Needen$77

Hi all,

I have an issue with my 96 with a 300 in it. I had an issue with that it shut off then refired (with truck momentum)..off on off on off on. i got it to my driveway and it was dead. I was splashing thru water holes and playing on muddy hill sides. I couldn't hear the fuel pump so i figured it died. When i was rolling it to my shop to replace pump it fired for a few seconds then died again. I replaced the pump to no avail . thats when i tested the old pump with a battery and it was fine. so i started testing the relays and fuses all good (moved relays around to test, fuses with powerprobe) check inertia switch by removing and checking with meter, good. Took a little blue box out from behind my ashtray (think its the computer and yes battery was unplugged when removing) opened it up looking for any burned circuits, good. I dug thru my haynes manual with not much help. I can take my powerprobe and directly power the pump and it will fire and run. I crawled under looking at my harness and i didnt see and direct signs of damage. So my next step is to follow voltage with my probe and see if i have a bad wire or what. It has been sitting for over a year due to moving and no time so i would think if it was a water issues that should have dried out. My question is are there any more relays or modules i can check first and does anyone have a better wire schematic then the Haynes one i have.

thanks

Chris_1

iTrader: (1)

The little blue box isn't your computer. Airbag module

Needen$77

opps thats no good. Im going back thru my Haynes manual but its crap. My other truck is a 97 Powerstroke and right now it seems simpler to me

Needen$77

figured out where the ecm is. how can you test to see if its bad or if its sending a fuel signal

Chris_1

iTrader: (1)

Test light at the relay. Take the relay out. in one of the holes you should get power for 2 seconds or so every time you cycle the key (prime). You also get power there for run, but only if the engine is running (or turning, I'm not sure which). Those signals are from the computer.

Needen$77

thank you much thats the plan. i read through the wire sch and i figure if i dont get that (then check directly) its bad

Needen$77

ok check the relay socket and i have constant on one (figure thats to pump, is that true?) and i do have the 2 second power on another. o took the cap off the relay and i was able to see it cycle and move. i went back and manually powered the pump, it primed, started and ran until that prime ran out. kinda scratching my head i need a better wire sch.

question the wire that leaves the relay does it go to the pump or does it have a stop before

Chris_1

iTrader: (1)

Relay to dash switch (dual tanks) to inertia switch to pumps.
You should have 1 constant source at the relay w/ the key on, then the computer closes the relay and that power heads towards the pump (by the route shown above, more or less).
You found the 2 second prime.
The other part is if it gets a signal from the distributor that the truck is running, it lets the pump run constant.
It sounds like the prime thing is happening at the relay. You could do the manual prime thing and see if the relay closes while it's running (until the prime runs out).
If that all checks out then the computer is doing it's thing, the relay is doing it's thing so you can then go to the inertia switch and run the same test - cycle the key and watch for the prime, then make it run and watch for constant power while it's running.
If power is getting to the inertia switch, everything is good to there and the problem is further along. No power there, it's between the relay and the inertia.

Needen$77

i will check, great idea about running and checking if the relay closes.

i do have power on both sides of the relay switch

thanks

Needen$77

Havent had a chance to check with the weather. I did read thru my wire sch again and it looks like from it the +wire to the pump comes from the inertia switch but that doesnt make sence. When i was testing last a had a constant 11v at the inertia switch?

Anyone out there with a good layout for the fuel pump wiring?

When i get a chance i and going to track the wires by color from the pump forward to try and interpert the wire sch i have

thanks