An Autotune Husqvarna Model 550 challenge

[fordf150]

The autotune will tell you with the fuel settings what fuel was last used and give you an idea based on the fault codes if there was an air leak.

When the product is used, AutoTune / Carb Control automatically sets the carburettor optimally in spite of variations in conditions, for instance, type of fuel. The fictional values below indicate a comparison between different types of fuel.
• Commercial petrol, 95 octane, high energy fuel 70-90
• Alkylate fuel e.g. Aspen 60-80
• E25, commercial petrol with 25% ethanol 40-60

 

[Chris-PA]

Today I have also been messing with the decompression valve, so I took some more measurements and then built an excel spreadsheet to calculate the closing force on the seat of the de-compression valve, the program also lets you vary the compression values of the cylinder, and then tell you If you have enough compression to close the valve. So basically you take a (0 - 5) lb food scale, and press the decompression valve down onto the food scale, and watch the scale. Do this first in the open direction and then in the close direction, enter the numbers into the excel calculator and my program will tell you If a specific engine by cylinder diameter (mm) will have enough compression to close the valve. My old decompression valve took 1.5 lbs of force to open the valve and 2.75 lbs to close the valve, and If the compression in the cylinder was less than 130 lbs, which a scored cylinder would have less than 130 lbs, then there would be an insufficient margin to close the valve. Also my Excel program will tell what that margin would be. In any case, I'm Not putting the old de-compression valve back into the New cylinder assembly. I enjoy doing the mathematics, measurements, and calculating stuff like that, and Yes there is very little error, and the results were 100% repeatable. I did the same for a New decompression valve also, and it took 1.5 lbs open and 6 oz or .375 lbs close, and it also would close at a way less compression value (less than 30 lbs compression). Just way too much fun.

Nice job, I like the way you approached that!

 

[smokey7]

Do these autotune saws give you a fuel trim map when they are scanned?

 

[Chris-PA]

Do these autotune saws give you a fuel trim map when they are scanned?

That's not really a useful way of thinking about these systems. "Mapping" is only relevant to a fuel injection system running open-loop/non-feedback, when fuel delivery would be determined by a function based on the input of various sensors. Here, there basically are no sensors, and the "mapping" is determined by the fact that it is a carb, plus wherever they leave the fuel solenoid when they cannot run closed loop.

Essentially, a non-feedback fuel injection system is an active system where fuel output is a function of the input of a lot of sensors (mapping). A carb is a passive system where fuel output is a function of air velocity over a fixed jet (at least for these carbs). Adding a feedback mode over top of either one means you are now setting fuel output as a function of (primarily) one measured value, not the map. For a car it is the O2 sensor, for these it is the results of the lean-out test (i.e.rpm response to a temporary change in mixture).

 

[smokey7]

Thank you I was wondering what info you see when they are hooked up to the scanner

 

[AVB]

From personal experience I know that a 55 will run with the decompressor completely missing. This from rebuilding one a couple years ago that did not have originally but the replacement PNC had a place for but no plug in it. When I first started the saw it started fine but just sounded off in a weird way so when back over my work. This is when I found the plug missing.

The picture of the piston looks more like straight gassing to me but that is just my opinion.

 

[Karla]

AVB, Thank you for your Input and Vote. Also Thanks for the Info on Model 55 running without a decompression valve, I really was curious about that one, but I wasn't about to sacrifice a chainsaw to see what would happen, If I did that with one of my chainsaws, Also still curious what the Autotune would do when it has a cylinder air leak like a missing or open decompression valve, I can't seem to get my brain around that one.

Also, My saga continues, Today I thought I would try and clean up the cylinder and see how bad it really was after I removed all the piston transferred aluminum. It actually looks pretty nice, I took some 400 grit wet/dry sandpaper and cleaned up really nice, so I may just need another piston and rings, but I also have a complete cylinder assembly on order, and still waiting. Today, I ordered a New additional piston and rings, and then I will have two ways to go.

