Another Diesel Starting Thread

[Steve777]

My S470D (Buck) is refusing to start, and I think that I have tried all my usual tricks and am looking for suggestions.

It ran just fine 3 weeks ago, when I used it to plow after a snow for an hour or two.

We got a big storm a couple of days ago, and it would not run. It started like normal, but never rev'd up the RPM after getting going, just puttered along for maybe 1 min and then died. Fuel was good (liquid, not jelling), and I was getting white smoke so I suspect there was some fuel coming in. Charging the batt and warming the engine and IP with a heater did not help, it just would not start. So I did some more investigating and the fuel filter looked pretty dirty. So today I got a new fuel filter. cleaned out the filter bowl, made sure fuel was flowing freely from the tank to the filter bowl, and put in the new filter. I bled the fuel line at the IP, got some air out and then a solid fuel stream. Tried starting again with the same results. It ran for maybe 20 sec at slow speed then died.

I am trying to figure this one out. There were a couple things I had thought of:

1. I didn't bleed the fuel lines enough. I was getting a solid stream of fuel at the IP bleeder, but maybe there is still air in there. I was thinking of putting some clear vinyl line in there temporarily to check.

2. Second thing I had thought of was perhaps the governor broke, and even though I pull back the throttle level, the engine isn't being set for more fuel. Any easy way to check this?

3. One other less likely thing is perhaps glow plugs. It was ~ 40F when I was trying to start it, warm enough that it should have caught even without the GPs working. But who know.


These engines are pretty simple, but I can't really think of much more that could be going wrong here. I suppose I could check compression but given that it was running fine 3 weeks ago seem unlikely that it suddenly lost compression just sitting.

Any other thoughts on what might be the problem here? Things to check?

TIA

 

[Looking4new]

I think I would bleed the fuel lines at the injectors, first.
Then I would try starting and if it did start but only idle I would loosen the fuel cap just to prove that the vent was doing its' thing. After that I would ask on TBN what else to check.

 

[Ilikeurtractor]

One of my tractors which normally started fine wouldn't start one day. Turned out to be stuck rings. It wasn't sitting that long before its last run. I don't remember how long exactly but no more than a couple of months. I had tractors sit for over a year that still started fine so I'm not sure how much down time affects stuck rings. White smoke indicates low compression which is a symptom of failed/failing rings.

 

[truckdiagnostics]

Don't know what your running for fuels system. The smaller high speed diesels run nozzle into a pre combustion chamber and they are real temperamental on spray pattern into the pre combustion chamber. Have had what you are describing where the pintal in the nozzle has stuck due to a bad batch of fuel. Yanking the nozzle not to hard and have them pop checked. Bosch nozzles real common.
steve

 

[truckdiagnostics]

Just remembered the Bosch nozzles will also sizes if you shut down real fast with out idling and letting cool.

 

[zzvyb6]

Your symptoms are familiar to me. Sounds like you ran out of fuel and now have some air in there. I crank mine with the injectors cracked open slightly until the air bubbles stop. Don't try to start it on full throttle, maybe 1/2 or 3/4. Also don't overheat the starter motor and consider using a starter charger until it begins to run in sputters. Funny how it catches on when all the air in the lines is flushed out. I had a problem with a cracked fuel pickup hose in the tank. Once the fuel level dropped below the crack, it sucked air. Both tanks.

Running a fuel pump dry is not good for it either. If that's happened, the supply won't be sufficient to run at full power. Consider towing it with a vehicle to get a good starting rpm if you have gears.

 

[Steve777]

Thanks to all.

Put a charger on it, then cracked the fuel line nuts at the injectors one by one. After they were all done it started up and ran great. There was a bunch of smoke coming out of it both before the bleeding and right after, so I am guessing that the air in the lines was delaying injection but not entirely eliminating it.

One other oddity, when it wasn't catching, every so often the starter would stop engaging but still spin. I think it was one cyl fired a bit and the pulse caused the starter to disengage. At least I hope that's what it was. Whatever it seems to have stopped with the engine running again.

I'll give it a few more starting cycles before our next snow later this week.

 

[buickanddeere]

Stuck rings ? How was that diagnosis made ?

 

[Ilikeurtractor]

If you're referring to my post, the diagnosis was made by pulling the pistons and replacing the rings. The old ones being stuck (wouldn't expand on their own from the piston).

 

[buickanddeere]

If you're referring to my post, the diagnosis was made by pulling the pistons and replacing the rings. The old ones being stuck (wouldn't expand on their own from the piston).

Something must have made then hot and took the spring temper out of them ?

 

[Ilikeurtractor]

Actually I didn't answer your question correctly the first time. The initial diagnosis was low compression and upon disassembly of the engine I discovered the stuck rings. I think it was carbon build-up in the ring grooves that were holding the rings from expanding. By that point I already had new rings so I replaced them. I suspect if I would have cleaned the grooves I could have re-used the rings and it would have ran as they did spring apart once freed from the carbon/gum or whatever one wants to call it. The engine only had around 1200 hours on it. I think the root cause was operating the engine under low loads for extended periods of time but that is just a hunch. As I read the original post it reminded me of similar symptoms of low compression. Of course the easy stuff needs to be checked first as in this case but it needs to be kept on the back burner that it may be something more sinister.

 

[buickanddeere]

Actually I didn't answer your question correctly the first time. The initial diagnosis was low compression and upon disassembly of the engine I discovered the stuck rings. I think it was carbon build-up in the ring grooves that were holding the rings from expanding. By that point I already had new rings so I replaced them. I suspect if I would have cleaned the grooves I could have re-used the rings and it would have ran as they did spring apart once freed from the carbon/gum or whatever one wants to call it. The engine only had around 1200 hours on it. I think the root cause was operating the engine under low loads for extended periods of time but that is just a hunch. As I read the original post it reminded me of similar symptoms of low compression. Of course the easy stuff needs to be checked first as in this case but it needs to be kept on the back burner that it may be something more sinister.

Ah , I understand now. Sounds entirely reasonable and makes sense.

 

[Ilikeurtractor]

Not to "rock-the-boat" on the bleeding injector lines theory, but in my experience I have never had to crack the lines at the injectors to get the air out from the injector pump to the injectors. I realize this was the apparent fix here, but if you look at how these injector pumps work there is essentially a check valve on the discharge side of the pump as it enters the injector line. If that is working correctly (and maybe that is the problem here), air will be forced through the line as new fuel gets pumps into the line. It is imperative there is no air in the line going to the pump, but once fuel is there the pump *will* pump it somewhere even with air also in the discharge line. What always seemed odd to me though was how an air pocket on the top of the injector line will come out and go down into the injector since it should stay at the high point but it does. I would be willing to shoot a video showing an empty injector line installed on the pump, tightening it up, and only cranking the engine until it starts and runs fine. I've done it multiple times as I'm sure others here have also. Again, not trying to start battles, just reporting what I have seen to help the general understanding and what one can expect.