fuel delivery
Thread Starter
|
New User
Joined: Dec 2006
Posts: 14
Likes: 0
fuel delivery
ok so here's the score. the problem is in an 88 2.9l. my fuel pump works when it wants to. after the truck has sat for a day or two i can usually start the truck up with no complications, it idles great and for extended periods of time. when i try to drive the truck, it will go less than a block before it dies and the pump will no longer come back on. since its an old truck i replaced the in-tank unit and the problem still persists. on a side note i hooked my old pump up to a 12v battery and it ran just fine. i'm thinking there is a kink in my electrical system that is switching the pump off. pressure at the rails, dirty filters, or bad fpr's should hold no bearing on simply turning the pump on. does this sound like a bad relay. and if so where is it because the haynes manual sucks. also i should be able to bypass it if somebody could tell me which prong outlets to jump.
Thread Starter
|
New User
Joined: Dec 2006
Posts: 14
Likes: 0
Also to add to the list of culprits, my fuel gauge which previously worked fine has taken a crap on me. could this compounded with my screwed up fuel pump be an indication of a bad fuel pump/fuel gauge sender, and where can i find it to test it.
Posting Guru
Joined: Sep 2004
Posts: 1,915
Likes: 1
From: Yokosuka, Honshu, Japan
you may have messed up the wiring when you replaced the in-tank pump. also could be a fuse that's blown due to messed up in-tank pump install. as far as the running issue goes, it sounds like you may have a bad TFI module that's not firing your fuel pump circuit(s). I can't remember if the '88s had both in-tank and under-frame pumps? You may want to check the entire fuel system out as well as pull some codes. autozone.com repair guides have info on the fuel system as well as wiring diagrams.
Thread Starter
|
New User
Joined: Dec 2006
Posts: 14
Likes: 0
the tfi module was checked at autozone. it repeatedly passed every single test they through at it. as far as the bad wiring on the fuel pump...my dad wired it up while i was at work, and knowing his temperment and attention to detail, i seriously doubt it was wired wrong. Plus the truck is reacting the same way it did with the old factory fuel pump, which still works fine when given 12v. this is leading me to think that the issue is not associated with the in tank pump, but rather an electrical issue. also just for my own curriosity when the pump isn't pumping, there is an audible click coming from inside the tank. what is that noise i'm hearing.
Postmaster
Joined: Dec 2001
Posts: 3,742
Likes: 2
From: UT
TFI modules have a way of only failing when "warm," which means they will check out just fine when "cold" Your case seems pretty extreme for that kind of thing though.
Fuel pump and the fuel gauge having problems at the same time sure makes me think something is wrong in the wiring. I know it's not a "magic bullet" answer, but sometimes the best answer for something like this is the tedious answer. Get a voltmeter and a wiring diagram. Start at the battery and work down the fuel pump circuit until the voltage drops (have the fuel pump test lead in the self-test connector grounded so the relay should be closed). The problem in the circuit is where the voltage drop is.
Fuel pump and the fuel gauge having problems at the same time sure makes me think something is wrong in the wiring. I know it's not a "magic bullet" answer, but sometimes the best answer for something like this is the tedious answer. Get a voltmeter and a wiring diagram. Start at the battery and work down the fuel pump circuit until the voltage drops (have the fuel pump test lead in the self-test connector grounded so the relay should be closed). The problem in the circuit is where the voltage drop is.
Posting Guru
Joined: Sep 2004
Posts: 1,915
Likes: 1
From: Yokosuka, Honshu, Japan
Also, worst case scenario is that the TFI module could be sending the proper outputs to the computer, but the computer may not be firing the fuel pump relay. Reason why I'm suspecting a wirirng issue and/or the TFI module is the fact that you can start it up, but once it's idled and gotten warm and you get going down the road only a short distance... well, you get the idea. You may want to consider both checking the fuel system electrically as well as pulling codes. Also, the fact that you said your fuel gauge worked before the in-tank pump was messed with also leads me towards checking the wiring to the tank. You should also check every electrical connection in the engine compartment as well as checking to see if the TFI module is tight on the distributor and has the heat sink grease on there and PLENTY of it. Also, read this thread on a "similar" issue: https://www.ford-trucks.com/forums/5...ont-start.html
Senior User
Joined: Apr 2003
Posts: 385
Likes: 0
Heat not an issue on such a short trip
It was stated above that you have two fuel pumps. The low pressure is the tank pump that you replaced. The other high pressure fuel pump is below the drivers door on the frame rail. Turn the key and see if it runs when you stall out.