Oh, Interresting when, I went to clean up the cylinder, I found old sanding swirl marks, definitely not honing marks. So it looks like this chainsaw may have gone to a refurbishment shop previously, and they tried to refurbish the top end by just cleaning the cylinder and replacing the piston and ring, So I am guessing this is the second time the engine failed, so it almost seems like there maybe more to this saga. Also it would kind of make sense, since I did find a couple teaspoons of fuel in the carburetor and fuel lines, and a little in fuel tank that had a greenish color and looks like oil, but No way to tell If it was the correct mixture. Oh, so I'm definitely back to the beginning with trying to figure out what went wrong, and now it appears maybe twice. Of course I picked up the chainsaw after the fact, So I have No clue what happened previously.

I still don't have the error codes for the carburetor, However reading thru the manul and error for the Autotune diagnostics tool kit, (I don't have the diagnostic tool, just the manual), It states under several codes "To make sure the throttle magnets are clean of metal" ie:

Error Code" "015 The carburettor wants to give less fuel than what is possible at high speed. Probable causes: Faulty throttle sensor signal. Throttle valve not working correctly. Check the throttle sensor using the Engine Diagnostic Tool diagnostics.
Check that the throttle sensor is installed and not damaged. Two magnets must be available in the magnetic sensor. Clean away any metallic objects if required. Check that the air valve is fully open at full throttle."

Note: Cleaning magnets is repeated on several Error Codes, so I checked my magenets ( two little white magnets on left side of carburetor, next to autotune module). Anyhow my carburetor had quite a bit of little metal whiskers or metal slivers on them, Not sure where they came from but I cleaned them off, and now wondering If My autotune could have had a problem with all those metal slivers. Also have No clue where the tiny pieces of metal came from either, Could that have been the original Problem? But surely a refurbishment shop would have checked the Autotune carburetor with the diagnostic tool, I would think ? Anyhow still having fun , nad getting impatient waiting for parts for my Model 550, LOL.

 

[SCHallenger]

! Good luck with your project. I'm in for the learning.

 

[fordf150]

The autotune software is actually pretty cheap. Can't get the updates without being a dealer but it will read and reset codes. If you have several of these saws or plan on working on several of them it might be worth purchasing

 

[Karla]

Fordf150, Yes - I agree, Infact I ordered the Diagnostic tool kit (583897101) on Thursday, and then cancelled the order on Saturday. I wasn't sure If I had the right one, so I called back on Saturday to ask a few questions, I could see that the kit included some interface cables and also the diagnostic box, but there was No CD software in the kit, (I assume you would have to have the CD software to run the box on your computer), and the price was $134.- which seemed like a good price. Anyhow when I asked about the CD software to run the box, I was told that I would have to be a dealer to get that disk. I also agree that what I'm interested in most is getting the diagnostics and testing, probably future updates are not as important to me,

 

[LegDeLimber]

Metal on the magnets?
if the saw has ever been near a shop that has a grinder (Chain, bench, handheld) etc.
Or a sander or a rotary tool (belt, palm, or air powered die grinder or "dremal" foredom etc)
Then you have a source of airborne metal particles.
Hand filing chains scatters bits more than you'd realize, also.
Hand sanding too.
You ever tap the file or slap the sandpaper to clear off a little of the crud?
Stuff gets really flung around by that trick!
Especially so from the sandpaper slapping.

Now how about that air hose we are sooo fond of?
Or your nice shop fan?
There's a couple of good sources of debris scatterers.
Ask your paint & body shop pal how bad an air hose and a speck of dirt/grit can mess up a clean area
And how far away it can throw it.

Some Commercial clean rooms even take into account how fast the people are walking around in them, because of how it stirs the air and any settled contaminates.

Now think of all the crud that's on the roads.
A saw riding in the back of a truck will see a good bit of dirty air swirling around it.
IF you ride a motorcycle, live next to a busy street, then you know how
grimy the air can be around the road.

Just some food for thought here. Hopefully it might help someone spot a trouble causer and be able to better cope with things.

 

[fordf150]

Fordf150, Yes - I agree, Infact I ordered the Diagnostic tool kit (583897101) on Thursday, and then cancelled the order on Saturday. I wasn't sure If I had the right one, so I called back on Saturday to ask a few questions, I could see that the kit included some interface cables and also the diagnostic box, but there was No CD software in the kit, (I assume you would have to have the CD software to run the box on your computer), and the price was $134.- which seemed like a good price. Anyhow when I asked about the CD software to run the box, I was told that I would have to be a dealer to get that disk. I also agree that what I'm interested in most is getting the diagnostics and testing, probably future updates are not as important to me,

$134 shipped is what i do so that is the going rate. they include the installation CD.

