What's new
CK5
Register an account today to become a member! Once signed in, you'll be able to participate on this site by adding your own topics and posts, as well as connect with other members.

Who is the 6.2 diesel expert around here?

thatK30guy said:
Now you guys mention the blockage I want to say it feels like that issue because at the initial startup it has no problem waiting for the GP's to heat up and then fire up. The engine will idle fine but with some smoking, of which I forgot to mention, and it will rev up fine also. Just when it gets warm or hot blooded it loses all power. Does sound like a blockage issue as quoted above. I hardly drive the truck and in the seven years I've owned it I haven't put many miles on it at all. Maybe 10K give or take. But I have put in supplement before each winter so not sure if that's affecting anything either.

If it's blockage in the lines is it simply a matter of unhooking at the highest point in the engine bay and blowing compressed air back into the tank? Then needing to drop the tank to clean it out?
Click to expand...

Can vary but if it's a blockage issue will often clear by blowing it towards the tank then cleaning the tank. Don't blow the lines from the fuel filter to the tank, will damage the lift pump doing that. Disconnect the line at the lift pump inlet then purge that line back to tank if it's a blockage issue.

The stock fuel flow on these is tank---selector valve (if dual tanks)---mechanical lift pump---filter---injection pump---return to selector valve (if equipped)---tank.


Smoking at startup will always happen in the colder weather (just condensation) but can happen when the injectors/injection pump are wearing out. Most often from the injectors getting worn out from ULSD fuel with no lubrication additive (such as biodiesel), or crap getting past the filter. Stock filter is only about 30 micron, injectors have tolerances in the 5 micron or less range.


Start off with the 3 diagnostic tests mentioned above, will get things started in the right direction.
 
thatK30guy said:
Can't remember what I had on the shelf but I recently tossed it out since it was old. Don't know why I bought a gallon of the stuff when I don't even drive the truck or rack a lot of miles on it. Should have just gotten a couple ounces of whatever. I feel the supplement may have gone bad or sour over time.
Click to expand...

Nice thing about diesel fuel and additives, they don't really go bad. Alot of the fuel I've been burning is over 30 years old hahaha.
 
My 6.2 belches a white cloud out after a cold start when it is below 40 or so degrees out--to some degree that is normal,I think my injectors might be leaking fuel into the cylinders after it is shut off and sits overnight or longer now though too.
It did this a lot worse before I replaced the electric pump I had on it that failed earlier this year,it lasted 16 years..(maybe because the mechanical lift pump couldn't pull enough fuel thru the dead electric pump ?)..now the white smoke clears up in less than 30 seconds or so..

I re-read your posts and see you did replace the fuel filter--it may have another "secondary" fuel filter located somewhere between the one on the firewall and the injector pump,usually on a bracket on the intake manifold behind the air intake...they often get forgotten and being finer micron and smaller, they'll plug up first usually..
Also,old rubber fuel hoses can separate inside and form a clot that may not show up right away too..they can crack and let air in,but not leak too,being under suction..

Another "long shot" is the gas cap may not be letting enough air get in the fuel tank,this will prevent fuel from being able to be sucked to the injector pump..
Seeing you say you let it sit a lot and rarely drove it much,its likely a fuel issue with algae or some restriction in the fuel lines or air leak causing the poor performance after it warms up...usually any air getting in the lines makes for tough cold starts and you'll have to crank it over a long time before it'll fire up though..

Might check the air filter if you haven't yet too---I found quite a pile of shelled nuts in my air filter housing,evidently a rodent was using it for a storage container (and a home!)--I dumped out a good sized mouse nest and pile of nuts that were almost halfway up the air filter housing about 2 months ago!...
Since a diesel needs a lot of air to run right,this made a noticeable difference in the power level after I dumped that crap out,and used my air gun to blow the air filter out until I get a new one!..was lucky nothing got past the air filter and got in the intake or engine..I drive my truck at least a few times a week too,if not daily!..and I've been putting 50 miles on it most every weekend the past 6 months or so too..
 
