Yanmar L100V Help Request

CallMeColt

Active member
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Wilson County, Texas
Howdy,

There are a few pieces of military equipment that run on the Yanmar L100V engine. I'm working on one of these engines & am having a hell of a time figuring out my problem.

I have an engine with a fuel cut of solenoid on the injection pump. I've confirmed fuel is getting from the tank & up to the injector. All air purged. Fluids & filters are all new & clean.

Issue I am having is when cranking it over, it will barley run... Chugs just above being stalled out. I'd guess like 200 RPM.

Valve gap is as it should be.

The engine did run fine & then all the sudden didn't.

Any ideas?

I've fixed quite a few Yanmar L-Series & never had this issue!
 

jeffhuey1n

SMSgt, USAF (Ret.)
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Howdy,

There are a few pieces of military equipment that run on the Yanmar L100V engine. I'm working on one of these engines & am having a hell of a time figuring out my problem.

I have an engine with a fuel cut of solenoid on the injection pump. I've confirmed fuel is getting from the tank & up to the injector. All air purged. Fluids & filters are all new & clean.

Issue I am having is when cranking it over, it will barley run... Chugs just above being stalled out. I'd guess like 200 RPM.

Valve gap is as it should be.

The engine did run fine & then all the sudden didn't.

Any ideas?

I've fixed quite a few Yanmar L-Series & never had this issue!
Change your fuel filter. Also check your fuel tank for debris.
 

CallMeColt

Active member
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Wilson County, Texas
I completly rinsed & cleaned the fuel tank. All new fittings, lines, & fuel filter. Cleaned the injection pump. Tried a new injection pump. Tested injector. Purged all the air. Fuel is fresh & clean. The only other thing I can think to try is a new injector but I don't want to toss more money at it.
 

jeffhuey1n

SMSgt, USAF (Ret.)
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I completly rinsed & cleaned the fuel tank. All new fittings, lines, & fuel filter. Cleaned the injection pump. Tried a new injection pump. Tested injector. Purged all the air. Fuel is fresh & clean. The only other thing I can think to try is a new injector but I don't want to toss more money at it.
I’m going through this in my head. I’ve been working fuel problems as well a bunch of issues that are normal in a 50 +/- year old truck. They also apply to small engines.
Fuel; sounds like you have that covered.Good clean tank and fresh gas, check
Replaced filter(s), check
Valves; checked (I wouldn’t have thought of this)
Fuel pressure checked with a direct reading gauge
(Have you looked this over?)
You need to inspect the spark plugs/glow plugs. I just fixed a Briggs and Stratton engine that wouldn’t run right, I fixed the problem by simply removing the spark plug and inspecting it. There was a small metal shaving that was shorting out the ignition. I cleaned the plug and it runs like a champ.
Fuel, Air and Fire are the ingredients of a good running engine. If there’s a problem with any one of these, engine don’t run. You’ve got the fuel done. The air sounds like you have it running correctly. The only thing left is your ignition system.
Hope this helps.
 

CallMeColt

Active member
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Wilson County, Texas
I have not checked fuel pressure. I'm not even sure what the pressure is supposed to be on these engines but I know it's high. Spark definitely isn't an issue because it's a diesel. I could do a compression test but am not sure how to do that on these. Generally, I just use the pull start & if there's enough resistance to not be able to pull it past the compression stroke, I assume there's enough.

What really has me off is that it ran fine. I shut it down & put all the covers on around the head & closed up the box where the plugs is. Then, it wouldn't run. I touched nothing that had anything to do with the engine's ability to run. Crazy!

Thank you for the input. I may just stick it in the corner someplace & keep it for parts. Or if I end up thinking/finding out more then I will try some more.
 

jeffhuey1n

SMSgt, USAF (Ret.)
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I found this link on the web. There’s several ideas for troubleshooting your problem. My thought on this concerns your chain of events. Engine was starting, running and shutting down normally. You performed routine maintenance on the engine and the best you can get is a very low rpm. Low fuel pressure can cause this level of performance. I got my rototiller out of storage to do some yard work. It wouldn’t start easily and would shut down fairly quickly at full throttle. When bringing the throttle down to its minimum rpm, the engine ran longer but eventually it died. Going to full choke, I could get the engine to run but it really ran rough. I had several issues to contend with. First, a fouled spark plug caused by bad gas. Drained the tank and flushed it out with fresh gas. Pulled the full bowl under the carb and cleaned it up then reinstalled. At this point I made a mistake by over tightening the bowl bolt. It prevented the fuel level from providing adequate fuel supply which is why it would run slowly for longer that full throttle. The obvious fix was fixing the bowl and inserting the plug very carefully, stop when fuel dripping has stopped bypassing the plug. Put everything back together and tried again. Same problem. Replaced spark plug, same problem. I replaced the plug, flushed the fuel tank, checked fuel supply, removed, fixed and replaced bowl, problem still bugging me. I pulled the spark plug and found metal sliver arcing out the plug which fixed only part of the problem. Fuel delivery was a pain in the drain. At the point of taking it to a shop I tried one last thing. Pulled the carburetor and inspected it. There was a yellow film all over the internal workings of the fuel system. I cleaned it all off with various brushes and scrapping tools. Finally, that seemed to do the trick. I think the metering valve that regulated the fuel in the bowl was covered in that yellow stuff. Once cleaned and reassembled the engine ran fine, in fact it was better than fine. Engine ran just like it was new .
How does this relate to a Diesel engine? There are similarities between the two types. Fuel reservoir, fuel delivery to the metering assembly. From there it goes to the combustion chamber where it is ignited by a heat source. Fuel ignites and you have a running engine. Diesel or electric, the basics are the same.
Hope this helps.
PS, check your ground wire(s). Gently pull on them to see if anything is loose. I lost count of the number of bad grounds that had to be checked, repaired, etc.
 