 

[Karla]

LegDelimber, Thanks for the input, and Yes I have lots of all those things in my shop. However, I did not take this one apart in my shop, and I'm sure this used chainsaw came to me in that condition. The saw was really very clean, but when I removed the carburetor from the chainsaw, I found those two little white magnets next to the autotune module of the carburetor, and there were these whiskers of metal sticking up on end, and stuck to the autotune magnets, they kind of looked like 1/8 inch pieces of steel wool. I tried to blow them off with my compressor but they stuck pretty good, I finally got a larger maget and was able to pull them off with it, again kind of interesting. Also the Autotune diagnostics manual mentioned metal debris on these magnets several times in there error codes, so they must have had a lot of experience with metal particles getting on these magnets, and somehow interfering with the Autotune throttle signal. Thanks again for the Info on clean shops, and clean bench tops, especially if your working on Autotune carburetors with magnets in them, Lol.

 

[Karla]

fordf150, I just ordered it again this morning, so I hope it is the right thing, and Thank you for your help.

 

[Karla]

More Info - I ran the Diagnostic Tool Kit on my Model 550, and I was surprised to see "No Error Codes" , I checked out all the numbers, and looked at all of the graphs and the Engine last run for 3 minutes (as found condition, and before the engine scored and possibly seized, Oh the engine also had 32 starts, that's a lot of pulling) was running mostly in the lower RPM's but was run for 20 seconds at 14,050 RPM's (No Load) which seemed a bit excessive. All of the temperatures seemed OK, But the fuel settings for H/L adjustments read 99/100 that seemed excessive too, but may correlate with the high RPMs, Not sure ? Again, No Error codes reported by the diagnostic software. I saved the current Information, and then ran the various tests for throttle, temperature, and fuel valves, and everything in the Autotune carburetor past the tests.

So, I'm Kind of back to thinking maybe it was the fuel mixture, If the carburetor was working the way it was suppose too, Still Not absolutely sure. But definitely had fun playing with the Autotune Diagnostics. Obviously after I rebuild the Top end (which by the way the parts just shipped today, so will have to wait a few more days), then after rebuild and a short run, I will do the diagnostics again and see what has changed from the Original run compared to the new top end.

By the way, Its Not about rebuilding the chainsaw and getting it running, its understanding why, Lol and I'm keeping the chainsaw for myself anyhow.

 

[fordf150]

What was your average fuel settings?

 

[Karla]

Fordf150, The average fuel setting was 77, Does that sound correct ?

Also, Just a quick note on your Avitar name, I had a Ford F150 in the 1980's , maybe like 1983, and I loved it, it was black and red, and silver. It had dual fuel tanks factory installed with fill nozzles from each side of the truck, and a switch on the dashboard, so you could switch tanks. A really neat truck and way ahead of its time,

 

[fordf150]

77 sound normal. I'm not an expert on these. Only had a few hooked up and still have lots to learn.

with normal fuel settings and no fault codes, passed pressure/vac test, not excessively dirty/plugged recoil and cylinder fins it sure sounds like run of the mill lean seize.

 

[Karla]

Thank you, one more time, and I really do owe you big time.

Karla

 

[Karla]

My new cylinder and piston arrived yesterday, so I rebuilt the top end, and did a little testing. I included a video of its first run, It sounds good a little smoke from the oil in the engine during the rebuild. Still waiting to test the autotune diagnostics and to do a master reset, to clear all previous history of the old engine, but it does run with the old settings. I also have not taken it out into the woods, and given a good load test yet either.

Anyhow, I wanted to make sure it would start and run with the existing autotune carburetor. I still really don't know what was wrong with it, but it is a pretty chainsaw, and I will keep this one with my collection. Lol.

I can't seem to Upload my "MP4" video, so another challenge to try and convert it to something else, so you can see my new rebuilt and running model 550. Lol.