Asking for 6.2 Detroit help from North Carolina

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v12venator

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Good evening all, I'm a new proud owner of a M1031 CUCV in southern North Carolina. I acquired the truck not running on 30 December and was able to get the truck running on the 1st of the year with a swap of the starter. On day one, I changed the engine oil and filter as well as the fuel filter.

Now I have two issues to deal with to get the truck road legal; starting and stopping safely when needed, and to figure out the wiring for the headlights and stop lights(courtesy lights and blackouts are desired, but not required right now). I've taken a look at the color wiring diagrams for the respective systems posted and will be digging more into those tomorrow to root out the gremlins, but I cannot figure out the reason why the engine lopes up and down in RPM at an idle.

I've looked at the GM 6.2 manual also posted and it mentions something about a metering valve on the engine, but I have not yet taken a look under the air cleaner to see if the fuel system leads there after the filter. Also to note, when I started the truck this morning to check and see if the RPM lope was still present, I found that it doesn't usually happen until after a few minutes of running at idle. After it showed the RPM lope again today, I turned the ignition cylinder to off, but the engine kept running. I attempted to choke the engine by blocking off the air intake, but to no avail, so knowing that it lowers engine RPM when using the transfer case, I moved to 4 low and stood on the brakes to finally stop the engine. Thankfully the engine did not run away and was hanging out at idle.

I haven't encountered this before, so asking at the parts store manager led me to purchasing a new ignition switch that I will also be installing tomorrow when digging through the wiring. Has anyone else had this happen before? If so, how did you find the solution?

Thanks in advance for your time,
v12venator
 

NDT

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Welcome. Let's start with the worst problem, the engine not turning off. Before you go through the agony of replacing the ignition switch, you ought to do some diagnostics first. The injection pump in the valley of the engine receives 12 volts which activates an internal solenoid to allow the engine to run. Is the voltage present with the ignition off? Very unlikely. More likely is the inside of the injection pump is gummed up causing the solenoid not to release when power is removed. If this is the case the injection pump needs to go for rebuild. The rebuild will likely fix the loping idle. These pumps only last about 10-15 years between rebuilds due to internal plastic parts.
 

v12venator

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Welcome. Let's start with the worst problem, the engine not turning off. Before you go through the agony of replacing the ignition switch, you ought to do some diagnostics first. The injection pump in the valley of the engine receives 12 volts which activates an internal solenoid to allow the engine to run. Is the voltage present with the ignition off? Very unlikely. More likely is the inside of the injection pump is gummed up causing the solenoid not to release when power is removed. If this is the case the injection pump needs to go for rebuild. The rebuild will likely fix the loping idle. These pumps only last about 10-15 years between rebuilds due to internal plastic parts.
Understood, I'll start researching into injection pumps now to price them out. I figure being a 34 year old truck, it probably will need it. I'll check voltage to the pump tomorrow with the multimeter just to make sure that it isn't receiving power when the ignition is not in the on position. As for my second problem, with bringing the vehicle to a halt, do you know if the CUCVs have the JB7 or JB8 brake systems on the wheels? Those are the only two options that I can find at my local parts store and I want to make sure I'm getting the right parts for the truck. Sorry for not being in the know about this stuff, this is my cherry-popping MV that I've owned.
 

NDT

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Should be JB8 you have hydroboost. Hey we all were at that point once so don't sweat it.
 

v12venator

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I appreciate it. I know before I get it registered, I'm gonna have to flush my brake system from the old DOT3 fluid in there cause my brakes don't really kick in until they're at the floor, so I'm gonna get that done as soon as I get the new pads and shoes in. Just to make sure the parts store isn't wrong, though, the rear brake shoes act as the parking brake as well, correct?
 

v12venator

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Raeford, NC
Welcome. Let's start with the worst problem, the engine not turning off. Before you go through the agony of replacing the ignition switch, you ought to do some diagnostics first. The injection pump in the valley of the engine receives 12 volts which activates an internal solenoid to allow the engine to run. Is the voltage present with the ignition off? Very unlikely. More likely is the inside of the injection pump is gummed up causing the solenoid not to release when power is removed. If this is the case the injection pump needs to go for rebuild. The rebuild will likely fix the loping idle. These pumps only last about 10-15 years between rebuilds due to internal plastic parts.
So, I just remembered that I had asked about this a while back and forgot that I took the multimeter out back to test the power to the injection pump. Coming from the positive terminal of the front battery, there was 12v to all three plugs on the injection pump that I could find. Coming from the negative terminal, there was no power going to the injection pump. I didn't know which side was ground on vehicles this old, but I had remembered that there were vehicles that had ground positive instead of ground negative, so I tested both. I've also taken some pictures if anyone is interested.

I am planning on replacing the two optimas with some 1000 cranking amp AGM batteries due to quality and warranty issues with newer optima batteries.20200319_123640.jpg20200319_123747.jpg
 

muttly

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It is negative ground. If you don't have 12 volts to ground on the pink wire and it runs there is a problem with the IP. By the way you should have silicone based dot 5 brake fluid in your brake system.
 

v12venator

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It is negative ground. If you don't have 12 volts to ground on the pink wire and it runs there is a problem with the IP. By the way you should have silicone based dot 5 brake fluid in your brake system.
Thank you for letting me know that, I was in the process of replacing all the shoes and hardware around the truck before I did a flush on the JB8 brake system. I had picked up a quart bottle of DOT 3, but thankfully I haven't put any in the master cylinder yet. I'll make sure to stop by the parts store and grab some DOT 5 today so that I have it after I've swapped everything out. I even went so far as to purchase new front calipers and wheel cylinders.

