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Discussion Starter · #1 ·
He is an interesting question. So I have two of the same tractors. 2000ish Simplicity Legacy 24.5 Briggs & Stratton Diesel. One motor has 700 hours on it and starts and runs perfectly. The other has 300 hours and from a cold start it chugs, puffs some smoke, and even sounds like it is knocking a bit. But then after 20 sec it runs smooth just like the other one. What is going on?
 

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You must have gotten a good one in the one that doesn't smoke and takes right off. I worked at Simplicity for 44 years of which most were in product testing and every Dihatsiu diesel that I ever started at lower temps chugged and choked and smoked and rattled just like you described. We did notice that different fuels did make some difference, Standard or BP now, was better than most but I'm sure you're using the same fuel in both tractors so that wwouldn't have any effect on the startup.

Mowman1
 

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Timing is critical on diesels,had 2 Long 910 diesels one would start right up the other was
a hard starter and slow to 'get going' the timing was slightly off on the hard one once the timing was set it started like the other one.
 

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Sounds like the pump timing may be set perfect on one while the other may be a tad off. Had a similar issue with one of my VW diesels years ago. Brought it in for repair running and starting perfect, got it back starting hard but running fine once warm.
After talking with mechanic, he explained how precise the pump timing is.
They re-set it and was fine.

Another possibility is 1 or more glow plugs not functioning. If 1 cylinder is not firing immediately like the others your condition will occur. Once that 1 cylinder lugs along not firing until it heats the fuel enough to combust. Once it fires all smooth out as described.
That's what is so great about diesels IMO, true combustion engines. The firing cylinders will carry the non-firing one or ones until combustion is made.

MU
 

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Discussion Starter · #5 ·
You must have gotten a good one in the one that doesn't smoke and takes right off. I worked at Simplicity for 44 years of which most were in product testing and every Dihatsiu diesel that I ever started at lower temps chugged and choked and smoked and rattled just like you described. We did notice that different fuels did make some difference, Standard or BP now, was better than most but I'm sure you're using the same fuel in both tractors so that wwouldn't have any effect on the startup.

Mowman1
That's cool that you worked for simplicity for that amount of time. Funny you mention the fuel. The one running fine is using shell. The other one I don't know what is in it because I just purchased it. I'll run it low and fill it up with shell and see if that has any effect.
 

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Discussion Starter · #6 ·
Sounds like the pump timing may be set perfect on one while the other may be a tad off. Had a similar issue with one of my VW diesels years ago. Brought it in for repair running and starting perfect, got it back starting hard but running fine once warm.
After talking with mechanic, he explained how precise the pump timing is.
They re-set it and was fine.

Another possibility is 1 or more glow plugs not functioning. If 1 cylinder is not firing immediately like the others your condition will occur. Once that 1 cylinder lugs along not firing until it heats the fuel enough to combust. Once it fires all smooth out as described.
That's what is so great about diesels IMO, true combustion engines. The firing cylinders will carry the non-firing one or ones until combustion is made.

MU
Pump timing? Is this something I can tackle on my own? I don't know much about diesels. How can I test a glow plug?
 

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Hold up, Dad had the same problem with the Kabota. Turns out that the mice like the air intake for nesting. Might want to check your air cleaner and air intake tube if it has one.
 

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Discussion Starter · #10 ·
So I talked with a diesel mechanic and he gave me a few things to check. He said being that the problem is only at a cold startup to check each glow plug. So I went to take them out today and they have rust all around the base and are stuck in the engine block. I did not apply much pressure to remove them instead I sprayed them with some penetrating oil and will continue doing this throughout the day before trying to remove them again. I don't want to risk breaking a glow plug off in the engine block or worse yet stripping the engine block.

The 2nd thing he told me to check. He said a dirty injector will drip cause excess fuel in the cylinder. At a cold start up this extra fuel will cause the smoke and rough idle until it all burns off. To check this he said I should be able to remove the glow plug before a cold start up and if the injector has a drip most times the glow plug will be wet.

Any other ideas?
 

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So I talked with a diesel mechanic and he gave me a few things to check. He said being that the problem is only at a cold startup to check each glow plug. So I went to take them out today and they have rust all around the base and are stuck in the engine block. I did not apply much pressure to remove them instead I sprayed them with some penetrating oil and will continue doing this throughout the day before trying to remove them again. I don't want to risk breaking a glow plug off in the engine block or worse yet stripping the engine block.

