HELP! 500i may get the parts cannon

[Mastermind]

This is more of a question than a statement, if the primer can leak out when operated, could it not suck air when running?

Excellent observation.

 

[Mastermind]

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[Ketchup]

This is more of a question than a statement, if the primer can leak out when operated, could it not suck air when running?

Great point.
I did pressure test that line but I didn’t try pressure with it hooked up to the injector. I’ll do that tonight.

 

[redline4]

Seeing there really is no fuel pump (as far as I know), wouldnt the fuel system on this run under a vacuum once it's going?
I'm just thinking along my field of work on cars and how the fuel system on the first couple generation duramax diesels ran. If you replaced the filter, you'd prime it with a button on the filter housing, and if you had a guage connected, you'd see up to 8-10 psi. As you cranked it and it started, youd watch the guage drop into a vacuum, typically 4"h20 on a good fuel system.
Soo, is that kinda, sorta how these fuel systems operate on the 500i's?

 

[Mastermind]

Seeing there really is no fuel pump (as far as I know), wouldnt the fuel system on this run under a vacuum once it's going?
I'm just thinking along my field of work on cars and how the fuel system on the first couple generation duramax diesels ran. If you replaced the filter, you'd prime it with a button on the filter housing, and if you had a guage connected, you'd see up to 8-10 psi. As you cranked it and it started, youd watch the guage drop into a vacuum, typically 4"h20 on a good fuel system.
Soo, is that kinda, sorta how these fuel systems operate on the 500i's?

It does have a vacuum operated fuel pump.

 

[Mastermind]

It does have a vacuum operated fuel pump.

 

[redline4]

It does have a vacuum operated fuel pump.

Cool. Thanks, I learned something today.

 

[Mastermind]

Cool. Thanks, I learned something today.

When we stop learning, the fun stops.

 

[av8or3]

The early 500i’s were recalled for fuel leaks. Not sure where, but I believe it was a fuel line. And I have to say, if one could land that MDG1 anywhere south of $750 they’d have themselves a good deal.

 

[Vahula]

When I pump the primer more than 6 times fuel leaks from the line where it connects to the injector.

Find the leak, find the problem. The fuel should go back to the tank.
The primer is part of the fuel system. If fuel gets out then there is possibility of air going in.
Your best friend will be pressure/vacuum pump. Everything should hold 0.8 bar pressure without leaking for 20sec if you plug the return and give pressure from the fuel filter hose.


first post

 

[Ketchup]

Find the leak, find the problem. The fuel should go back to the tank.
The primer is part of the fuel system. If fuel gets out then there is possibility of air going in.
Your best friend will be pressure/vacuum pump. Everything should hold 0.8 bar pressure without leaking for 20sec if you plug the return and give pressure from the fuel filter hose.


first post

Welcome!
Fuel leaks from the point where the line connects to the injector pump. The primer does not leak. The line shows no visible signs of damage and held pressure but I will test it installed on the injector when I get home.

 

[thompsoncustom]

That’s definitely something I wonder about. I read somewhere the voltage of the Mtronic system is pretty unusual. The injector looks relatively similar to an Mtronic solenoid, but larger. Based on the gauge of the wiring, the Voltage is probably pretty low. I was reluctant to experiment there, but when I swap the part I’ll see what I can figure out.

In this case I believe the injector is stuck closed, not open. The TS500i can have flooding problems related to the injector sticking open. But the only time this saw runs is when I intentionally flood it.

With that in mind, I don’t really understand why the saw will pop but not run. It tries to start on almost every single pull. I feel like there must be a tiny bit of fuel getting through as part of the start cycle, but the run cycle isn’t functioning. That points to the module rather than the injector. I hope it’s not that because software is required to replace the module.

Ya let me know what ya find out even tho I will never own a saw with autotune/mtronic's it's still interesting. I also assume it pulses a very low voltage quickly but if you figure out the right voltage at least you could operate it and see if maybe the injector is sticking closed but just cracking enough with each duty cycle to allow it to pop off. If nothing else it would be nice to see the injector do a full travel both directions.

 

[av8or3]

You know, that fuel injector depends on a minimum pressure to be able to squirt fuel when the electrons tell it to open. If it’s leaking, you might not be getting the pressure you need, and since it does leak you should change it. It’s a fire hazard otherwise. The early ones were recalled for a leaking fuel line. That could be the line they changed. IDK
Me thinks you could be overlooking the obvious.

 

[av8or3]

Also for your consideration, the reason the primer bulb is there I think is to fill the fuel system outside the tank and create a pressure in the line between the pump and the injector so it squirts when those electrons hit it when the starter is first pulled. Maybe??

 

[Stump Shot]

Without personal experience on this particular model's issue, all I can offer is that to my line of thinking, the word "leak" and "fuel injection system" don't sound good in the same sentence together. Least ways in all the times I've seen it on other equipment, fix the leak and you've fixed the problem. Seeing as the leak is going to have to be addressed anyways, might as well start there. Even if it doesn't cure the problem, you're still one step closer to the finish line, and have ruled out an issue, and know to look elsewhere.
This also goes along with my teachings from the Karl Childers School of Small Engine Technology, "Always look at the easiest thing first."

 

[huskihl]

I got one pinched in a log and all it would do afterwards is fire and die repeatedly.

There is a case compression sensor. It was sensing that I’d yanked the impulse hose off the barb.


Might not help your problem, but it might lead you closer to it

 

[HumBurner]

...case compression sensor.

That phrase gives me a headache

 

[lehman live edge slab]

Also for your consideration, the reason the primer bulb is there I think is to fill the fuel system outside the tank and create a pressure in the line between the pump and the injector so it squirts when those electrons hit it when the starter is first pulled. Maybe??

That is the sole purpose of the primer, brings the system up to pressure for a cold start. They say prime minimum of 8 times, but no matter how many times you primer it they shouldn’t leak.

 

[lehman live edge slab]

I got one pinched in a log and all it would do afterwards is fire and die repeatedly.

There is a case compression sensor. It was sensing that I’d yanked the impulse hose off the barb.


Might not help your problem, but it might lead you closer to it

Also supposed to have a temp sensor in the stop switch

 

[av8or3]

Somebody got a smokin deal on that MDG1.