one ninety XT dies

History first. It is a allis chalmers one ninety XT of unknown year to him or I. By comparison of on line pics it appears to be early to mid 70's. He purchased it recently and it has an issue. First off it runs fairly good while just simply driving (road gear) with exception of surging (like a tanker half full of liquid will feel) kind of........

Then when he hooked it to a 5' brush hog it will perform under load for no more then 30 minutes, begin to bog down, then if you decrease throttle it simply dies. Remove fuel supply to filter housing it has good flow, new fuel filter installed, but will not restart without assistance from either. It then spits, sputters, carries on for few seconds, straightens up and idles, has good throttle response, will drive around fine. BUT put brushhog back to work, 20-30 minutes same thing over and over. I can see fuel returning into tank through the return line at a very high rate at idle.

WHATS BEEN DONE........ fuel tank drained, cleaned (full of a lot of junk), sediment bowls, shut off valves all removed cleaned. New fuel filter (twice). New manuel primer installed (on filter housing).

 

We are at total loss except that I read a few discussions on a governer having issues. Does it sound like it could be this? How do we inspect for this problem? I am a auto mechanic but not dealt much with implament things.

Ok a few weeks back both sediment bowls were removed completly including the base. We drained the tank completly, added a home made extension to my shop vac, vaccumed the inside, power washed it out with high pressure washer, blew dry and left it open to completly air dry. I then added 3" extensions to both of the bowl housings so that when I threaded them back into the tank they would not draw any remaining trash we may have issed. So I have these little stand pipes about 2.5 to 3" protruding up into the tank. Sediment bowls are good and clean. This was all done chasing this dying issue. While I had the lines all open on the tank I used compressed air and blew good back to the primer so I knew the supply line was open and without restrictions. When it dies and I remove the supply line fuel runs free flowing to the primer. The primer is new, once again replaced chasing this issue. It has a brand new (from dealer) fuel cap, replaced chasing this issue. We even tried to run it with a homemade pantyhose fuel cap so that we were guarenteed to not be air locking, same results. I can blow back into the tank through the return line with my mouth, so if restricted it is minimal at best. The return fuel flow appears to react with RPM's watching it return into the tank, however I am unable to watch it while working the tractor due to being to much of a risk of being hurt.

The only improvement so far is that the "surging" issue is gone. I am beginning to wonder if it is a fuel issue at all??? Possible turbo, air inlet issue??? It has new air filter and I shop vac'd and blew air completly thru air inlet to turbo.