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Eratic behavior from an 85' 6.2 (more below) requesting help please (Two vids in one)

dbrannon79 said:
Don't do tictoc. does he have a FB account? I may need a replacement IP at some point for my 93 6.5 If they are not too expensive. I assume you got a military take-off?
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He has instagram, I haven't found Facebook, and yes sir that IP is a CUCV varient, he gave it to me for $200 (did not care about shipping) as he had no need for it anymore

Drove well home (https://photos.app.goo.gl/Fz9xu31iuht4VfF56) it's literally ONLY when I let off the throttle that I'll start to rev up and down, drives perfect with throttle on, got it up to 80 MPH even.

I'm ending it for the night, I don't know anymore, not even he knows what it could be
 
Have you or anyone else ever removed the top of the IP? the top section that houses the fuel shutoff solenoid. I am asking because if it was and was not re-installed properly. Now don't go trying to remove it. not until you come back with what you plan to use to stop the engine from running away like Will said.

Take us back down memory lane here. when did the surging start and what was done leading up to and when it started.
 
dbrannon79 said:
Have you or anyone else ever removed the top of the IP? the top section that houses the fuel shutoff solenoid. I am asking because if it was and was not re-installed properly. Now don't go trying to remove it. not until you come back with what you plan to use to stop the engine from running away like Will said.

Take us back down memory lane here. when did the surging start and what was done leading up to and when it started.
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I personally never took it off, that being said, don't know if the previous owner did either, ive owned this Blazer for about 2 years now, and it did not act like this until November of last year

I did not do anything mechanically wise to it prior to this, that being said, this did occur after I installed a new radiator due to my old brass one blowing up on me on a road trip (https://www.reddit.com/r/Diesel/s/ltjNXpXojq)

Even then. The surging didn't occur until a few weeks after that
 
it can be a hair pulling experience. these rigs require a LOT of patience and will test your skills LOL. sometimes you gotta take a step back, sleep on it. you'll eventually get it. just don't give in, in the end you'll come out on top. Plus you'll come out knowing your truck like the back of your hand too!
 
nycxjeremyy said:
Trying to, dear God this is so ANNOYING, we've tightened hoses, took off the turbo housing, everything, we're just stumped at this point
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Look to see where the sending unit and pickup tube goes into the fuel tank.
If it is under the truck box, then :
Remove the filler neck ground strap.
Remove the filer neck mounting screws, the hose clamps loosened, hoses broke free from the filler neck, and or, tank and then remove the filer neck.
Disconnect the truck box wire connectors.
Remove the eight truck mounting bolts and lift the box from the truck and, if available set the box on a couple of saw horses.
With compressed air, blow the dirt, rocks and debris from around the sending unit/suction tube, disconnect those tubes and hoses, a hammer and punch if You dont have the wrench, then tap the retainer ring in a counter clockwise rotation until it clears the fuel tank, once again blow dirt and debris from around the sender unit cover.
Lift off the sending unit and inspect the suction tube and pipes for rust through holes or breaks.
 
I think he's got a k5 blazer. it would be drop the tank or cut an access panel in the floor! personally I would drop the tank while placing an order for a new tank and sending unit from RA. 40 year old tank is bound to have the lining coming loose or rust in it along with the sending unit too.

installing new would eliminate that area as a problem completely.
 
Will L. said:
Stop playing with it.

Remove and replace the old hoses & clamps.
SAE30R9 to withstand the modern fuel.
High quality clamps not cheap chinese junk.
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Do you have a link to quality clamps?

I posted a link to some stainless, not worm gear clamps, years ago.

Seems I'm out of some.

Do you recommend the type of clamp you can tighten or spring clamps
 
Game plan for this weekend (plus a small update):

- Take a jug of diesel, a fuel line, and an electric fuel pump (5PSI or so) and do a test to smoke out (or, fluid out) the leaks.

- Replace all rubber fuel lines and clamps, look over metal lines aswell

If anyone has anything else I should do, please write them down, we will also more than likely be dropping the tank too

Update: started up fine (didn't stutter and die, and then take forever to start) and even ran smoothly (granted, I poured in half a bottle of ATF fluid in the tank) no surge while idling or driving

Vid: https://photos.app.goo.gl/69o7ec2yNtVSywy68
 
Ideally, add a stainless steel T fitting at the inlet of the ip and attach the pressure sensor for a fuel gauge there. Mount the gauge in the cab so you see it while driving. Low fuel pressure creates running problems, heavy aeration will show up on a fuel pressure gauge as will bad lift pump, lack of flow, etc. low incoming pressure does damage to the ip besides just making it run bad or not at all.

Unfortunately I’ve no suggestions of a quality gauge kit that doesn’t cost a chunk.

Adding a gauge right now has good & bad. Good because it can always help diagnose issues. Bad because if you solve all the other problems- it can run perfectly, but if you make a mistake installing the pressure sensor- that can replace the problem you solved and make you think it’s something completely different. Likelihood is minimal but possible.

It is tempting to just add a T between rubber lines. Don’t.
Also tempting to buy a low cost mechanical gauge and just run fuel line into the cab like I used to do. Don’t.
When either of those go wrong it creates a very bad day.
 
As discouraging as this might seem, realize that You will find the culprit and it then will all be as new and good to go for a very long time.

It ran good for a distance, during that run the fuel level in the fuel tank dropped some.
Possible that if there are holes rusted through the pickup tube that those holes got exposed and now it is allowing air incursion ?
 
Strap down a five gallon fuel jug on the floor in the right side passenger area. Providing this Blazer still has the mechanical lift pump bolted to the block.
Disconnect the hose right at the lift pump, bring another hose from the fuel jug to the lift pump and start a siphon, plug the hose into the lift pump at first sign of fuel. The fuel hose can be threaded through the pour spout of the fuel jug to help in not creating a mess.
Now take it for a drive and see how it performs.
 
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