M1008 Starting/Running/Idling Problem!

[ilovemyblazer]

Hey guys, I got my first CUCV running the other day, its only got 32,940 miles.

Before I started it I changed the fuel filter, changed the oil, added plenty of fresh diesel (the tank was empty when I got it) with a little diesel 911, checked and topped off coolant.

After a little messing around I got it running, and **** does this sound like a strong motor! You hit that pedal and she jumps right up and screams! (in a good way )

MY PROBLEM: Like I said it runs great when you hit the pedal, but it doesn't like to idle. If you come off the pedal really slow I can get it to idle for about 5-10 min but then it will stall. If you come off the pedal to fast she'll die right away. I've had it running for a total of at least 30 min so I know by now its sucking up the new fuel. Also my Water In Fuel light never goes out.

Also there is a screw that is right in front of the air filter and it sticks up at a 45 degree angle, I turned once then turned it right back to its original position and that seemed to make it worse.

Any help would be greatly appreciated! Thanks alot!

 

[Warthog]

Have you download the free Technical Manuals for the truck?

One of the things to check is the excess fuel return line. There is a check vave that will plug up if the injector pump is failing.

The check valve is on top of the IP. It screws into the top cover and the has a rubber hose that makes a 90 degree turn.

Unhook the hose, unscrew the valve an look thru it. There is a glass ball inside. You should see light coming thru the glass ball. If the ball is blocked with black specks the IP needs a rebuild. Also some people will break the glass ball out.

 

[Matt65]

Have you download the free Technical Manuals for the truck?

Welcome to the Forum ILOVEMYBLAZER.
I have a link to the CUCV TMs in my signature. They are VERY helpful at troubleshooting.

 

[DriverSideImpact1008]

Rather than block up the "CUCV Videos" thread, I'll ask here.

Any updates? Stuff you've replaced? Things you've checked/found, etc?

 

[ilovemyblazer]

I couldn't figure out why it runs great at higher RPMs but stalls at idle.

Things replaced under my ownership: Oil change with Fram filter, topped off coolant, Pass. side alternator belt, Fram fuel filter, Fresh diesel with a little Diesel 911 added, Interstate batteries.

Its hard to start at first but when it does I can keep it running as long as I hold it at higher RPMs, if I come off the pedal really slow I can get it to idle fine for a little while then out of nowhere it stops.

I towed the truck to a diesel mechanic that was willing to look at it in his spare time, he is thinking I need new injectors.

Thats about all I know, I bought it straight from gov liquidation, not a private seller.

 

[ilovemyblazer]

Things you've checked/found, etc?

OHH! And my "water in fuel" light never goes out, it is always on when the ignition is on.

And my "gen 1" light never comes on.

 

[DriverSideImpact1008]

Yeah that could be just about anything. Injectors being worn out or something with the Injection Pump are likely causes. However, could just be that the injection timing is incorrect. Or could be that it's sucking air into the system somewhere. Are there any leaks?

As for the GEN light not coming on. I would first check the output of the alternator and check the GEN 1 light bulb. It is tied into the system (if the light goes out, the alt. doesn't charge). Also, new belts would be a great idea.

I found some WIF light discussion/info on thedieselplace.com:

The water-in-fuel light systems vary over the years and, in early years, was only an option. It usually uses a capacitive probe that senses the presence of water in the tank. Early year 6.2 systems have the probe in the fuel tank along with a water-siphon hose that allows you to siphon water out of the fuel tank. My 82 and 83 diesel Blazers both the siphon tap with a T-handle shut-off on it and I think my 82 K10 truck does also. I've been told though, that some pickups don't have it - and it might have been an option.

GM began using this system ca. 1980. Many of the early systems also have relief valves built into the tank-lines to allow fuel flow when fuel gets gelled. 1980 diesels have a water sensor that turns on when it senses any water at all. It was changed in 1981 to a sensor that must be submerged for 15-20 seconds before it triggers which would often equal over one gallon of water in the tank. In 1983 the system was changed to trigger at a 1/4 gallon of water in six seconds. I've got several diesel Chevettes that have even a more complicated system.

You could also just have a bad sensor. But - I know with my newer - square filter 6.2s, e.g. my 86, 87, and 89, the water light comes on whenever there is high vacuum on the inlet side of the fuel-pump. Why - I don't know. I never had to think about it much - since changing the filter has always fixed it. Light comes on - I need a new filter. I've never found any water in there. Same goes for my 85 diesel Isuzu truck.

There is a pressure sensor in the fuel filter assembly on the later model trucks. It turns the water-in-fuel light on when the pressure changes when the fuel filter clogs. If you read the owner's manual, it says that when the water-in-fuel light comes on there is water in the fuel "or other conditions exist which require fuel system service" followed by "take the truck to your local GM dealer for service"... The clogged filter is basically what they are talking about when they say "other conditions". The early model trucks are not equipped with that sensor.

The WIF light could be related to your idling/dying problem. Although it could just be a bad WIF sensor too.

 

[ilovemyblazer]

Well there are no leaks anywhere on this truck. Its the first vehicle Ive ever owned that doesn't! But I'll definitely check out all the things you listed. When shes running Ill post a video!

 

[epartsman]

You may not have enough pressure coming from your lift pump or the sock on the fuel pick up in your tank might be clogged. Since they ran it dry any junk in the bottom of the tank will now be residing there.

 

[rickf]

I SERIOUSLY doubt the injectors are worn or bad. You need to go through the proper troubleshooting procedure before condemning the expensive stuff. Start with the basics like fuel pressure and fuel flow tests on the lift pump. You say there are no leaks but how are you checking for a leak in the suction side of the fuel line? It will not show on the ground.

Rick

 

[DriverSideImpact1008]

I SERIOUSLY doubt the injectors are worn or bad. You need to go through the proper troubleshooting procedure before condemning the expensive stuff. Start with the basics like fuel pressure and fuel flow tests on the lift pump. You say there are no leaks but how are you checking for a leak in the suction side of the fuel line? It will not show on the ground.

Rick

^^ What he said.

 

[cpf240]

Perhaps get a clean can of fuel and run a hose from it directly to the IP input. I've seen videos of SS members doing this when ground-hoping 6.2 / 6.5 engines they got from GL. This would eliminate the entire fuel system, minus the return line(s), from the equation.

 

[Hasdrubal]

This may sound a little too simplistic. Perhaps the idle is set too low, this would cause the symptom described. Try turning it up..

 

[chevyCUCV]

Quick go take it back from the mechanic. Unless he owns a 6.2, i would not leave it there.

Read the manuals and fix it yourself. Otherwise it will likely get messed up. Nobody know's these engines. Injectors will not cause low idle. Maybe smoking/hazing of the exhaust

 

[Jeremiah_Johnson]

Check your air filter, I bought a 85 m1009 the other day that ran rough at idle removed filter and that improved idle .. so I replaced filter much better now !!