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Case 448 -- Can't get to run right... no matter what I try!


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#31 KennyP ONLINE  

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Posted November 28, 2015 - 08:15 AM

 I'll go hide in my corner now.

Don't do that! We all have that issue once in a while! And I need someone to keep me in line!


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#32 cmn135 ONLINE  

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Posted November 28, 2015 - 09:58 AM

Definitely test the coil. Failing coils get worse as they warm up. I had a bad one and it caused all sorts of erratic engine behavior.

#33 Case448 OFFLINE  

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Posted November 28, 2015 - 03:35 PM

Alright, this is getting REALLY wierd now.

 

I borrowed a coil and plug wires off my friends running Case 446 and put them on my tractor.

 

Layed the spark plugs on top of motor and turned over, now have solid spark and appears spark is consistent.

 

Put the plugs in motor and attempt to start.

 

Will not start. Finally after a lot of cranking, acts like it wants to start, but will not. Get occassional massive backfire out of carb. Nearly gave this young girl walking by on the street a heart-attack, she thought someone had shot at her. Sounds like a loud cannon.

 

Tried to start with quick-start. Won't even fire on that, which tells me, it is NOT getting spark once plugs are put into the engine.

 

It's obviously an ignition problem. Almost acts like a fuel problem (like its not getting gas) -- but won't even fire on quick-start.

 

WHATEVER it is, has been getting progressively worse for the last week I've worked on it.

 

I am getting REALLY sick of this. Now it is getting down-right baffling. I don't know what else to check.

 

I'm JUST about ready to dump the Onan and look into repowering.

 

Someone please help!?!


Edited by Case448, November 28, 2015 - 03:37 PM.


#34 tater195 ONLINE  

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Posted November 28, 2015 - 03:57 PM

Re run the compression check. My money is on a valve problem

#35 KennyP ONLINE  

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Posted November 28, 2015 - 04:07 PM

Have you checked the troubleshooting guide in the manual?

B48M Troubleshooting.JPG

 



#36 Case448 OFFLINE  

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Posted November 28, 2015 - 10:40 PM

Re run the compression check. My money is on a valve problem

 

I suspect your right.

 

Messed around with it more this afternoon. It acts like it wants to run, but like its "missing something" which is making it struggle to start. It sputters like it wants to run, but refuses to start running.

 

I now know:

It has consistent and strong spark, timing is good, points are good, condensor is good, plug wires are good, plugs are good.

It has fuel, fuel is new, tank is full, bowl is full, carb rebuilt, fuel pump pumping sufficient fuel, float level set, carb now sealing where was leaking before.

 

Remaining issue HAS to be compression related, and/or the fuel not getting into the cylinder(s) (valve-related).

 

Will re-run compression check / compare to prior numbers, and look into valve lash / valve situation some time this coming week.


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#37 Case448 OFFLINE  

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Posted November 30, 2015 - 11:49 PM

Here is what I found tonight:

 

Compression is down 30-40 percent on both sides from my numbers three weeks ago (when it was running good, just before all these problems started.)

 

Valve lash as follows:

 

Drivers side exhaust:          .017   (supposed to be .012)

Passenger side exhaust:    .020   (supposed to be .012)

Drivers side intake:             .025   (supposed to be .007)

Passenger side intake:       .012   (supposed to be .007)

 

I realize valve lash is wrong, but what would valve lash wrong (like the above) do (if anything) to cause my symptoms?

 

Or, do I still have another problem, yet to be determined?



#38 gopher OFFLINE  

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Posted December 01, 2015 - 12:19 AM

Sounds like you found your problem . That much off can cause erratic vacuum effecting gas flow along with low compression.  



#39 Alc ONLINE  

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Posted December 01, 2015 - 06:20 AM

Hope to hear that was your problem , good luck



#40 KennyP ONLINE  

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Posted December 01, 2015 - 06:44 AM

Those valve lash setting would make it hard to get enough fuel in the cylinders to run right.



#41 cmn135 ONLINE  

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Posted December 01, 2015 - 09:04 AM

The valve last can definitely shift a bit of when you cleaned them up you removed them and reinstalled. Most recommend rechecking lash after an hour or so of run time.

#42 Case448 OFFLINE  

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Posted December 01, 2015 - 10:46 PM

First of all, you should all know, I am of a sound mind, and I'm far from dumb.

 

Cause you might think I'm not too swift after this one.

 

Maybe theres as simple answer for this, maybe not.

 

I took the front of the motor off so I could fix my starter issue (mounted too tight to fly wheel, with about zero lash, should be .020.)

 

Printed out the instructions from the manual for how to set valve lash. Found the TC mark, re-measured the valve lash, and, all are set (if anything) a little too tight. Now, I know what I saw last night when I posted the previous (far looser) measurements. WHAT in the WORLD would explain THAT?

 

So, the valves where not closing all the way last night when I got the bigger measurements.

 

Could this be related (somehow) to the starter/flywheel gears being locked together? (doubtful).

 

Could I have some bent valves?

 

Is there some kind of a compression release on this motor that keeps the valves partially open?

 

Couldn't be carbon between the valve & seat, was clean when put together, only ran for about 4 hours total.

 

Well, this may at least explain some things, one of the intake valve lash was .002 -- which means that valve was not closing all the way. Others were only slightly tight.

 

I'm starting to think this motor is possessed.

 

Any ideas on THIS one?


Edited by Case448, December 01, 2015 - 10:46 PM.


#43 KennyP ONLINE  

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Posted December 02, 2015 - 05:47 AM

Are you positive you were on TDC with the other measurements?



#44 Case448 OFFLINE  

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Posted December 02, 2015 - 11:04 AM

Are you positive you were on TDC with the other measurements?

 

Possibly not. I could not get to the TDC markings when I made the initial measurements, I was not aware of where they were, or if you could see them without removing the front shroud. I just went to the loosest looking point on the rotation, and measured there.

 

So maybe this changes everything, yet again.

 

I will look more into the whole situation today, and come back here with accurate information sometime tonight.



#45 gopher OFFLINE  

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Posted December 02, 2015 - 11:35 AM

I'm thinking you can see timing marks through breather boot hole in shroud.






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