Aredecom

I have an EFI 89 F150 I6 auto, single tank. Truck just died on the highway yesterday, and would not restart. Seemed fuel related because at first it seemed like it wanted to start, then just cranked and cranked. Had a buddy tow me home and am trying to diagnose it today.

When I turn the key, I do hear the fuel pump engage for a second or so. But with a fuel pressure gauge on the schrader valve on the fuel rail, I am getting 0 pressure. Nothing at all.

Haynes book says to check low pressure fuel pump first by removing the fuel tank supply line from the reservoir. Forgive me if this is a silly question, but haynes is cheesy and does not have a lot of pics or location descriptions. On the rail under the truck up front is the fuel filter (fairly new) then a fuel pump (is this the low or high pressure pump? and where is the other pump?) and then some canister with both the fuel line and return line running through it, is this piece the "reservoir"?

If this is the reservoir, I would remove the upper rear tank supply line and engage pump to see if I get a good fuel flow.

If I do, then I need to do the "under pressure" check on the regulator. Where is the regulator? And is it typical to have no pressure at all with defective regulator in some cases, or is it usually low pressure?

Let me know, and I'll test and post results. Thanks in advance.

runninonempty

I am watching this thread because I think my truck might have a fuel problem too as it has the very same symptoms. My truck is doing the same thing:

"Seemed fuel related because at first it seemed like it wanted to start, then just cranked and cranked. "

However, my mechanic thought it jumped time and after changing the timing cain and all the truck is still doing the same thing. Cranking but doesn't start. I have a thread going on this now (say it ain't so).

I really wanted to say that I agree with you about the Haynes books having little info on certain things. Frustrating.

Aredecom

I'm assuming the piece I think is the reservoir is in fact the reservoir because I can't find anything else along the fuel lines that could possible be it. So I disconnected the rear upper line. Only got a couple drops of fuel come out so the line is pretty dry. Tried grounding the fuel test port and pump did not come on. Tried turning the key on too, and got no fuel coming out of that line.

I think on this truck the fuel pump behind the fuel filter is the high pressure pump, (Which is the one I hear come on with the key turned on) and there is a low pressure pump in the tank that is supposed to be keeping the reservoir filled up. If that's right, it seems like the low pressure pump would be the one at fault. Which stinks because I have a full tank of gas. Is there one of those stop ***** at the bottom of the tank fill up neck to keep you from siphoning the gas out?

My other concern/question is about the pump not engaging when I ground the FP at the DLC. Does this confirm the low pressure pump is bad? Should this engage the HP pump too? If so why would it run for a second with the key on, but not when grounded? Could this mean there is another problem I could try to rule out?

Aredecom

I forgot to turn the key on when I grounded the FP at the DLC. Tried again with the key on and all I get is the FP relay clicking. No fuel pump noise, no gas out of the reservoir line.

94Bronc

step one. check inertia switch(located left kick panel by e-brake pedal) i know its a "collision" switch basically, but sometimes they get thrown anyway.
i'd check voltages to both pumps. i dont know what the harness looks like, but its supposed to have i believe .5 volts sounds to me like its probably the tank pump. not sure if it has the check ball or not, but if you know anyone with a motorcycle jack, one worked perfectly for me

the low pressure pump is tank side

to help explain how the circuit works: When ignition is turned on, EEC power relay is energized, closing its contacts. Power is provided to both fuel pump relay and timing device in EEC module. Fuel pump runs through contacts of fuel pump relay. If ignition is not turned on within one second, timing device in EEC module will create an open ground circuit.
Opening ground circuit of fuel pump relay de-energizes fuel pump. This circuit provides for pre-pressurization of fuel system. When ignition switch is turned to "START" position. EEC module operates fuel pump relay to provide fuel for starting engine while cranking.

Aredecom

Sorry should have listed that, I did check inertia switch. I'm also thinking since the high pressure pump kicks on for 1 second or two with the key on, the relays are good. And since I have absolutely no pressure and a dry line, I'm thinking you are right in is the low pressure pump in the tank. I will check the wiring going to that pump if I can get access to it for voltage just to rule out the circuit going to the LP pump before I go replacing the pump itself.
I'm contemplating removing the bed instead of the tank. I see where the 6 bolts are, they don't look rusty, I can probably get a couple guys to help lift the bed off and back on, but it will be hard to drain a full tank, and I don't have access to a tranny or motorcycle jack, so maneuvering that much fuel by hand will probably suck. Why is it a fuel pump always seems to take a crap in a full tank? 3rd fuel pump I've had to replace over the last couple years (different cars) all 3 had a full tank. Go figure.

62champ

You are on the right track with getting access to the tank pump. Many repair shops prefer that method as well. Back in 2003 my father took his 96 into a shop to get the rear tank pump replaced. He said he looked through the window in the shop about 30 minutes after they started and saw the bed of his truck 8 feet in the air being supported by the arms of a lift.

Four guys (or girls if you know a softball team...) can lift the bed on and off. Also heard about a guy who did it by himself. He tied into the four corner stake holes, connected them all in the middle and then had some pulleys connected to a good size tree limb and up it went. Moved the truck and then put it on a couple of saw horses. Getting back on would require an extra set of eyes.

As far as the fuel pump location goes, someone explained to me once that the fuel pumps used today can create a lot of heat while working, so they are located in the tank because the fuel actually keeps things cool. That was out of one mouth, so might not be totally correct.

Aredecom

I got the tail lights and harnesses out of the way, the filler neck loosened up, all 6 bolts wire brushed and WD40'd, got the first nut off, and the second nut free spins top and bottom together. And of course my son borrowed my 18MM deep well socket, so I have to wait for him to bring it over to even get started on the 4 back ones...
I guess I have to grind the top half off, and hope I can punch it through.
Always something huh?

Aredecom

Got the bed off, wasn't too bad other than having to grind off 2 of the bolt heads. Just waiting for the parts store to get the pump and strainer in, should be soon. Hopefully get this done by the end of the day. Thanks for the answers and suggestions.

Aredecom

I checked for voltage at the low pressure pump, and when that checked good, I figured I needed a new pump. Bought it, put it in (with new strainer, and gas looked clean, no rust, could see bottom of tank was clean), turned key, I can hear both pumps operating, but still have 0 pressure at the fuel rail. Tried pinching off the return line and primed the line by turning the key on and off several times. 0 pressure. Pulled the fuel line off the front of the fuel filter and turned key, I am getting a pretty good dribble for the 1 second the pumps are on, so the reservoir and filter are not blocked, I don't think anyway.
Sprayed starter fluid in the TB just to make sure it was a fuel related issue, (thought maybe my Fuel pressure gauge was dead?) and it fires right up. Tried to keep it running with starter fluid for 15-20 seconds thinking maybe the lines were dry and a running engine might start pulling fuel through. No luck, still no pressure, 0. Truck dies from lack of fuel.

Is the high pressure pump shot, even though I hear it come on? Should fuel be spitting out at a really high pressure, or is it normal with just 1 second of running to just get a kinda medium stream for a second or two?

Where in line is the fuel pressure regulator? Is it before the fuel rail, and possible blocked? Or is it after the fuel rail?

I thought a bad regulator would more often than not, cause excessively high pressure, or sometimes lower than normal pressure. Is it possible for a fuel regulator to cause a no pressure situation? (Even with return line pinched?)

Trying to figure out where the fuel is getting stopped at? Seems like the pumps are working and no blockages in the LP pump lines, reservoir, hp pump, of fuel filter.

Trying to figure out where to check next? Any suggestions?