6.2L cranks but won't start?

[DoctorCheney223]

Hi Folks,

Here is the situation:

Outside temp is 97 degrees. Vehicle does have fuel as I added 2 more gallons just to make sure it wasn't a stuck gauge. This is a 1986 M998 with a 6.2L that ran perfectly yesterday. There are three other occasions when trying to start the vehicle it took approximately 15-20 seconds of cranking the engine before it would start. There is white smoke coming out of the exhaust pipe while the engine is cranking.

I don't know where the fuel filters are located on this vehicle so I can't check for clogged filters and I haven't yet pulled a fuel line to verify if the fuel pump is working properly.

Any ideas of what this might be before I have to pull a fuel line and check?

thanks,
Ron

 

[Chief_919]

White smoke coming out when you crank? That means it is getting at least some fuel. My first check would be the glow plugs.

 

[DoctorCheney223]

Any way to determine if the glow plugs are not functioning correctly? This is my first diesel and have no clue but I will start doing some research ASAP.

thanks,
Ron

 

[kipman]

Does the glow plug selonoid make a thunk sound?

 

[ida34]

Check for power at the glow plug terminal with a volt meter or test light. It should light while the wait light is on then they should stay on for a short time after the wait light goes off. If you are getting power to the plugs then check the individual plus by connecting a test light to positive power then touching the terminals on each glow plug with the connector off. This can be with the ignition switch off. If a glow plug does not light the test light it is shorted internally and is bad. I would bet you have a few plugs failed.

 

[kipman]

Chuck, you post was better than mine.

 

[DoctorCheney223]

Does the glow plug selonoid make a thunk sound?

When I move the lever from STOP to RUN, I do hear a thunk sound. Is that the sound you are talking about or is there another one that I should be listening for?

Also, the "wait" light goes on and off instantly and doesn't have ANY type of waiting period.

thanks,
Ron

 

[Chief_919]

Also, the "wait" light goes on and off instantly and doesn't have ANY type of waiting period.

There is your problem- your glow plug system has an issue. Now we need to know if you have an old system or a new system.

On the firewall, drivers side, is a protective control box, a black box with cannon plugs where the wiring goes in.

Give me the NSN on it and we can go from there in troubleshooting. If it is an old one, I will bet your glow plug controller is bad. But there is one that has a temp sensor where the glow plug controller went, and others that don't use the controller or temp sensor so I need to know what one you have.

Also, before we do much more, verifiy you have a good ground to the frame from the engine and from the PCB. Grounding issues sometimes cause this.

 

[Hell On Wheels]

If the volts check out, food for thought, check the injector pump lining marks on the center top front of the pump, where it mounts to the housing. The lines should be aligned. Sometimes mechanics do not tighten these mounting bolts to the right torque and these bolts will get loose. I have had a few in my life time. Just to ensure and eliminate this troubleshooting procedure.

Check the fuel water separator as well, located in front of the washer reservoir. Get a cup and turn the engine for approximately 15sec to see if you get bubbles out of this, if so you have water in the fuel.

If you replace the controller insure you wait about ten minutes for it to adjust to the temp. I would change out controller and glow plugs at the same time. Bad controllers stems from not waiting for the wait to go out before starting. This problem could have been the previous owner’s bad habit.

 

[DoctorCheney223]

Give me the NSN on it and we can go from there in troubleshooting. If it is an old one, I will bet your glow plug controller is bad.

Here is the info located on the cover of the PCB.

NSN: 6110-01-395-9585

Manufacture: Prestolite Electronics, Inc.

 

[Chief_919]

Here is the info located on the cover of the PCB.

NSN: 6110-01-395-9585

Manufacture: Prestolite Electronics, Inc.

Old one, so you have a seperate glow plug controller that is likely bad.

However, instead of buying a new controller, since they are obsolete and no lonegr made, I would look for a new style PCB that eliminates the need for a controller.

6110-01-491-2152
6110-01-491-2142
are the two best ones.

 

[Retiredwarhorses]

It sounds like your Glow plug controller is toast...But it gets worse...It also most likely took out your glow plugs. This is what I would do......Replace your PCB "Blackbox" with a KDS yellow label EESS, Replace the Glow plug controller "GPC" in the water cross over tube with the "Yellow banded" KDS Temp Sensor. I prefer the Yellow label KDS EESS unit over the "Green" Label "KDS".
If you cannot find a Yellow label model then try for the Green label version, the Green label Version Does NOT require the Yellow banded Temp sensor, only the yellow label version requires Temp Sensor.
Now Pull all you glow plugs and test them...But better yet, Call Kascar and order 8 new Non-swelling glow plugs, they have a thermal resistor built in and you can;t smoke them due to a bad GPC or EESS, they reach max temp and basically shutdown.
I CANNOT stress the importance of being ever so careful in removing your old glowplugs, if they are swollen you run the risk of them breaking off while removing them. DO NOT FORCE them out! They make a tool for stuborn ones.
You can also remove an Injector so you can catch the broken piece also.
I would remove them one at a time, if you come upon a stuck one move on to the next one, then double back to work on that one or 2 or 3 etc....Yikes.

Lastly...If and when you are done replacing your PCB with an EESS and new Glow plugs you will need to install the second most important item, An Aux ground Harness....The HMMWV suffers from terrible grounds.
The Harness can be made locally, I have a HMMWV that will NOT start without this Harness. You can guy everything local, Get some nice Heavy Gauge wire, I like #8. The Harness Looks like a spider..if that makes sense, You start at the left rear Engine Block ground stud:
Run one new ground to a mounting bolt of the EESS
Run one new ground to the Generator Grnd
Run one new ground to the Starter
Run one new ground to the Ground stud on the firewall, this ground can
be accessed by removing the Gauge panel, look to your far right and you will see a stud that feeds from there to the engine side.
Terminate all 4 ends into a common 9/16 or 3/4in Electrical connector that has a Hole in it, Attatch that to the Engine Grnd stud found at the left rear of the Engine Block.

Once all this is Done I can say without reservation that your starting issues will be gone forever...Minus dead batteries,No fuel or bad Pump.
I have had 5 HMMWV's and I have done this to every one of them.