Dolmar PS-510 starts and dies

[ILENGINE]

Lets see if you guys can figure this one out. New NGK BPMR7A spark plug, new OEM fuel filter. Saw starts after about 4 pulls cold and runs a few seconds and bogs down and dies and takes another 4 pulls to restart. Have checked internal carb screen, checked carb adjustment, and checks fuel passages and carb diaphragms are in good shape. Also there is no loss of spark when checked with a spark tester while the engine is running and/or bogging down and dying.

 

[StarTech]

If it not the carb then is probably the crankcase sealing causing a lean out condition.

 

[ILENGINE]

@StarTech Good consideration but not that complicated. This thing acts like it is running out of fuel but it isn't a fuel problem.

 

[StarTech]

Okay then there is the impulse hose that could loose or have a hole in it. I do not see any Dolmars here so I miss that on the IPL. Also could be a hole or split in the intake manifold. The image of the carb appear to have an oddball impulse setup.

I also been have a lot problem with Zama needle seats leaking here causing a flooding problem. Ever Stihl got involved with Zama their carbs are just failing a lot more than in the past. Needle seat and main nozzles problems.

 

[ILENGINE]

Okay then there is the impulse hose that could loose or have a hole in it. I do not see any Dolmars here so I miss that on the IPL. Also could be a hole or split in the intake manifold. The image of the carb appear to have an oddball impulse setup.

I also been have a lot problem with Zama needle seats leaking here causing a flooding problem. Ever Stihl got involved with Zama their carbs are just failing a lot more than in the past. Needle seat and main nozzles problems.

Impulse setup is below the intake with a horn that sticks off the bottom of the carb Other end connects to the crankcase. Haven't had issue with this style of saw with split or damaged pulse lines or intake tubes. The impulse line looks similar in material to molded fuel lines used on other brands as well as Dolmar. The 6400-9010 I have seen a few inpulse lines split but not this saw. And normally when the carb goes goofy on Dolmar/Makitas they dump the entire contents of the fuel tank into the crankcase.

I have already diagnosed and repaired the saw. When I tell you what the problem is you will think I am wrong.

 

[StarTech]

With some of the crazy problems I have seen in the last few year anything is possible but glad you have it fixed and it does sounds like one for the books.

 

[ILENGINE]

@Rivets @slomo @Scrubcadet10 Any of you guys have any thoughts before I reveal the answer.

 

[ILENGINE]

With some of the crazy problems I have seen in the last few year anything is possible but glad you have it fixed and it does sounds like one for the books.

I come across this issue enough that I have to keep several different parts numbers of this item in stock for the various models. I come across this issue on Husqvarna and Stihl and helped another shop diagnose this issue on a Echo a few months ago.

 

[Rivets]

You state you have good spark at all times and it is not a fuel problem, so only thing left is compression, which I doubt is the problem. Can you narrow down which of these three system was causing the problem, or will it give away the answer?

 

[Craftsman Garage]

Hmm... Is it a Valvetrain problem or a plugged exhaust screen? Never heard of this engine brand before.