Community Forums

aeron · 11-07-2022, 03:34 PM

I have read previous threads about issues with the F53 fuel pumps not getting enough voltage (i.e. 7 v instead of 12).

I am having the same issue. I get 12 v coming to the fuel pump relay from the PCM but only read 7 +- at the inertia switch.

I have swapped the horn relay with the fuel relay with no joy. Horn works though

Could this be a problem with the Powertrain Control Module itself?

I appreciate any thoughts or suggestions. Especially from those that have had this issue and were able to fix it...

GypsyR · 11-07-2022, 06:52 PM

I found a "green" corroded connector on the backside of the plug that the fuel pump relay goes into on mine. I have no doubt that it was either causing an issue or about to.

For testing I bought and used a solar panel type digital gauge as an ammeter with a shunt hookup to measure what actually the fuel pump was using. So I didn't have to run back and forth with a multimeter and such, basically. After I was satisfied my fuel pump issues were over I just kept the ammeter on the dash. I don't really need to know the power draw of the pump all the time but it also reads out system voltage more precisely than the factory dash voltmeter. I also have no other use for the ammeter/gauge and it was cheap.

aeron · 11-08-2022, 06:23 AM

Thanks for the response GypsyR. I changed the fuel pump and it works fine when I hot wire 12 volts to it and the engine runs OK although it seems to be a little rich.

This vehicle sat on an RV site for a number of years without moving and then in storage for a couple of years before I bought it to restore.

I removed the fuel sending unit to extract the varnished fuel and changed the pump at that time because there was a fair bit of corrosion and I wanted to be on the safe side.

It ran OK getting the RV into the shop a couple of times but then wouldn't start and that's when I checked the voltage at the pump to find only 7.6 v.

GypsyR · 11-08-2022, 12:13 PM

In the course of my fuel pump adventures (https://www.irv2.com/forums/f23/rela...es-508562.html) I lost faith in my ground for the pump. It disappeared all the way up in the engine harness somewhere. I split it, installed my ammeter shunt, and grounded a leg directly to the closest frame rail. I only kept the existing ground wire because it disappeared into the harness and I figured something else needed it for a ground too maybe.

One thing that buggered me was debris kept flaking off the tank walls from stale gas sitting too long. I noticed when the filters clogged with the crap my pump voltage would drop, as would the amps it drew. From five amps to as low as 2.8. The engine still ran like that but it was pretty crippled to drive.