Need help ASAP, 1989 f150 dual tank stalls and is getting no fuel

[CanukGMC]

The quick and short version of what happened:

I have a 89 F150 4x4 lariat with the 302 8cyl and dual gas tanks. I was driving to work and the truck died. I have spark and enough juice to turn it over so I must be getting no fuel. When I turn the key to the on position I do not hear the fuel pump whine as it primes, it's dead silent. I'm assuming the fuel pump is dead.

Are there any fuses to check?

I did check the switch that goes off when in an impact and it was not tripped off so it's not the problem.

My hayes manual (which i find is wrong ALOT) says that 87-89 f150's have a single fuel pump that is external to the tanks and found along the left frame rail? Can anyone confirm? Someone told me they thought it might have 2 pumps but I switched tanks and the truck still didn't start (or make a fuel pump sound) so unless the planets aligned and BOTH pumps blew simultaneously I would assume there's only 1 pump.

A quick call to NAPA and they told me they have 6 pumps listed for this year!

My main concern is if anyone can confirm if this is an external pump like my hayes manual says. I'm going to climb under the truck after work and try to find this mysterious pump along the frame rail but I'd hate to be looking for something that doesn't exist. I just really really hope it's not in the gas tank, there's so much rust (this is an 800$ beater) I just don't see a gas tank extraction going well. Thanks for any quick replies!

[rhandwor]

If you ever changed the fuel filter the external pump sits next to it. The problem some do and some don't have one. If you have one they have a small primer pump in the gas tank. If you have an external pump take a test light and make sure you have power to the fuel pump. If an in tank pump check for power at the plug.
If no power check the fuel pump relay along side the drivers side fender it is green in color.

[CanukGMC]

Originally Posted by rhandwor

If you ever changed the fuel filter the external pump sits next to it. The problem some do and some don't have one. If you have one they have a small primer pump in the gas tank. If you have an external pump take a test light and make sure you have power to the fuel pump. If an in tank pump check for power at the plug.
If no power check the fuel pump relay along side the drivers side fender it is green in color.

Thanks for the reply. I looked on the drivers framerail beside roughly where the tranny is and there is what I think is the fuel pump mounted there. It's tucked in behind the front driveshaft for the 4x4, has (from what I can feel) power lines running into it and what appears to be fuel lines going in and out.

When clicking the key forward and backward I can hear (and feel) the fuel relay on the drivers fender clicking inside but NO sounds at all are heard after that (no buzz or whine from the pump). I think the pump is dead, I'm having a real hard time telling how the thing is mounted in there as well, I think maybe I should buy a new one (gag, 220$) and then be able to tell how it's in there and replace it.

Have I missed any steps anyone? Sound like a dead pump? Thanks again for any info.

[Scrapper]

go to autozone.com and it will tell you about pump and where it's located. i never said you have to buy there it's just a thought.i buy at car quest.

[Selectron]

Just because the relay clicks, that doesn't mean it's working properly - the switched contacts could be pitted or dirty, and unable to pass sufficient current.

One check which you can do very quickly is to test for voltage at the inertia fuel shut-off switch, using either a meter or a 12V test lamp - it should receive 12V briefly as the fuel system is primed when the ignition is switched to the Run position. Depending where the switch is located, you'd probably need an assistant to turn the key while you check for voltage.

If you have a meter or a test lamp it would be worth making that very quick check before spending cash on a new pump.

[Selectron]

Just giving this a little more thought, and if you have the inline high pressure pump, you'll also have a pump in each tank so if you aren't hearing any of them then that's almost certainly an electrical fault and you'd be wasting time and money replacing a pump.

I'd suggest having an assistant turn the key while you get your ear right down close to the tanks and verify for sure that the in-tank pumps are silent. If all pumps are silent, then you likely have an electrical fault between the fuel pump relay and the inertia switch.

The wiring diagram below covers the years '87 to '89 and it looks like you'll have to do some electrical fault-finding. It's a simple circuit - when the relay is energised, current flows via the relay's switched contacts to the inertia fuel shut-off switch, and then takes two paths - one path feeds the inline high pressure pump, and the other path goes to the tank selector switch - one of the two in-tank pumps will then receive current via the switch, depending on which tank is selected.

If you're not too handy at reading wiring diagrams or if you're not too sure about electrical fault-finding then let me know and I'll go into it in more detail.

'87 to '89 fuel pump diagram

[spytearbite]

collapsed fuel line from one tank to the next or the solenoid pump is short, in-op, etc.

[CanukGMC]

Originally Posted by Selectron

Just giving this a little more thought, and if you have the inline high pressure pump, you'll also have a pump in each tank so if you aren't hearing any of them then that's almost certainly an electrical fault and you'd be wasting time and money replacing a pump.

I'd suggest having an assistant turn the key while you get your ear right down close to the tanks and verify for sure that the in-tank pumps are silent. If all pumps are silent, then you likely have an electrical fault between the fuel pump relay and the inertia switch.

