Trooper fuel pump fuse shorting out

dwarnock

Fuel pump fuse blew and the truck would turn over but not pick up; mechanic replaced it and it lasted ~6 months. Blew again a few months later, replaced it and the third time it blew, just a months later, we replaced the fuel pump. Expensive.
Now, 8 months later, it blows again. Mechanic replaces it and it immediately blows; he switches the relays and it works... for a day.
Blows while driving home and while waiting for the towtruck, I try to start it again and it actually started but then died out, twice (no fuel, doh). It didn't do that before when it blew...
just the turn over and no pickup.

Mechanic sez he is outta ideas...
Anyone have any ideas?
Thank you!

atfdmike

With an intermittent problem I would start looking at the wiring harness to see if it is pinched somewhere and shorting to ground. Also, the ecm needs to see oil pressure to keep the pump running, so if your pressure sending unit is bad, or intermittent, that could be another possibility, and I don't think that would cause a fuse to blow. If the fuse blows each and every time the truck quits, then I think you are looking at a pinched wire or bad component somewhere in the system.
One guys opinion.

troopermom

We've got a '91 trooper, my son drove it home on Sat and it would turn over but not fire on Sun. We've looked at fuses, spark plugs and now are thinking relay (?) Do both relays die at the same time? We've changed the fuel pump (pain in the behind)and it's been running ok. Anybody have other ideas to check along with relays? Thanks

atfdmike

Hi, not personally familiar with ignition, but if starter cranks and fuel is present then try checking igniter in dist.

Disconnect high tension cable between coil and distributor.
Hold coil high tension cable end approximately .23 inch (1/4 inch) from suitable ground.
Engage starter and check to see if spark jumps across gap. If spark is not present, check for defective ignition coil. If ignition coil is satisfactory, I would check power transistor, which is a little more involved.
The power transistor, in-line between the ignition coil and ECM, is the switch that triggers the coil. By calculating various inputs, the ECM controls ignition timing through its control of the power transistor. The ECM considers input from the crank angle sensor, throttle valve switch, coolant temperature sensor, air flow sensor and vehicle speed sensor when calculating ignition timing. I would check for loose or corroded connectors on these items as well.

thomas30

Did you ever find the problem, I have the same one. Please e-mail me if you did thomas_d_mills@yahoo.com Thanks Thomas

jdwenger

Hi, I had the same problem and figured out that the problem is with the sending unit the rubber insulation where the leads go through the plate wears out and it shorts out causing the fuse to blow. the reason that the truck will still start sputter and die out is because there are two seperate fule pump fuses one for exelerating and one for idiling or something

grabber7

How do you change out the fuel pump in a 2002 Trooper?