Guyfang

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Do you have the TM's and or manuals for this engine? Have you read them?

Stop throwing money and parts at it. This is not a complex engine. It needs fuel, air and compression to run.

How did you test the IP?

Using the word "assume" will get you in trouble every time. Know. Get informed. If you don't have the tools to test compression, fuel pressure and rpm, get them, or borrow them. Then and only then can you know what is what.

You need to check one thing at a time. Test just that. Know it's good, then go to the next step. Start with air. It is easy. But often overlooked. Then compression. It's easy. Get a compression gauge and know how to install and use it. Know what it should read, before you start. Then fuel. The tech spec's for this is in the books.

This can not be an electric problem.
 

CallMeColt

Active member
361
59
28
Location
Wilson County, Texas
I found this link on the web. There’s several ideas for troubleshooting your problem. My thought on this concerns your chain of events. Engine was starting, running and shutting down normally. You performed routine maintenance on the engine and the best you can get is a very low rpm. Low fuel pressure can cause this level of performance. I got my rototiller out of storage to do some yard work. It wouldn’t start easily and would shut down fairly quickly at full throttle. When bringing the throttle down to its minimum rpm, the engine ran longer but eventually it died. Going to full choke, I could get the engine to run but it really ran rough. I had several issues to contend with. First, a fouled spark plug caused by bad gas. Drained the tank and flushed it out with fresh gas. Pulled the full bowl under the carb and cleaned it up then reinstalled. At this point I made a mistake by over tightening the bowl bolt. It prevented the fuel level from providing adequate fuel supply which is why it would run slowly for longer that full throttle. The obvious fix was fixing the bowl and inserting the plug very carefully, stop when fuel dripping has stopped bypassing the plug. Put everything back together and tried again. Same problem. Replaced spark plug, same problem. I replaced the plug, flushed the fuel tank, checked fuel supply, removed, fixed and replaced bowl, problem still bugging me. I pulled the spark plug and found metal sliver arcing out the plug which fixed only part of the problem. Fuel delivery was a pain in the drain. At the point of taking it to a shop I tried one last thing. Pulled the carburetor and inspected it. There was a yellow film all over the internal workings of the fuel system. I cleaned it all off with various brushes and scrapping tools. Finally, that seemed to do the trick. I think the metering valve that regulated the fuel in the bowl was covered in that yellow stuff. Once cleaned and reassembled the engine ran fine, in fact it was better than fine. Engine ran just like it was new .
How does this relate to a Diesel engine? There are similarities between the two types. Fuel reservoir, fuel delivery to the metering assembly. From there it goes to the combustion chamber where it is ignited by a heat source. Fuel ignites and you have a running engine. Diesel or electric, the basics are the same.
Hope this helps.
PS, check your ground wire(s). Gently pull on them to see if anything is loose. I lost count of the number of bad grounds that had to be checked, repaired, etc.
That issue you described is extremely common in gasoline small engines. It's the ethanol added to modern gasoline at the pump.

A diesel engine doesn't ignite with a head source. It it pure combustion via compression. Everything is mechanical unlike with gasoline. A lot of the L- Series engines I have don't have anything electrical on them at all.
 

CallMeColt

Active member
361
59
28
Location
Wilson County, Texas
Do you have the TM's and or manuals for this engine? Have you read them?

Stop throwing money and parts at it. This is not a complex engine. It needs fuel, air and compression to run.

How did you test the IP?

Using the word "assume" will get you in trouble every time. Know. Get informed. If you don't have the tools to test compression, fuel pressure and rpm, get them, or borrow them. Then and only then can you know what is what.

You need to check one thing at a time. Test just that. Know it's good, then go to the next step. Start with air. It is easy. But often overlooked. Then compression. It's easy. Get a compression gauge and know how to install and use it. Know what it should read, before you start. Then fuel. The tech spec's for this is in the books.

This can not be an electric problem.
There is nothing I can find as far as a Technical Manual for the L100V, military or civilian. I searched everything high & low. The V series are different than the AE series so you can't use those as I have them for other military generator sets & equipment. The biggest difference is in the governor system.

Brand new air filter. Intake valve is properly spaced. I can hear the air sucking.

