And yet another no start 6.9 thread...

Selahdoor said:

One of the reasons many of us have converted to manual glow plug circuits.

At a time like this, you are really cycling those things a lot.

They are just mini electric heater elements. And as with all electric heating elements, they have a finite life span. A finite number of cycles are available.,. The more you use them, especially when they aren't needed again, the shorter they will be around.

Click to expand...

Well said.

Rattlenbang said:

it ran for an hour after that at idle, so there could be some seafoam still in there

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Not that this will help with the starting or lack thereof, but This is to clear something up. These engines have a fuel return system on them. Whatever fuel isn't used by the engine is returned to the fuel tank. This means that, after an hour of running, the can of Sea Foam may still be mostly in the fuel system, but it's been fully diluted by the rest of the 3/4 tank of fuel. It's no longer anywhere in full strength.

Try plugging in the block heater for a 2-3 hours before your next startup attempt. If it fires up easily, that's 100% confirmation that glow plugs are not working.

These trucks don't have water tight electrical connectors and there are several spots in the wiring harness that can corrode. Your glow plug light can still come on and you'll still hear the relay clicking but you may not be getting power to the glow plugs. Use only motorcraft glow plugs and thermostats.

Other brands of glow plugs are prone to burning the tips off when they fail, and can damage piston and/or valves due to tight clearances in the engine.

The thermostats on these engines are very specific and cannot be interchanged with generic thermostats. The correct thermostat does not have an internal bypass (bypass on an IDI is a separate check-ball type valve that is mounted in the thermostat housing).

I also like that clear tubing idea. I put one in temporarily years ago and decided to keep it because it's such an effective diagnostic tool for catching air leaks.

Do you hear the glow plug relay click and have a red glow plug lite in the dash for several seconds when the ignition key is on cold? Even if it clicks, it does not mean that the relay is making contact.

I am on my 4th glow plug relay in 20+ years.

If the relay does not click first try jumping from battery plus to the small terminal on the relay that has the purple wire attached for 6 seconds cold, then crank. That is the relay ON terminal. If no click or still no start, try jumping directly across the two big terminals on the relay with a short heavy cable. That will bypass the relay and power the glow plugs manually, again about 6 seconds cold, then crank.

At long last found the problem. After endless cranking I eventually got fuel dribbling out the injector lines. I tightened them up and nothing. I've gone through glow plug circuit and getting 12v to plugs, bad plugs replaced. I replaced all the return line components and hoses, including O-rings on injectors. Even though I had it running at one point, Something else had to be wrong besides air leakage into the system.
So I pulled the cover on the injection pump. I had done some reading up on this pump and had a general idea what I should be looking for. I visually checked shutoff solenoid, and yes, it was working. I actuated the throttle and saw the governor mechanism doing what it should. But then I noticed that the metering valve didn't seem to do anything. I stuck a small screwdriver in there and discovered that the fuel shut-off mechanism was stuck in the closed position. Even though the solenoid would retract, the following mechanism would just sit there, keeping the fuel shut off. I manually moved it back and forth several times until it was completely loose and would flip forward. The spring that moves it is very weak.

I put the cap back on, and cracked all the injectors and hit the starter: fuel immediately began leaking. Tightened them off, let the glow plugs cycle and it started right away.

What was really screwing me up was the fact that if you grind the starter enough fuel does come out of the injection lines, even with the fuel shut off. I'm experienced with 2 and 4 cylinder marine diesels that send very little fuel to small injectors and thought this little quantity of fuel was normal, especially since everything checked ok. Once I fixed the problem the volume of fuel coming was obviously a hella lot more. Live and learn.

I suspect people who have engines that won't start and suddenly do after a seafoam soak might be having this same problem. In my case, because it never did soak in the pump as I ran it all through, it never had a chance to dissolve the goo that was causing it to stick.

Glad you found the problem!

Sent from my SM-G950U using Tapatalk

Next thing on the list. She starts and runs fine but it has this strange problem of stalling when you stab the throttle. And while this rig is completely new to me and don't know what to expect, it seems awfully sluggish and throttle response is very slow. Its a big motorhome and not sure what I should be expecting. My last one was smaller with a 413 gasser in it with a 4 barrel so of course it would be pepper....

What is your air filter condition like?

Also fuel pump may not be supplying enough supply/pressure to the IP.

Filter is fine. I dont know the pressure but it seems to pump a lot. Cracking any of the lines it sprays fuel like crazy. I plan on replacing it the next few days as maintenance item.