bobcat 720 wisconsin vh4d fires on 2 cylinders only

[wjberezo]

Hi: I have a mid 70s 720 with a vh4d. It fires on 2 cylinders only. looking at the machine from the back it's the 2 cylinders on the right side. The first cylinder will be the number 1, I'm not sure what the other one is (I think it's the 2 cylinder). I put in a new distibutor. I put in new plugs. I've checked the spark, it's getting spark. I've checked the plugs, they're sparking. I removed the head, the valves seem ok they move up and down. I checked the compression it's about 60 -70 on all 4 cylinders. The cylinders are getting gas. I've replaced the intake and exhaust manifold gaskets. Any ideas ?

 

[OldMachinist]

Did it fire on all 4 with old distributor? If so does the cam the points ride on in the distributor look different on the new one?

 

[OldMachinist]

Did it fire on all 4 with old distributor? If so does the cam the points ride on in the distributor look different on the new one?

Here some info from the Wisconsin manual on timing and firing order. It says the cylinder shrouds are stamped with the cylinder numbers.

 

[wjberezo]

Did it fire on all 4 with old distributor? If so does the cam the points ride on in the distributor look different on the new one?

no it didn't fire on all 4. I can't remember exactly when I lost the 2 cylinders. I hooked up the timing light to the #1 cylinder (this is one of the cylinders not firing). The timing checked out fine. There is current running thru to the number one spark plug. I pulled the plug and grounded it to the block while the machine was running, you could see the spark jump the gap. For some reason the number 1 cylinder will not fire. Like I said there's compression and it appears to be getting fuel/air that's what's so puzzling about this.

 

[OldMachinist]

no it didn't fire on all 4. I can't remember exactly when I lost the 2 cylinders. I hooked up the timing light to the #1 cylinder (this is one of the cylinders not firing). The timing checked out fine. There is current running thru to the number one spark plug. I pulled the plug and grounded it to the block while the machine was running, you could see the spark jump the gap. For some reason the number 1 cylinder will not fire. Like I said there's compression and it appears to be getting fuel/air that's what's so puzzling about this.

Just to be clear you have the spark plug wires right.

Looking from the flywheel end.
#1 is on the left side of the engine nearest the flywheel
#2 is on the right side of the engine nearest the flywheel
#3 is across from #1
#4 is across from #2

 

[jerry]

Just to be clear you have the spark plug wires right.

Looking from the flywheel end.
#1 is on the left side of the engine nearest the flywheel
#2 is on the right side of the engine nearest the flywheel
#3 is across from #1
#4 is across from #2

Like OM says, really take a good look at that dist cam as there is a difference. check this thread. http://www.skidsteerforum.com/DesktopDefault.aspx?tabid=54&frmView=ShowPost&PostID=42281

 

[wjberezo]

Like OM says, really take a good look at that dist cam as there is a difference. check this thread. http://www.skidsteerforum.com/DesktopDefault.aspx?tabid=54&frmView=ShowPost&PostID=42281

I'll check the cylinders and firing order. I'll check the cam on the distributor

 

[wjberezo]

I'll check the cylinders and firing order. I'll check the cam on the distributor

Sometimes I'm about as bright as a bag of wet cats. I went home and checked the cover over the cylinders and sure enough I had the 1 and 3 cylinders mixed up. I swapped the 1 and 3 wires from the distributor and it runs like a damn. I guess what really threw me was the engine seemed to run fine on the 2 and 4 cylinders. I thought there would be back firing if I had plug wires mixed up. I think that's threw me. Thanx so much for your help

 

[OldMachinist]

Sometimes I'm about as bright as a bag of wet cats. I went home and checked the cover over the cylinders and sure enough I had the 1 and 3 cylinders mixed up. I swapped the 1 and 3 wires from the distributor and it runs like a damn. I guess what really threw me was the engine seemed to run fine on the 2 and 4 cylinders. I thought there would be back firing if I had plug wires mixed up. I think that's threw me. Thanx so much for your help

Good to know you got it sorted out.
Please post where you bought you new distributor and part number in case someone needs one in the future.

 

[wjberezo]

Good to know you got it sorted out.
Please post where you bought you new distributor and part number in case someone needs one in the future.

sure no problem I got it from standard magneto sales and the part # is IAD-6004-2P