Eratic behavior from a 1985 6.2. Requesting help please

[nycxjeremyy]

This is genuinely confusing me, the first half of the video is of it idling, it then began to surge out of nowhere, this is all after I changed the fuel filter, added howes additive and used diesel 911 to ungel the fuel last week, it actually ran relatively well after doing that and then today it began to surge again.







The second video is of me starting it after leaving it alone for 1.5 hours (30°F), notice how it behaves when attempting to start







Failing IP? Lift pump failure? Air in the lines? I'm not sure anymore, this is driving me insane, i don't know anymore, any help would seriously go a long way.







Video: https://www.reddit.com/r/Diesel/s/tkmbTC6sbC



---------------

UPDATE:



So we actually took it to the on base DIY shop and did a smoke test, there was a indeed a bolt missing on my turbo which we fixed immediately, but the surge was not remedied.



I took it out for a test drive and when i rolled up (letting off the throttle) it began to surge again.



Missing bolt on Turbo:

New video by Jeremy

photos.app.goo.gl

Surge at idle: https://photos.app.goo.gl/G3vtcf6rsojggC4g7



Hard start (took 7 tries): https://photos.app.goo.gl/UshScC3UKLt8p5EN8 https://photos.app.goo.gl/Ahb3dKVVzBVuZA1f9



I definitely have a faster time getting up to speed, but the surge is still there, a friend of mine who does own a 6.2 is adamant it's a failing IP, but I've been told that it could be the Lift and/or Fuel pump, but I don't know anymore, I'm about to throw in the towel here. If it is an IP, it's going to be an expensive repair, im just an E3, don't necessarily have all the funds in the world

 

[backwoodsman]

I'd check for a plugged fuel return line. If it's plugged, it can't purge air from the injection pump, and it sort of kicks the cold advance in & out, which can cause surging, and the hard starting happens when there's too much air in the IP for it to get fuel to the injectors. Easiest way to check for that would be to remove the fuel return line from the injection pump, and attach a hose running into something to catch the fuel. Then see if the problems go away.

 

[ChuckN]

Just spitballing here based on what I was told when I was a youngun in high school.

I don’t know if these diesels are prone to it, but I know that some of the GM diesels could pull oil past the valve seals. The fact that it’s surging upon deceleration brought that to the front of my mind. Feel free to ignore me, just thought I’d put that out there.

Chad

 

[Blue Ox]

Fuel supply, fuel supply, fuel supply. Everything I'm seeing there is low fuel pressure or air.

As @ChuckN said dump the return into a bucket, or temporarily replace with a clear hose to observe bubbles. You shouldn't see more than champagne bubbles in it.

If you have the original box filter try cracking the bleeder when someone else is cranking it. Disconnect the solenoid wire from the top front terminal on the pump so it doesn't try to start. You should see solid fuel as soon as you start cranking.

 

[ChuckN]

Fuel supply, fuel supply, fuel supply. Everything I'm seeing there is low fuel pressure or air.

As @ChuckN said dump the return into a bucket, or temporarily replace with a clear hose to observe bubbles. You shouldn't see more than champagne bubbles in it.

If you have the original box filter try cracking the bleeder when someone else is cranking it. Disconnect the solenoid wire from the top front terminal on the pump so it doesn't try to start. You should see solid fuel as soon as you start cranking.

Fuel supply, fuel supply, fuel supply. Everything I'm seeing there is low fuel pressure or air.

As @ChuckN said dump the return into a bucket, or temporarily replace with a clear hose to observe bubbles. You shouldn't see more than champagne bubbles in it.

If you have the original box filter try cracking the bleeder when someone else is cranking it. Disconnect the solenoid wire from the top front terminal on the pump so it doesn't try to start. You should see solid fuel as soon as you start cranking.

I’ll recredit that to @backwoodsman .

 

[Blue Ox]

I’ll recredit that to @backwoodsman .

You're a good man Chuck.

My bad on the misquote.

 

[nycxjeremyy]

Fuel supply, fuel supply, fuel supply. Everything I'm seeing there is low fuel pressure or air.

As @ChuckN said dump the return into a bucket, or temporarily replace with a clear hose to observe bubbles. You shouldn't see more than champagne bubbles in it.

If you have the original box filter try cracking the bleeder when someone else is cranking it. Disconnect the solenoid wire from the top front terminal on the pump so it doesn't try to start. You should see solid fuel as soon as you start cranking.

Video of the air test is up! Please let me know whay you all think

https://www.reddit.com/r/Diesel/s/rZMjyYOR5y

 

[nycxjeremyy]

Video of the air test is up! Please let me know whay you all think

https://www.reddit.com/r/Diesel/s/rZMjyYOR5y

 

[backwoodsman]

That's a LOT of air, and it's getting into the fuel system somewhere. Normally there shouldn't be any air there. It's hard to start because the injection lines fill up with air and it just has to crank a while to get the air out of them. Make sure the fuel filters are on tight enough to seal, and check the petcocks on the primary filter. Then check everything from the IP to the tank until you find the leak. An electric pump upstream of the primary filter might help find it faster. I've seen rubber fuel hose get slightly porous to air when it gets old, but I think that's too much air for that.

I don't see anything in the video that makes me think there's any other problem.

 

[squaredeal91]

I concur. Seems like it's sucking air to me. Going to need to check fuel lines. Probably sucking air between tank and lift pump. If you have dual tanks there's more lines. Make sure the selector switch isn't tripped between tanks.

 

[Blue Ox]

Yeah, air.

You've already gotten good advice on tracking it down.

All I can offer is when you're cranking it and trying to purge the air to start it, don't pump the throttle. It's not a carburetor. Go to WOT and hold it so it's trying to deliver maximum fuel. That will help it bleed itself.

But, obviously, got to find that air leak. Clear tubing is your friend. Keep moving it through the fuel system until you find the point of origin.

 

[Rickf]

I had a 6.5 TD with an air in the injector lines issue. It turned out to be the metal fuel pick-up line at the tank developed a pin-hole from crap setting on it.