6.5 air bound in fuel and not shifting into 4th gear

[Matt508d]

Okay guys, my name is Matt, I just started my own company and I bought a 2000 gmc dump (6.5) and I'm having serious fuel issues. I'm going to do my best to explain everything to make it understandable and clear as to what my problems are. I'm pretty familiar with mechanics but not diesels this is my first one. And everybody I know (a lot of people ) cannot figure this out.
My problem::::
Right now if I go start my truck in the driveway it will idle until there's no more fuel left in the tank. If I take it on the street and start moving distances like miles it will starve it's self of fuel and die, I'll pull over crack the bleeder open on top of the bowl/filter and it's wicked air bound. It takes about 30 mins (there is a lot of frickin air In there) once it's bled it's back on rippin, but it's very un predictable, when this truck runs it runs super mint for a 6.5
NOW! Let me go further into this, the guy who I bought the truck from sold it to me because of this problem, I have ZERO leaks AND I have new EVERYTHING.
This is what's done:
Rear fuel tank taken out, new fuel tank in the front with sending unit (sock/screen) taken off inside.
New fuel lines up to lift pump.
New lift pump.
Lift pump hot wired to ignition In fuse box and grounded straight to the battery.
New lines from lift pump all the way up to the bowl ( I think this is what I can see)
New PMD and I also have it sitting on the lip of front bumper just till I figure this problem out lol
And crank shaft sensor ( can't remember the name)
Another sensor to do with fuel replaced that I can't remember.
Someone of older age told me that it possibly could be a electric issue in the steering colomn and I'm not at a good fuel pressure and that's why I'm not shifting into fourth gear
Yes as of right now I only have three gears and it's a automatic. I don't know if that has something to do with this fuel issue or if it's a hole mother separate problem.
So there you have it this is quite a **** show for me, I just wana get this truck reliable so I can do some loggin and hauling with it...anybody that could shoot me in a solid direction or have any advice, ANYTHING would be helpful at this point.

-MAtt

[Dvldog8793]

Howdy
30 minutes of bleeding with the filter line open...?
If your lift pump is working properly, I think you have a fuel tank/pick up issue. If your tank pick up is not in the fuel then you will starve and suck air and it will continue to pull air even with the bleeder open.
I would start at the tank and pick up and work forward. verify that the new pick up is intact and doing what it is supposed to do.
After that, all fittings or splices would be suspect.
Regardless of how new they look, disassemble and check and reassemble.

I would hook up the lift pump as it was from the factory and not hot off the ignition.

First solve the air problem then most likely your drivability issues will be fixed.
Then move on to the transmission issue.

There are many posts here about how to locate air leaks into the fuel system. Do a quick search.

Hope this helps.

[Matt508d]

Yes 30 mins and every time I crack it open air comes out, it's not a pick up issue because it runs mints at idle or even driving around my yard, but as soon as u get on the street and go further then a half mile 7 out of ten times it'll die. It's got a full tank of fuel. Sending unit is brand new and working properly and my truck won't run if I hook the lift pump up to harness, I was even told that you can run these trucks without the lift pump being on because of the IP is so strong. And trust me I've probably spent close to 8 hours researching this site and a few others I've read all the threads but there isn't any with my exact issue. I wouldn't have taken the time to think and write up a thread if I found one about my problem already lol

[trbankii]

I agree with DvlDog about not bypassing stuff. The wiring setup, filter sock, and such are all there for a reason.

One thought - is the fuel cap definitely the diesel version? If it happens to be a gasser version, it won’t vent properly and you’ll create a vacuum in the system.

A non-functioning lift pump is a good way to eventually burn out an injection pump. It’ll work for awhile, but I certainly wouldn’t trust the “so strong” you don’t need it recommendation.

Thirty minutes of bleeding clearly states you’ve got air coming in somewhere. With the system totally drained, you should only take a few minutes at most to prime the system from the tank to lift pump to filter.

Again, agreeing with DvlDog, fix the air in the fuel issue first and then you can start working on the other issues.

[Robyn]

Quick check

With the engine off, open the air bleeder on the filter then power the lift pump.

Within a very short time you should have fuel coming out the bleeder.

You can also open the water drain line up on the front of the engine and check it there.

If fuel comes out readily then the lift pump is working.

Next, start the engine and with engine at idle open the water drain cock up front.

Fuel should come out and the engine should continue to run.

If engine dies the lift pump is bad.

Get a clear plastic tube (temporary) connected to the top return line on the front facing portion of the IP (LARGE ONE ON VERY TOP IS FUEL INLET)

Run plastic line up by wipers for visual.

Operate rig and watch for air in return


This rig had a dual tank system ???? Tank switch leaking air ????

If line from the old rear tank is not plugged, DO SO

If the fuel lift pump is working then the air is getting into the system from the pump rearward to the tank, or in the tank (pickup tube)


Any leaks on the engine side of the lift pump will show fuel leaking on the ground.


