1988 Ford F-150

s.ed , Since tapping on the old ones gets your truck running chances are good the new pump will fix the malfunction. Your truck has a ' EEC IV ' computer and there ways to extract its codes but it takes more than just turning the key a number of times. Doing a google search on EEC IV errror codes will give you lots of places to learn about how you go about readings the codes.

Thanks for the reply. I will check out the EEC IV. I figure my biggest concern will be wheteher the tanks are dirty enough to fowl up the new pump. The truck is in decent shape for its age but the previous owner said this started when the tank was switched from the front to the back one, which he barley used.

There could be other problems with the daul tank set-up . Have you the same troubles on the front tank too or just the back one? When changing the pump it would be a good time to install a new fuel filter too, while you have tools out and the line opened.

The problem is present when using both tanks. I do have a new fuel filter to install with the new pump. What is the process to de- pressure the fuel pump to remove it?

"This valve provides a convenient point to monitor fuel pressure, release the system pressure prior to maintenance, and to bleed out air which may become trapped in the system during filter replacement. "

that was taken from the autozone site :

removing the electrical connector on the pump while the truck is running would do it too :-/ but you didn't hear that from me

You said: The truck is in decent shape for its age but the previous owner said this started when the tank was switched from the front to the back one, which he barley used.

This rung a bell - I converted to LPG (liquid pet. gas - I am in Oz)years ago and allowed the petrol tanks to remain empty for years. The resulting corrosion led to me having to replace both tanks and both senders/pumps. So, if the previous owner did not use Tank 2 - allowed it to remaini almost empty - , the odds are that its internals, and probably the tank, are a write-off. I always urge people to keep both tanks topped-up and rotate their use. Unused petrol (say, in tank 2) deteriorates to Hell in six months - a few more months and it is barely recognisable as petrol.

Thanks for your help, you've been great! I really hope that when i replace the pump and filter i can use the one tank only without the other and have no problems. I would hate to see the bill to replace two tanks and pumps! if need be i figure i can just run the truck with one new tank. Option two would be to find a garage that may be able to "clean" the tanks.?

One last follow up. Today I went out to start the truck it starts then immediatley shuts off. I believe all the tapping on the fuel pump finally killed it. Also, I hear about a fuel pump relay switch and fuel pump auto shut off switch. I need to rule everything out, i dont want to put a bundle into a 20 year old truck.

In fact this is what I did - as I mostly use LPG, I only replaced the tank/sender/pump on Tank 1. Petrol is only used for starting and, if necessary, to extend the range. I would be battling to get by with one tank if I was using petrol - my 5 litre V8 eats the stuff (which is why many F150 people here switch to LPG). Your six will be less thirsty and, maybe, what you use it for means that one tank will do the job. And you are right - even just replacing one tank cost plenty. As to 'cleaning the tanks', my mob, when I asked them to solve the odd fuel problem had me come in and see the state of the tanks and the pump/senders. The latter had obviously had it - they were visibly composting. And they refused, point blank, even to consider anything other than replacement for the tanks, for safety reasons. I suppose you could try sandblasting the inside of the tank and then coating the inside with a series of petrol-resistant coatings - tricky. A safer bet would be a good front tank from a wrecker. But I think I agree with my mob that replacement is safest. Then again, if your are in the US, there must be vast numbers of your model being dismantled. They stopped assembling them in Oz in 1989 and they are as scarce as hensteeth.

I replaced Gas Pump and Filter last night. I actually heard the pump operate and it starts. Guess time will tell.

Obviously the in-tank LP pump is working and, if the petrol gauge works then the sender is OK. You could try filling Tank 2 and see if it works when you switch to it. If it doesn't then you have the choice of fixing it or doing without it. But if you take the latter route, there is a mod which your dealer will be able to arrange to permanently put it out of circuit . Just relying on the dual function gadget when you do not need it leads to problems, as I found.

How did the filter seem? Mine is original and I wondered whether I should replace it - we have had a few problems lately.