6.2l diesel glow plugs not working

[peterpar]

I am new at this so cut me some slack.

I have an 85 6.2l diesel and the glow plugs wont turn on right away but if u turn the engine over for a second then the they turn on and its this same way all the time and i know its not the light because i can turn the key on for 30 sec or so and crank it for along time and it wont start just spit out white smoke like the fuel isnt warm enough to egnight.

It also dosnt shut off right away either it will continue to run for 10 to 20 seconds after u turn the key off and then it wont start right away just like there is no fuel in the pump?

Even before this started to happen after it was shut off for more then about two hours it would crank for quite awhile before it will fire and even then it will fire a couple of times like it was just out of fuel or something any ideas on either of those?

I think the glow plugs is just the controler and once it resets it will work and i just need to replace it?

I also think the fuel not shutting off is the fuel shut off in the injector pump but not sure?

but with it not starting right away ever i have no idea what that is just not good fuel pressure or something and its like that in the cold or hot dosnt matter its worse in the cold thow?
:mad2::mad2::mad2::nonod:

 

[ak diesel driver]

tell us more about your truck. IIRC the 85 still uses the round vertical cylinder glow contoller. Common replacement item and fairly expensive. I'm wondering if you LP is working or your getting drainback or air in the system. Replace the return line coming out of the front of the IP with clear tubing and watch for air bubbles while running also check to see if it empties when it sets.

 

[RI Chevy Silveradoman]

WELCOME to the Forum! :welcome5:

Take the time to fill out your signature, as it gives the members information as to what engine you have, and any mods that may have been done. It really makes diagnosing much easier for everyone. :cheers2:

 

[peterpar]

ok thanks i will do that in the moring when it warms up a little its kinda cold here right now to do mcuh and thanks for the addvice.

and also im not sure which it has i traced the wires back to a little box deal that has a plug on the front and a few of the wires need replaced because there is soem insulater missing what gage do i use and all the plugs should still work they are only a year old and thanks for all the addvice.

 

[iamdave0887]

85+ used the one piece glow controller similar to the 6.5 controller.

The 85+ 6.2 one is gray in color with a 4 pin connector that attaches to the back. the 94+ 6.5 one is black with a 3 pin connector(same plug just one pin removed from controller)

82-84 used the circular GP controller that threaded into a water port. The circular thread in controller was a piece of :shiiiiiite: that never worked correctly. Some would cause the GPs to cycle on and off very fast. Others would cause the GPs to randomly come on/off when the engine was already running.

the 82-84 setup used a separate relay/contactor that was mounted on the driver's side fender under the hood. the controller would ground the energizing coil of this relay/contactor to turn the glowplugs on.

UP to 1986 the ford 6.9s used 12 volt glowplugs and used the same controller, and the controller was garbage in that engine as well. Ford swapped to a different controller and relay/contactor setup with a resistor to drop the voltage to ~ 6 volts for the glowplugs starting in 1987, which was the last year of the 6.9. The 7.3 IDI came out the year after and ran the same 6 volt plugs.


The one piece glow plug controller of 85+ on the 6.2 was actually a very simple unit. Here's a wiring diagram of how the controller is wired. However where is says "glow plugs 6 volt" is wrong. The glowplugs are 10.5 volts each, not 6 volts. the 6.2 and 6.5 never used 6 volt glowplugs, ever.



Pin E is ground for the relay.
Pin D is "engine control" or a switched 12 volt ignition source
Pin C is input from the glowplugs basically telling the relays controller card "glow plugs on" and for how long.
Pin B is input from the ign switch when the key is turned to "start" to tell the controller "engine cranking".

Very simple system, although i have some doubts on that diagram. Where the inhibit switch is placed, makes no sense. the glow plugs would still function but the controller card wouldn't be sent the "glow plugs on/length of time signal" so it may leave it on too long in that case, not prevent the plugs from coming on.

The easiest way to prevent the plugs from coming on when the engine is warm would be to cut the 12 volt switched power to the controller(Pin D), basically rendering the system in-operative due to lack of power for the controller to function.

I'm going to have to verify this on my truck one of these days.