Tywi

Hi, so yesterday I was testing my fuel pressure and I had around 40 psi when the pump was running then it quickly dropped to 0 when the power was cut, turned out to be the fuel pump oring. Today I installed the new oring and now have 0 fuel pressure.. I thought it could be a clogged filter so I tested right at the feed outlet of the gas tank and plugged the other end of the pressure tester, still no luck. There is fuel flow just really low pressure.

OG BBF

have you tested voltage at the pump when running?

$lacker

iTrader: (9)

It would be appear to be the connection between the new pump and the fuel line in-tank
When I replaced my pump, I didn't pay sufficiently close attention during disassembly and therefore found reassembling the little pieces at the junction a bit confusing. If that area is not tightly sealed, you would have flow but no pressure.
This is assuming you didn't disassemble another area of the fuel system as well

Tywi

That's the reason I changed the o ring. After I changed it I tested by blowing into the fuel feed nipple and couldn't blow into it, but I was able to draw air from it. I also tested the voltage but wasn't sure which pins to test, depending on which I tested I got battery voltage.

Tywi

So I tested the voltage and it was around 4 volts with the pump running, I'm guessing this is the problem. I checked the fuel pump ground, tried bypassing the speed relay, and tested the fuel pump resistor with no luck. Anything else that could cause low voltage? The voltage going to the sensor in the tank is battery voltage.

OG BBF

most likely a wiring issue along the circuit. If I was you I'd do the relay mod so the pump sees 12v directly from the battery and see if this cures your issue which most likely it will. Then it's a case whether you want to follow the circuit to try find where the problem lies or just leave it running off the battery/relay setup.

Grab a 4pin relay, hook up terminal 30 direct to the battery (fuse the wire 30amp/40amp will be ok) terminal 85 to a clean ground on the chassis. Now if you look at the wiring that goes to the plug on top of the pump there will be a thick white/red stripe wire. Cut this in half leaving plenty wire length either side of where you cut. Hook the loom side of the wire you cut to terminal 86 and hook the wire that's on the pump side to terminal 87.

if you still have issues once this is done, check the in tank wiring to the pump it's self for any issues.