Do I need a new fuel pump?
#1
Race Director
Thread Starter
Do I need a new fuel pump?
93 LT1
I know fuel pressure should be at 42psi, key on engine off.
Mine is anywhere from25-30psi, it never goes above that at key on engine off.
Weird thing is, running the fuel pressure is fine.
Idle: 36-38psi
Vacuum off FPR: 42psi
Snap throttle test is good as well.
Any input?
I know fuel pressure should be at 42psi, key on engine off.
Mine is anywhere from25-30psi, it never goes above that at key on engine off.
Weird thing is, running the fuel pressure is fine.
Idle: 36-38psi
Vacuum off FPR: 42psi
Snap throttle test is good as well.
Any input?
#2
Team Owner
Tell me how it is after shutdown. So if you turn the key on without cranking, pressure shoots up to 42. Turn the key off. Will it hold pressure for a while? What about the hose in the FPR? Does it smell of gas?
#3
Race Director
Thread Starter
Oh yeah, it hold pressure for a while. Injectors, fpr and fuel filter are about 3 years old. Fpr line does smell like gas, but it has been like that since new, and it's a part from the dealer. Don't know what fuel pressure is at load.
It's just odd that it doesn't make 42psi at key on anymore.
It's just odd that it doesn't make 42psi at key on anymore.
#4
Pro
Sounds like a voltage issue to me. When you start the car the alternator is running. Maybe hook up a battery charger to check key on pressure and see what happens. In either case I wouldn't worry about replacing the pump unless the car was running funny.
#5
Team Owner
Oh yeah, it hold pressure for a while. Injectors, fpr and fuel filter are about 3 years old. Fpr line does smell like gas, but it has been like that since new, and it's a part from the dealer. Don't know what fuel pressure is at load.
It's just odd that it doesn't make 42psi at key on anymore.
It's just odd that it doesn't make 42psi at key on anymore.
Lets try this. Use proper hose crimpers and crimp the return line. Turn the key to run and see if it gets pressure?
BTW, when you did the pump, was the pulsator replaced by a fuel hose that was rated for immersion or was the pulsator kept?
#6
Race Director
Thread Starter
Never replaced the fuel pump. Not sure if it has ever been replaced either. Car only has 84k miles. With that said, went to go start it just now, had 25psi of fuel pressure. It fired up perfectly. Have not noticed any weird drivability problems.
#7
Team Owner
Do the crimp test first and see if the feed or fuel line crimp changes anything. Crimp return line and turn the key to run. See if it gets to the right pressure. If not, have your assistant turn the key and a second after, crimp the feed line to see if it holds the pressure
#10
Race Director
Thread Starter
That is probably too low so kudos to the ECM for compensating. I'd definitely check what the stock fuel pressure is before going too far. I place NEGATIVE value on most SOTP dyno feelings. ECM compensates, you feel it is running "just fine" and one day, circumcisions force the car out of the adjustability area and we have a problem then. Usually far away from home.
Do the crimp test first and see if the feed or fuel line crimp changes anything. Crimp return line and turn the key to run. See if it gets to the right pressure. If not, have your assistant turn the key and a second after, crimp the feed line to see if it holds the pressure
Do the crimp test first and see if the feed or fuel line crimp changes anything. Crimp return line and turn the key to run. See if it gets to the right pressure. If not, have your assistant turn the key and a second after, crimp the feed line to see if it holds the pressure
#11
Team Owner
I believe the lower 2 are the vent and return line and the top which is bigger is the feed. I'd use hose crimper pliers
#12
Melting Slicks
93 LT1
I know fuel pressure should be at 42psi, key on engine off.
Mine is anywhere from25-30psi, it never goes above that at key on engine off.
Weird thing is, running the fuel pressure is fine.
Idle: 36-38psi
Vacuum off FPR: 42psi
Snap throttle test is good as well.
Any input?
I know fuel pressure should be at 42psi, key on engine off.
Mine is anywhere from25-30psi, it never goes above that at key on engine off.
Weird thing is, running the fuel pressure is fine.
Idle: 36-38psi
Vacuum off FPR: 42psi
Snap throttle test is good as well.
Any input?
Of course it failed after 10 years on a 107F day, the little woman was not happy. So I average 10 years till the fuel pump stops working...
#13
Team Owner
Nothing to do with 10 years or 107 degree weather. It was the wife. If you had been driving solo for 20 years it would have been fine. The Automotive Gods were trying to screw with you since you missed the ritual carburetor sacrifice.and that was the best way
#15
Team Owner
#16
Race Director
Thread Starter
How do I know if the FPR is not leaking? There is never raw gas in the fpr vacuum line. Always a gas smell, even with the new fpr. Injectors are 2.5 year old Bosch 3. Leakdown on fuel pressure is slow. I'll have to run another test to give an approximation.
#17
Team Owner
IDK if the pulsator is leaking since it is slipped on and old. Old stuff won't perform as new usually will. I guess if you want to buy the kit that will remove the problem, THIS is it. No running to the parts store for anything and it will come with the bolts to replace the screws you take out when removing the pump assembly. Assuming you don't strip any of them. It makes another R&R less of a scary thing.
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1993C4LT1 (04-18-2018)
#18
Race Director
Thread Starter
I've been doing the research on the racetronix 255 kit. How does all that extra wiring run through the car? I don't understand the wiring kit at all, to be honest. I know it's an option, but I don't want to risk it on factory wiring.
#19
Team Owner
First off, if you are stock, either kit is fine. The 255 kit gives you the extra room to move if you should need the fuel for whatever reason. Blower, bigger motor, nitrous, etc. It is $10 more so why not? The wiring probably runs under the car but I have the 255 but didn't get the wiring. I doubt there is a risk of it blowing up. Besides, you have the problem right now. Add more parts, introduce more variables. KISS