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Root cause was a faulty fuel pump check valve. I ordered a Dorman 3/8 fuel pressure check valve on Amazon for $25. Save yourself $20 shopping at other locations. Part number is 800-196. Fuel pressure after an hour is still at 30 psi versus immediately dropping to zero. I'll add more details and pictures to my build thread. Here is a picture of what the part looks like. I am surprised that my brand new Delphi pump assembly never worked as I've had this start issue since day one.
According to my GM service manual, for 1989 Corvette, there are 4 reasons for fuel pressure to drop.
1. In-tank fuel pump check valve not holding.
2. Pump coupling hose or pulsator leaking.
3. Fuel pressure regulator valve leaking.
4. Injector(s) sticking open.
Did you ever check to see if #1 or #2 here might be the real problem? Your check valve "fix" tells me this is probably what should have been repaired. There are many, many Corvette's that hold the fuel pressure correctly, that don't have this extra check valve! Note that this "fix" is not mentioned in the Service Manual.
Did you ever check to see if #1 or #2 here might be the real problem? Your check valve "fix" tells me this is probably what should have been repaired. There are many, many Corvette's that hold the fuel pressure correctly, that don't have this extra check valve! Note that this "fix" is not mentioned in the Service Manual.
Hi HRR,
#2 ruled out when I replaced the pulsator with hose and 4 clamps.
This repair verifies that #1 is the root cause, the fuel pressure regulator is acceptable as is, and the remanufactured fuel injectors I installed from FIC are not leaking.
You are correct that the true repair would be to R&R the fuel pump assembly and replace the fuel pump. This is a Delphi assembly that I purchased on Amazon which has a lifetime warranty. There are a lot of great reviews from Corvette owners on this product. I was just unlucky. I will probably put in a warranty claim down the road, but this fix resolves the hard starting I've had since I rebuilt the car. Check out my build thread. The new Delphi unit's fuel pump check valve was defective out of the box.
Fuel pumps are not cheap, and this is a great way to rule out the problem, and possibly fix if you are not interested in pulling the fuel pump assembly out.
According to my GM service manual, for 1989 Corvette, there are 4 reasons for fuel pressure to drop.
1. In-tank fuel pump check valve not holding.
2. Pump coupling hose or pulsator leaking.
3. Fuel pressure regulator valve leaking.
4. Injector(s) sticking open.
Not mentioned in this section but mentioned earlier in the manual is any connection in the fuel supply line, such a damage or loose fittings or any damage to the fuel line from the tank to the engine bay. Also mentioned are the fuel pressures acceptable, 34 to 47 psi.
My own 1989 C4 will hold pressure for over an hour, measured at the fuel pressure test connector. I have an aftermarket adjustable fuel pressure regulator, however stock regulator should also hold pressure after shut down.
I hope this information will aid in finding your problem.
my 85 only reaches 22 psi and does not respond to acceleration of the gas pedal, just idles and is very hard to start. I have changed everything but the fuel pressure regulator and check valve.
Mine goes up to 22 psi and then drops immediately. Once it finally starts, it goes to 22 and stays. Changed the pump twice and got the same results. Changed filter as well
So I replaced the fuel pressure regulator diaphragm. Got it all back together and no change on pressure. Actually less pressure. Pump sounded weak. Took it back and Brooklyn at autozone said that fuel pump was wrong.
She said is was universal pump and had a max flow of 22 psi, which is all I was getting. My injectors need 24 psi.
So the correct pump with higher psi is ordered now. Hopefully that fixes my issue.
From: Liliha Bakery stuffing my face with coco puffs!
Originally Posted by Jackson007
So I replaced the fuel pressure regulator diaphragm. Got it all back together and no change on pressure. Actually less pressure. Pump sounded weak. Took it back and Brooklyn at autozone said that fuel pump was wrong.
She said is was universal pump and had a max flow of 22 psi, which is all I was getting. My injectors need 24 psi.
So the correct pump with higher psi is ordered now. Hopefully that fixes my issue.
Wrong again...fuel pressure should be closer to 36-39 psi for a '85. It would be wise to recheck fuel pressure after you changed the pump a 3rd, 4th, 5th...
Last edited by stew86MCSS396; Jun 6, 2021 at 06:14 AM.
Wrong again...fuel pressure should be closer to 36-39 psi for a '85. It would be wise to recheck fuel pressure after you changed the pump a 3rd 4th 5th...
if you read my latest post from yesterday the 5th, I posted a video of what it’s doing now after a new fuel pump was installed the third time in 4 weeks. What could be causing them to fail
Problem solved!