WHEN WAS THE FUEL FILTER CHANGED LAST ???

Missy

[Matt508d]

Quick check

With the engine off, open the air bleeder on the filter then power the lift pump.

Within a very short time you should have fuel coming out the bleeder.

You can also open the water drain line up on the front of the engine and check it there.

If fuel comes out readily then the lift pump is working.

Next, start the engine and with engine at idle open the water drain cock up front.

Fuel should come out and the engine should continue to run.

If engine dies the lift pump is bad.

Get a clear plastic tube (temporary) connected to the top return line on the front facing portion of the IP (LARGE ONE ON VERY TOP IS FUEL INLET)

Run plastic line up by wipers for visual.

Operate rig and watch for air in return


This rig had a dual tank system ???? Tank switch leaking air ????

If line from the old rear tank is not plugged, DO SO

If the fuel lift pump is working then the air is getting into the system from the pump rearward to the tank, or in the tank (pickup tube)


Any leaks on the engine side of the lift pump will show fuel leaking on the ground.


WHEN WAS THE FUEL FILTER CHANGED LAST ???

Missy


Fuel filter is brand new and I've yet to do all that with the clear line could this problem be traced back to a steering column?

[Robyn]

Steering column ????

Nothing there that's going to have anything to do with air in the fuel system

[Matt508d]

Yes steering column is there anything electrical that could be tied to my problem, the air is in the not because of leaks but I feel like it's electrical. If it was leaking somewhere id be airbound all the time no? The truck won't stay dead so it's very hard for me to diagnose it, I had it hooked up to a computer today for ****s and giggles and everything was perfect fuel pressure and all, something is starving it or telling it not to drink fuel. And like I said I was told it could be an electrical issue in the column.

[Dvldog8793]

Howdy
The fuel system needs the lift pump.
Nothing in the steering column will cause air to enter the fuel system.
If there is air coming in before the LP you probably will not see a leak.
If there is air coming in AFTER the lift pump you will get a puddle/drips.

30 minutes is TOO long for a bleed time. If it takes that long to get the air out with proper bleeding then there is a big problem in the actual FUEL system.

The electrical parts of the system (IP control, LP control, EFS, OPS...etc) will not have anything to do with air in the system. The air has to come from someplace that should not be allowing it in.

If these electrical parts are failing and cutting fuel to the engine, in properly sealed and controlled fuel system, the engine will just die.

If it had a dual tank system, I would check and make sure ALL the lines were run properly to convert to a single tank. If the tank switch was just plugged and left in place that can be a problem.
On dual tank systems the return line was also switched.
Check out Robyns methods of trouble shooting for air.

From what you describe, I think you have air intrusion before or at the lift pump.
Until you can find out where the air is coming from, you will be chasing ghosts.

[Matt508d]

My lift pump is brand new and hot wired so it's constantly on as soon as I turn the key, and this problem occurred and started before the tanks got separated so they eliminated the rear tank and bought a brand new one with sending unit, there are no leaks or drips ANYWHERE we ran a pressure test last night and everything was perfect. I have the clear line spliced in after the lift pump like Robyn said but the truck hasn't died yet
So I don't know anything yet. This problem I have isn't something easy or normal I feel like, and I keep asking about the column because I've followed wires coming from my sending unit that go into the column then back out up top

And all you people are positive that it couldn't be anything to do with the column?

Thanks for all the help and suggestion guys and girls lol I really hope I solve this my company is a stalling point because I don't have a truck to haul with ( this 6.5 is too un reliable)

[rapidoxidationman]

Listen close, cuz it's been said before:

You
are
sucking
air
into
the
fuel
system
.

The only point in the fuel system that (should) have vacuum on it is upstream of the lift pump. Start there. I'm going to guess you don't have fuel lines in your steering column.

Bad idea having the lift pump turned on and off solely by the ignition switch. In an accident, you may not be able to turn it off and might just be pumping raw diesel fuel into or onto something you don't want to be, like something that could ignite it. Common practice is to wire it through an oil pressure switch - do a search and find how that works in your favor.

[a5150nut]

My lift pump is brand new and hot wired so it's constantly on as soon as I turn the key, and this problem occurred and started before the tanks got separated so they eliminated the rear tank and bought a brand new one with sending unit, there are no leaks or drips ANYWHERE we ran a pressure test last night and everything was perfect. I have the clear line spliced in after the lift pump like Robyn said but the truck hasn't died yet
So I don't know anything yet. This problem I have isn't something easy or normal I feel like, and I keep asking about the column because I've followed wires coming from my sending unit that go into the column then back out up top

And all you people are positive that it couldn't be anything to do with the column?

Thanks for all the help and suggestion guys and girls lol I really hope I solve this my company is a stalling point because I don't have a truck to haul with ( this 6.5 is too un reliable)

Was the new tank and pickup unit Diesel or Gas ???.
The sock on a Gas pickup is finer than on a Diesel tank. Some that are sold as Diesel are also Gas socks. That would restrict
you fuel supply and the vacuum created would suck air into the line between the tank and lift pump. Most likely the rubber hose on top of the tank.

