6.9 Possible Fuel Starvation?

[bobbyw1200]

1985 f250 6.9idi
Inline electric lift pump.
New fuel filter before pump
New canister filter
Water separator bypasses
Manual pump bypassed


Hey guys I'm trying to track down an issue with a truck I just bought. The previous owner said he ran the tank dry and sucked up crud taking out the inline filter before the lift pump. I replaced the pump and filter with the reccomended airtex and wired it into the fuse block. Problem is when I'm driving it easy it has good power and no problems but when I'm at highway speed it cuts out and the exhaust pitch changes and I lose power. I have no tach in it from the factory but with the gearing I have it shouldn't be near the governer yet. Could it be air in the lines or something more? Thanks

 

[FoolhardyIDI]

Sounds like you have air intrusion into your fuel line. First things first. Are you anywhere near 1/4 tank? The pick up in the tank likes to break off and you will start to suck air at 1/4 tank. Also check your tank selector. If the fuel pump sucked up a bunch of crap. Some could be in the selector keeping it from closing it self off. Trying to pick up fuel from both tanks. Also check you IP and make sure its not leaking so bad that its causing the problem. Also mileage could be a fator. If the IP is worn out to bad to keep up with the fuel pressure demand.

 

[bobbyw1200]

It has right under 200,000 miles and I believe its the original IP. Both pickups I believe are broken but I filled both tanks to see if it would help and it didn't. No leaks at the pump or lines up to it. I have two return line caps leaking but I am going to replace them all this weekend and see if it helps. I also noticed at highway speed I get random spurts of bluish smoke when it cuts out. Is there any way to check the tank switch? I can move it back and forth and it sounds like it's working

 

[IDIoit]

i would pull the lift pump and switch and blow some air in the lines.
i dont know if you can blow air back through the valve.
and since there cheap enough, i would replace the lift pump and filter.
mine did this also.
turned out to be a piece of the old pick up obstructing the pick up on the rear tank, the front tank was fine.

if i were you, id pull the bed off, or drop the tanks and address the entire fuel system at once.

nothing worse than chasing air intrusion which turns out to be a clogged or obstructed fuel line.

by the way, welcome to the forum

 

[OLDBULL8]

I'd bet the FSV is full of crap.

 

[bobbyw1200]

I have already replaced the lift pump and filter with no avail. I will try blowing the line out and see if it helps. Could I do a volume test at the Schrader valve to determine if I have sufficient flow? It does this on both tanks and has no difference if it's cold or warm.

And thanks I'm glad to be part of this forum I've been reading it a lot and it looks like there's alot of very knowledgeable people on here. I appreciate the help and will return it at any opportunity I can

 

[79jasper]

So what pump are you actually running?
You say airtex, so I think mechanical on the block pump.
But you also say in line electric?
Pull the lines off the selector valve. Blow through the valve in all ports/directions, but you have to turn the key on and switch the selector. Then blow into the lines to the tank.
Use lower pressure.

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[bobbyw1200]

It's an airtex electric inline recommended on here. I will try blowing the lines out tomorrow

 

[79jasper]

I just don't remember anyone here recommending an airtex. Most here hate them.
Here everyone like the duralift.


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[theguruat12]

Interesting that yours just cuts, I've never had that happen. When mine would starve, it would all of a sudden take off like a rocket for about 10 seconds, THEN die.

 

[Waystro]

Interesting that yours just cuts, I've never had that happen. When mine would starve, it would all of a sudden take off like a rocket for about 10 seconds, THEN die.

Man first time that happened to me.

She sure was Fun tho was like I had a Jet engine strapped to the truck.