Another thing I forgot to mention on the start ups: On any hot day during the summer the truck will start up on the first try after the GP's have warmed up. On a day below 60-65 degrees it will usually crank after cycling the GP's twice. Get down to 50 and below it takes 3-4 tries with the GP's. Anything from 40 and lower you're wasting your time and draining the batteries.
 
Ahh,the infamous "square" fuel filter on the firewall noted for having air leaks in its base ?...huh..surprised the military would trust that thing in combat situations!..I'd ditch that and get a spin on base & filter like a WIX 24309 and 33123 filter..


Wont start reliably below 40 degrees ?..
Sounds like my 6.2..:surepal:...but mine would stand a better chance at starting below 30 if I plugged in the block heater (which is too small IMO,at 400 watts to do much)--and had two NEW batteries,not "good used ones",and I also put SAE 30 oil in it in July,which is now too thick and needs to be drained and replaced with 10W-30 or something similar ..

I only have 7 glow plugs too,one refuses to come out..but as long as the batteries don't get drained,it'll start at 15 degrees with no block heater as long as it has 15W-40 or thinner oil in it,and the batteries can crank it over long and fast enough..

You may have one or more glow plugs not heating up--I'm not familiar with the military trucks setup,being a 24V/12V combination ,but testing the glow plugs is the same method far as I know--unplug the wire going to one,and hook up a test light to the battery positive terminal,and touch the probe to the glow plug tab,and it should light up if the plug is working..ones that test "dead" need to be replaced..
Then you must test each wire to see if they are all getting power when the key is turned on..

I used AC 60G glow plugs ,with a manual push button "override" so I can leave them on longer,they take longer to heat up than the stock 9G's that will swell up and burn out,then be a pain to remove,and the stock glow plug controller wont let them stay on long enough to heat up enough..my truck started much better once I did that..

Using light weight oil probably did the most to improve cold starts,that and installing a gear reduction type starter after the "direct drive" monster ingot died,they crank a lot faster and drain less amps ..

If the same tank of fuel has sat a long time in your truck,it might be stale or have algae in it now,which can cause many of your symptoms..
I had a full 40 gallon tank of diesel,with about 5 gallons of kerosene and whatever "brew" the former owner tried to run it with, in my Suburban when I bought it in late 2009,I ran it as often as possible in the yard in hopes of keeping the batteries charged,but they died after a year,and I would swap in 2 more batteries every few months and start it,but it gets tougher to get to run each time...now it has maybe 1/8th of that tank full left in it,and its a real chore getting it to start..

The guy had it set up to run veggie oil but claims he never did use any,I'm betting he did,and the bottom of the fuel tank has a pile of goop in it from him using fryer oil,drain oil,and whatever else it would run on in it maybe..

I had to take the top cover off the IP last time I tried starting it ,the fuel shut off solenoid wasn't opening the fuel feed because it had gummed up--I used carb cleaner to free it up,then had to use starting fluid (last resort!) to get the dam thing to start finally..last time I attempted to start it on a 80 degree September day I got attacked by wasps that built a huge nest under the hood,so I haven't tried to start it since--probably wont have any luck now that its below 40 here though..I'm not a big fan of diesels in winter at all..
 
diesel4me said:
Ahh,the infamous "square" fuel filter on the firewall noted for having air leaks in its base ?...huh..surprised the military would trust that thing in combat situations!..I'd ditch that and get a spin on base & filter like a WIX 24309 and 33123 filter..


Wont start reliably below 40 degrees ?..
Sounds like my 6.2..:surepal:...but mine would stand a better chance at starting below 30 if I plugged in the block heater (which is too small IMO,at 400 watts to do much)--and had two NEW batteries,not "good used ones",and I also put SAE 30 oil in it in July,which is now too thick and needs to be drained and replaced with 10W-30 or something similar ..

I only have 7 glow plugs too,one refuses to come out..but as long as the batteries don't get drained,it'll start at 15 degrees with no block heater as long as it has 15W-40 or thinner oil in it,and the batteries can crank it over long and fast enough..

