Fuel Problems

[DirtyD]

Hey everyone. I'll start by saying that I've read every thread I could find on this topic.

I have a 92 f250 7.3 with 110k miles. It was a farm truck though and is in fairly rough condition aside from the engine.

I'm having some major fuel issues which started out minor and progressively became major this winter. I was getting surging while driving, it would die if left to idle, and I'd have to crank for a bit to re-prime fuel after it sat for a while. It was doing this with full tanks, and it didn't matter which tank I had it switched to, so I know the problem is at the tank switch or forward.

What I've done:

-replaced fuel filter
-replaced return lines
-replaced lift pump and the rubber line that feeds it.

I had a clear line between the lift pump and the filter before I replaced the pump, and there did appear to be quite a bit of air in the line so the problem is between the filter and the switch. Now that i've replaced the pump, there is obviously quite a bit of air in the system. As I crank, I can see fuel in the clear line pushing back and forth 6 inches or so, but it's not actually flowing, just swishing back and forth.

My questions:
-is the lift pump a diaphragm pump? If so, it seems like there is a check valve of something that isn't doing it's job. Do I need to prime the lift pump somehow to get it pumping?
-Is it possible there is just crap in the line behind the lift pump that is keeping fuel from flowing? I don't feel like this is likely.

At this point, even if there were a small air intrusion, I would expect the pump to at least push fuel and air... but it's not. It would take a really big hole to make the lift pump fail like this, and I don't see anything that could be causing it.

Also: please don't turn this into an electric fuel pump lynch mob. I want answers : )

Thanks,

doug

 

[marmot]

You should buy a facet...ah just kidding no lynching today it's sunday. They are nice however. It sounds like you have an air leak, are there any signs of damp fittings at the return lines or any other fittings? The lift pump is a diaphragm pump no check valve although the duralift pumps do have one.. Replace ALL the rubber lines under the hood including the return lines(sounds like you may have already). Also I think the fittings on the fuel filter housing, drain heater etc are notorious for leaking air so take a close look. Good luck.

 

[IDIoit]

get an electric lift pump.
consider yourself lynched.

seriously. if you have a leaky fuel line, it will suck both and it will run like crap.
lift pumps only prime by cranking the engine.
an electric pump, you dont have to prime either, just feed it power.

if your lift pump is not pumping you have 1 of 7 issues.
1)youre out of fuel
2) you have 1/4 tank and your shower head is busted
3) a cloged line or a pick up
4) old and cracked rubber lines
5) a broken nylon line
6) a dysfunctional new lift pump. (yes it does happen..OFTEN)
7) a busted FSV

compressed air put into the line that feeds the lift pump to the tank is a good way to find out whats going on.
do this with the fuel caps off and listen for bubbles.

 

[DirtyD]

It definitely seems like I installed a defective lift pump : (. Maybe I'll just bite the bullet and put in an electric pump. Then at least I'll be able to get enough flow to see if I'm still having a problem with air intrusion. Will any fuel pump from the auto store due? Yep, I replaced all the return lines and I can't find any wet lines anywhere, including on the return lines/caps and back toward the tank switch. I'm 90% sure my leak is before the filter because of what I was seeing in the clear lines. And again, the tanks are full and it didn't matter which tank it was switched to. I like the compressed air idea, I'll try that once I get the pump working.

I'll just keep plugging along. This really sucks, I'm tired of working on this problem!!!

 

[DirtyD]

Is the FSV the fuel tank switching unit?

 

[marmot]

yep

 

[DirtyD]

It was the original lift pump that was pulling air I think. It's running strong now with an electric pump. Now to find/make a cover plate.

 

[C_Luft]

Your local auto parts store should have a big block Chevy fuel pump block off plate. I bought one anticipating I was going to purchase a facet pump but never got around to doing it.

 

[IDIoit]

that block off plate is not BBC specific, its most GM applications.
this plate does need to be modified to fit our IDI's
a little grinding and your good.
i left my bran new lift pump in so it can feel the same abuse it gave me

altho a over the counter pump will do for now, they only put out 5-ish psi.
sometimes it wont feed the IP enough and starve it for fuel.
now im no expert but if you starve an IP long enough, it may be prone to premature ***********.
i have a Bull Moose, and it needs the PSI!!! im running it at 9 psi
huge difference in performance from the 2psi my mechanical supplied
not to mention that IT WILL effect a pulse detector when you try to time it.

a lill phrase i coined...
"YOU CANT FEED A MONSTER LESS AND EXPECT IT TO **** MORE"

 

[stealth13777]

There's a specific block-off plate that requires no modification. I just installed it. I suggest reading the tech article on facet dura lift install in its entirety, it helps.

Spectre 42473

The article says other plates are larger and thus need to be modified to fit.

http://www.oilburners.net/forums/showthread.php?t=72265
And this thread is one where I asked for fuel pump options recently. The guys on here gave a ton of good info on pumps that work with our fuel system.




Sent from my iPhone using Tapatalk

 

[sjwelds]

Yes. The above one is correct. I used a different brand and it hit the lip above the machined area on the block.

This one bolts on and no problems.

 

[laserjock]

You must be registered for see images attach

I would love to know if this one would fit without grinding.... takes care of my turbo oil drain too. Hmmm.....


Edit... heres the link.

http://www.summitracing.com/parts/mor-65398/overview/

 

[jim_22]

It was the original lift pump that was pulling air I think. It's running strong now with an electric pump. Now to find/make a cover plate.

I by-passed my (new) lift pump to see if it had died. It did. After much struggle to make it run, went electric. Could not find the block-off plate anywhere within driving distance, calling several auto stores in the Boston area. I looped a piece of hose output to input on the lift pump because I needed to drive the truck. That was 2 years ago.

 

[madpogue]

I looped a piece of hose output to input on the lift pump....

You should use some clear hose, and partway-fill it with just some random light veggie oil dyed purple or pink or something, just to confound people looking under your hood.

 

[IDIoit]

mine is still on the truck with both inlet and outlet open,
only problem with that is the first time i fired the truck with the e-pump,
it sprayed diesel everywhere lol
its a great degreaser!