The wiring diagram below covers the years '87 to '89 and it looks like you'll have to do some electrical fault-finding. It's a simple circuit - when the relay is energised, current flows via the relay's switched contacts to the inertia fuel shut-off switch, and then takes two paths - one path feeds the inline high pressure pump, and the other path goes to the tank selector switch - one of the two in-tank pumps will then receive current via the switch, depending on which tank is selected.

If you're not too handy at reading wiring diagrams or if you're not too sure about electrical fault-finding then let me know and I'll go into it in more detail.

'87 to '89 fuel pump diagram

Great info, thanks a ton. I'd love it to just be the relay, I'll head out now and see if I can measure voltage at the plug going into the intertia switch while turning the key. I'm guessing I'll see a 12v spike (or any spike for that matter) if the relay is working fine. I was under the truck last night looking for the fuel pump (in line) and had my brother turning the key on and off while I was under there to confirm there was NO sound from the pump itself (and not that maybe it was just real quiet because something was seizing in it) and there wasn't even the slightest sound, also while under there I very closely listened for the tanks pumps as well and heard nothing, I didn't put a stethoscope to the tanks to check for sounds but I'd assume the pumps would make more noise than the relay I could hear clicking in the engine bay. I'll post what I find in a bit. Thanks again


EDIT: I pulled the plug to the intertia switch, ran a voltmeter over the 2 points (on the harness) and got anywhere from 0.00 to 0.003v when in the off position and 5.8 to 5.9v in the on position. Could the voltage be too low? I'm not sure if the pump needs a direct 12v or if the 5-6v showing is enough. I again listened carefully and unless the tank pumps are extremely quiet heard nothing other than the click of the relay when turning the key. I also jumpered the intertia switch harness and still had no sounds so the switch must be good. I've unplugged the tank selector and will start testing voltages along it but from the wiring diag I think the selector would have little to no effect on the in line pump at the very least.

EDIT 2: Using the wiring diagram I checked the tank selector circuit. None of the colours matched what was on my harness (power for example seemed to be coming from a yellow wire with a white stripe). I don't think the colour matters though. I could read (from the power wire) anywhere from 3-6 volts accross all the prongs with the key in the on position, with it off I got nothing accross anything. I popped the dash apart and tested the switch, from the left side three prongs I could get continuity from the middle pin of the three to the upper and lower pins with the switch in either selected position but never both at the same time, the right side was the same thing. So I'm pretty sure the switch is ok. What sucks is that I have no parts in town, I live in a remote area and have to order all my parts ahead of time. I think I may need to just order a new pump and see what happens, I have no idea how the wires are attached to the current pump as I can only feel around but can't see what's going on and I don't want to just start pulling on them to see if they "let go" and end up breaking a harness. I guess worst case I order a new pump, look at it to see how the old one comes out (thanks for the NO pictures and NO help hayes manual, ever so useless again) and then remove the current one and replace it hoping for the best unless anyone else has any ideas? I'm totally stumped and NEED my vehicle, I literally live on my own lake in the forest and can't walk to work, I've been either hitching a ride or been praying a friend won't mind driving 30mins out of his way to come pick me up <sigh>. I swear new things break everytime I fix something else, I should just leave stuff broken so nothing else will break.

[spytearbite]

I would more like take my test light and peg to ground each (+) hot wire path to each relay/solenoid/inertia switch, etc. until the light loses current to ground and from say... The first test light out of ECM box #8 has current up to junction brown to the solenoid switch to the inertia relay.
If there is a connector you can remove off of either relay, remove it and ground your test light at that junction (brown wire) path forks of to both the solenoid fuel line switcher and the inertia switch both have (+) current to said component.

Then, jump to the next wire out of said relay/solenoid so the )+( is still flowing to the next solenoid/relay...

As far as your low voltage? Those are the analog voltage signals the ECM or computer computes. Meaning, 0-to5V is how you read the analog as you throttle up say is that rheostat switch like a house light switch?
Where, a batter reads at max volts on down. Meaning, the ECM needs 12V like the headlight and tail lights and all that is non-sensor'd runs at 12Volts, give or take a few Ohms resistance and all that is wire resistance you are chasing and finding out your wire output to the calls for that 0-to-5V you are reading now.

To me without giving all that detail, it seems you are hitting some good (ECM = Volts-Out Signal) voltage type numbers.

[CanukGMC]

K good to know on the volts, makes sense the voltage would step up as the pump needs to flow more. Since I'm showing proper voltage at the intertia switch then it has to be outputting volts from everywhere before that so the relay must be switching and outputting as well at the ecm. I guess the fault has to be below the intertia switch which basically means at the pump itself since it's just wire and then the pump on the end. The entire circuit isn't dead (I should have mentioned) switching tanks does change my gas gauge to reflect the switching action (one tank is only half full so when I switch to it the gas gauge reads appropriately). I have a feeling that either the pump itself is totally dead (and shorting internally) or maybe the wire running to it is broken\corroded. Unforuntately I'm having trouble telling how it's even hooked up to the pump itself and I think the only good way I have is to reverse engineer how it's in there by buying a new pump unless someone can confirm for me how the wires attach to the pump? Some kind of harness? It's so hard working on something when you have no idea what it looks like and are going entirely by feel.