I may get a compression gauge if I can find one that will work on these engines cheap enough. I'm not sure how to get an adapter in there to measure it with a gauge. Even at that, I'm not sure what it should be. My best guess after everything is that this is the problem, though I'm not sure how.

I tested the injection pump by taking off the high pressure line & watching for fuel with no bubbles to come out. Also made sure it wasn't a dribble. Then, I do the same at the top where the injector is. Once it's all fuel with no air, on all the other ones I have worked on, next pull/crank, it fires right up. I also checked the timing using the marks on the fan & it's right where it should be. No spacers under the injection pump were changed.

Tested the injector buy putting it in a bottle & watching the spray pattern. It was clean & even.

The only electrical thing that matters in this application is for the fuel pump solenoid as it's a key started engine. I tried eliminating it so it was regular feed & also put a completely separate 12v source to it & confirmed 100% that it is open & flowing.

I'm just stumped!
 

Coug

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Location
Olympia/WA
This is the link for the Manual for the engine. Hope it helps.

Good grief, I looked through that manual and there are more warnings than instructions!
The first 13 pages after the table of contents is nothing but warnings, and warnings on almost every page throughout. I'd wager over half of the total content in the manual is some type of warning or caution.
I'd hate to think who this product manual is actually intended for, if they require that many warnings, they probably aren't allowed out of their padded room without a helmet on.
 

CallMeColt

Active member
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Location
Wilson County, Texas
Good grief, I looked through that manual and there are more warnings than instructions!
The first 13 pages after the table of contents is nothing but warnings, and warnings on almost every page throughout. I'd wager over half of the total content in the manual is some type of warning or caution.
I'd hate to think who this product manual is actually intended for, if they require that many warnings, they probably aren't allowed out of their padded room without a helmet on.
Yanmar sells worldwide & it needs to meet every legal requirment for the warnings. Pshh, if you sell in California you need all kinds of extra warnings. I can't imagine all the ones required in all the European countries!
 

Guyfang

Well-known member
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Location
Burgkunstadt, Germany
Good grief, I looked through that manual and there are more warnings than instructions!
The first 13 pages after the table of contents is nothing but warnings, and warnings on almost every page throughout. I'd wager over half of the total content in the manual is some type of warning or caution.
I'd hate to think who this product manual is actually intended for, if they require that many warnings, they probably aren't allowed out of their padded room without a helmet on.
Why do you think the size of Army TM's has doubled. Look a a "new" TM.
 

jeffhuey1n

SMSgt, USAF (Ret.)
Steel Soldiers Supporter
1,410
159
63
Location
Laramie County, Wyoming
That issue you described is extremely common in gasoline small engines. It's the ethanol added to modern gasoline at the pump.

A diesel engine doesn't ignite with a head source. It it pure combustion via compression. Everything is mechanical unlike with gasoline. A lot of the L- Series engines I have don't have anything electrical on them at all.
I was unaware that ethanol added a coating to everything in the fuel system. Good info for troubleshooting any gasoline type engine.
Now that you mention it, I remembered a warning I was given when I got my first multifuel, never leave it in gear. A slight push can start you up and off it’ll go whether you’re in the driver’s seat or not. I definitely need to increase my knowledge of the engines. My past experience has been most gasoline engines and turbine engines that were used on helicopters. That narrows the field even more. Fuel (delivery), fire or combustion and air. The three basic ingredients of a running engine. There is a forth ingredient. Mechanical. You can have everything else correct but if there’s a crack in your fuel control or head gasket or some other mechanical problem, the engine will not work. I hope you can find the gremlin in your hearing, good luck.
 

Coug

Well-known member
852
403
63
Location
Olympia/WA
I was unaware that ethanol added a coating to everything in the fuel system. Good info for troubleshooting any gasoline type engine.
Now that you mention it, I remembered a warning I was given when I got my first multifuel, never leave it in gear. A slight push can start you up and off it’ll go whether you’re in the driver’s seat or not. I definitely need to increase my knowledge of the engines. My past experience has been most gasoline engines and turbine engines that were used on helicopters. That narrows the field even more. Fuel (delivery), fire or combustion and air. The three basic ingredients of a running engine. There is a forth ingredient. Mechanical. You can have everything else correct but if there’s a crack in your fuel control or head gasket or some other mechanical problem, the engine will not work. I hope you can find the gremlin in your hearing, good luck.
It isn't so much that the ethanol coats things, it's that it is hydroscopic, it pulls moisture out of the air. It's also an oxidizer, so it makes the fuel go bad quicker.

The oxidized fuel coats things in a layer of gunk, as well as plugging smaller passages.

The moisture combined with the alcohol in the fuel converts to acids and eats away at the metal of the carburetor (which is why most small engines these days have plastic carburetors, because it's expected they will sit around unused for long periods of time)

Fuel sold at marinas should be ethanol free, because they had a lot of problems with boats running ethanol fuels winding up dead in the water from all the water absorbed into then condensing out of the fuel and collecting at the bottom of the fuel tank and then the carburetor.
 
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