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Need Help, Rear Fuel Pump keeps quitting.

 
Old 01-30-2019, 01:50 AM
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Unhappy Need Help, Rear Fuel Pump keeps quitting.

Been dealing with this issue for a while now and it has me at ropes end. I have a 1987 F150 4x4 with an EFI I6 300 that has a dual tank system. A year after I got it, it started having bad intermittent stalling issues. I didn't have the money to fix it at the time so it sat for a while.
2 months ago I got the cash to get the truck repaired. Took it to a nearby Yinglings to have them work on it. They had it for the better part of 2 months trying to fix the intermittent stalling issue. They trouble shot the problem down to the fuel system.
From there, found the high pressure rail fuel pump had failed. It was replaced along with a new fuel filter and fresh gas. Testing revealed clogged injectors and a leaky rail pressure regulator. Injectors and regulator were replaced. During testing the issue came back, the high pressure fuel pump was running constantly, but wasn't getting any fuel from the low pressure in tank pump. Replaced REAR in tank fuel pump with brand new unit. Cleaned tank and added fresh fuel. During testing, the brand new fuel pump failed. Further examination found the tank selector valve was not allowing fuel to pass. The valve was removed and replaced with fuel filters making the rear tank the only usable tank. The brand new pump was replaced with another brand new pump, cleaned tank, and fresh gas. Tossed on a new distributor, spark plugs, and wires. The truck ran decently, and it was believed the issue was solved.

I picked up the truck and drove it home. Parked it over night, wouldn't start the next morning. I checked the battery, it was good. The truck cranked but would not fire. It cranks a little higher than 500 rpm. Checked for spark with an adjustable spark tester, it bridged a 1/4 inch gap. with no issue. Started looking at the fuel system. Turned the key and listened for the pumps. High pressure pump started and kept running well past when it should have turned off. The REAR low pressure pump did not come on at all.
I jumped the connection for the emergency fuel cut off switch, no change.
I pulled the tank selector switch and jumped the switch, and found no power running into the selector switch.

I know power is going to the high pressure fuel pump, so I'm pretty sure the fuel pump relay is working.
I don't know where to go from here. I don't have the tools or location to drop a tank with the negative temps outside.

Any help would be greatly appreciated as the truck is the only vehicle that has heat.
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Old 01-30-2019, 10:44 AM
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First, I'd invite the "repair" shop to refund 100% of what they charged NOT to fix it. 2 months is ridiculous.

For the continuous fuel pump, click this & read the caption:


(phone app link)


For the rear pump not running/no power to tank select switch, get a Haynes and study the wiring diagrams for your truck. Read this caption before buying a Haynes, though:


(phone app link)
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Old 01-31-2019, 12:11 PM
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did you check the fuel pressure?
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Old 03-02-2019, 12:59 AM
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Hi, thanks for the replies guys!

I have some good news and bad news.
Good news is I can't find the issue so I'm going with the nuclear option and replacing the entire fuel system myself.
Tanks, pumps, lines, wiring, injectors, everything.

Bad news is while using a small amount of engine starter fluid to confirm that no fuel is indeed the issue buy getting it to run for a second or two, I noticed a large grey cloud come out the back of the engine.
The engine ran for another second then made a short sound and stopped.
Now the starter can't crank the engine over even though I hear the electronics engage.
I fear I may have just confirmed the lack of fuel as the big issue and seized or wrecked the engine in the process.
It's presently too cold out to try turning it over by hand so that will have to wait til morning.

May what ever God there is have mercy on this engine.
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Old 03-02-2019, 01:11 PM
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Remove the spark plugs before attempting to turn it by hand.
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