[Selectron]

I'm not sure exactly how you've measured the voltage at the inertia switch, - if you've taken the connector off and put both meter probes across the two connector terminals then that's the wrong method.

The connector should be left connected to the switch and you should try to probe into the back of the connector. So the meter's negative lead would be connected to a known good ground point, and the positive lead would probe into the back of the connector. If you can't get a probe into the back of the connector then pierce the wire with a sharp pin and measure voltage via the pin. The wires should be a brown one and a pink/black, and it's preferable to measure the voltage on the pink/black.

According to the wiring diagram, the pumps are not variable-voltage, so you should have the full 12V on that wire.

If you used the correct method and you got a reading of around 6V then you're dropping voltage at some point prior to the inertia switch, and the most likely suspect would be the relay. You could try unplugging it, scraping the relay's external terminals clean and then re-inserting it, but if the switched contacts are pitted/dirty internally then that won't help and it would need to be replaced.

You're correct in saying that the tank selector switch would have no effect on the inline pump even if the switch were faulty, so I wouldn't even bother looking at that right now.

If you've already measured the voltage correctly at the inertia switch and if it's low, then start looking for a problem prior to that point.

If you weren't using the correct method then that would be the next step. If you find that you do indeed have the full 12V then the problem is at a point beyond the inertia switch.


Edit: I wrote that before I read your second edit. If you're only getting 6V or less at the selector switch then you probably were measuring the voltage correctly at the inertia switch so the fault is probably prior to that point.

You could check the other relays and if you have another identical one which is feeding something non-critical (horn relay for example) you could try temporarily swapping them.

[spytearbite]

Originally Posted by Selectron

According to the wiring diagram, the pumps are not variable-voltage, so you should have the full 12V on that wire....If you used the correct method and you got a reading of around 6V then you're dropping voltage at some point prior to the switch, and the most likely suspect would be the relay.

Yep, my point exactly. You are in the diagnostic mode and have; ECM readings and Battery readings. Since Selectron uses the abstract that you should have 12v to the relay components, it would seem there is a resistance that is half grounding? 6V are being grounded is hard to believe but I am not that sharp in the diagnostics.

I use way too many variables not knowing the product in hand. So, now you know more or less in the generic abstract, a battery uses 12V as opposed to ECM voltage reads (0-6V give or take a few 10ths) is so complex, Solect makes it look way too easy.

[rhandwor]

Pull the cover off the external fuel pump. Disconnect the positive wire then use a voltmeter and if you have 12 volt buy a new pump. You can run a temporary wire from the battery and connect to the pump. If it runs the truck follow the wire to the connector check for voltage at this point. My diagram says 12volt from the relay to the pump. Check the wire color at the pump it should be the same color at the relay terminal.

[CanukGMC]

Thanks for the replies. I've been out there literally kicking the truck for a while. New pump is in so I could tell how it's hooked up finally. Dropped the front driveshaft (ujoint promptly fell apart, hurray more work to do) and CURSED my face off at the way the electrical was connected. It's on some kind of suction cup rubber boot forced onto the ends so pulling and PULLING AND PULLING with pliers wouldn't even remove the terminal ends until I snapped and yanked INCREDIBLY hard and ripped the boots right off (yeah I know). Measured the volts at the two wires that go into the fuel pump with the volt meter at 20v setting and got 0 when key is off and 0.01 when the key was turned on. Pressed them up against the (completely different) terminals on the new pump and nothing happened.

I'm friggin losing it on this one. I just don't know wtf the problem is and everything is so rusted and hidden and seized I'm going nuts. I want to just shortwire the relay but it has some kind of plastic lid over it that I can't get off for the life of me, I'll probably just snap it right off and improvise a fix for later, I need this truck running and I'm going nuts here.

[rhandwor]

For a temporary repair use a standard SR-106 Relay or cross reference. I used one of these for my tractor horn. Buy 25 foot of No.12 wire and 10 foot of no.16 wire. Buy an inline fuse holder with a 20amp fuse. Buy terminals after looking relay and fuel pump connectors. Connect from the battery positive at always hot side of starter relay. Use a splice connector to heavy 20 amp fuse holder both sides connect to battery side of relay. From solenoid side run a No.12 wire to the fuel pump connector. Use tie raps and tie to wiring harness.
Use silicon and seal all connectors and use a good quality crimping devise.
Note another wire should to intank pump make sure it is connected.
Find a space in the fuse panel for acc. note this only gets power when key is turned on. Hook up no.16 wire from here to the relay I terminal. This is a steel relay and the ground is the mounting bracket. Clean and a place to mount this using a self tapping metal screw buy after looking at relay. Remember to buy a fuse also. This way you can use the truck until proper repairs are completed.
Don't use accessory to play the radio while setting waiting for somebody as the fuel pump will be running. Remember the rool over valve won't work this way unless you run the power to it and it is still hooked to the pump.
Always do electrical work when rested not mad as you will make much more progress. I would try a temp hot to roll over connector push button disconnect and if it runs wire to this point.