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



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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