help with 6.2 diesel

bbareconstruction

Active Member
Joined
Mar 13, 2010
Location
wilkesboro
When I bought the truck it had terrible throttle response, I mean like press the peddle and wait 5 seconds to hear it rev. A mechanic friend has rebuilt several injection pumps like mine before so I bought the kit and we rebuilt it. Now the thing revs fine, sounds fine, runs fine, as long as your on level ground or down hill. On even the slightest incline, it just looses power. You can be running 65 and it'll just go down until your to 30. I know these things aren't know for being powerful but come on... It's geared 4.56 with 35s. It just runs too good on level ground to make me believe there's nothing wrong with it. Checked the fuel pressure to the IP and it's getting around 5 psi idling and at wot, doesn't change, even on the hills where it looses power. Is it my IP? What else is there to check?
 
Sounds like you own a Cuck Vee!

5 pounds sounds ok but certainly on the low side. My first suspect would be fuel blockage but your pressure isn't dropping. When was the last time you changed the filter? Have you done a compression check?

Mine is no powerhouse but I can cruise to 65mph with 37's all day long if I don't care about fuel economy.
 
155hp is what the J code 6.2s had, which is slightly more then the civilian ones, in a 5800lb truck is not the first choice for a getaway vehicle... That being said, mine aren't that bad, even the one I had on the hummer 37s and they're a heavy tire. What kind of hill are we talking? Saluda mountain or highway overpass? Does it have good power on flat roads and just loses it up a hill? If so then I would say fuel starvation. How easy does it start? Is the fuel timing set properly?
 
It runs as fast as I feel safe driving it, around 70-75 on level road. But on any incline at all, even slightly up hill, the speed drops until it down shifts, the continues to drop to around 35. It can pull a little hill at 35 in 2nd. I can't drive it anywhere without a convoy of traffic behind me trying to pass. We adjusted the timing until it felt like it was ideling right and revving the smoothest, barely able to tell that helped. I immediately thought it was starving for fuel but we tee'd a gauge on it and drove it. Never dropped below 5 psi, even when it was loosing speed on an incline with it floored.
 
It starts OK, had one injector line loose that made it hard to start while it was leaking but we tightened it. Even thought I might have another small leak so we put a piece of clear tubing on the return line and no air bubbles so assuming no more leaks. Thank you for help trouble shooting BTW. This thing is beating me up. About to put a small block in it, lol
 
You'd have to look up compression specs but I would be looking at either engine integrity or injector issues. Sounds like your fuel system is in good shape as far as flow and air concerns. I would suspect your IP outside of the other issues. I believe when you tear down an IP you need to have a calibration machine for timing as during installation is just line up the hash mark when bolting it to the engine.

Another thing to look at is your vacuum valve adjustment on the IP, is your transmission not downshifting early enough? Is the kickdown switch forcing it into 2nd soon enough? I know on mine, once I dog the engine on a hill, it is game over. Everything is a full throttle assault :)

I hope you find the answer. Swapping a 350 is not the solution and will really hurt resale value as most want the original 6.2 and 24v system. Even though the 6.2 isn't exactly a powerhouse, I think having it in tact makes a CUCV more valuable then it just being an axle donor...
 
I've been afraid it may still be in the injection pump. My friend that rebuilt it isn't really a diesel guy. He worked for a garage for a guy that changed out a ton of 6.2's for gassers and his boss has him rebuilding a lot of db2's. It appeared that he knew exactly what he was doing. The rebuild kit only comes with gaskets and seals/orings. The rotor in the pump was worn so he swapped it out with another one from his work. If it turns out to be the IP, where's the best place to get a replacement? I'm pinching pennies on this truck now.
 
A good IP will set you back about $400-500. I personally would go to a reputable Stanadyne dealer. There are also many online that have good feedback. I'd avoid the cheap ones you see on eBay. Most are simply worn out pumps that have been resealed.
 
Agree with the above comments. Injectors typically lead to smoke and rough running. As far as I'm concerned you can't rebuild a pump without a bench. You can replace some seals and internals on some pumps but as far as a full rebuild it requires a bench. Pump performance is a crap shoot without benching.
 
Agreed

I pretty can do anything minus laying down a good paint job...I won't touch the inside of an IP. Best to spend the money and let a pro have at it.
 
Agreed, honestly I had one someone swapped in a small block with a 2barrel carb and it just wasn't the same. Couldn't hear it running was a weird sensation. Did have more power and would burn the tires off but part of the "joy" of having a cucv is the deafening diesel knock, no power and slow driving...
If you aren't hooked on the "cucv army truck" part of it and it was just a heavy duty truck to you (your lucky if its not in your blood already, get out while you can or hang on and clear spots for more as they seem to multiply) then by the time you get a good I/p you could have swapped in a gas engine. And with gas coming down so much, the thought of 2500rpm cruising at 55mph isn't as big a deal or pain in the wallet.
If your like me then a cucv is a stripped down diesel truck with no radio, (and your not going to change that). Get a good I/p but don't expect miracles. They still wont pull a hill like today's diesels. Everyone thinks "diesel and 4.56 gears, this things gonna be a pulling machine" but they are only rated to pull 3k lbs. and now you know why...
 
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