6.5 diesel

[DeanRV]

Before replacing all those parts, did you have any fuel leaks? I replaced the lift pump a couple of days ago. For the fuel lines, did you replaced them with rubber?

 

[DeanRV]

The diesel crew here will surely chastise me for this, and I am absolutely not a diesel guy. However the balancer on these engines is notorious for coming apart and causing a lot more damage before it's done. Have you inspected the balancer? I am guessing here, 100%, but just throwing it out there in case it's not been considered.

Richard

 

[DeanRV]

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Before replacing all those parts, did you have any fuel leaks? I replaced the lift pump a couple of days ago. For the fuel lines, did you replaced them with rubber?

I'll take your advice and change out the fuel lines and reseal the fuel gauge sender in the tank. Would someone know how much fuel line I'll need and the sizes? My truck is the extended cab with 8 foot box

 

[someotherguy]

You've quoted my reply twice where I asked about the balancer but haven't said anything other than "Funny you mention" - so I'm wondering what's up with the balancer?

Richard

 

[DeanRV]

You've quoted my reply twice where I asked about the balancer but haven't said anything other than "Funny you mention" - so I'm wondering what's up with the balancer?

Richard

So sorry, I have a brand new balancer and pulley on my bench. I haven't put it on yet, trying to fix the stuttering part and I've also cleared the fault codes and they haven't come back, no other codes.

 

[DeanRV]

I've been racking my brain on what could be causing the rough running of my truck and I'm not 100% certain but I think it's air in the system. I've replaced the lift pump thinking it was not keeping up with the demand also it was over 6 years old. One thing I forgot to do is change the rubber o ring on the inlet and outlet side. I definitely do not have a diesel leak but could air still get in from this location? To rule it out I'm going to remove the line and add the o ring. What size do I need?

 

[Erik the Awful]

Check for air in the fuel.

Your fuel pickup lines can't be leaky or cracked and sucking air. Your pressure lines need to be bled of any air and tightened down, but not cranked to deformity.

When running idle I've been watching the clear tube from the return and no bubbles. I turned off the engine and watched the clear tube for about a minute and a bubble came up from the hard line return. Started the truck up, bubbles go away and when I turned it off bubble came up from the hard line into the clear tube.

Given the age of the truck, the suction side of the lift pump is suspect. There are o-ring seals at the fuel sender on the tank and by this age they are toast or even disintegrated, allowing air into the system. In my case, I replaced everything: tank, seals, fuel lines and lift pump. This cured the problem.

First, ensure all your o-rings are new and that the hoses and hard lines are not cracked. That's from the lift pump (does it have one?) all the way to the injectors themselves. If you're getting air anywhere in there, you're going to have the problems you're describing.

Don't trust the injection pump to self-bleed all the air bubbles out. I have zero experience on the GM 6.2/6.5, but I've worked on Isuzu diesels that absolutely wouldn't run right if there was any air between the injection pump and injectors, and they wouldn't clear out. On the Air Force nitrogen carts, you had to crank the engine with the injector nuts loose. Once one of them started spitting a good stream, you tightened it. When the second one started spitting and you tightened it the engine would usually fire up, running rough. Then you had to scramble to tighten the other two before they sprayed JP8 everywhere.

If the engine runs, while it's idling crack each injector loose until it shoots a solid stream, then tighten it down. Repeat seven more times.

 

[DeanRV]

Update
Changed the vacuum pump, started making weird noise. Changed harmonic balancer and pulley. Replaced both viton o rings on the lift pump and....still gave air bubbles in return line. So next step is dropping the tank and replacing all the fuel lines but I'm not going to fo it, will take it to local shop. I'll have it done around end of August and will update this thread when it's completed.

 

[DeanRV]

Forgot to ask, what size fuel line? I'm going to go rubber lines, from tank to lift pump, lift pump to ffm what size would it be? From return line to tank what size? I'm going to get the diesel rated rubber lines myself and just pay labor

 

[smdk2500]

Update
Changed the vacuum pump, started making weird noise. Changed harmonic balancer and pulley. Replaced both viton o rings on the lift pump and....still gave air bubbles in return line. So next step is dropping the tank and replacing all the fuel lines but I'm not going to fo it, will take it to local shop. I'll have it done around end of August and will update this thread when it's completed.

I went back and read to refresh all I seen was posted is you have a bubble when the engine is not running. Is that correct? If so that is normal. My 95 does the same. What you are looking for is bubbles when it is running. Replacing the lines from the tank forward probably isn't a bad idea considering the age. The supply line should be 3/8 and I think the return is 5/16. You will have to have adaptors at the fuel tank side to adapt the sending unit to a barb style fitting and will have to do the same at the lift pump.