Massey Ferguson Industrial 20 Perkins Gas troubles

   / Massey Ferguson Industrial 20 Perkins Gas troubles #1  

brookmere

New member
Joined
Mar 20, 2016
Messages
8
Location
Brook mere B.C. Canada
Tractor
MF Industrial 20
1972 Perkins gas engine, rebuilt 250 hours ago. (16 years ago!). Was running ok but started to backfire through exhaust when accelerating. I cleaned the advance mechanism in the distributor, replaced points, condenser, rotor, cap, wires, plugs, set valves, rebuilt carb with Massey kit (set float etc.), replaced solenoid fuel shut off with new, cleaned fuel delivery system, new gas etc., and a new ignition switch. Compression is 135-140-135. I static timed it then advanced it slightly to help at higher rpm's. (per MF manual)
After all that it seems to run ok and accelerate smoothly for 5 minutes or so, then starts to miss and will backfire if I try to accelerate. Like really backfire, hurts the ears and alarms the neighbours and wildlife for miles! Sometimes when it starts to miss I turn it off and start it again and it will be ok for another 5 minutes.
I have run out of ideas and I would really welcome input from anyone with suggestions. Thanks!
 
   / Massey Ferguson Industrial 20 Perkins Gas troubles #2  
It sounds like a fuel restriction, from the needle valve in the carb, back toward the tank, leaning it out to the point of backfiring. Then letting it set for 5 minutes, allowing the fuel bowl to fill, and let it run another 5 minutes, then lean out again.

On the older models they had a mesh screen on the elbow that goes into the carb., where the fuel line attaches, and would cause this problem on many other brands. I checked Massey parts, and it just shows a plain elbow as OEM. Unless someone changed it out somewhere along the line. Did you remove that elbow when you rebuilt the carb.??
 
   / Massey Ferguson Industrial 20 Perkins Gas troubles
  • Thread Starter
#3  
It sounds like a fuel restriction, from the needle valve in the carb, back toward the tank, leaning it out to the point of backfiring. Then letting it set for 5 minutes, allowing the fuel bowl to fill, and let it run another 5 minutes, then lean out again.

On the older models they had a mesh screen on the elbow that goes into the carb., where the fuel line attaches, and would cause this problem on many other brands. I checked Massey parts, and it just shows a plain elbow as OEM. Unless someone changed it out somewhere along the line. Did you remove that elbow when you rebuilt the carb.??

Thanks for your reply. I did remove that elbow, no screen. I will go through the fuel delivery again and look for restrictions.
 
   / Massey Ferguson Industrial 20 Perkins Gas troubles #4  
Would it be possible the fuel cap is not venting, causing a bit of a vacuum in the tank, thus restricting fuel delivery that way..?? You could start it, and when it gets to that point, loosen the fuel cap,and see if there is a difference. Or, just loosen it from the get go, and see if it does it then. Do the easy stuff first...
 
   / Massey Ferguson Industrial 20 Perkins Gas troubles
  • Thread Starter
#5  
Would it be possible the fuel cap is not venting, causing a bit of a vacuum in the tank, thus restricting fuel delivery that way..?? You could start it, and when it gets to that point, loosen the fuel cap,and see if there is a difference. Or, just loosen it from the get go, and see if it does it then. Do the easy stuff first...

I will try that, it seems too easy, but sounds logical and I didn't think of it. Thanks!
 
   / Massey Ferguson Industrial 20 Perkins Gas troubles #7  
I would try another condenser. Sometimes new ones are no good. I don't see that you replaced the coil. Can you try a different one?
 
   / Massey Ferguson Industrial 20 Perkins Gas troubles
  • Thread Starter
#8  
I know, but how can it run so well for 5 minutes and then go goofy? I set the static timing at 12 degrees and then they want you to set it at 26 degrees at 2100 rpm. I thought I had done that, or close to it, even though you have to be a contortionist with mirrors to see through the window to the flywheel. I will keep trying and re-timing will be on the list for sure. Thanks.
 
   / Massey Ferguson Industrial 20 Perkins Gas troubles #9  
I know, but how can it run so well for 5 minutes and then go goofy? I set the static timing at 12 degrees and then they want you to set it at 26 degrees at 2100 rpm. I thought I had done that, or close to it, even though you have to be a contortionist with mirrors to see through the window to the flywheel. I will keep trying and re-timing will be on the list for sure. Thanks.

That's pretty advanced for static timing. The usual range is around 6° BTDC at 400 engine rpm If you set it at 12° BTDC then your advance mechanism will increase it by some amount and it may be too advanced.
 
   / Massey Ferguson Industrial 20 Perkins Gas troubles
  • Thread Starter
#10  
The MF manual says 12 degrees static, but my next step is to fiddle with the timing again and I will try retarding and re-setting the static timing. (Thursday's job) I have checked the fuel system again, through and through. I removed the carb and re-set the float level, which was a bit off, run it without the fuel cap etc. I am wondering if when I installed the distributor I was a tooth off? But then, when I set the timing, I used the valve position as a guide for TDC, and of course the position of the rotor, #1 wire, and it lined up, so it must be installed correctly? I just know it will be something uncomplicated I am overlooking, staring me in the face, so all your opinions are greatly appreciated.
I haven't tried a new condenser yet, will do Thurs.
 

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