Hello again, Here's my situation... Getting the Banana ready for it's smog test appt at the shop last night (it WAS today) Check engine light had popped on and it had been starting to sputter and surge at the idle occasionally for the last few days so I took a look at the MAF and saw dirty wires. Aha I can fix that, a couple squirts of MAF cleaner, plug it back in and voila! No more light, the Banana ran down the road around the block, over the hill and through the dale like a champ. I shut her down and call it a night.
This morning, hop in and fire the Banana up like usual and all I get is a nice peppy crank over. The Banana has had a bunch (pun intended) of new parts throw at her recently... new battery, starter solenoid, plugs and fuel pump relay and fuel filter. All within the last couple of months.
Out of complete disbelief, I ground on the ignition for a little while and she finally kicked over and sputtered to life. I let her idle a couple of minutes and things seemed fine so off we go. I make it about a block before the Banana starts hiccupping and bucking like something possessed and dies.... kaput.
The Banana has a 3.0, manual transmission and at least half a tank of fuel. Long story short and a tow truck ride home again, half a day trying unsuccessfully to pull a code, any code.... nothing. She will half-heartedly cough and spastically run with ether shots and near as I can tell I'm not getting fuel to the fuel rail relief port. I'm really hoping there is some way to diagnose a faulty fuel pump without having to drop the tank and fish the damn thing out.
I'm not hearing it run when the ignition is turned on but then again I don't think I've ever heard it run. Can you suggest any other things to try before I replace the pump itself???

 

Maybe get a second set of ears down closer to the pump to listen as you cycle the ignition...

 

Thank you for the suggestion, yes I had the husband listening and then he turned the key while I did the listening... I'm still hoping the fuel level isn't low enough to expose the pump, but it's probably unlikely to muffle the sound much. The fuel pump very well could have been going bad all along, causing the intermittant sputtering and surging symptoms the Banana has been showing...
I really don't want to have to drop the tank, lol... it's a midship mount in the extended cab body style. The Banana is a 2 wd and is lifted, which is a plus. Has anybody dropped one of these tanks without too much trouble? For some reason I'd rather pull an engine then drop a tank, must be a girl thing....

Is it pssible to add an external fuel pump between the tank and the engine, maybe in line with the filter that is mounted under the cab in the frame??? That way I can just leave the one in the tank alone

 

If you can't hear the fuel pump run, check the in cabin fuel pump inertia cutoff switch, located in the passenger side floor board, on the firewall just above the carpet line.

Check to see if its electrical connector is properly plugged & locked in place, or if it has been kicked by a size 12 & tripped & its little red post is sticking up, or maybe it has a corrupt internal connection (some have been reported to be defective), so thump it to cause it to trip (the little red post atop the switch will pop up), then push it down to reset it in a new contact position & listen for the fuel pump to run for a couple of seconds & cut off at KOEO, before you crank the engine.

If no joy, try thumping the fuel pump/tank with a broom handle, or thump the bottom of the tank & listen for the pump to wake up.

If still no joy, since you have the extended cab, look underneath the cab, drivers side about where the drivers seat is, for where the wiring harness feeds through the floor board. There is a TSB out for chaffed/broken wiring there, that'll cause your kind of intermittent problem & Rockledge has a post with photos of his super cab wire repair.

If still no joy & you come to suspect the fuel pump has gone belly up, its said by those that have done this, that its easier to unbolt the bed, unfasten the fuel fill neck, unfasten the rear taillight wiring harness, remove the tailgate to make things lighter & slide the bed back to rest on the rear tires, or saw horses & rear tires, so you can access the fuel pump from atop the tank, without having to empty & drop the tank. This would also offer good access to the fuel pumps electrical contacts, so maybe consider doing another thump/wiggle test on the wiring, maybe rig a ground wire jumper for the pump, just to make sure it isn't a corrupt wiring, connection, or ground problem before replacing the pump.

A bunch of thoughts for pondering, let us know what you find.

 

You are my hero Pawpaw, some outstanding suggestions that I am going to print out and implement immediately. I think the idea of removing the bed to access the tank is sheer genius for one, but the wiring very well could have issues as I've aleady had to repair other places that have corroded or have suffered some sort of abuse. The gauge is still functional so I know some power exists in the sending unit...

 

Finally found the post by Rockledge & in there is a link to the TSB, although it pertains to 98-99 super cabs, if yours is wired the same way, it might be worth a look, if you find your having a voltage drop to the fuel pump at the tank.
https://www.ford-trucks.com/forums/3...und-today.html

Keep us posted on your trouble shoot.

 

Ok I am up too late after working the night shift but the Banana taking a siesta on me and making me have to fire up the big dog (1974 F250 4x4 with a 460 draining the tank at 7 mpg) to get to and from work is going to get old in a hurry!
I thought I should report what I have found so far in my diagnosis. So far no joy has been found. I've tapped and thumped and had to restrain the impulse to bludgeon the bloody hell out of various parts of the tank and/or truck in general and the pump has no inclination to sing that I can determine.
The wiring has been painstakingly tracked from stem to stern and it's actually in decent condition with no breaks or pinches. The fuel cut-off switch is right where it should be and had not been tripped. Connectors are all seated securely, no fuses are blown or burnt. Relay clicks and still not a whisper of pressure at the fuel rail relief valve.
I am going to rig a ground wire jumper to see what happens there next .... Just ran out of day to do what needs to be done... Thanks again for the great brainstorming .... I'm still hoping I won't have to drop the tank OR pull the bed ultimately but hopes fading fast lol!

