Fuel Tank Switch/no-start
02-28-2017, 05:29 PM
#1
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Fuel Tank Switch/no-start
Hi
I have a new-to-me 1985 5.0 v8 f150. The truck has 2 tanks, but no tank selector in the dash. There are two switches I cant identify, in the vicinity where the dash selector might be. Image attached
After running great for a week I'm down to a no-start situation. The truck died at a stop sign and I pushed it a few blocks home. I can't test the fuel pressure as I don't believe there is a schraeder valve for doing so on the rail line.
The high pressure sending unit receives 12 volts when cranked. The ODB1 reader shows a code 11 every time i try it, meaning system ok. It even showed an 11 when I unplugged the sending unit to break the circuit and see if I could pull a code.
The rear tank is always full of gas and only the front tank seems to work. I was hoping I could switch to the rear tank/pump to see if the problem was the front fuel pump.
I don't have access to most of my test equipment, just a multimeter and some basic tools.
Again, the truck just cranks with no sign of turning over, there is spark (i removed a plug and checked for spark. It really feels like a gas issue and this 2 tank situation is really weird to me, leaning toward that being the problem.
Thanks so much for any time you can spare.
Tom
I have a new-to-me 1985 5.0 v8 f150. The truck has 2 tanks, but no tank selector in the dash. There are two switches I cant identify, in the vicinity where the dash selector might be. Image attached
After running great for a week I'm down to a no-start situation. The truck died at a stop sign and I pushed it a few blocks home. I can't test the fuel pressure as I don't believe there is a schraeder valve for doing so on the rail line.
The high pressure sending unit receives 12 volts when cranked. The ODB1 reader shows a code 11 every time i try it, meaning system ok. It even showed an 11 when I unplugged the sending unit to break the circuit and see if I could pull a code.
The rear tank is always full of gas and only the front tank seems to work. I was hoping I could switch to the rear tank/pump to see if the problem was the front fuel pump.
I don't have access to most of my test equipment, just a multimeter and some basic tools.
Again, the truck just cranks with no sign of turning over, there is spark (i removed a plug and checked for spark. It really feels like a gas issue and this 2 tank situation is really weird to me, leaning toward that being the problem.
Thanks so much for any time you can spare.
Tom
Last edited by TomandBob; 02-28-2017 at 05:35 PM.
03-01-2017, 01:25 AM
#3
Old Timer
Do you hear your high pressure pump under the drivers door on the frame rail run for a second (prime) when you turn your key to the on position? Probably need your head down there and have someone turn on the key for you.
Do you have the EFI engine?
Check fuse # 15 & #18.
If you give it a shot of starting fluid, does it start?
The tank selector switch might be located to the right of the heater controls.
Do you have the EFI engine?
Check fuse # 15 & #18.
If you give it a shot of starting fluid, does it start?
The tank selector switch might be located to the right of the heater controls.
Last edited by vjsimone; 03-01-2017 at 08:29 PM. Reason: Correcting text/ Adding text
03-01-2017, 11:42 PM
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WOW. I completely overlooked that switch. Will update tomorrow.
Thank you!
EFI
15 & 18 in good shape.
Think all 4 wires on the switch are red. Aftermarket something that is now long gone i think.
Thank you!
EFI
15 & 18 in good shape.
Think all 4 wires on the switch are red. Aftermarket something that is now long gone i think.
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03-02-2017, 02:55 AM
#8
Old Timer
03-03-2017, 01:31 PM
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After giving it a charge, I tried it with the tank switch changed. I could hear the high pressure pump. No start.
I pulled the cap and sanded the contacts and rotor, and she fired right up. After a few minutes began to run rough, then died and back to where I was.
At least it is narrowed down though. The distributor looks to be aftermarket, recently changed by the previous owner. The ignition coil also looks new, but tested right for voltage and resistance.
I figure I'll change to a higher quality distributor, and possibly change the ignition module I've been reading about while i'm in there. Does that sound reasonable?
Many thanks
Tom
edit: maybe just the cap and rotor first
I pulled the cap and sanded the contacts and rotor, and she fired right up. After a few minutes began to run rough, then died and back to where I was.
At least it is narrowed down though. The distributor looks to be aftermarket, recently changed by the previous owner. The ignition coil also looks new, but tested right for voltage and resistance.
I figure I'll change to a higher quality distributor, and possibly change the ignition module I've been reading about while i'm in there. Does that sound reasonable?
Many thanks
Tom
edit: maybe just the cap and rotor first
Last edited by TomandBob; 03-03-2017 at 01:48 PM.
03-03-2017, 03:25 PM
#10
Old Timer
Hold off on any new parts for today, the PO most likely changed the dizzy to try solve something.
Do you have an Automatic or Manual tranny ?
Were you able to confirm your ability to switch tanks?
Can you hear the pumps in the tanks? (You might need to unplug your High Pressure Pump to hear).
You can use your OBD test connector to run the pumps continuously, vice the 1 second key on scenario.
Do you have an Automatic or Manual tranny ?
Were you able to confirm your ability to switch tanks?
Can you hear the pumps in the tanks? (You might need to unplug your High Pressure Pump to hear).
You can use your OBD test connector to run the pumps continuously, vice the 1 second key on scenario.