'88 F-150 fuel delivery issues

[tseekins]

My '88 is a dual tank with a transfer pump on the rail. Last fall, I had an issue where I was driving along and the truck started to hitch and buck and then bogged way down like it wasn't getting any fuel. I took the truck to my very trusted mechanic and after a day of testing, he determined that the front pump had failed. I replaced the pump and sending unit. The tank is also only 3 years old. All was well until last Sunday, I was driving along and the same symptoms appeared yet again. I took the truck back and after a day of testing, he determined that the new front pump wasn't working properly. OK great, he repaired it under warranty and my cost was nothing. I picked the truck up this morning and drove the truck for about 10 miles and idled for a short peiod of time in a Hardies drive through window and just as I was rounding the corner of my street, it bogged down again.

Each time the truck has done this, I immediately switch to the rear tank and the engine runs normal.

If any of you guru's have any ideas, I would love to hear them. I'm going to take the truck back to him, but I would like to tell hime where to start looking.

Thanks

Tim

[Ford Breakdown]

I know my '95 had a well documented problem the switching between tanks, they had a wiring upgrade as I recall. Might see if there's something similar available for your year.

[BigSix1]

Perhaps the tank selector isn't switching fully to the tank that you're on when the starvation occurs?

Does you temp. spike when this happens? That's what happened to my '88 F-150, when the selector switch went bad.

You can reverse the lines (all FOUR of them) on the tank selector valve, and see if it runs fine on the supposed "bad" tank, albeit when "selected" by the OPPOSITE setting of the tank selector switch on the dash (since you've reversed the lines at the switch manifolds, on the frame).

You can switch the lines because the hard plastic fuel lines (with the "hair pin" plastic "keepers") DO flex enough to allow this, even though they seem so hard that they might break. Mine did not break--I had to switch them on the SHOULDER of the highway, DURING A CLOUD BURST, in order to go about 2 miles, to the next gas station. Arrgghhh!!!

Technically, you're supposed to replace the plastic "hair pin keepers" after one use.

Good luck.

Peter

[tseekins]

Originally Posted by BigSix1

Perhaps the tank selector isn't switching fully to the tank that you're on when the starvation occurs?

Does you temp. spike when this happens? That's what happened to my '88 F-150, when the selector switch went bad.

You can reverse the lines (all FOUR of them) on the tank selector valve, and see if it runs fine on the supposed "bad" tank, albeit when "selected" by the OPPOSITE setting of the tank selector switch on the dash (since you've reversed the lines at the switch manifolds, on the frame).

You can switch the lines because the hard plastic fuel lines (with the "hair pin" plastic "keepers") DO flex enough to allow this, even though they seem so hard that they might break. Mine did not break--I had to switch them on the SHOULDER of the highway, DURING A CLOUD BURST, in order to go about 2 miles, to the next gas station. Arrgghhh!!!

Technically, you're supposed to replace the plastic "hair pin keepers" after one use.

Good luck.

Peter

Thanks Peter, good stuff there. I never considered doing that. Last weekend I replaced the tank selector valve, "non electrical" with a genuine ford part and the problem still exists. I'm leaning hard towards changing the selector switch on the dash. I'm also beginning to think that the problem has been something simple all along.

I'm assuming that since the selctor valve in non electrical, it operates on pressure from the tank selected, opening one valve thus closing the other within the valve body.

Tim

[BigSix1]

Thanks Peter, good stuff there. I never considered doing that. Last weekend I replaced the tank selector valve, "non electrical" with a genuine ford part and the problem still exists. I'm leaning hard towards changing the selector switch on the dash. I'm also beginning to think that the problem has been something simple all along.

I'm assuming that since the selctor valve in non electrical, it operates on pressure from the tank selected, opening one valve thus closing the other within the valve body.

Tim

Tim,

You're welcome--I hope it helps! I never considered switching the lines until a friend-of-a-friend mentioned it to me--and none too soon! Shortly thereafter is when the bad selector valve stranded me, so that I had to switch the lines to use the gas in the nonempty tank (that I couldn't switch to via the switch on the dash.)

Yes, per my friend who is a Ford tech, and worked on these trucks for years, yes, the selector valve does operate on pressure from the selected tank--seems goofy, no? But that's how it is.

You might consider the possibility that the new selector valve is defective. While it seems traumatic to switch the fuel lines, as they are plastic and pre-bent to line up to their proper ports on the selector valve "manifold," I did that to mine years ago, switched them back to their proper ports within a day or so, and they've not leaked in the intervening 2-3 years. If all else fails, and you suspect the tank valve, you may wish to try this. If so, hopefully your lines will not be damaged either.

Someone in the 460 forum has a stavation issue, and is going to use a special 02 sensor to measured fuel/air ratio in realtime, using a laptop. If I can find the post, I'll put a link here. Sounds like a pricey diagnostic tool, but interesting.

