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RVing message boards => Tech Talk => Topic started by: F53ultrasport on October 03, 2017, 06:32:24 PM

Title: F53 fuel pump voltage and grounds
Post by: F53ultrasport on October 03, 2017, 06:32:24 PM
  First of all. Im new. Great info. Im going to save lengthy backstory for now. 1997 F53. Replaced fuel pump and filter. Starts and runs. Has 30 psi fuel pressurs at idle, pressure drops to 20 and teens as you drive it and it sputters and backfires. Gets worse the longer it runs til it will no longer move. Does anyone know what the voltage is supposed to be at the pump connector?

I measured around 6 volts with what i thought was a good ground at the frame. My thinking is that the pump needs closer to 12 volts to put out max pressure. I assume there is some voltage drop on a 35 foot coach, but not 6 volts drop.. Also, i have checked and cleaned the grounds at the engine block and frame rail at the passenger side front of the coach. It did not raise the fuel pressure.

Does anyone know if the pump is grounded else where besides the front?

I know there is a ground in the connector, but i thought that ran to the front near the battery and engine block where i just cleaned with a dremel.

I am going to run a wire from battery direct to pump and see what happens with the pressure.

Is it possible that the voltage supplied to the pump is supposed to increase as the throttle is opened and maybe 6 volts giving 30 psi fuel at idle is normal.


Thanks in advance for your ideas.
Title: Re: F53 fuel pump voltage and grounds
Post by: jubileee on October 03, 2017, 11:50:18 PM
Pressure is controlled by fuel pressure regulator. Located on fuel rails near front of engine. Pull off vacuum hose and if gas is present, regulator shot. Been a while since I checked one, but I think if the regulator is good and you pull the vacuum hose off at idle,the pressure should go up.
Title: Re: F53 fuel pump voltage and grounds
Post by: rls7201 on October 05, 2017, 07:58:06 PM
There is a fuel pump relay in the fuse/relay box, under the hood. It's possible the relay contacts are bad. Thus the low voltage. You should have 12+ volts at the pump. It's a standard Bosch style relay. Swap it with one of the other relays and see what happens.
Did you change the fuel filter on the left frame rail?