Totally Confused
Postmaster
Joined: Oct 2003
Posts: 4,516
Likes: 1
From: SoCal
When you turn the key to run the computer grounds the wire from pump relay & turns on the pump circuit..
If he runs the jumper as shown at the link & the pump runs, the problem is a break in the wire between the computer & the relay or a bad computer or no power to the computer.
If he runs the jumper as shown at the link & the pump runs, the problem is a break in the wire between the computer & the relay or a bad computer or no power to the computer.
Senior User
Joined: Oct 2005
Posts: 145
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From: ventura, CA
Are there fuses anywhere for the computer that may be blown? I agree with Jbabbler - it sounds like your ECU isn't alive, hence isn't firing the injectors. The spark control module works independently which is why you're getting a spark, and you've confirmed your pump works fine. You don't have a "pump isn't turning on problem" - your pump isn't turning on because your ECU isn't happy about something (sensor), is dead/bad, or isn't being powered.
Thread Starter
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Junior User
Joined: Feb 2004
Posts: 54
Likes: 0
ok this just happened out of the blue. before i replaced the pump the first thing i checked was the fuel cutoff switch so thats no the problem. and i run a 12v jumper wire within the fuel pump relay the fuel pump runs and when i crank the engine it still runs and still doesnt start. and yes now with the new pump i get 40psi with the old pump i got 22psi and the reason i posted it twice is that im just really wanting to get it fixed. and taking it to the shop is not a option. thank you guys for all the imput even though i kind of make it confusing. thanks 
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Joined: Apr 2004
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New User
Joined: Dec 2005
Posts: 3
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From: Near Waterbury, CT
Similar issue in 88 F-250 5.8 L
Originally Posted by mike_23us
ok this just happened out of the blue. before i replaced the pump the first thing i checked was the fuel cutoff switch so thats no the problem ...snip
Originally Posted by mike_23us
<snip>... and taking it to the shop is not a option. thank you guys for all the imput even though i kind of make it confusing. thanks
(This is my first post to FTE, please bear with me if I didn't post properly
)I've checked my EEC Power Relay and Fuel Pump relay and they're good (also installed replacements before I tested the old ones on the bench -- no success in starting/firing off the fuel pumps).
I think the fusible link (the heavier brown wire with a little yellow stripe) is good going to the EEC Power Relay, but I have a sneaking suspicion that the wire is damaged in the harness. Tried to do a continuity test through the insulation just after the fusible link to the relay wiring harness, but I can't do it myself. I have to get somebody else to help me make sure it's a continuity problem.
I'm relatively new at vehicle electrical wiring. I dont see any breaks where I can see the wire, but is it unusual to have wires break in the wiring harness in a vehicle that's 18 years old? The harness seems to route from the starter relay over the radiator, under the coolant recovery & air cleaner and then it's very difficult to trace it after this. when it gets near the firewall and ECM.
Thanks
-Jim
- Side note for testing relays: I applied about 5.5 V from batteries to the relays' small pins and heard the relay close the circuit for the big pins. I then measured continuity across the big pins. I needed alligator clips to do this by myself. I believe the computer fires the relay and usually it delivers about 5V DC so that's why I did the 5.5 Volts with a couple of D cells in series.
</snip>
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Post Fiend
Joined: Dec 2001
Posts: 10,562
Likes: 4
From: South Jersey
Jim,
It sounds like you tested the relay OK. With a vehicle that old a wire could get damaged, even in a harness.
We have a forum for F series trucks, they may know if this is a common problem, see the link below.
https://www.ford-trucks.com/forums/f...splay.php?f=28
It sounds like you tested the relay OK. With a vehicle that old a wire could get damaged, even in a harness.
We have a forum for F series trucks, they may know if this is a common problem, see the link below.
https://www.ford-trucks.com/forums/f...splay.php?f=28
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