Air in line?

[TDSECK]

Last summer the day before my 500 mile vacation trip I started my Suburban to fill'er up at the local diesel station.
It ran for 30 seconds then died, started again fired a few times and then would not start.
So took my car instead, It sat for a good 2 months until I found a 6.5 diesel mechanic that would come to my house.
There was no check engine light also no code when he ran a scan on the computer.
He checked voltage on the OBD2 port, oil pressure switch, fuel solenoid, and relay for the lift pump, I think. He advised, new glow plugs & injectors if they have not been replaced.
Everything check out then of course it started. He thinks it was air in the fuel line.
Before I had this issue I change the oil & fuel filters and installed a new lift pump. Are there any issues with lift pumps that are other than the GM mfg?
(I realized the lift pump was not working when I tried to prime the fuel filter. I do not know how long the lift pump was not working from the last filter change of 7-2016)


I have been replacing the fuel filter since I bought this truck in 2011 with no issues, by using the lift pump hot wire to prime.

This morning it started right up ran for a minute then died, started & died then started and ran good all the way to work (about a 45 minute run).


Last spring the PMD failed, so I after much research I bought a Flight Systems unit and mounted It to a large Heat sink that I have been holding onto for years, all was fine till the filter, oil lift pump job.
Any advice is much appreciated, as this forum is fantastic for any driving a 6.5

[Robyn]

You may have a pin hole leak in the line from the tank to the lift pump.

These can be problematic to find.

How much fuel in the tank ???

[TDSECK]

A bit under 1/4 tank

When i replaced the lift pump i gently pinched the rubber section of the fuel line where I had replace a rusted out section with hose.
The tank rusted out about 2 years ago, once I pulled that I saw that the fuel lines and rear brake lines where very rusted so i replaced all that.
Since this issue started with the replacement of the lift pump do you think it is safe to assume that where I pinched the fuel line and or the lift pump is leaking air in to the line???

[Robyn]

Anything is possible.

Did you replace the fuel pickup screen/gauge sending unit.

These trucks have a sock in the tank that can plug up, and they have a bypass valve that will allow fuel to be sucked into the fuel line just above the sock.

There is a valve at that location and IT CAN LEAK and allow air to enter the fuel line when the tank level gets down in the 1/4 tank range


You need to be sure your connections and plumbing from the inlet of the lift pump to the bottom the the tank are clear of issues and air tight.

You may even have a small pin hole between the pump and the tank that you can't see and that is not leaking fuel.

A pin hole leak will allow fuel to drain back to the tank and air to enter.

Even a small amount of air will create all sorts of misery...

[a5150nut]

And if you should replace the sock and fuel pickup be it is Diesel and not gas.

[artfull dodger]

And if your going the whole drop the tank route to change the sock, and if you haven't replaced the fuel line from tank all the way to up in the engine area away from the rust, do so now. My first 6.5 was in a burb that used to be a paramedic response rig. The dept that owned it was having the same issues with thiers and it ended up being rust pin holes in the line behind parts of the chassis that you could not see. And it wasn't leaking fuel or even wet with fuel in that area. But it was crusty enough that is was sucking air. Any diesel will be intolerant of air in the fuel. A good solid leak free fuel line to the IP and return line to the tank is very important.

[TDSECK]

Up Date
Always have a spare PMD to swap out the one in use!
The second shop that checked out this problem wanted to replace the injection pump so I gave him a used PMD that I had just bought from E Bay.
Of course, that was the problem, the 4 month old PMD had failed.
My 6.5 runs fine now.
I had bought a Flight Systems PMD so I am reluctant to buy another of that brand, Do you think just bad luck or suggest a Stanadyne, Dorman, D Tech or what?

[arveetek]

I had bought a Flight Systems PMD so I am reluctant to buy another of that brand, Do you think just bad luck or suggest a Stanadyne, Dorman, D Tech or what?


I've been really happy with the D tech models. I'm just now on my second one after several years of trouble free use, right up until it died. I believe all PMD's, no matter the brand, have a very finite life span.

Casey