Double D

I just bought an 88 pickup that seems to have a bad fuel pump. I drove the truck home with a soaked rag of fuel in the airbox and the truck runs like a champ. I'm searching for info on how to jump the fuel pump and see if it works before I pull the one from my 86 fora swap. I am looking for the fuel pump wires to run a 12v b+ to see if it works. I have been reading but it seems as though others have succeeded in fixing their problems with less info. Thanks in advance.


1-21-11 UPDATE: I have the truck running but still have a problem and need help. please skip to end of thread. Thank you




UPDATE-------

recap-

truck will run with pouring fuel in manually

with jumper on b+ and FP - truck will idle for 2 seconds and die

no jumper - engine will crank but not turn over.

with jumper - fuel pump runs in key on position.

no jumper, no fuel pump noise.

COR does click nice and loud back and forth with key toggle on and off

1-12-11 UPDATE PLEASE jump to the end of the thread as most of the problem solving and information on page 1 has been ruled out. here is where i am:


last night I changed the fuel filter. Same problem. However I do not throw any more codes.
I drained and dropped the gas tank, pulled the fuel pump and bench tested it.
I have solid 12 volts inside and outside the tank at all contacts.
Pump spews fuel like a super soaker water gun
tank now has new fuel.
i have good flow of fuel all the way up to the fuel filter
All my hoses and vacuum lines are in good shape (almost brand new) so I wanna say its not a vacuum line.

xxxtreme22r

how does an soaked rag of fuel in the air box provide more fuel to the engine?

If anything it restricts air flow to the engine which means it needs less fuel to run, but i don't see how less air and less fuel allows an engine to run better.

I've done some crazy stuff to keep an engine running but that one has never crossed my mind.


on a side note, downloading the FSM for your vehicle will tell you how to jump the fuel pump. Or at least it should.
http://www.ncttora.com/fsm/

4Crawler

iTrader: (3)

Might give the fuel pump test jumper a try:
- http://www.4crawler.com/4x4/CheapTri...shtml#FuelPump

Double D

I have unplugged the harness under the pass side of the step rail by the edge of the seat. Yellow harness with blue wire (should be fp+ and white/black wire should be FP ground) I get 12v to the blue - white/black on the car side of the harness with key in crank position without actually cranking. (clutch out) I'm assuming thAt this means my electrical system is working properly and its the fuel pump that is bad. Is this logical and i'm I testing the correct wires.

4Crawler

iTrader: (3)

Well, hard to say for sure. That says you are getting 12 volts under no load (i.e. no current flowing). But under load, that voltage may drop as the motor current tries to flow. If the circuit opening relay contacts are pitted or if the wiring has a marginal connection that might happen.

xxxtreme22r

assuming it's the wiring as 4crawler mentions, look at your fuel pump wire connection at the tank, they could be pretty well rusted.

Double D

Hey xxx with 6000+ posts i'd think youd understand that when trying to make it home a couple miles away and pouring gas with no rag into the airbox, an 8th of a mile is about as far as you get. With the rag, (not stuffed in there just neatly placed) and the same amount of gas you can go a WHOLE mile or more. And by the way, with the rag in place, truck runs like a CHAMP. So rather than placing your face in hands in disbelief, do it in shame.

FSM ----- Downloaded.

4crawler ------ THANK YOU. Probably the most detailed bit of info so far.

Double D

yes the harness was unplugged so the fuel pump was out of the loop if i understand what your asking xxx. I think

Double D

who woulda thunk if I opened the DIAGNOSTICS cap i'd see FP and B+. LOL
I LOVE FORUMS

xxxtreme22r

so the motor has enough suction in the air tube to draw the fuel from the fuel soaked rag up the air tube into the throttle body, down the intake tube into the motor? all while properly distributing the fuel equally into each cyl? With a draw through turbo setup I can see that.

Double D

Thanks XXX and 4crawler. I dont mean be a D I CK but the rag thing does work.

Double D

Not the rag, just the fuel.

xxxtreme22r

haha yeah, I edited that, because the first time sounded like I said the rag was sucked up. (which can be a possibility though) haha.

Double D

ok so with b+ and fp jumped and yellow harness under pass seat back together, it turns over for a half second and then dies. I turned it over a few times to see if it could be fumes from having the RAG in the box prior. (it is out now) Before, it would just crank without turning over. ???

xxxtreme22r

I would think with it jumpered and not running the fuel pump is not getting the required power.

If I understand that jumper properly your basically taking the ecu among other things out of the control loop and applying full time 12V to it.

xxxtreme22r

is there a resistance check you can do to test the fuel pump directly? I would start at that same connector you used earlier to test for voltage and test the continuity there and then again directly at the fuel pump connectors at the tank. In that order. If there is a big difference then you will know it's a problem within that stretch of wiring. Possibly like I said earlier with the connectors on the top of the tank. If there is no difference then the fuel pump is most likely bad.

Double D

also, with the jumper, i can hear the FP running if I stick my head down by the gas tank. I can get it run for a sec but only if I dont push the gas pedal

Double D

So your saying that even though fuel pump "sounds" like its running consistent, it still may be bad? And having a jumper, does this eliminate the AFM being a possible problem?

xxxtreme22r

will it idle at all without the gas pedal pressed?

I want to say yes, hopefully 4crawler can confirm so don't quote me on that.

On a side note, for instances like this I am so glad I have a carb'd truck. Working on our BMW is bad enough. haha.

Double D

And with the fuel pump running, I can hear liquid splashing around in the tank. But nothing seems to be spilling. I just bought the truck and when I start it (rag in place) and get going, the fuel gauge will slowly rise to about half tank. Could I actually be out of fuel or is the gauge true.