fuel problems

[eclipseguy]

So I was on my way to the dump with a load of trash. Then my tuck just dies no warning no sputter just dead. I got a tow home and started working on it. I started with checking the fuel presser valve( no pressure). Then i realize the pumps are not turning on..... (both of them). I then changed the fuel pump relay with a spare i had. Tried to start it again and nothing no fuel..... so upset with it. i go in side. I get home from work and thought i would try starting it and it cranks right up........ what the heck.... any one have any ideas....... thanks for your help

 

[IMenriched]

does it start cold?? liker after it has sat over night??

there is a Fuel pump relay that could be bad and a inline fuse before the relay...these power the Fuel pumps

then there is the ignition module, or TFI...it also has fuel pump control to it as well....reason for the 1st question...it's classic sign of the TFI going bad when it shuts off, suddenly and restarts later....but still needs to be checked

 

[eclipseguy]

yeah it satarted after i got back from work the next day... i have not checked them....

 

[eclipseguy]

truck died agian today. same thing no warning.

 

[IMenriched]

truck died agian today. same thing no warning.

really hints that it's a TFI (ignition module)...it can be removed and tested

 

[BillRod]

I just went through something similar with my son's 88.

Turns out it was bad wires in the wiring harness, right behind the power steering pump.

I went through all the diagnostics on the pumps, relays, inertia switch, grounds etc etc. I got a lot of help here with things to check and look for but could not find any faulty part. I even replaced the FPR, (only $14 @ Checker)

I finally traced the power wire from the front pump to the connector near the master cylinder, (kinda looks like an old fashioned barrel fuse holder, Gotta squeeze it to pull it apart) I had continuity between the pump and the connector.
Then I tried the ohm meter between that connector and the inertia switch connector by the air filter box and had no continuity.

I started to unwrap the wiring harness under the master cylinder where all the connectors are and found the power wire for the pumps was broke inside the insulation.
I also found a bunch of other wires that were broke or worn through the insulation. I guess I'm lucky things did not short out and take out the computer.

There's nothing right there that looked like it would rub against the harness to compromise the wires but I guess after 20 years....

I would suggest tracing the power wire from the front pump up to that connector then over to the connector by the fuel pump relay/air box.
That one is a gray 2 prong that connects to the intertia switch inside the cab.

Let us know how it goes.

Bill

 

[eclipseguy]

so the tfi was not the probplem... so tomorrow im going to trace the wires

 

[Big Jim M]

ignition modules are known to fail when hot and go again as they cool.. I once drove 300 miles with bags of ice on my module.. It kept going just fine thataway. Changed it the next day at home.
Big Jim

 

[eclipseguy]

i changed the tfi out and it still did the same problem.... but i got thinking how would a thing that controls spark tell the fuel pump to stop pumping. cuz when it dies the pump dose not turn on....

 

[IMenriched]

i changed the tfi out and it still did the same problem.... but i got thinking how would a thing that controls spark tell the fuel pump to stop pumping. cuz when it dies the pump dose not turn on....

If everything else is working.....the TFI does control the Fuel pump connection too. found this out by leaving the key on and then unplugging and plugging in the connection on the TFI and the fuel pump primed again every time I reconnected the TFI.


considering that you have a new TFI in....it maybe the relay for the fuel pump.

you should be able to hear the Fuel pump prime every time you turn the key just to the on position, (not all the way to the start).
If that is not being heard then back track to wards where the power is getting supplied....considering it is intermittent, hints...toward the relay

 

[eclipseguy]

OK so I was looking up on other post that had a similar problem. I realized that when i replaced the "fuel pump relay" i actually replaced the EEC relay. lol so i took the new one off of the EEC and put it on the fuel pump relay and it started right up. then i took the new fp relay and put on the old one and the truck would not start. I redid that test about 3 times and got the same results....... so i figured i found the problem. but then i was showing my friend what i had done. I put on the old one and it started right. my thought is the really is bad. it just needs a vibration to wiggle to get the inerds to work again.... I HOPE.... thanks for your guys help .... will post if it was not the fix.