Back to the fuel pump, has anyone had any experience with the injection pumps that are available at the O'reillys? I can get one here the day after I place the order for it, whereas with Advance or AutoZone, I have some lead time to wait until it gets in.
 

v12venator

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I recommend: http://www.badgerdiesel.com/store/shop.aspx.
do not know what Oreillys price is but these guys have done three for me. once paid they will send you a pump in the mail, you send yours back and they refund the core charge.
very easy to deal with and pretty fast delivery.
Those prices are a whole lot better than what I could get at the O'reilly's. I'll definitely be looking into them, hopefully they'll still ship with this corona lockdown happening around the country. Thank you
 

v12venator

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Just posting an update for the folks that are interested. I replaced the fuel injection pump in the truck, a 2520 I believe, with a rebuilt 2544 from Oreilly's and have been able to start and stop the truck on demand. Thank you all so much for the help.
 

cucvrus

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Good Deal. I am glad everything worked out for you. The CUCV with a new injection pump is like a new vehicle. It makes huge improvements on drivability and reliability. Thank you for sharing this post. I have great results with most replacement parts that are available. At this point you have to take what you can get. The 6.2 diesel is not a very popular engine anymore. Time and technology has past that era of diesel engines.
 

kdaniels

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Just posting an update for the folks that are interested. I replaced the fuel injection pump in the truck, a 2520 I believe, with a rebuilt 2544 from Oreilly's and have been able to start and stop the truck on demand. Thank you all so much for the help.
Why did you elect to go with Oreilly’s ? Price difference? Time constraints ?
 

v12venator

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Why did you elect to go with Oreilly’s ? Price difference? Time constraints ?
I figured with the corona nonsense causing a big ruckus that the Badger Diesel shop linked above wouldn't be quick to ship like before the outbreak. With the O'reillys having one in the state, it would be much quicker to start rummaging through all the wiring issues this truck has. Might have cost a bit more, but I would really like to get this truck up and running and tagged so I can start putting it to work.
 

v12venator

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Just to post an update, I've started diggin into the wiring on the truck and am slowly coming back up from the deep dive. I screwed myself when I hooked up the service light circuit to the positive terminal on the rear battery instead of the negative and double-volted that mess. All I had to do was replace the fuse for the service lights and remove the fuse for the horn since it is stuck on, but I thought I knew what I was doing without double checking my T's and I's.

Having said that, there is now a short or excessive load on the circuit when I try to test my turn signals or hazard lights with no relay clicking. Also some electrical smoke to top it off, so I've split my harness at the firewall and will be inspecting the fuse panel and harness connection for any signs of melting or cross-contact where it is not needed. Just wanted to thank everyone in the thread again for the help with the fuel pump earlier.

EDIT: Adding picture of the truck for eye candy.
20200331_122306.jpg
 
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v12venator

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Progress update for the day. I looked at the back of the fuse panel today as well as the wiring diagrams in the -20 and noticed the diodes on the back of the hazard and turn signal flashers that looked a little melty. I figured that if those were enough to kill a horn circuit, they might be enough to kill the flasher circuits as well, so I nipped those off and behold, I have turn signals again with relay clicks. Now all I have to figure out is where in the circuit my break is for the front left marker lights and I'll have a fully lighted truck. This page is a great resource for MV owners and I cannot thank you all enough.
 

v12venator

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One more quick update. Got all of my service lights worked out and they are operating as designed now. Also scratched in the starter relay mod as well as dressing the harness up with some hockey tape for more structure. Replaced all the bulbs in the instrument cluster and cleaned that up while I had it disconnected. All I need to do now is get a horn for the truck to be road worthy by the state and I can get tagged. Anyone know if old diesel fuel in a cucv will cause the truck to blow white smoke like crazy? I'm guessing it is the age of the fuel since the truck did not run for a few years before I got it and it had a full tank when it came into my possession.

EDIT adding picture of relay mod and link to video of all hazards flashing.

20200428_190154.jpg

 
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v12venator

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Weekly update for anyone that is interested. Got to ripping into the brakes today and I was going to flush all of the yellow fluid out of my system until I noticed that my cylinder wasn't pushing fluid out when breaking the bleeder. I dug around a little bit and checked the other side and didn't have brake fluid coming out of either back cylinder. Found out that there is three different junction blocks between the master cylinder and the rear brakes and will be breaking those lines soon to see where my stoppage is. I have ordered the new brass proportioning valve from Jegs since I want to rebuild most of the brake system anyway in the truck, but I cannot find the rear lever controlled proportioning valve that is linked to the rear differential. Does anyone have a good link I can follow to replace that or should I remove it and add a bypass line?

Thanks in advance
V12venator
 

Sharecropper

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In 1988 GM issued a bulletin to remove that rear proportioning valve. It was Bulletin #88-320-5. Not saying you should or shouldn’t, just trying to be helpful. I removed mine years ago after I installed rear disc brakes.
Also it may be helpful to others here on SS if you can post the specific part number and photos of the Jegs valve you used.
 

v12venator

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In 1988 GM issued a bulletin to remove that rear proportioning valve. It was Bulletin #88-320-5. Not saying you should or shouldn’t, just trying to be helpful. I removed mine years ago after I installed rear disc brakes.
Also it may be helpful to others here on SS if you can post the specific part number and photos of the Jegs valve you used.
Understood Sharecropper, I'll put my ugly peepers on that bulletin just to see what it was all about. I just ordered the Jegs 631290 valve last night because I had been linked to on another thread here on SS and I thought it had been agreed upon to be kosher. The link is here and the link to the SS thread that I got the link from is here

I've still got to go through and back check the other stops in the brake lines between the rear wheel cylinders and the master before I rip off the old proportioning valve. Is the electrical connection on the front prop valve shown in the wiring diagrams in the TMs? I'm not sure if that could be some sort of electro-magically controlled valve that might somehow be stopping fluid from going to the rear brakes or not.
 
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