Dolmar 5105 constant starting issues

[Dan M]

Hi all

I purchased a used Dolmar 5105 and it worked fine last year in 2018. This year it has given me many issues. It's been in shop 3 times and each time it takes them about 2 weeks to get to it then another week or two to fix it based on delivery of parts. I don't have any experience with 2/4 cycle engines other than tune ups, but figured now is a good time to start learing more.

This year so far, the general issue i've been having are it will start, work for a short period of time (generally a few hours) then i can't get it started again. After taking it to shop, they will "fix it". The first day i attempt to use it , will be fine, then 2nd i can't get it started again.

The first two times it's been in shop, the following work has been done (cleaned fuel system, cleaned carb, replaced spark plug, replaced air filter, tuned carb). The last time it was in shop, the shop sent it back to factory with sales rep and they "found something they didn't like" with the cylinder and it was "factory rebuilt". Since getting it back, it started up first day i used it. 2nd day, couldn't start it. After about a week of daily start attempts, i was finally able to get it to start. I then started it up every day for a week until i had time to use it.

Last week, i got it started up and used it for maybe an hour (stopped and started it several times). The next day, I couldn't get it started. When put in choke, it will attempt to start on 2nd pull. When moved to run, it will not start. If i let it sit over night, next evening, same thing will happen.

Similar scenario has been happening all year. I will get it back from shop, it will work one day, then i can't get it started again so back to the shop it goes and repeat. I've lost a lot of time waiting on shop so I'm looking for things i can do myself to get this thing working or at least identify the issue and get some parts ordered.

Last week of not starting, I would pull spark plug, sometimes it would be wet, other times not. If i turn it upside down, i may get a few drops of fuel out or I may not. After putting plug back in, it would either (a) sound like it was starting on 2nd pull in choke then not start in run or (b) in run, start and immediately die. On my start attempts last week, i ran out of fuel. I filled it up on Saturday and since then I have been able to get it to sound like it was going to start in choke, but then i can't get it to start at all in run.

I checked plug gap and verified the air filter is clean.

Should i change carb settings and try starting again (read on here about turning L out 1 turn and H 1.5 turns)?
Should i pull carb, clean and inspect?
Should i check fuel pressure? If so, how would i go about doing that?
Should I get a compression tester and verify cylinder pressure? If so, what should it be?

Come to think, I have a spark plug test light, i can verify that the plug is getting signal.

I'm open to any suggestions.

thanks in advance

 

[Jeff Lary]

Sounds like it may be an electrical/ coil issue? Get it started again and use it if you can.... Then when you go to re-start it if it does not start pull the plug and check it for spark right then. Sometimes a hot or warmed up coil will fail.
To do this you will need to remove the plug as soon as you discover it will not start, and ground it well. Make sure the " nut shaped" portion of the plug is in good contact with the engine cylinder then in a darkened place (so you can see the spark) pull the saw over fast a few times. If the plug does not show good Blue or bright orange fire it may be a coil issue if it does fire / spark you have a carb/ fuel issue. I have a 5105 brand-new it sits on a shelf,.. it starts like crap and I hate it. I grab on of my 25 year or Jonsereds or Partners when I need to work. So I may be biased , good luck

 

[cuinrearview]

If you flood it good one time, it could give you trouble for a few days if it doesn't dry out. The wet plug is a pretty good indicator. Once you've been running it the choke should never be needed. Sometimes I'll flip the choke on and off to engage fast idle when they're hot. I suppose also the cat in the muffler could be plugged, but that's a long shot. The next time you can't get it to start, pull the top cover, pull the plug, leave it upside down open for the night. Re-assemble and try the cold start procedure the next day. Is this an easy start model? I've never had to pull an easy start cold more than a half dozen times before it pops. A non-easy start usually takes about three.

 

[Ronaldo]

The 5105's have a tank vent issue that is fairly easy to fix. I had a lot of starting issues with mine when it was new and sat overnight or for a couple days. The vent does not allow tank pressure to release and just sitting will actually flood the carb. Need to access the tank vent (look up an IPL) then with sidecutters or scissors nip a very very small corner of the flexible duckbill type vent material. This has completely solved my starting issues.

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[cuinrearview]

The 5105's have a tank vent issue that is fairly easy to fix. I had a lot of starting issues with mine when it was new and sat overnight or for a couple days. The vent does not allow tank pressure to release and just sitting will actually flood the carb. Need to access the tank vent (look up an IPL) then with sidecutters or scissors nip a very very small corner of the flexible duckbill type vent material. This has completely solved my starting issues.

Sent from my SM-S320VL using Tapatalk

That's good to know. I've had about a dozen of these and have never experienced that.

