In need of some technical assistance , m1028

[cstarbard]

Hey all-

New member 23 y/o from MA and proud new owner of a M1028 CUCV. I apologize if I am posting this thread in the wrong place, as a newbie to the forum I'm not sure. Forgive my ignorance as well on any questions below, I am not a bad mechanic but this truck is my first foray into diesels and CUCVs so there's a lot I don't know, basics included.

Bought my truck at 27k miles, all stock, and have put about 5k on it, ran flawlessly when I got it, but I'm noticing some quirks that I'd like to resolve before they escalate;

1. Worst and most recent issue: when going up hills, both light and steep inclines, I start to lose speed. I know that sounds stupid at first, but my truck used to climb any hill 40-45mph fine when I bought it. Of course it would require a little more throttle to maintain speed uphill as the grade increased, and I understand it is geared quite low at 4.56, but it seemed pretty normal then. Drove as I would have expected. But now, even if I give it more throttle uphill to try to keep up speed, it doesn't seem like the throttle response does much, and I start to slow down. It doesn't seem to want to rev higher (and I know it can). If I keep applying throttle gradually, it continues to lose speed until it downshifts and starts screaming. I'm not suspecting transmission issue (atf is very clean and full to spec) because it doesn't feel or sound like its slipping? Am I dealing with a fuel issue? It almost seems as though under load especially, its wanting for a little more fuel. Could the mech pump be going? Also there is a regulator in the injector pump, is there not? Something with a glass marble and a spring? Is that suspect? Fuel filter looks to have been replaced recently, I'm guessing its not clogged but I wouldn't know.

2. Sometimes coming off a main road (holding 40-50mph for five or more miles), if I slow down and come to a stoplight, etc., the truck runs very farty and doesn't want to idle down. Starts to shake a bit. Could this be related to the above or is it a separate issue? Potential causes?

3. I'd like to service the transmission because I love maintaining things... I got Dex 6, I believe its spec'd for Dex 3, any problems using the Dex 6? It says its Dex 3 compatible on the container, and I'm all for using the best and most appropriate lube I can get. But please correct me if this is a bad choice. Also, I have only ever had cars & trucks with manual transmissions out of preference, so can anyone give me basic pointers and best practices for servicing my transmission? Or is it as simple as drop the pan, new gasket filter etc and refill?

4. Least important but quite annoying: Temp light on lower left of speedo comes off and on randomly and frequently, often faint. Coolant is full and clean, isn't losing or burning any, never shows symptoms of overheating. Any ideas what the issue with the light is?

Many thanks in advance! These trucks are a ton of fun and I'd like to keep this old beast healthy and strong.

Chris

 

[snowtrac nome]

The light can be many things from a bad sensor to a shorted wire first off I would verify the engine isn't overheating. For the power issue first thing I would do is replace the fuel filter the transfer pump sits along side the front of the engine just like a chevy v-8 and should be making around 5 psi with good flow just like a carbureted engine. If all that checks out than you will have to dig deeper but your problem most likely is a fuel filter.

 

[cstarbard]

Thanks, I appreciate the help.

My struggle with the temp light has been, how do I know if its overheating? When the light first started coming on intermittently I would stop driving, open the hood and take a look, and I never saw anything weird. No steam, all radiator hoses are crack free and leak free... haven't lost a stitch of coolant in 5000 miles... I can ALWAYS hold onto the radiator hoses while running. I would think they should be to hold at operating temperature, and definitely if it was running too hot? What should I be looking for in terms of symptoms of overheating?

For reference, I don't work the truck hard, I don't pull trailers ever or much of any weight, and I dont ever go faster than 50 because I feel bad for high it revs with the low gearing.

Yeah, I thought I ought to change the filter for posterity if nothing else... do I need to be concerned about bleeding the filter after I swap it? Can I accidentally get air in the lines by swapping the filter?

I thought about swapping the pump too but it looks like a royal pain to get at and again I was worried about getting air in, bleeding etc.

Like I said, newb here

 

[cucvmule]

I have to agree with snowtrack nome about fuel filter. After changing I always pour out the fuel in filter into a glass jar and look at closely after settlement. Helps to see if it is water, dirt, rubber hose, or the worst, RUST.

As for the dim light, wire chaffing, or sensors would be my starting point.

Good Luck, and diesels are great ounce you understand the process of Detonation.

 

[gimpyrobb]

Clean all your grounds! 80% of all electrical issues are ground related.

 

[snowtrac nome]

As for bleeding the filter on a cucv its a 2 man job you, replace the filter, than crack the bleeder at the topof the filter housing, and remove the pink wire from the injector pump, now have your buddy crank the engine until you have a stream of fuel come out with no bubbles . Also remember not to crank the engine too long, once the system is bead you can re install the pink wire and restart the engine.

 

[Tinstar]

Mods can you move this thread to the CUCV forum?


Good advice already given here but thread is in wrong place. No sweat!

Have you downloaded and read the TMs?
Fuel Filter is easy.
Fuel pump is a......challenge.


Recommend install of gauges.
Water temp
Oil pressure
Trans temp
RPM
I love my MVs stock, but I have to know, for my piece of mind, those things at a minimum.

Read the TMs and old threads in the CUCV forum.
Excellent information
Whatever the issue, someone’s already dealt with it.
Guys with extensive experience with CUCVs are more than happy to help.

