Need some fuel system help to fix my 85
03-18-2019, 10:06 PM
#1
Instructor
Thread Starter
Need some fuel system help to fix my 85
So I had to park my vette for awhile away from where I lived. It sat for about 2 years. Came back and it wouldnt start. I could get it to run for a few seconds by spraying starter fluid into the intake. I drained the tank by running the fuel pump thru the obd harness and , changed the fuel filter with no luck. Figured my injectors were probably plugged and I am pretty sure they were the original ones, so I just finished swapping them out with some bosch 3 24#'ers. Wanted to pressurize the system to check for leaks before I put the plenum and runners back on. turned it over for awhile and wasnt getting any fuel pressure and Im not positive, but I dont think I can hear the fuel pump running. Used the obd trick again to run the pump and I checked the pressure with my harbor frieght guage and only getting 19#'s according to it, but it wont pressurize the system turning it over. Anyone dealt with anything similar? Im guessing my next step is to replace the fuel pump and relay, but I hate just throwing parts at a problem without being sure. Does the obd jumper bypass the relay? Any tips would be great. Thanks
03-18-2019, 10:23 PM
#2
Race Director
Check for Corrosion on the fuse ,
You may want to try 2 gal of fuel with Seafoam or Techron in the fuel - pumped onto a catch bottle to flush the system . I ran it through 3 times. Mine sat for a few years the Sea Foam Worked.. Been 8 years and the pump is working fine.. good luck
You may want to try 2 gal of fuel with Seafoam or Techron in the fuel - pumped onto a catch bottle to flush the system . I ran it through 3 times. Mine sat for a few years the Sea Foam Worked.. Been 8 years and the pump is working fine.. good luck
03-19-2019, 08:53 AM
#3
Le Mans Master
Member Since: Oct 2004
Location: South-central Missouri
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I'd have to look to see what is normal fuel pressure for an 87, but you said it is low? If it is low with the motor not running, that is an indication that either the pump or one of the clamps or hoses on the pump assembly (inside the tank) is leaking.
If the pressure is low when idling, that indicates restriction to flow (e.g., filter) OR too the pump. Start with filter and then blowing out or replacing the fuel lines (if corroded).
Do a "leak down test". Turning the ignition switch to ON, w/o starting the motor, and then turning the switch to OFF, the pressure should remain within a pound for a minimum of 30 seconds (to several minutes). If pressure is not holding, that could be an injector(s) are leaking, OR possibly a check valve in the fuel pump has "gone south".
FWIW, I changed my fuel filter at 45k miles, and the sucker was choked with crud! It's about due now for another filter, I recon....
If the pressure is low when idling, that indicates restriction to flow (e.g., filter) OR too the pump. Start with filter and then blowing out or replacing the fuel lines (if corroded).
Do a "leak down test". Turning the ignition switch to ON, w/o starting the motor, and then turning the switch to OFF, the pressure should remain within a pound for a minimum of 30 seconds (to several minutes). If pressure is not holding, that could be an injector(s) are leaking, OR possibly a check valve in the fuel pump has "gone south".
FWIW, I changed my fuel filter at 45k miles, and the sucker was choked with crud! It's about due now for another filter, I recon....
03-19-2019, 09:41 AM
#4
Le Mans Master
Pressure for the 85 should be about 39 PSI. You should be able to turn the key and within 10 seconds the pump should prime the lines to 39. If your only getting 19, then as noted above there is a restriction someplace. I would pull the pump and check the filter on the pump. Blow out the fuel lines. You might need to replace the pump. Pump is easily accessed by removing the door and the rubber dam.