My TFI didn't fail after 180k miles, and I used it in scorching off road conditions. However my pick up coil in the distributor did fail and it was heat sensitive. Even so, it still required 85 deg days running the AC and such to appear. The distributor has to be removed to replace this $20 part, and you will have to re time your ignition. Just passing along possible causes. Check the high pressure pump first.
Good luck.
My TFI didn't fail after 180k miles, and I used it in scorching off road conditions. However my pick up coil in the distributor did fail and it was heat sensitive. Even so, it still required 85 deg days running the AC and such to appear. The distributor has to be removed to replace this $20 part, and you will have to re time your ignition. Just passing along possible causes. Check the high pressure pump first.
Good luck.
Trending Topics
Posting Guru
Joined: Sep 2004
Posts: 1,915
Likes: 1
From: Yokosuka, Honshu, Japan
The thing is, if it were a fuel pump / pressure issue alone, it would never start and idle that I'm aware of. Somewhere there is an electrical issue causing the high-pressure in-line pump to shut off, which would also shut off the low-pressure in-tank booster pump as well. I just noticed there was something in a previous post about clicking in the tank? I would seriously investigate that, as it may mean there is still an issue with the in-tank pump / sending unit. I would also investigate the distributor and TFI module as well as all of your relays. Could be something as simple as a relay problem as well. You could probably track it down by connecting a voltmeter or test lamp to the inertia switch when the problem duplicates. If the voltage goes away or test lamp goes out, that would probably point more upstream in the circuit (relays, ECM, etc.) than down, however, if one of the pumps is shorting / grounding out, that would also cause issues, but should blow a fuse, but could cause relay issues as well.
FTE Stories
Ford Trucks for Ford Truck Enthusiasts
Top 10 Fords at 2026 Carlisle Ford Nationals
Joe Kucinski
3 Best / 3 Worst Parts of Modern Ford Ownership
Brett Foote
10 Amazing Upgrades That Solve Common Ford Truck Owner Headaches
Pouria Savadkouei
Every 2026 Ford Engine Explained
Brett Foote
10 Ugly Ford Trucks That We Still Kinda Love
Joe Kucinski
10 Things Every Truck Owner NEEDS (2026 Edition)
Michael S. Palmer
Rezvani's Latest Post-Apocalyptic Monster Is a Ford F-150 Raptor Underneath
Verdad Gallardo
Top 10 Most Expensive Ford Trucks Ever Sold on Bring a Trailer
Joe Kucinski
2027 Ford Super Duty Buyer's Guide (Every Model, Engine, & Package)
Brett Foote
Rub my Belly
Joined: Jan 2004
Posts: 3,093
Likes: 1
From: Lawrence, KS
Something simple to check also would be a ground wire. There is a black wire that is grounded (near the battery) on the radiator core support and goes to a black cylnder type conenctor. If it is unplugged or has a bad connection it will not start. I'm not sure if it's the ground to the fuel pump relay and other electronics or what but I do know that if it is unplugged that the high pressure fuel pump won't work. Just a thought.
Thread
Thread Starter
Forum
Replies
Last Post
Tim Hodgson
1987 - 1996 F150 & Larger F-Series Trucks
3
Feb 12, 2015 09:56 AM
lovemy150's
1999 - 2003 7.3L Power Stroke Diesel
5
Jun 7, 2014 05:59 AM
streetlude95
1987 - 1996 F150 & Larger F-Series Trucks
7
Mar 6, 2012 05:23 AM
Chickenmantoo
Bronco II
1
May 6, 2002 09:55 PM