Dealerships can do the same thing, I believe, with a "Flight Recorder," but I'm not sure how new the vehicle has to be to be compatible with that tool. When I worked at the Ford dealer in the late '90's they were doing it to new trucks then.

Good luck!

Peter

EDIT: Tim, here is the link to the guy with the diagnostic 02 sensor--he seem's to really know his stuff, too--perhaps he's got some more ideas for you? http://www.ford-trucks.com/forums/74...n-460-a-2.html

[tseekins]

Thanks again Peter! Your a gem!

Tim

[tseekins]

Originally Posted by BigSix1

Tim,

You're welcome--I hope it helps! I never considered switching the lines until a friend-of-a-friend mentioned it to me--and none too soon! Shortly thereafter is when the bad selector valve stranded me, so that I had to switch the lines to use the gas in the nonempty tank (that I couldn't switch to via the switch on the dash.)

Yes, per my friend who is a Ford tech, and worked on these trucks for years, yes, the selector valve does operate on pressure from the selected tank--seems goofy, no? But that's how it is.

You might consider the possibility that the new selector valve is defective. While it seems traumatic to switch the fuel lines, as they are plastic and pre-bent to line up to their proper ports on the selector valve "manifold," I did that to mine years ago, switched them back to their proper ports within a day or so, and they've not leaked in the intervening 2-3 years. If all else fails, and you suspect the tank valve, you may wish to try this. If so, hopefully your lines will not be damaged either.

Someone in the 460 forum has a stavation issue, and is going to use a special 02 sensor to measured fuel/air ratio in realtime, using a laptop. If I can find the post, I'll put a link here. Sounds like a pricey diagnostic tool, but interesting.

Dealerships can do the same thing, I believe, with a "Flight Recorder," but I'm not sure how new the vehicle has to be to be compatible with that tool. When I worked at the Ford dealer in the late '90's they were doing it to new trucks then.

Good luck!

Peter

EDIT: Tim, here is the link to the guy with the diagnostic 02 sensor--he seem's to really know his stuff, too--perhaps he's got some more ideas for you? http://www.ford-trucks.com/forums/74...n-460-a-2.html

My brother in law who is also a die hard ford truck man has had plenty of 80's and 90's vintage F-series with dual tanks and he's convinced that something in the rear tank tank somehow controls the entire system.

This morning I went hand over hand from fore to aft tracing the fuel system, electrically and plumbing, and I'm not convinced of his theory.

I have no frayed or chaffed wires or bad connections thus no indication that a ground would exist unless t he second new fuel pump is also faulty. No fuel leaks either.

I think it's the switch. I'll keep everyone posted.

Tim

[blloyd]

"teeskins", I have an 88 F-250 with a 351W and it has been running very good for many months when I filled both tanks.
Last weekend when my front tank got around 1/4 full it started cutting out
and barely running and like yourself when I switched to the full back tank it
started running perfect.
I will keep an eye on your results !!

[jemini]

I have a 1988 F250 that had plenty of fuel delivery issues. I put in two new tanks, sending units/low pressure pumps, and eventually a new seelctor valve. Then another in-tank pump after the new one failed with less than 40 gallons of gas having been pumped through it.

You can test the switch with a volt meter to see if if works consistantly while switching. i did this but found the switch good.

I found that you can hear the whine of the in-tank pumps if the truck is running and you put you ear close to the tanks. Switch the tanks and listen for the whine. There is enough fuel reserve in the selector valve to give you enough time to get under the truck to listen before stalling if that pump is shot.

After I found/suspected a second failed in-tank pump, I drained the remaining gas in the tank by disconnecting the line at the selector valve. Then I pulled the tank again (very annoying) and the sending unit/pump. I tested for continuity across the pump wires and got zip. The pump was warranted by Advance Auto so they exchanged it no problem. When all was said and done and put back together both tanks and selector valve did there thing correctly.

[EPNCSU2006]

You can also jumper between the fuel pump trigger wire and the signal return wire in the test connector to force the fuel pump relay on constantly without having to run the engine.

[jemini]

Good point!

[tseekins]

Ok all, thanks so much for your input and valuable suggestions. The problem has been resolved.

1. I replaced the fuel tank selector valve, did not fix the problem.

2. I replaced the selector switch on the dash board. Did not fix. The pump was simply not running.

3. Replaced the ground wire to the front pump and I'll be damned but we have FUEL!

I drove the hell out of it today and all seems to be fine. Hopefully I'm not speaking too soon, we all know how tempermental these old rigs can be from time to time.

Thanks again!

Tim

[lisagoud]

I have found ground wires to be tyhe problem most of the time. Akso, don't forget about the fuel filter in the bottom half of the selector valve assy.