Poulan PP4620AVX

[Gary123]

Looking for help getting this started. Quit on job. Has white spark, new plug and fuel. Even sprayed starting fluid  in cylinder after cleaning coil and flywheel, checking with multi-meter and by-passing shut-off switch. Cleaned carburetor, replaced fuel line and there is a fuel-spray when spark plug is removed. Saw doesn't even "pop" or try to start with starting fluid. Cleaned spark-arrester and checked for piston and cylinder scoring. Will check for compression, once my new gauge arrives. What in the world am I overlooking, here? Thank you. ??? :P8)

[hms11]

As a quick and dirty compression test until you get the actual tool:

If you hold the saw by the pull cord, how smoothly and quickly does the weight of the saw drag it down?

The smoother and faster the drop, the more likely you have a compression issue. If it "glugs" and catches on the way down, it is more likely to be fine on compression.

This does not replace an actual compression test. 

[Gary123]

Thank you. I'll give this a try. The compression on this Poulan is definety NOT what my Stihl has, but I thought the Poulan would certainly pop or make an effort to start with the spark and starting fluid. Thanks for the help.

[sawguy21]

Remove the muffler, check for galling/scoring on the piston and put the starting fluid away. That stuff is a death sentence for seals and pistons.

[Gary123]

Thank you. I'll check for this, again, though the cylinder and piston seemed un-scored on first look. Maybe I can add some photos, as there were some black streaks at top of piston and above the rings. Looked like carbon, which may be normal. I'll double check for scoring or galling. Thank you, again.

[Gary123]

Okay! Finally got my compression gauge and had following readings on three chainsaws: 

Poulan PP4620AVX was 45 psi. This is the one that won't start though it's been cleaned and adjusted, spark and fuel check-out, and there's no apparent scoring on the cylinder or piston. Even tried new plug, fuel and starting fluid. Won't even "pop" or try to start.

Stihl MS200T registered at 42-45 psi. This was also cleaned and starts and runs great! Can't figure this out. Everything online says compress SHOULD BE 110-160 psi. Yet this chainsaw is great!

Finally, my Stihl MS290 checks-in at 62 psi. After a good cleaning and adjusting, this too runs great even though the compression seems lower than I'd expect.

I checked my lawnmower, just to make sure the compression gauge was working, and that checked-in at 90 psi. And...I measured the chainsaws 3-4 times each and they still came up with what seems like low compression. Go figure. All the chainsaws check-in at what I think is low compression, yet only one won't start in spite of everything checking-out okay.

Also have one other question. I have a fuel tank on the MS200T that leaks on the ground when I turn it over to fill it. No cracks are visible and, though it's hard to see, I am wondering if the leak may be from the hole and plug where the fuel line and vent go through. This may not seal properly and I wonder if there's a "fix" short of buying a new fuel and vent assembly.

Thank you, again. It's great having this forum!

[Pine Ridge]

I'm not an expert on compression guages or chainsaw mechanic. I'll bet something is not right with the compression guage, someone will come along soon that has some knowledge about them. If the other two run fine and show compression readings that low it has to be something inaccurate with the guage, they shouldn't even run if they were truly that low on compression.

[lxskllr]

Well, as long as the gauge is consistent(but wrong), it looks like the Poulan is in good shape compression wise. Could it be a timing issue?

[ladylake]

 If theres fuel spray coming out of the plug hole its flooded, the carb might be dumping fuel in as you try to start it keeping it flooded. Try choke off and hold it wide open when trying to start it, this most times take 10 or more pulls before it will fire.  If the carb is dumping fuel in I've unhooked the gas line to get them to fire but you will need to got through the carb if that's the case.  Steve

[Fishnuts2]

Check the four bolts on the bottom of the crankcase.  These are known to come loose and cause all kinds of problems.

Make sure your compression tester has the Shraeder(?) valve in the end, not by the gauge itself.  If it is only by the gauge, the length of the hose will increase the volume of your cylinder and make the readings look lower than they should be.

[Gary123]

Thank you-all for your excellent help and suggestions. I'll try responding to all four or five previous posts and hope, with your help, we can find a solution. First, the compression gauge I have does seem to measure "low" on the three chainsaws I tested. The Poulan at 45 psi., the small Stihl at 42-45, and the Stihl MS290 at 60. These all seem low (but consistent), and the two Stihls start and run great!  I checked to see if the gauge would go higher and measured my B&S lawnmower engine, and that registered 90 psi.; so, to me, that kind of ruled out a faulty gauge. 


The one-way or Shrader valve is on the gauge itself, so there could be a loss of pressure in the 1-ft. tube, as one person suggested. None of my friends have another compression gauge to check my gauge accuracy, so the "jury's still out" on returning my gauge to Amazon for another. Also, searching, I did not see a gauge with the valve on the tube.

I did disconnect the fuel supply by emptying the fuel tank and, surprise-surprise, the Poulan started and ran about five seconds before stopping. "What in the world?" I thought, and tried repeating the success. I filled the fuel tank and emptied it, several times. I even disconnected the fuel line and readjusted the high-low screws to 1 1/2 turns, and tried ether without the fuel connected. It just wouldn't fire! Just can't identify a variable, here. I'll try again, later today, now that the chainsaw sat a spell, and see if it tries starting. The idea of "flooding" may still be an issue. The spark plug is wet, when I pull it out, but I disconnected the fuel line and went to straight ether as a solution. 

Finally, I checked the four crankcase bolts and they were tight. 

Thank you-all for your help on this one. I know there's an answer and I sure am learning a heck-of-a-lot finding it!

Gary

[sharp edge]

          Gary
The first thing I do is put a teaspoon of #30 oil in the sparkplug hole, then some either, then put the plug back in. If it start, it means you have a screw-up ring on the piston. this happens alot to saws. 
what you have going for you is, its a easy saw to work on and a cheap one, I have two the next size bigger.

SE

 

[ladylake]

 Sounds to me like the carb is dumping too much fuel in and needs. to be rebuilt.  Once theses saws get flooded even with the gas line unhooked throttle wide open it will take over 10 pulls to get them to fire again.  Steve