 

OK, good drill down trouble shooting & feedback. Considering the vintage of this ride & you saying some of the wiring has been messed with, Murphys Law may be in play here, so a couple more thoughts that are easy to check came to mind. I forgot that your 91 has the fuel pressure regulator under hood on the fuel rail, so while your at it, pull its vacuum line to make sure its dry/Not wet inside with fuel. If its wet inside with fuel, the fpr diaphragm is leaking fuel into the vacuum line & that'll end up unmetered in the intake manafold to be ingested by the engine & mess with fuel trim, so in that case the fpr should be replaced. Yah I know, you said the fuel pump isn't running, but when it does, if the fpr IS leaking it'll corrupt fuel trim.

Second thought is the fuel pump power relay, even though you can hear it "click", doesn't mean its passing under load current through its contacts to the fuel pump without voltage drop. So use your multimeter to back probe the in cabin inertia switch electrical connector, to ground, to measure under load B+ voltage when you go to KOEO.
If you have B+ without voltage drop that point, it'll indicate the fuel pump power relay & wiring are ok that far & there isn't much wiring remaining between the inertia switch & fuel pump, so that check point gets most of the fuel pump wiring & electricals tested.

As I indicated in a previous post, if you come to suspect the fuel pump, after moving the bed back for access, you could do one more inspection & voltage drop test AT the fuel pump electrical connector thats atop the fuel tank, before removing the pump, just to make sure there is no voltage drop between the in cabin inertia switch & the fuel pump electrical connector & check that its pins/sockets are clean, without corrosion & tight fitting.

If all that checks out, Then pull the fuel pump. Let us know what you find.

 

Ok so yesterday I had some time to crawl under the Banana and see what I could find. Found and eliminated one annoying slow drip from the pan (loose bolts) and I checked for any loose plugs or bad sections of wire. No joy. I did discover a blown fuse under the drivers side carpeting, 20A, replaced it but still not sure where it goes. Finally decided the pump isn't healing on it's own so I pulled out my bed liner, drilled 4 holes over sending unit location and sawzalled a nice "inspection hole" in the bed. I really didn't want to drop the tank or take off the bed lol! I will tack on a couple hinges and a latch and just consider it a handy portal to the tank.
I pulled out the pump/sending unit and nothing obvious seems wrong with it. I jumped the wiring to an extra battery I have handy (while the pump as still in the tank and the darned thing ran like gangbusters!
It says it has power to it with the original hookup but it does not run when the key is turned at all. Headdesk
Just for fun, I replaced the in frame filter and checked the fuel lines for obvious leaks or cracks and it all looks normal. The filter DID have some brackish fuel in it but was not plugged. I replaced everything and tried to turn it over again ... still no joy??? It's like there is no connection between the ignition and the pump.... The Banana isn't big enough to hide any real mysterious switches or connections... I'm hitting a wall once again.

 

Computer may not be giving signal for the pump to run.

(it runs through jumper only)

Check your grounds to computer and inertia switch

Before you have computer checked.

 

With your multimeter on the 20 volt DC range, the fuel pump electrical connector dis connected, back probe the fuel pump electrical connection with your meters Red + test probe, the Black - probe to a good clean, unpainted, no rust chassis ground connection & do a NO load voltage drop test at the fuel pump electrical connector.

If no load voltage is ok, then hook up the fuel pump to its electrical connector & back probe its electrical connector with your meters red B+ lead, the black B- lead to your above good ground connection & measure the KOEO Under Load voltage & post that number.

If the under load voltage at the pump is low, back up & do an under load voltage drop test at the in cabin inertia switch. If no joy there, back up & do a voltage drop test at the output side of the under hood fuel pump power relay connection & let us know what you find.

 

Well I finally figured out the problem. Thank you again Pawpaw for your patient help with the strange problems that crop up here. I have to say you were right on the money with your suspicions about the problem being electrical in nature. In fact it turned out a ground wire was stretched to just a single thread but it was hidden beneath shrink wrap so it wasn't readily visible during every inspection we have done on the Banana's inner workings.
When I started checking each component for voltage drop I discovered the shrink material on the small ground wire to the main battery. I snipped it off and there was the problem. Now everything is put back together again and I have a nifty new access hatch in the bed of the Banana for future fuel pump failure repair. It's a win-win \o/ Boy am I glad I didn't send the Banana to a shop for diagnosis. I don't need a repair bill right before Christmas!
Thank you to all who offered suggestions, you guys are great!

 

Allright, way to persist & hang in there on your trouble shoot. Good observation find, fix, feedback & to hear all seems well & the "Banana" is "on the road again", sure beats having to feed that F-250 doesn't it!!!! You've earned an "Attagirl" for your excellant trouble shooting skills!!!!

 

Thank you Pawpaw, your insightful posts make it easier for folks such as myself to find the problem and avoid unnecessary repair shop bills. I appreciate the method your advice is offered, without being condescending, to folks with considerably less hands on experience working on the occasionally mysterious modern vehicle.
This might sound odd but I look forward to the next time I have vehicle issues to resolve!