L3650GST Glow Plugs / Will not start

[Rebel]

I hate to say this but it sounds like an injection pump problem.

One thing to check is the fuel shut off solenoid (assuming it's not built into the pump). Make sure that with the key in the run position and linkage is fully extended or retracted (which ever the case) buy manually push or pulling on it.

Another trick is gasoline on a rag. With the air cleaner removed while cranking the engine wave a gas soaked rag around the air inlet (DISABLE YOUR GLOW PLUGS FIRST!) If you have good compression the engine will temporarily run on the fumes from the gas.

 

[Rockyridge]

(When cranking we do have voltage at each of the glow plugs - I don't have it here at the office but I it was slightly less than the full 12V - I think closer to 10 but I'm not certian of that off the top of my head.)


Im confused, maybe some real diesel people can provide some education here. I thought the only time there was any power (voltage) to the glow plugs was when the key was turned to the left (or what ever needs to be done with your equipment) to pre-warm the cylinder before starting on cold mornings. Other then that the glow plugs have no function and if there is 12V there that indicates some other problem. Do some diesel engines provide power to the glow plugs every time they are started or possibly under certain conditions under control of some sensor?

Thanks for any information you can provide.

 

[dkcobbs]

Saturday we went ahead and pulled the intake manifold, removed and tested each of the glow plugs and all 4 tested good. We also rechecked the fuel supply and had fuel at each of the fuel lines going into the injectors. We pulled one injector but couldn't reconfigure the fuel line to allow us to test it. Removed the air hose to the intake manifold to rule out air obstruction. When all is said and done, we are back to where we started except for rulling out the glow plugs. Very good suction on the air intake when cranking, fires consistently but not quite enough to start. My basic understanding of diesel is you all need is fuel, air and compression and we seem to have all three. Just about ready to give up and pay the piper for the dealer to work on it.

 

[Rebel]

My basic understanding of diesel is you all need is fuel, air and compression and we seem to have all three.

That is correct, but you also have to have proper timing. I am a diesel tech by trade and work on stationary engine generators. Unfortunately I'm not familiar with the injection system that Kubota uses. (Not a Kubota owner yet...got a deal cooking though).

Based on all of your input I think we can narrow it down to 2 possible problems;

1. Air being admitted to and or trapped in the injection pump, it takes very little air induced into the fuel supplied to the injection pump to cause problems. Are you sure that all of the air has been eliminated from your system? Sometimes an airlock can give a guy real headaches. The gas on a rag trick can be used to help work the trapped air out of the system.

2. Your injection pump is toast. The injection pump shops that I deal with on occasion have told me that since the introduction of ultra low sulfur fuel they have seen a rash of failures on pumps with a lot of hours. Everybody would be well advised to run a lubricity additive in their fuel to prevent premature failure due to the relative dryness of the ultra low sulfur fuel.

 

[DiezNutz]

1. Air being admitted to and or trapped in the injection pump, it takes very little air induced into the fuel supplied to the injection pump to cause problems. Are you sure that all of the air has been eliminated from your system? Sometimes an airlock can give a guy real headaches.

Amen. Dkcobb, when you pulled the feed line off the pump to do the "elevated reservoir" trick, the pump could've lost prime - it doesn't take much. Could you tell that the pump was actually drawing down the fuel? Sure I realize this didn't cause the original trouble but it has a way of masking the real problem and making it impossible to diagnose. Also, it does nothing in the way of proving or disproving that your fuel filter is clogged.

Btw- On all but the coldest days, if you cranked the engine long enough, it would start w/out glow plugs because compression alone eventually heats a cylinder enough to sustain combustion.

The injection pump shops that I deal with on occasion have told me that since the introduction of ultra low sulfur fuel they have seen a rash of failures on pumps with a lot of hours. Everybody would be well advised to run a lubricity additive in their fuel to prevent premature failure due to the relative dryness of the ultra low sulfur fuel.

Just playing devil's advocate...while the sulfur content has been reduced, the refiners are supposed to be putting in additives (mainly corrosion inhibitors) to restore the lubricity of the fuel. Common misperception is that sulfur is the lubricant; it is not but the processes that remove it also reduce the fuel's natural lubricity (so I guess net effect is it might as well be). It also makes the fuel more corrosive, hence the extra corrosion inhibitors which also have the added benefit of restoring lubricity.

Perhaps more realizable problems from switching to ULSD are older seals failing (I wonder if leaks don't account for some of those pump rebuilds), and plugged filters (and pump) 'cause ULSD has a way of loosening old deposits.

Now with all of that said, yeah I'm still gonna run additivies like I always have



not many people realize that other additives have been introduced to maintain the same degree of lubricity. Or so they say.

 

[dkcobbs]

On at least three occassions, including last week after testing the glow plugs, we have cracked the fuel lines at the injectors and made certian that we had fuel at all four injectors when we cranked the engine. It is my assumption (always subject to being corrected) that if we had an air lock problem then we would not have fuel at each of the injectors.