suspect they are dirty based on my testing on a 3 year period. His probably haven't been touched ever so I would say it can stand to be changed for rebuilt ones. Cold start valve could stand to be cleaned too after all these years.
Of course you are right. He should diagnose the problem first then fix it and after which, change those injectors out
Without any testing, I would not declare that. Could be the check valve in the pump, fuel pressure regulator or leaking injectors
I checked the fuel pressure and just when I turn the key on and no start, it only goes up to 32psi and as soon as the pump stops the pressure drops off with in 3 to 5 seconds.Oh and I did change the fuel filter.
Last edited by Bruce Seabold; 06-12-2018 at 12:48 PM.
06-04-2018, 01:30 PM
C4 Corvette Fuel Issue
