Fuel Pump Voltage
Thread Starter
Instructor
Joined: Sep 2000
Posts: 229
Likes: 3
From: NJ
Fuel Pump Voltage
I have a modified '88 coupe that seems to be having some fuel related issues. I have a fuel pressure gauge on an aftermarket fuel pressure regulator up front.
It usually reads 40-45psi at idle or when the pump primes the system prior to starting. I've had an issue where sometimes the fuel pump doesn't prime the system. Everything else is working.
The fuel pump setup is the stock in tank pump with a booster pump mounted just outside of the tank at the rear of the car. It appears to be powered off of the same small wires that powers the stock pump.
When the pump primed the system (engine off), it was only getting about 9.5V ... and about 10-10.5V with the engine running.
QUESTIONS:
Is this normal?
It seems low to me. Probably a voltage drop issue. If so, would 8-10 gauge from the battery be sufficient?
The only other thing that could be happening is that one or both pumps is going bad.
What do you think?
Thanks,
-JRW
It usually reads 40-45psi at idle or when the pump primes the system prior to starting. I've had an issue where sometimes the fuel pump doesn't prime the system. Everything else is working.
The fuel pump setup is the stock in tank pump with a booster pump mounted just outside of the tank at the rear of the car. It appears to be powered off of the same small wires that powers the stock pump.
When the pump primed the system (engine off), it was only getting about 9.5V ... and about 10-10.5V with the engine running.
QUESTIONS:
Is this normal?
It seems low to me. Probably a voltage drop issue. If so, would 8-10 gauge from the battery be sufficient?
The only other thing that could be happening is that one or both pumps is going bad.
What do you think?
Thanks,
-JRW
Team Owner
Joined: Sep 2003
Posts: 25,413
Likes: 2,745
I don't quite understand your "tandem" install of the fuel pumps. Seems quite restrictive I'd think regardless of the voltage you supply to them.
You do need to sort the power (12V) and the wiring but I'd think the entire fuel system needs maybe rethought. Perhaps I'm missing something here but you've actually supplied limited information so .........
If both pumps are running from the single source of power wiring there's no doubt you'll have issues.
You do need to sort the power (12V) and the wiring but I'd think the entire fuel system needs maybe rethought. Perhaps I'm missing something here but you've actually supplied limited information so .........
If both pumps are running from the single source of power wiring there's no doubt you'll have issues.
Thread Starter
Instructor
Joined: Sep 2000
Posts: 229
Likes: 3
From: NJ
I ended up running a separate 12awg to a new relay and everything seems to be fine. My guess is that the stock 16awg wiring is not large enough to support the larger fuel pump.
Will post back if I run into further issues.
-JRW
Will post back if I run into further issues.
-JRW
Burning Brakes
Joined: Feb 2002
Posts: 804
Likes: 5
From: Fresno CA
That is pretty typical. I installed this kit from Racetronix and it raised the voltage back at the pump to alternator output voltage.
http://www.racetronix.biz/itemdesc.a...%2D013&eq=&Tp=
http://www.racetronix.biz/itemdesc.a...%2D013&eq=&Tp=
