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CUCV/K30 6.2L is a dog. Help?

J

Jesse Jaymes

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Feb 14, 2006
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Las Cruces, New Mexico
Hello people-

I have been over on the K5 portion for a while asking for assistance at times for my 1974 K5. I have been craving a "bullet proof" truck for some time, and just this past week bought a 1986 M1008 CUCV. The military K30. All the goodies I have been drooling over for years, the 4.56 gears, 14FF and the Dana60 front end. Yes, it's the NP208, but I am not going to rock crawl with this, so a 205 isn't necessary.

Since I got it home, I took it out for a quick rip. Just sand and hills. DISSAPPOINTED.

The thing is a DOG!!!. Now I am pretty new to trucks, and wrenching. I own a '04 Dodge Cummins. I am aware that these are only rated around 155 HP.

But I was trying to go up a sand hill. Maybe a 30 foot climb. I had the petal floored in 4 Hi. It just sat there, and was not spinning a thing....

Now, I know this is pretty vague, and there could be a million "what-ifs". With help, we can cross those when we come to them, so thanks in advance.

But is there much I can do for performance mods ? I want to get some bigger tires so I can atleast drive it 55 mph to get out somewhere, but with the lack of power with 265/16's on it, I can't afford to.

Engine seems "sound", but loud and clanky. Thought they all sounded this way. 82K on the odo. No smoke, white or black. Duals.

There is a bad issue with "losing prime". I have already begun researching that. It's a PITA to start, due to fuel. Has a manual glow plug relay.

I know people get pist with so many new questions. I have used the search function a bit. So any links to old threads or other will not upset me.

Also wanted to know if there are labeled pics anywhere. Everyone is talking about injector pumps, etc. I do have an idea where this is, cuz I needed to bleed air from the lines, or at least try to. I would like to change the fuel filter to start, but I do not think I will ever be able to start it again after getting air in the lines.

Any help will be appreciated. TIA

Jess
 
Hey Jess!

Sounds to me like your lift pump has failed. The lift pump is found on the passenger side of the engine right up at the front. Its the round canister looking thing. Changing it out is a very easy process, undo the diesel lines, undo the two bolts, pull it off then shove the pushrod up against the camshaft while you drop the new pump in. Replace the lines, bleed the system, then start the truck right up.

The new lift pump should help keep your fuel system primed, and will supply the proper pressure to the injection pump. The engine would be pretty doggy if the lift pump had to suck it's own fuel up through a failed lift pump and all the lines to the tank.
 
I'd agree with Russell, but just like with anything else, start basic--fuel filters (yes, there are two) and air filter. I'm pretty sure the CUCV setup is the same as other 6.2's--one fuel filter on the firewall, and one hanging off the back side of the intake manifold, you'll have to pull the air cleaner assembly to find it. Let us know how you make out . . .
 
Thanks for replying guys.

Yes, a fuel filter is in the works. I do not think they are that much cash, it probably needs replacing just for GP, and it looks the be the easiest thing to replace. So I will start there after I drive it for a week to enjoy it. Just in case I cannot get it running again.

You know the feeling with new toys. Don't want them broken the day you bring them home.

I have also found a thread on changing the lift pump. Think I printed it somewhere. Lift pump is the same as a fuel pump on gassers, and in the same location, right?

Sorry about being so vague on the initial.

I wanted to know about a thread I found somewhere else. It may have been on the Steel Soldier web site. It was a military manual/update. It was titled something about losing prime, and had two parts to switch out somewhere. Yeah, I guess that's pretty vague also, but it certainly sounded like a cure for the prime issues I am having. Something about check balls to keep the fuel from returning to the tank.
 
As long as your fuel system does not have any leaks, it is very unlikely that your injection pump is loosing it's prime when it sits. Think about if you shove a straw into your drink, suck up on the end to lift some liquid out, then quickly cap the end with your finger. If you make a good seal, the liquid will not return to your cup.

Same goes with your diesel's fuel system. The injection pump is currently drawing fuel up out of the tank through the fuel lines, and when the truck is shut off, there shouldn't be any way for air to replace the fuel that is in the line, so it'll stay primed.

Yes, the lift pump is exactly the same as a fuel pump on a gasser, and is in the same spot.

When you open up your lines to get at your lift pump, that's when you'll be introducing air into your lines. Not something to be entirely scared of though. Your primary fuel filter has a bleeder on it, which you'll use to purge that air out.

All you gotta do is unplug the thick pink wire that is plugged into the injection pump, and get a friend to crank the engine over until most if not all of the air is bled out by the lift pump. Once it is out, crank the engine over a bit with the bleeder shut, then plug in the injection pump, and fire it up! It should start easier than it does right now due to the lift pump feeding it. Make sure you rev the engine up a little bit right after it fires up incase a couple air bubbles make their way into the injection pump. You want that engine to keep spinning even if the fuel is cut off to push all the air out through the injectors.

I'd personally change the lift pump out first, not the filters. It is pretty much a guarantee that you'll wind up getting some dirt into the fuel lines, and it'd be better to catch that stuff with your old filters rather than dirty up a brand new set right off the get go. Definitely change the filters after you finish though, they can make a big difference in power too. A good set of Wix filters from Napa (Napa Gold) shouldn't be more than 50 - 60 bucks for the pair.
 
Maybe the CUCV's are different, but starting in '84 the civilian 6.2 trucks only had 1 fuel filter. From my understanding if it has the rectangular style on the firewall that is the one and only filter. '83 and older had a large round primary and a smaller secondary.

I've had a similiar type problem on my K5 several times, and each time it was a different issue.
1. lift pump was bad, once replaced the problem was fixed.......however the only issue I ever had was starting, once running I never noticed any difference in performance
2. fuel filter was not seated all the way on the base, after removing the filter and reinstalling it the problem was resolved
3. the batteries were not supplying enough juice to obtain the needed cranking speed.....the 6.2 is VERY hard to start without enough cranking speed, even though it may sound like the batteries are good and they have enough power to crank the engine over for a long time it still won't start. The issue on mine were the terminals on the cables were partially corroded and were not letting the full amperage go to the starter.

Back to the original comment about it being doggy, the 6.2's are not powerhouses in any way so it's hard to tell if there is actually an issue or it's just behaving normal. To be perfectly honest, I'm not too surprised it wouldn't spin the tires in 4 high, especially on a sand hill which will suck a lot of power. My perfectly fine 6.2 can't pull high range on steeper dirt hills.
 
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