Hello All,

I've had a Quad Commander installed for about 8 months with the fuel pressure option and until recently have been seeing about 7psi with +/- 1 psi variations. At WOT, I never saw less than 4. The sender is the one supplied by Quad, and it is mounted in the outlet port of the fuel filter canister. The CP3 location was unavailable, due to the Jake vacuum pump.

What I am seeing now is a steady 3-4 psi reading, with no drop at WOT. Rarely, the pressure starts to read 7 psi again and sometimes it spikes to 10+ psi. I cannot relate the spikes to any conditions like low or full fuel. It will sometimes just spike for a while and then go back to a steady 3-4 psi.

I have read the threads about a poor sender ground, and also about clogged fuel filters, but the clogged filter seems unlikely because of no drop at WOT. The bad ground is possible, but I cannot see any good way to ground the sensor.

Other than this problem, the Quad Commander is great and really helps me understand the operating parameters of my truck.

Any ideas would be gratefully received.

Thanks,

 

mine is gettin the reading from the same place as you, but mine is 10psi never dropping below 8. smarty on 5. im using the quad rp/fp gauge too. for the ground, theres a bolt on the drivers side fender that i used that already had some stuff grounded to it, so i just piggy backed it and everything seems fine. i wish i could be getting my fp reading off the cp3 though

brett

 

The good news is the in tank pump does a better job than the filter mounted pump. I only get 8 at idle and can drop the 0 at WOT. Now you could try to jump the fuel relay and pull the fuel hose and see how well the fuel pump can fill a container ( volume). It does not sound like a ground problem.

good luck

 

I had the same issue with my sender. i had moved it to the FF housing to allow for a Jacobs. I started occasionally getting weird fluctuations. I ended up deciding to go with the BD Brake instead, so hoping the fluctations were a ground issue and knowing the sender worked fine when I had it at the Cp3, I moved the sender back. Now, at the Cp3, pressure is consistent again. I think its a ground issue with the aluminum housing. Maybe try running a ground wire to something steel from the sender and see if that cures it?

 

Thanks for all of the replies.

A couple of questions for those who responded:

Rusty - where did you attach the ground wire to the sender/fuel filter canister? I can see a few places to get a good ground on the other end (fender, battery).

ShortBed - I have looked in the service manual for the pressure/volume specs on the LP. Several people have written about the test procedure, but there should be a spec - like 1 qt in 10 seconds; 7 psi with engine at 750 rpm; etc. Can you tell me what the spec(s) are?

CTD - I'm wanting to keep the Jacobs, since it works great for me with the 48RE. I can't see an easy way to ground the sensor. Any suggestions?

Thanks,

 

ill take and post a pic in a little while!

brett