 

[cucvrus]

Running poorly and lacking power makes you work the engine harder. Change the fuel filter and see if that helps. I had a truck that did the same thing with the temp light flickering. I changed the fan clutch and the problem went away. They have a huge radiator and cooling system and it is almost impossible to over heat one. But the fan clutch not working as designed can make to cooling system work hard and just barely be able to keep up under load. And under load means what you used to do 45-50 up hill at half throttle you are now going 35 - 40 at full throttle. Burning fuel creates heat and the full throttle is putting a lot of fuel into an incomplete burn. Building heat in the engine. The fuel is burning inefficiently. Diesels and all engines create a lot more heat under load. Report back. Welcome new guy.

 

[cstarbard]

Thank you all sooo much!

This has been a great sanity check. I have kind of figured that this all had to be fuel related... I suppose there isn't much else going on a big old diesel...

The lack of gauges has been quite annoying. I appreciate that suggestion and I have been thinking the same thing, would be nice to know with some quantitative data what all systems are actually doing, lol

I really appreciate all this guys, I'm going to start with the filter and see where that gets me.

The filter is the same as a civillian 6.2 is it not? So I should be able to get one at Napa, etc.?

 

[cstarbard]

One question still remains-

The pressure regulator (?) on the injection pump- a unit ive heard about, that has a spring loaded glass marble in it- does this in fact exist, and what is it called?

I'd like to have one on hand if this is something that might be troublesome down the line.

Chris

 

[Tinstar]

Did you get Truck at surplus auction or private seller?
Some guys try and “improve” Truck/systems and just make things worse. Usually much worse.

Mileage really means nothing on these as just sitting for years takes a steep toll on everything rubber, etc.

There are several things you could/should do to improve reliability. Doghead relay, etc
Read the stickies and old threads. Info about what to change and replace.

Buy the best parts you can afford. It does make a difference.
Tackle one job at a time.
Don’t let small issues become big ones that leave you stranded.

And of course......pictures.

 

[cstarbard]

Alright guys here's another question-

First thing in the morning, only then, first start up of the day, my rear wheels are easy to lock up.

I'm assuming that my wheel cylinders could stand to be replaced. I have had this issue with all my old beater trucks w/ rear drum brakes. BUT: I've heard these trucks use DOT 5 fluid and I'm told dot 3, 4 CANNOT mix with DOT 5.

Since I'll inevitably lose some fluid replacing and bleeding wheel cylinders, and would like to top off master cyl, how do I know if I have dot 5?

Chris

 

[cucvrus]

you may have oil on the rear brake shoes. The check ball in the top of the injection pump should be in place. If you have to remove it to get the truck run better. You are in need of a rebuilt injection pump. If it has the original pump or an older one you would be doing yourself a favor by changing it out. Huge improvement in power and drivability. Back to the rear brakes. you need hub/drum seals and no use cleaning the brakes. Change them and have the drums resurfaced or replaced. I just paid $80. to have 2 M1028 drums cut. But new ones are twice that. Good Luck.

 

[Tinstar]

It will say DOT 5 on the container.
Most shops won’t have it.
It is more expensive but worth it.
I buy mine on amazon.
It is NOT compatible with others.

Have you replaced your rubber brake lines, front and rear?
If their original they need replaced regardless.
They can cause issues and oil on pads can also cause problems as already noted.

 

[dependable]

Another thing that can cause sticky rear brakes at start of day is DOT 5 leaking out of wheel cylinders. If there is no gear oil on brake shoes, there is probably some brake fluid, which can be harder to detect. Defiantly replace the axle oil seals while you are in there in either case. As mentioned above, replace the flex lines too. They can fail form the inside and lock the brakes, although that usually happens after they heat up some.

You should stick with DOT 5 unless you are going to replace the calipers, wheel cylinders and lines, it is unlikely you can flush them out enough. The mixture of the brake fluids can eventually cause system failure, usually the calipers binding. Eastern surplus sells DOT 5 for around $60 a gallon.

 

[snowtrac nome]

its not a regulator its a return check valve when you relieve the body pressure on the pump the timing will advance. This is how the cold advance works with the green wire energized and the engine running you will get a steady stream of fuel off the return line coming off the top of the injection pump. With the solenoid de energized it will drop back the flow, but you must have a continuous flow of fuel to properly fill the delivery valves on the injection pump. if your filter is plugged you will not likely return any fuel as you will barely get enough to run the truck.

 

[cstarbard]

Thank you all yet again.

I'm all for preventative maintenance so I will go take a look at the stickies, etc.

When I said how do I know if I have Dot 5 brake fluid, what I meant is how do I know if the truck currently has Dot 5. I read somewhere that most CUCVS had it from the military but "most" makes me nervous since Dot 5 isn't mix-able with Dot 3, 4 etc.

Is there some characteristic of Dot 5 fluid that I could easily recognize looking in the master cylinder or should I just assume it has Dot 5?

I got the truck private sale but the previous owner is a friend of my dad and I think he got it at auction. Either way he isn't into turning wrenches on his stuff and only put 1000 miles on it so I doubt he did anything to it... especially considering coolant was down a gallon when I got it!!

I got a good pump to keep on hand as well as a filter. I will let you know how situation changes with the new filter installed and bled.

Also doing an oil pan gasket soon, mine is leaking terribly, have any of you done that before? It looks like I have the clearance to do it without jacking/ lifting motor up but I'd love to know if that's correct.

Finally: I'm putting the truck away for the winter in a month or so so that the New England salt doesnt destroy this fine beast, would love tips on winterizing the truck, what I should do to store it when the time comes...

Thanks.

 

[german m1008]

... take a glass of water with a little of your brake fluid...... when the brake fluid floats above, it’s Dot 5....... when it mixes, it’s 3, 4 or 5.1