 

[Dan M]

Sounds like it may be an electrical/ coil issue? Get it started again and use it if you can.... Then when you go to re-start it if it does not start pull the plug and check it for spark right then. Sometimes a hot or warmed up coil will fail.
To do this you will need to remove the plug as soon as you discover it will not start, and ground it well. Make sure the " nut shaped" portion of the plug is in good contact with the engine cylinder then in a darkened place (so you can see the spark) pull the saw over fast a few times. If the plug does not show good Blue or bright orange fire it may be a coil issue if it does fire / spark you have a carb/ fuel issue. I have a 5105 brand-new it sits on a shelf,.. it starts like crap and I hate it. I grab on of my 25 year or Jonsereds or Partners when I need to work. So I may be biased , good luck

This is all cold starts. 2nd pull on choke, it sounds like it's going to run. Then in run, it doesn't start.

I'll check for spark using my inline tester first if nothing consistently there, check coil. If i get a consistent light, then I'll pull plug and ground it to see where on tip it is igniting and check for color.

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[Dan M]

If you flood it good one time, it could give you trouble for a few days if it doesn't dry out. The wet plug is a pretty good indicator. Once you've been running it the choke should never be needed. Sometimes I'll flip the choke on and off to engage fast idle when they're hot. I suppose also the cat in the muffler could be plugged, but that's a long shot. The next time you can't get it to start, pull the top cover, pull the plug, leave it upside down open for the night. Re-assemble and try the cold start procedure the next day. Is this an easy start model? I've never had to pull an easy start cold more than a half dozen times before it pops. A non-easy start usually takes about three.

I only use choke on cold. Seems to flood (at least i think so based on smell) after 2-3 pull attempts in run. Plus fact that tipping it upside down gets some fuel out plus occasional wet plug.

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[Dan M]

The 5105's have a tank vent issue that is fairly easy to fix. I had a lot of starting issues with mine when it was new and sat overnight or for a couple days. The vent does not allow tank pressure to release and just sitting will actually flood the carb. Need to access the tank vent (look up an IPL) then with sidecutters or scissors nip a very very small corner of the flexible duckbill type vent material. This has completely solved my starting issues.

Sent from my SM-S320VL using Tapatalk

Odd you mention this, something to check. One of my initial thoughts was it wasn't getting enough fuel (the few times it started but immediately died). Something good to keep in back pocket if nothing else works. Now that i think about it, might be why repair shop had sales rep take it back to factory.

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[Dan M]

Should i worry about doing an initial carb setting? From my limited knowledge and research, i think this saw its supposed to not go to lean or too rich to start to allow for adjusting the carb (i did order a wire tach/ hour meter , since it's self powered and i can't get saw to start not sure what idle rpm is currently set).

I was thinking maybe good to go through the above items and set an initial carb position.


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[cuinrearview]

You can try it

 

[Dan M]

You can try it

what would be a good initial carb settings? I read here when searching before posting, L being 1 turn out, H being 1.5. what about S?

 

[Ronaldo]

That's good to know. I've had about a dozen of these and have never experienced that.

I'm thinking there was thread started here about the 5105 and its tendency to flood too easily and Carl Miller of Miller Mod Saws in NW Missouri let us in on a fix that he found.(he is a Dolmar dealer) I actually got to watch him do the fix on mine at the Iowa GTG.

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[cuinrearview]

Just turn that in a ways. It doesn't effect your tune. That's just idle speed.

 

[Dan M]

Just turn that in a ways. It doesn't effect your tune. That's just idle speed.

I was asking because I wasn't sure if that would would cause it to immediately die (as i experienced a few times) should I actually get it to start.

 

[cuinrearview]

It could, if it's not turned up enough. But if you're idling fine sometimes it's probably not it. What are the H and L at now?

 

[Dan M]

It could, if it's not turned up enough. But if you're idling fine sometimes it's probably not it. What are the H and L at now?

a couple weeks ago when it was running, it seemed to be idling high.
I can't say for sure where the screws are as the saw is at home and I'm not. But, from memory looking at it last night, mostly turned in for both.

 

[cuinrearview]

If that's all true you may have an air leak.

 

[Dan M]

If that's all true you may have an air leak.

What do you mean air leak?

 

[cuinrearview]

Air entering the intake stream or crankcase, causing a lean burn condition.

 

[Jeff Lary]

I'm thinking there was thread started here about the 5105 and its tendency to flood too easily and Carl Miller of Miller Mod Saws in NW Missouri let us in on a fix that he found.(he is a Dolmar dealer) I actually got to watch him do the fix on mine at the Iowa GTG.

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If you ever find that thread I would like to read it. Yes my saw will flood very very easily.