The 2nd thing he told me to check. He said a dirty injector will drip cause excess fuel in the cylinder. At a cold start up this extra fuel will cause the smoke and rough idle until it all burns off. To check this he said I should be able to remove the glow plug before a cold start up and if the injector has a drip most times the glow plug will be wet.

Any other ideas?
You don't have to remove the glow plugs to verify they are heating properly-at least I did not on my vw. Just feel the plug for warmth. Cycle them a couple times to get warm.You should be able to feel if they are getting hot.
As far as timing, I know on the vw they used a dial indicator and other type gages to verify the timing.
I have no idea how the brigg's engine timing will be.

MU
 

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Testing glow-plugs with a multi-meter set on ohms. Off the bat I'm not sure what the resistance is. Have many different brigg books but not this engine.

But to test wither the glow plug is working, Unplug the glow-plug wire from the glow-plug. Take your multi-meter and set to ohms. (The icon for this looks like a horseshoe) Doesn't matter which end red or black. But place one on a ground. (battery or engine block) take other end and touch the glow-plug terminal. Now you should see if current can pass through or not. If not - bad glow-plug. If yes current does pass through that means glow-plug good, but the wiring to it is possibly bad. Lastly could be just a bad connection with a dirty terminals. But this will help you figure out if it's a glow plug issue or not.
 

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Discussion Starter · #13 ·
After a little soaking I was able to remove the plugs without any damage. I soaked with pb blaster and then used a small impact to remove them. The reason why I wanted to remove them was the mechanic told me sometimes when you have a leaky / dirty injector the fuel will drip onto the glow plug so if you pull the plugs and they are wet right away you know what the problem is.

I used my multimeter and tested all the plugs are fully operational, contacts are clean, and they are getting power. So I think we can eliminate plugs as a cause.

Now onto the injectors. I am thinking about removing one injector at a time a swapping them with my other tractor. By doing this hopefully I find as soon as I replace one injector the cold start symptom will be corrected. At that point I will know which injector needs to be replaced. I priced out just replacing all 3 injectors but they sure don't give those things away. They are a couple hundred to replace all 3.
 

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Before doing all that I'd run the tractor at least a couple tanks of fuel thru it and the harder you work it the better.Idling and light work will cause lots of problems with diesels that can be cured by working them.
 

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As long as you have the GP's out (or can remove them), hook them up to a battery and see if they actually work. Caution! they get hot quickly! Testing them with an ohmmeter only confirms that they're not bad, it doesn't mean that they actually work.
 

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My guess with the black smoke on startup it's either injectors or fuel pressure issue. Both can play a big roll in how a diesel runs. But messing with the fuel pressure be very careful. It's not like a gas engine with 60 psi. Some diesels are up to 2000 psi and can slice your hand open real easy if things are not done correctly. Need to relieve the pressure first before pulling it apart. Some diesels also have a fuel pressure regulator. Which if bad can put way to much fuel in the engine on startup. good luck
 

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dont know if you solved your problem yet but i would go with the pump timing. I had a legacy diesel that i built a new motor for after the first blew up. timing slightly off cause black puff at startup. timing is easy to adjust by rotating the injection pump. The valve cover needs to be removed, lines loosed from the pump, 1 bolt on the rear of the pump loosened, and the 2 adjusting bolts loosened so the pump can be turned. The end of the pump has a bolt that you remove for a dial indicator to be screwed in so you can set it to spec. its about a 20 minute job
I found a manual online from Briggs when i built the motor early last year.
 

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Discussion Starter · #18 ·
Need to keep you guys updated. So I took the injectors in and had them cleaned. The gentleman @ Rockford Diesel Injector Service was very kind in the sense he showed me how they tested and cleaned injectors. My spray patterns were off a bit in 2 and the 3rd was really bad. I just reinstalled the injectors yesterday so I will try to restart the motor tomorrow and see what happens. Thanks hammer for the tip on the fuel pump timing. If this doesn't solve my issue I was give that a try next. I also found the service manual that you speak of and have a copy on hand.

How many hours did you have on yours before it blew up? Or why did it blow up?
 
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