You may have one or more glow plugs not heating up--I'm not familiar with the military trucks setup,being a 24V/12V combination ,but testing the glow plugs is the same method far as I know--unplug the wire going to one,and hook up a test light to the battery positive terminal,and touch the probe to the glow plug tab,and it should light up if the plug is working..ones that test "dead" need to be replaced..
Then you must test each wire to see if they are all getting power when the key is turned on..

I used AC 60G glow plugs ,with a manual push button "override" so I can leave them on longer,they take longer to heat up than the stock 9G's that will swell up and burn out,then be a pain to remove,and the stock glow plug controller wont let them stay on long enough to heat up enough..my truck started much better once I did that..

Using light weight oil probably did the most to improve cold starts,that and installing a gear reduction type starter after the "direct drive" monster ingot died,they crank a lot faster and drain less amps ..

If the same tank of fuel has sat a long time in your truck,it might be stale or have algae in it now,which can cause many of your symptoms..
I had a full 40 gallon tank of diesel,with about 5 gallons of kerosene and whatever "brew" the former owner tried to run it with, in my Suburban when I bought it in late 2009,I ran it as often as possible in the yard in hopes of keeping the batteries charged,but they died after a year,and I would swap in 2 more batteries every few months and start it,but it gets tougher to get to run each time...now it has maybe 1/8th of that tank full left in it,and its a real chore getting it to start..

The guy had it set up to run veggie oil but claims he never did use any,I'm betting he did,and the bottom of the fuel tank has a pile of goop in it from him using fryer oil,drain oil,and whatever else it would run on in it maybe..

I had to take the top cover off the IP last time I tried starting it ,the fuel shut off solenoid wasn't opening the fuel feed because it had gummed up--I used carb cleaner to free it up,then had to use starting fluid (last resort!) to get the dam thing to start finally..last time I attempted to start it on a 80 degree September day I got attacked by wasps that built a huge nest under the hood,so I haven't tried to start it since--probably wont have any luck now that its below 40 here though..I'm not a big fan of diesels in winter at all..
Click to expand...

I'd say it's pretty well documented on this forum that you don't like diesels at all haha, but you also set those engines up for failure.
30w oil in most diesel engines is similar to 75-90w in a 350 or 454. 5w-40 or 15w-40 covers the US except places with regular -20F-colder winters.
Only using 7 glow plugs instead of 8. Unthread that last plug, cover the plug in a rag, start the engine. Very few won't launch out.
Diesel going stale? Petroleum diesel chemically can't do that.
CUCV's 24v system is only the starter, rest of the truck electrical system is on the other side of a large resistor that drops it to 12v.
CUCV isn't a combat vehicle, it's support only. Civilian Utility Cargo Vehicle.
Starter fluid in a 6.2/6.5 usually ends up with bent rods or the starter getting ripped off the block due to the 21:1 compression ratio and glow plugs.
Agreed the filter "brick" is well known for air problems.
Resistance tests (such as glow plugs) often give false readings. Will test good yet doesn't get up to the designed temps. Unknown maintenance history as well, those plugs could be 30 years old haha.
 
Yeah,I admit to not being a huge 6.2 fan,but for what I've put mine thru,I cant complain..hard cold starts are my biggest peeve..and the cost of glow plugs that seem not to last me very long--more have rotted the hex off than have died electrically thanks to salt spray..
I even put grease on the last set I put in it and they are already rusty..
Diesel fuel being 50 cents per gallon more,and the mpg being around 16,makes it cost more to run than a gas powered truck..

I only used SAE 30 this summer in this 6.2 for the first time,I was curious to see if it would run any quieter,seeing that was the reccommended viscosity for temps above 32 F according to the chart on the sun visor..it didn't,and I do not plan on using it again..previously I only used 15W-40,even that seems too thick below 25F or so,I am tempted to try 10W-30 diesel or even lower viscosity when I change it soon..I added a quart of 5W-20 to the SAE 30 last week when the temps dipped into the 20's when it was a quart low to help thin it out till I change the oil..

