fuel pump gone for the fourth time in 8 months

[mechjames]

Today while coming down from a ski resort, my truck stalled out. Thankfully i was able to coast it in a parking lot. The computer was acting a bit strage, sometimes the check engine light would come on in ACC, and sometimes it wouldn't. Also sometimes the tach would go up a couple hundred rpm while cranking, and sometimes it wouldn't. There was even a couple times that I think the check engine light blinked while in the ACC position without being in the self test mode.

I've reset the computer a few times, swapped relays and checked the fuses in the power distribution box.

Back in January i had my fuel pump go out on me. Changed it and a week later it went out again, changed the fuel filter and pump this time and it lasted about a month. did it one more time while changing the fuel pressure regulator and it has been fine since.

There isn't any fuel getting to the engine, but I can get the engine to run on starter fluid / carb cleaner. It sounds as if its misfiring, because back in January I ran carb cleaner through the intake and it ran smooth for about 10 seconds. Its not doing that now.

Because its nightime here and two degrees out, I'm going to see if there's power at the tank connector, and try to just apply 12 volts to the pump and see if I can get it to turn over. If it is the pump again, what other component in the fuel system could be causing the pump to stop working? The filter and pressure regulator has been changed. I'd like some ideas so I can check/change it if the pump is actually dead again.

Any help would be great!

 

[Tbars4]

....Hopefully, this should be of help..
http://www.explorerforum.com/forums/showthread.php?t=221335

 

[mechjames]

After testing today, here are the results:

-Jumped fuel pump power at the eec connector, relays click, fuel pump gets only 8 volts.
-relays have been checked and swapped in for known working relays 3 times.
-i have hooked up a fully charged battery directly to the fuel pump connector, and the truck will start and run perfect and for as long as the battery is hooked up to the pump, except for these points:

1. sometimes the check engine light will come on in ACC position and sometimes it won't. when it doesn't the tach doesn't work and I have no spark.
2. eventually after cycling the ignition switch anywhere from 1 time to 10+, the check engine light will come on, I have spark, and the truck will run.

- while running the truck with the battery jumped fuel pump, i get only 11 volts at the fuel pump connector. troubleshooting chart shows it should be within 0.5 volts of the battery voltage. the battery voltage is about low 14V at idle
- with the pump only getting 8V for the prime, its not enough to start the truck. it will try to start, but is unsucessful. when i prime it with the external 12V source, and hook the connector back up, it will run from anywhere from a few seconds to 20 seconds, provided i pump the gas pedal (its like its running on fumes, before you run out of gas)

from these points, i believe the computer is at fault. something must have shorted out yesterday. the pump is working fine when jumped to the battery. should I go find another ecm?

 

[Tbars4]

...Maybe someone else will chime in here...

...You can have a bad pcm relay, loose/corroded fuses, or a bare wire short......The pcm being bad is a last resort but it does happen..I'm also curious on your battery and cables...I have seen bad cables do these types of problems too...A bad neg cable or ground can reak havoc on the electronics...

 

[mechjames]

pcm relay has been swapped with a new one just to be sure, as well with the fuel pump relay. i've gone through all the fuses, they don't seem to be corroded, a short should blow a fuse but i doubt it would cause a low voltage problem.

battery cables look stock, but look alright. i changed the ends on them about 6 months ago, so its got clean wire to the battery. didn't look corroded when i stripped them clean.

i've also had a code 214 for a while. it could mean crank sensor, cam sensor, wiring in that circut or bad pcm itself. there's a wrecker nearby that has a engine computer for 24.95 CDN, so i'm going to try that. it might cure my 214 problems as well. its not much to lose.

at least i don't have to drop the tank for swap #4

will update later tonight.

 

[Tbars4]

...Cable end replacement are for a temporary fix and can be considered another short...

...The battery cables corrode inside the sheathing and this is not visible from the outside..This is a very common problem...

 

[cjones101812]

what is the voltage into and out of the Fuel Inertia Swt?? if it's battery voltage then you have a voltage drop between there and the fuel pump.

with you having to turn your IgnSwt up to 10times for the Check Engine light to come on have you checked the IgnSwt electrical connections and the mechanical parts of the Swt??

 

[mechjames]

i have installed the new computer, and instead of the pump having 8 volts to prime, it has 11, and running a nice high 13 like it should

i lost about 3 volts before. and my intermittent ecu power / check engine light / tach not working / no spark hasn't happened since. truck seems peppier too. wonder if I had low fuel pressure before the voltage dropped enough that it woudn't start up right.

i still think the connector has some issues. i've bypassed it right now with some quick connect connectors, but while i did that i grounded out positive by accident to the frame, and blew the small 20amp in the power distribution box. i know this wasn't blown before, because I had voltage at the back, and after it grounded out, i had none.

does the ecu regulate voltage/amperage to the pump? its running perfect now, even better then when i bought it.

 

[DeRocha]

I would just like to add some additional troubleshooting info In case others come across your thread.

To confirm the pump is no longer getting power check the fuel pump inertial switch located below the glove box. Pull back the carpet behind the glove box and find the fuel pump inertia switch (pictured below). Use a meter (or test light if thats all you have) and connect either wire of the switch to HOT, and then ground the meter to a suitable ground. The meter should read 12v when the fuel pump is running and ~7v when its not.

As you may already know the fuel pump will only run when given 12v... When you turn the key from run to start the inertia switch (pictured below) will see 12v for only 2 secs or while the tac registers > 0 RPM. After 2 secs of zero RPM the computer will shut off the fuel pump relay and you'll only see ~7v at the inertia switch and fuel pump. Seeing 7v is weird but that is what you'll get if you check the wiring.