Questions about... 1987 F150, 302, dual tanks and what appears to be a fuel system related problem.

Some items.
Wont run now but ran well when shut down.
Good spark at coil and plugs, Good fuel filter.
Will start and run breifly.. maybe 3 - 5 seconds on its own. Will start and run briefly if using starting fluid. doesnt backfire when trying to run, or in spinning over....So, not a timing chain issue.
Checked power to inline fuel pressure pump.... on rail between forward tank and fuel filter -- none.
Running a jumper wire from the NEG battery terminal to the pigtail just behind the air cleaner housing, I can get the pump to run and the engine to start and run fine...but the pump stays engaged. So I know it is not the relay or fuze link. When pulling the jumper wire out of the pigtail the engine quits in a couple of seconds.

Any suggestions on what else I might try next, or what the problem might be?

Thanks.

Hover

 

Hover,

Hi and welcome to the forum.

This is a long shot but since no one else has chimed in I figured what the heck.

1. Does your truck have one of those inertia switches? You know, the switch that is suppose to remove power to the fuel pump when in an accident. I know that these switches are re-settable.

2. Are you sure that you are not bypassing the relay when you are using the jumper wire and putting power straight to the pump? That would still make the relay a possible faulty conponent. On some cars/trucks the same model relay is used for the pump and other engine conponents. If so, you can swap them for a test.

Hope this helps,
Lee

 

Lee..


Thanks for the reply.
1) Yes, there is an inertia switch on the inside firewall just forward of the clutch pedal. It has a two wire connector and I cant measure any voltage there with key one or off. There is a white button on the top to push down for a reset, however it is currently all the way down. I can lift it a bit so perhaps it will raise up if it is activated, but, for now it is and stays down. Perhaps the inertia switch is bad?

2) With the ingition turned On, and the jumper from the NEG teminal on the battery to the pigtail by the fuel relay, the relay clicks and the pressure pump runs, and the engine will start and runs fine.. Perhpas the "green" relay on this 87 F150 is bad? I guess a replacement would be the only way I could check, but if something else is the problem, I wouldnt know......

For what is worth, and I dont think it really matters,
-the fuel guages have not worked for years, but everything else has worked fine.

-I took the front/rear tank selector out of the circuit and it still runs just fine. (with the jumper) Naturally, the fuel guage is pegged "full"
As far as the front/rear selector goes, there is a connector to it with 6 wires, and a second connector about 6 inches downline with .. I think 7 wires..... On the downline connector wires carries 12 v, but the front/rear selector toggle plug does not have a pin to that 12v wire..... there is about 8v or so on a separate wire (downline) next to the 12v wire, which feeds one of the 6 blades on front/rear selector toggle. Perhaps thats a problem, too!

I guess I will just have to start somewhere and pick some replacement parts, one at time.
Also, I have No Idea how to get error/fault codes so I better go figure that out.

Thanks for your reply... and...If I figure this thing out, I will post to the fuel and electrical forums for others.

Hover

 

http://fordfuelinjection.com has the procedure for getting the fault codes, as well as a list of codes. The inertia switch sounds fine, since the pumps power up when you manually activate the relay. I have a couple wiring diagrams I could email you that might help you diagnose the electrical part of it. The engine computer turns the relay on (well it's supposed to) so first thing would be try to figure out if the wire from the relay to the computer is not cut. Basic layout of the wiring is this: from the relay, hot power goes to the inertia switch, then from there, the wire splits - one branch goes to the high pressure pump on the frame rail, and the other goes to the tank selector switch. Then from the selector switch there are two power lines, one to each tank pump. The other three are for the gauge - one goes to the gauge, and the other two come from the tank level senders.

 

Thanks for the web site on error/fault codes and insight on the wiring.

The problem is solved and here is the story. What appeared to be a fuel/ fuel pump/ fuel relay problem was electrical. I had finally had given up on finding the problem and thoght the best thing to do for the moment to get up and running was to run a separate wire from the NEG terminal on the battery to the pigtail by the fuel relay. To connect to the NEG terminal, I had to unwrap the tape from the large NEG cable to frame groung and two smaller (10- 12 guage wires) that were double back against themselves. I wanted to see where the best place to tap into a wire would be.
After unwrapping the taped wires, one of the factory connectors on one of the smaller wires had become corroded and was completly disconnected. It was a poor connection and just one of the little blue connectors we use everyday. It is important to note that wiithout removing the tape the problem would never have been solved...... Even so, everything worked correctly, except for the fuel system. After a new connector was installed, the boost pump ran for the two seconds or so when the ignition was tuned on and it started right up...
Problem solved.

So, the moral of the story is to those of you out there with a similar problem that what appears to be fuel, could very well be electrical.

Thanks for your suggestions.

Hover

 

Good Job!!!!!!!!!!!!!

 

Sounds like you had a bad PCM ground. That'll make the PCM do some crazy things.
Glad you got it fixed

 

Thanks for posting the fix. More people should do that!
I am having a problem like yours right now on my 85. The fuel guages aren't working either. Maybe that's a clue the ground wire is deteriorating?
I took out the rail pump and and it runs fine on the bench. It must be the power/ground circuits are different for starting vs running.

 

Mecheng.

Welcome. I hope it provides some help for you in your quest.

Let me add that this... When I finished, my fuel guages do not work either, but then they did not work before I experienced this problem.
Both tank sending units for the fuel quantity were replaced by Ford in 1989 or 90... thereabouts. They worked for a couple of years and then quit. They have never worked since.
I understand that the 1987 F150 has sending units only in the tank, not pumps. There are later models that have both pumps and sending units in the tanks. I dont know what your 85 Model has, but I have heard that if if you have combined sending unit/pump and the your guages wont work, you wont get the pump to work either. The 87 model and later models have a rail pressure pump to get the psi up to the needed level (58 psi -- I think) I have also heard that the toggle (front/rear tank) switch can cause the same symptoms.

Anyway, I dont know if any of this helps you, but I would for sure be checking the wires at the NEG battery terminal. Clearly there are different circuits for starting, and the fuel system..... at least on the 87 Model.

Hover

 

If it has EFI, 85 to about 92 or so, with dual tanks, it will have a low pressure pump in each tank and a high pressure pump on the frame. Around 92 or so, they went with just a high pressure pump in each tank with check valves in the sending units instead of the big switching valve on the frame.

The fuel pressure should be about 40psi key on/engine off and about 32psi idling.

 

Thanks guys,

Well I checked my wiring and no problem was found with voltage or resistance. This time my wife turned the ignition on while I was under the truck(I Do trust her!) The pump sounded like it had gravel in it. So I went with my instinct and replaced the "Master' brand fuel pump I bought from Advance Auto 3 3/4 year ago. Sure enough it solved the problem.
It makes the fourth time I have replaced that brand. The first three were on a Chevy TBI Celebrity. The counter guy refused me the fourth replacement so I went GM and never had another problem. Unfortunately the Ford Bosch pump was $225 last time I checked at the dealer. The Master pump was $75. The tank pump are Master replacements too and one is coming up on three years, yuck!

Mecheng

 

I have a 87 f150 pickup that died all of a sudden. When I turn the key the fuel pump doesn’t come on. Relay is working but still no pump. Fuel pressure is zero. I can read 12 v from relay but no voltage at inertia switch. No voltage at fuuel pump connectors. Wondering if issue is with inertia switch and if so can I bypass. Thanks.