I un-threaded that glow plug and DROVE my truck a half hour,let it idle in my driveway another 10 minutes,it didn't show any sign of coming out--it huffed a few puffs of compression out after I started it and it sealed itself up and held the entire time !...
I even revved it to the govenor a few times..still refused to come out--so I screwed it back in and said "screw it"..

I fully expected it to blow out like a bullet,but it didn't--at that point I gave up ,I wasn't willing to break it off ,my injector lines are rusty and are unlikely to unscrew without twisting up and breaking..

Previously I had tried chucking the glow plug in a drill and I spun it in reverse for several minutes..that too didn't do anything!..the tip must be bent at a 90 degree angle or swelled up really big!..

I dislike using starting fluid and only have done it reluctantly a few times when all else failed--I know not to use the glow plugs,and to let them cool off at least 5 minutes if I had activated them before using any ether--and I also rigged up a jumper wire so I can crank it over from under the hood--that way you can get it spinning over at full speed before you spray the ether--if you just douche it with the engine off and try starting it,yes,you will have severe kick back and horrible sounds as it binds up during the compression stroke...getting it spinning good first helps a great deal to avoid damage..

Still,it is only as a last resort "emergency" situation I'd use ether...
I've only used it when I was pissed off enough to not care if I destroyed the engine--that would force me to put a gas engine in it like I wish it had all along--or just junk it,the truck is getting pretty rotted all over and anyone else but me would have scrapped it decades ago--I actually saved it from the crusher in 2003 when I got it!..
 
thatK30guy said:
What would be the issue of the smoking at start up and idling? Seems to go away once warmed up.
Click to expand...

That's not necessarily a problem, depending on the quantity and color of the smoke.

You have a bunch of good suggestions here. It does sound like a fuel delivery issue, it's just a matter of determining which segment of the fuel system isn't delivering. A pressure gauge on the filter housing is a useful tool. Remember that (unlike a typical EFI system), this injection pump contains a small fuel reservoir. A fuel blockage often shows up as good starts followed by fuel starvation a little bit later (when the pump reservoir empties out).

We've been down this road before. There aren't many things that can go wrong, and we'll walk you through each step. Start checking fuel and let us know what you find. :popcorn:
 
red EOD said:
CUCV's 24v system is only the starter, rest of the truck electrical system is on the other side of a large resistor that drops it to 12v.
Click to expand...

Technical side note - the glow plugs are operated through a resistor as you said, but the rest of the truck has a dedicated 12V system. It pulls from the front battery and the main 12V alternator. It's not running through the resistor bank (which wasn't a great idea in the first place).
 
campfire said:
Technical side note - the glow plugs are operated through a resistor as you said, but the rest of the truck has a dedicated 12V system. It pulls from the front battery and the main 12V alternator. It's not running through the resistor bank (which wasn't a great idea in the first place).
Click to expand...

Ah yep forgot about that.
 
The 6th or 7th post in the thread mentioned the return line check valve on the IP. It hasn’t been mentioned since.

Use pliers to squeeze the red clamp on the IP holding the hose that comes off the front top of the IP. remove the hose and then use a deep 9/16 socket to pull the check valve off. Once off look inside. There is supposed to be a glass ball with a spring inside. It is also supposed to be clean. If the glass ball is gone, then someone probably broke it off to allow the truck to run. Which is a great “get home to fix it” trick.

If the ball is still there and if there are little black specks against the ball. Then the IP is coming apart inside and needs to be refreshed. The black specs limit flow and the flow increases as rpm increases. Once it starts building back pressure to the IP. It will turn the engine off. Which is another trick. If your on/off solenoid ever jambs with the engine on like one of my m1009 trucks did a few years ago. Just squeeze the return line with some pliers and the engine will turn off.
 
Last edited:
Unfortunately winter temps are arriving so the truck is getting parked until spring time. While I just purchased a 140K btu shop heater I still have too much crap inside the shop to even make room to park another truck in there.

I'll keep asking questions and learn until spring time. I'm definitely saving this thread.
 
When you are starting it in the colder temps, are you holding down the throttle at all? When I had my 86 M1009, I daily'd it during several Chicago winters and never had a problem starting it except for the time I killed a battery cell....and that time my block heater cord was ripped.... but in the winter temps, I would hold the throttle down maybe halfway while cranking and it would fire up.

