Hi Guys ,,, I have a 94 Ford F150 / 4.9 , that is having a problem I need help with ,,, this is a high mileage engine ( 300,000) , have replaced spark plugs , rotor cap , new plug wires , air filter , fuel filter , . It starts up fine , but it will , best way I can describe it , surge ,, it dogs down sometimes at idle , or when driving , but it will pick right back up and run normal , at least to me . I'm trying to trace this problem down ,, it doesn't seem to be electrical , not sure if a oxygen sensor , fuel injector acting up , EGR , or what !! Need some thoughts here on what to check , Any feed back would help OH ,,,, also replaced solenoid pack in trans , it is electronic , is this a fuel problem possibly , , it has dual tanks , but runs on the front tank , the rear doesn't work ,, had a problem way back with the front tank pumping gas to the rear tank while driving , we had to plug the rear fuel line to stop this at time,,, could not find switch over valve , it may be located under fuel tank , couldn't find on the frame rail ,, any way NEED HELP

 

First thing, pull the computer diagnostic codes. Without knowing what those might be you are thrashing around in the dark.

 

Thanks Harte3 , yes you are right ,, but I believe I have found the culprit,,, not a full fledged mechanic here but , I happened to google it and lo and behold a Ford forum enthusiasts post from way back describing a problem I briefly mention in post about possible fuel selector switch ,,, reason I'm leaning toward this because I stepped outside and happen to smell a order coming from rear tank I don't use , I had actually had plugged this hose to rear tank while on the road when this happened , like 3 yrs , it had pumped my front tank that was full , into my back tank and over flowed !!! I had to cut the line at the time and plug ,,, and quite frankly didn't think about it until now and I read that post someone else had had a problem with their switch over valve that did the same thing . Fuel check valve in tank , a part of the fuel pump assembly , which can be purchased separately , just a pain to have to get to basically, like raise the bed ,,, I have a front and rear switch on the dash , cheaper of the two to replace . But how hard is it to change the fuel pump / fuel delivery module in the tank ??? It had a new pump installed about 3.5 yrs ago . Never done this before , guess that part wasn't replaced when was !!! Or am I great confused ??? And yes ,, I will check codes , being this is a OB1 system , I have to use the hand held scanner from back in the day to perform KOEO and KOER

 

Low fuel psi will give a slower idle, stumble on acceleration and stumble at cruising anything over about 1000 rpm. You want 50-52 psi.

Start with getting the loaner pump pressure tester from autozone or oreilly and before you leave the store, make sure it has the Ford adapter in the kit in one piece. Those things like to disappear for some reason when other people rent them.

If you aren't in the rust belt and can get the nuts off the bed bolts, its fairly easy.

1) clean out bed, remove tool box, bed liner, etc (time varies on this one)
2) remove 6 nuts from bed bolts under truck
3) disconnect 2 wiring harnesses up behind the rear bumper towards the drivers side
4) disconnect both filler necks from the bed inside the fuel doors, also undo the hose clamps holding the filler necks to the supports under the truck outside of the frame rails
5) Get some good friends or an engine hoist and 4 cheap ratchet straps to grab the bed's round holes in the stake pockets at the corners. You can put the tail gate back on and close it, or wedge a piece of wood from side to side of the bed to keep the sides from pulling together at the rear if you use the engine hoist.
6) Spend a bunch of time cleaning the tops of the tanks, frame rails, fuel pump QD's etc and get side tracked seeing how many other projects should be done while the bed is off like shocks, etc.
7) Start trouble shooting your fuel pumps.

I went through 2 aftermarket pumps: Spectra and Precision and none of them lasted more than a month in my rear tank.

I finally bit the bullet and dropped $300 at rock auto for a true Motorcraft pump and its has been working great for a while now.

The bottom of page 2 begins my fuel pump woes, trouble shooting and fixing:

https://www.ford-trucks.com/forums/1...eshooting.html

 

Ok , thought I give you all an update as to where I am at the moment. Harte3, I pulled the codes the other day , and know I have a few issues to work thru ,,,, here they are : koeo : 111 736, 281 ( these I didn't quite understand ), Let it set and re did it ,,, koeo : 173, 628,,,,( know I have trans slippage ,, it is a E4od ,, think that's how you all say it ) ,, now my code definitions tell me 173 is ,, hego,, heated exhaust gas oxygen voltage indicates "rich" (bank 1) .. then I performed the , koer : which gave me 1 , 412 , 1,735,385,366,324,12,173,538,536,& 632 ( I realize I didn't perform , turning the steering wheel , tapping the brake , or engaging the od toggle switch on shifter ) . Waited a while and re did koer : and got 1, 538,537,632,538,537,and 632 ,,, but this is where I am on codes . I just need to know what to do !! Now Thank you to bigredtruck for responding ,, great info , on how to correctly do the fuel pumps,,, I realize this is a big issue ,,,I want to do away with rear tank , or by pass altogether ,, for reasons that I never use the rear tank ,, maybe I should alternate the use of tanks ,, but the fellow I purchased it from yrs back ,, had the problem and the gas soured in the tank , it stayed there all these years till about 4.5 yrs ago , where I lost a whole tank of gas from front flowing into rear tank ,,,guess when check valve opened up in rear tank . I haven't a garage to work in and not going to pay the price these mechanics want around here . Love my Truck , but there has to be another way to plug this off and just disconnect the rear pump , I going to have to drop it right at our apartment in the gravel and fix this thing ..