Can you lift and support the bed to access the top of you fuel tank? If so remove the pickup unit and remove the sock and give it a test drive. If it works find a Diesel sock and get it on there right away. Or put in an inline filter rated for the volume a Diesel flows.

And get the OPS switch back in the lift pump system. It is a BIG safety issue. If you are DOT inspected you will probably get red tagged. No fun and no income.

[Dvldog8793]

There are many things that could cause your truck to just stall. Some of them are located in the steering column.

BUT...if you are stalling due to air in the fuel system then you have an "air in the fuel system" problem and that has nothing to do with the wiring in the column.
IF the truck is stalling due to air in the fuel than that should be where you concentrate your efforts...and there are only so many places that you can get air in the system. No matter how it has been checked or how sure you are, there still is only finite number of places for air to get there. One or more of the places is the culprit...there is no new sneaky way for air to get in there.
The only things that are not covered on this sight would be things unique to your truck.
The possibility of a different type of fuel tank/pick up...or the tank switch or something else that has been done just to your truck.
If it were me, I would start at the pick-up and tank as you know that it was modified from the factory condition.
Also....I would rewire the lift pump using the OPS.

[trbankii]

I agree with DvlDog - if you’re getting air in the fuel, it’s a leak problem - somewhere.

a5150nut has a valid point about whether the fuel sending unit was the correct one - that could be causing the “air leak” without there being anything obvious in the actual lines.

There are things in the steering column that could be causing an electrical problem that would cause stalls. But there is nothing in the electrical column that’s going to introduce air into the fuel lines - plain and simple. Air in the lines is a physical problem, not an electrical one.

I also totally agree with the advice to not wire the lift pump directly. There are reasons for the safety feature. Burning down your truck due to bypassing the safety is only going to give you more problems to fix. ;)

[Matt508d]

Ok so I was just standing over he engine starring at it and realized and saw a fuel line coming off the fuel filter bowl going under my intake manifold to the front of the engine and I can't see where it's going to I'm guessing the IP? But it's saturated with fuel and I just looked at another 6.5 and that exact line is and was extresmly dry. Could this be my problem ? If it is why doesn't it stall every time I use it and not just randomly? And how hard is it to do that line ? It looks like I have to take my manifold off to get to it ? I will try and post a picture when I get home.

[Dvldog8793]

Has the truck EVER left a fuel puddle or smelled of diesel fuel under the hood or even dripped fuel?
By your description it sounds like the fuel line that feeds the pump. It should come up by the pump to a fitting on the top.
Possible that it is deteriorated enough to be wet like that and is allowing air in...but that line is a pressure line so it would let fuel out under pressure.
I am pretty sure you can fish that line out without removing the manifold but its been a long time since I did it. I think you have to take the fuel manager loose to get at the fitting. tape a pull string to the old line so that you have a way to get the new line in there. Use GOOD fuel line.

That line could also be wet from the bleeding procedure.

As said earlier if you had to bleed for 30 minutes then there should be a pretty serious problem.

[Matt508d]

Has the truck EVER left a fuel puddle or smelled of diesel fuel under the hood or even dripped fuel?
By your description it sounds like the fuel line that feeds the pump. It should come up by the pump to a fitting on the top.
Possible that it is deteriorated enough to be wet like that and is allowing air in...but that line is a pressure line so it would let fuel out under pressure.
I am pretty sure you can fish that line out without removing the manifold but its been a long time since I did it. I think you have to take the fuel manager loose to get at the fitting. tape a pull string to the old line so that you have a way to get the new line in there. Use GOOD fuel line.

That line could also be wet from the bleeding procedure.

As said earlier if you had to bleed for 30 minutes then there should be a pretty serious problem.






I coud be exerateing when I say 30 minutes, but it did seem that long. And no fuel leaks or puddles only leak is that line, my valve covers have what I thought was oil on them(my friends 6.5 same thing) but now I'm thinking it's from that line. I will have to dig into this weekend when I get the time.

[Dvldog8793]

Pulling the intake is not that hard. If you really think that is the problem area, pick up a set of gaskets and find out.
IF that is a fuel leak, MOST of the time it will leak into that valley and drain out the back with a puddle under the bellhousing pan. Sometimes people think it is an oil leak because the fuel is so crappy looking by the time it hits the ground.
The only way I see this being the source of all the air is that maybe the leaky line is allowing the fuel filter/manager to drain. If that is the case then you still need a source for the incoming air.....

If you have wet valve covers, it probably is oil. They are notorious for leaking. Don't waist money on gaskets get a product called "the Right Stuff" and follow directions on this site.

[Whitectc86]

i'm having this same sort of problem right. but my problem is fuel leaking out of the fuel heater grommet. but my truck wasn't stalling it was just leaking alot of fuel on the ground.