I wouldn't be surprised if it was the IP. I've been told before that if you buy a CUCV that hasn't had the IP replaced, be ready to replace it. These are 30+ year old trucks and the CUCV's, especially the pickups and even more so the ambulances, sat around for long periods of time with minimal driving. If you do in fact need that IP rebuilt, look up Badger Diesel. They are in Wisconsin, they can rebuild your IP and can even ship you an IP while you ship your core back to help speed up the process for you
 
My pickup will usually not start under 30 degrees unless I press the accelerator down at least party way,and all the way if it sounds like it isn't going to start--the cold starting instructions on the sun visor state to "fully depress" the accelerator when its below 32 degrees..

My truck "almost" started Saturday after it sat outside overnight in 25 degree temps,but the batteries started losing the guts to spin it over at full speed--once the starter starts slowing down,I have learned to just give up--go get the battery charger ,plug in the block heater,wait 5-6 hours,and don't be surprised if it still refuses to start..

I converted a old pressure washer engine & cart that had a cracked pump from freezing ,into a portable gas powered 12V "jump starter" by putting a GM internally regulated alternator on it .
.
That was what got it to start Saturday-(picture below)--I now take it with me wherever I go in winter along with some gas for it,in case I cant get it to start somewhere "on the road"..mostly I avoid going anywhere if its very cold,or snowing,I hate trusting the unreliable p-o-s in cold ,bad weather..

I fear the starter will die next after having to crank the ever lovin piss out of it every cold start..probably have to buy two new batteries for it to get thru the winter..truck is barely worth the cost of them,and the inner fenders are so rotted I have had to patch them up just so the batteries wont fall thru..

I also keep a spare hoodie ,a blanket,tarp,and some non perishable food in the truck in case I have to wait for a tow for a long time..PICT0049.JPG

I recently bought one of these too--may end up using it to heat up the intake before a cold start ..weed torch.jpg
 
With my m1009, I would plug in the block heater when I woke up in the morning. It would go for an hour while I got ready for work, ate, breakfast, etc. That was enough time to get the engine started. I wouldn't use the block heater again unless it was parked for a full 8hrs at work. Usually I would leave to go grab lunch, so at least it had some run time part way through my shift. In extreme cold, yes, I held the throttle down about to the floor. It always started. As long as the glow plugs are all in good condition, it should start even at 0 degrees. The 24 volt starting system helps I'm sure
 
The glow plugs sap down the batteries a lot, before I even crank the engine over,I think they are why it wont start with batteries that aren't top notch new condition...it cant spin over fast enough and long enough,once I cycle the glow plugs once or twice..it is like they should have a separate battery just for them,and let the other two spin the starter..

J.C. Whitney used to sell a series/parallel solenoid switch that let you put 24 volts to just the starter only ,on 12V vehicles with two 12V batteries,one of those would probably spin a 6.2 12V starter really fast and get the cold bastid to start..
I had a 6V VW that I converted to 12V ,but left the 6V starter in it--it spun over so fast it sounded like it cranked faster than it ran at idle!..fired right up instantly every time..and it never seemed to harm the starter,because I never had to crank it over for a long period..

I need to dump the SAE 30 out,and put some lighter viscosity oil in my pickup,that isn't helping cold starts any--unfortunately we got over 6" of snow since Sunday here ,so I'm not enthused about crawling under it today--I have to get it running to plow my driveway today..glad I no longer live 65 miles north of here,where my sister lives--they got 25.1" since Sunday!..
But the 6-8" I'm getting will be enough to put me in traction,my back is killing me just sitting here typing..:(
 
diesel4me said:
the cold starting instructions on the sun visor state to "fully depress" the accelerator when its below 32 degrees..
Click to expand...

Yes, and half throttle above 32 degrees. I have found best results by flooring it during every cold start, regardless of ambient temperature. Extra fuel isn't going to hurt anything, and seems to help.
 
You must log in or register to reply here.

Latest Posts

Top Bottom