This message is a reply to an archived post by doc37172 on April 15, 2011 at 09:30:58.
The original subject was "ZA Low Oil Pressure".
Below is a post from awhile back about an oil pressure problem I was have with my ZA. Since a lot of folks tried to help on this issue, I thought it would be good post a follow-up. I mic'd the rod journals and while the bearings looked OK, I concluded that the journals were out of tolerance and that standard bearings would not help. However, since I had already ordered them I eventually just replaced them and sure enough it now holds 35-40 lbs all day long. I think cleaning the crank case somehow disturbed the crap that was boosting the oil pressure. I wasted a lot of time concentrating on the oil pump being the problem.
Initial Post:
Ok guys, I'm gonna post one more time on this problem even though Charlie and others have trued to help. Here's the deal step by step:
1. ZA sitting in barn about 8 years. Got it started and it held 18-20 lbs pressure
2. Drain oil (30wt detergent), pulled side plate, cleaned about 3/4" sludge from crankcase and oil pickup screen, blew out oil lines and checked filter base for blockage. Everything looked pretty clean
3. Installed spin-on adapter and NAPA 1061, refilled oil and started. Still held around 18-20lbs
4. Checked oil pump regulator passage which looked clean (it has the internal adjustment screw with 3/4" ball and spring) Adjusted screw about 2 full turns which raised pressure to 30-35lbs
5. Pressure washed and ran tractor around maybe 30 minutes...noticed pressure had dropped back to 20lbs even at later cold startup
6. Tried adjusting screw some more but no real change
7. Changed gauge...no difference
8. Drained oil, pulled side cover and checked pickup screen...looked clean
9. Added oil and restarted...now pressure goes immediately to 18 lbs but drops to <5 lbs in about 15-20 seconds
10. Pulled oil pump...shaft keys, keyways and gears look Ok to the eye. Cleaned pump, reinstalled and checked clearance with plasti-gauge - looks Ok at around .002
Restart...pressure now peaks at 15lbs and drops quickly to <5 lbs. Engine sounds Ok and starts easily.
My conclusion is either a bad pump or excess pressure leak-off somewhere. My next step is to check bearing clearance, but unless something serious happened in the 60-90 minutes it's been run since I had good adjustable pressure, I don't see why bearing clearance would cause such a sudden change in pressure. My other thought is to replace the old regulator ball with a new piston style regulator, spring and retainer, but I hate keep throwing parts and money at the problem. I've seen other posts of a similar problem but haven't seen responses which indicate diagnosis and solution. Any more ideas would be appreciated.
The original subject was "ZA Low Oil Pressure".
Below is a post from awhile back about an oil pressure problem I was have with my ZA. Since a lot of folks tried to help on this issue, I thought it would be good post a follow-up. I mic'd the rod journals and while the bearings looked OK, I concluded that the journals were out of tolerance and that standard bearings would not help. However, since I had already ordered them I eventually just replaced them and sure enough it now holds 35-40 lbs all day long. I think cleaning the crank case somehow disturbed the crap that was boosting the oil pressure. I wasted a lot of time concentrating on the oil pump being the problem.
Initial Post:
Ok guys, I'm gonna post one more time on this problem even though Charlie and others have trued to help. Here's the deal step by step:
1. ZA sitting in barn about 8 years. Got it started and it held 18-20 lbs pressure
2. Drain oil (30wt detergent), pulled side plate, cleaned about 3/4" sludge from crankcase and oil pickup screen, blew out oil lines and checked filter base for blockage. Everything looked pretty clean
3. Installed spin-on adapter and NAPA 1061, refilled oil and started. Still held around 18-20lbs
4. Checked oil pump regulator passage which looked clean (it has the internal adjustment screw with 3/4" ball and spring) Adjusted screw about 2 full turns which raised pressure to 30-35lbs
5. Pressure washed and ran tractor around maybe 30 minutes...noticed pressure had dropped back to 20lbs even at later cold startup
6. Tried adjusting screw some more but no real change
7. Changed gauge...no difference
8. Drained oil, pulled side cover and checked pickup screen...looked clean
9. Added oil and restarted...now pressure goes immediately to 18 lbs but drops to <5 lbs in about 15-20 seconds
10. Pulled oil pump...shaft keys, keyways and gears look Ok to the eye. Cleaned pump, reinstalled and checked clearance with plasti-gauge - looks Ok at around .002
Restart...pressure now peaks at 15lbs and drops quickly to <5 lbs. Engine sounds Ok and starts easily.
My conclusion is either a bad pump or excess pressure leak-off somewhere. My next step is to check bearing clearance, but unless something serious happened in the 60-90 minutes it's been run since I had good adjustable pressure, I don't see why bearing clearance would cause such a sudden change in pressure. My other thought is to replace the old regulator ball with a new piston style regulator, spring and retainer, but I hate keep throwing parts and money at the problem. I've seen other posts of a similar problem but haven't seen responses which indicate diagnosis and solution. Any more ideas would be appreciated.
