Mechanics

IS MY FUEL PUMP FAILING?

1998 Mitsubishi Montero • 205,205 miles

Hey Guys,

I have a 1998 Montero Sport LS with a 3.0 V6. The timing belt broke on it awhile back and the car set up for about a year or so. Well I finally decided to get it fixed. So I replaced the timing belt and idler and tensioner. Well I got the car running, started right back up ran good for about two hours. After a couple of hours of just sitting running I took it down the road and it died.

After towing it back home, I turned the key on and didnt hear the furl pump engage. So I was thinking it was the fuel pump. So I tested all fueses and wires and im getting 10.5 Volts on the plug to the pump, weird thing is im getting 1.5V from the ground? So in turn, From the hot side to the frame with my volt meter I get 12V but if I use the ground to the pump im getting 10.5 volts on the hot to the pump. The Fuel Pump relay is fine and when it engages im getting 12 volts across the coil on both sides.

I pulled the return line from the motor, couldnt get anything out. So I pulled the tank out and inspected the pump, straight wired it to the battery, it came on. So I installed it back in the tank, ran a straight jumper from ground on pump to fram turned key on and the pump runs, but constantly. Out of curiosity took the return line back of turned the pump back on, still no fuel coming out of it. So I took the line off from the fuel filter after the fuel filter and fuel flows from it out of the filter fine. Hooked it back up, tried it again, no fuel coming from return line. So I then unhooked the line again along with return and lightly blew dry air through to see if maybe somehow line got clogged, all of the fuel came out of the return line then so that ruled out that theory. Hooked it all back up except for return and turned on pump again, no fuel. So after turning over the engine so much my battery finally died so I hooked up a charger/booster. The pump will them run without the jumper while the engine is turning over, so that rules out the possibiltiy of bad crankshaft or cam sensors. Still wouldnt turn on for the 2 second initial prime.

Is this pump going bad? Is the regulator possibly bad? Only conclusion I have left is the ECM is failing
AD
Avatar
Cooldude4u2no
February 22, 2012.




What concerns me is the 1.5 volts voltage drop on the ground. That may be your entire issue. I would clean or re locate the ground and try it again before doing anything else. It needs a full 12 volts for the pump to run.

Roy

ASEMaster6371
Feb 22, 2012.
If I jump the ground straight to frame the pump runs continuously. But I'm still not getting any fuel from the return line. The pump seems to pump fuel out of the tank thru filter no prob. But it seems it won't pressure up to push fuel out of the return.
AD

Tiny
Cooldude4u2no
Feb 23, 2012.
I am curious as to what fixed the problem?

Tiny
Cooksnmrcs
Jun 29, 2013.

AD