Got a new toy today

[1990BerettaGTZ2.3L]

Ok she's a 1986 Chevy K30 3+3 crew cab with a 6.2L diesel and sm465 and np205 transfer Dana 60 front Dana 70 in the rear, ok I think it's water in the fuel but everytime I switch it on the tank I just filled which would be the left runs like crap, when it's on the right it does ok but not what it should, what's a good tune up to do on these as far as fuel filter of course and other stuff I don't know slot about these but can learn being a gasser guy all my life any help would be sweet

[Money pit Beretta]

Koots is the man to talk to on this.

[1990BerettaGTZ2.3L]

Ok should I say it lol I think so here kootsy kootsy kootsy kootsy kootsy koo lol I had to

[Koots]

Hahahaha right up my alley!

You've got yourself one tough fvckin truck with all those parts combined. The SM465 makes it even stronger than the M1008 1-1/4 ton trucks used by the military. They had the crazy strong TH400 3-speed, but the 465 is about one of strongest 4-speed manuals available for our trucks.

Anyway, the tank switching problem might be from a leak somewhere in that tank system and all the way up into the tank switching valve (that tees of to both tanks). If there is even a tiny crack in the system, it will suck in air, which seriously messes with a diesel. If you got the time, I'd even drop the tank and inspect the sending unit.

A quick way to diagnose these engines is to stick a 1/4" piece of clear tubing/line onto the return line of the injection pump. It's only about a 6-8" piece of rubber tubing coming off the top of the pump, facing you when you are looking under the hood from the front. That way you can run the truck and check for bubbles in the return line. It makes it super quick to go through some of the diagnostic process with an old mechanical diesel.

Most of the later 6.2's usually had trouble with the sending units and the rectangular fuel filter on the back of the intake causing all the leaks.

As for maintenance, I would replace the fuel filter(s) (should only be one with the 86), the air filter and change the oil (I've used Rotella 15W40 most of the time). That's about all the simple maintenance you need to do for the truck...

If you want to get it running perfect, I would test and pull the glow plugs (10mm or 3/8 long socket should clear the spade connectors). If you pull those, soak them with a good penetrating oil a few days before hand and liberally a few hours before you pull them. That way, if you have some swelled plugs, You will have an easier to time working them out without breaking them off. Just be patient and don't force it to come out past the initial crack to loosen it.

THEN, I would pull the injectors off and have them cleaned, tested, rebuilt or replaced. I used this opportunity to replace my long body 6.2 injectors with the 6.5 turbo short body injectors. They are preset with a higher pop pressure for better burn, but any injector can be rebuilt to pop at higher pressures, so the main reason I did it was because it makes installing the 6.5 turbo system that much easier on the older engines.

Anyway, that's about it for maintenance on these trucks. They can be a lot of work to figure out, but they start making a lot of sense once you really start digging into them and seeing how they tick.

[1990BerettaGTZ2.3L]

Thanksan next time I got time I'm diving head first into it haha

[Koots]

The only thing I would advise to keep to the professionals is the internals of the Injection Pump. I've pulled a few apart now and know how they fit together, but it's a complicated piece of machinery and lots of things to go wrong LOL Just pulling the top cover and adjusting the fuel is all you need to know how to do with it.

These pumps are lubricated by their fuel, which ULSD is not very good at anymore. Best advice to keep these pumps alive is to run TCW3 2 stroke oil in the fuel tanks. My diesel never clogged up with it and it always ran and sounded smoother with it in their. As long as it's low smoke and low detergent forumula's, it should be in every tankful.

I used to use 1/2 a quart or a full quart when I would fill it up. Most of the time a 1/2 quart was enough to darken the fuel a little and run nice.

[1990BerettaGTZ2.3L]

I firgired out my furl problem my fuel box isn't working tgat switches the tanks and when I bought it I filled the left tank well $100 later u found out it was just sucking off tge right even though I was switching the button, but other than that she runs like a tank, scares me at 45 mph though cause I found out my steering dampener shocks bad so it feels like the wheel is falling off the front end shakes tge truck bad!! But got a moog super trail boss on the way

[Koots]

That's good that you got it figured out. I always heard of people having trouble with these dual tank setups, especially as the truck gets older and maintained less.

Do you have any diesel truck shops around? Most diesel shops should be able to test, clean and adjust the pop pressure on your injectors and do it at a significantly better price than most places online will quote you. If you want the best, grab some genuine Bosch replacement nozzles (which can be had for under $20 each) and have those installed and adjusted. This is usually what the best injector rebuild will consist of anyway.

Anyway, go enjoy your truck!