Compression 1973 4000SU diesel: Cylinder 1 = 380 psi; Cylinder 2 = 360 psi; Cylinder 3 = 360 psi. All measurements take when engine was cold. Engine had a vibration at 1800rpm. We took it apart and found nothing wrong. Now trying to figure out how to rebuild. Option 1 (minor overhaul) = hone, rings, bearing and rework head. Option 2 (major overhaul) = sleeve engine, pistons, rings, bearing and rework head. Option 3 = Reassembly engine? This little tractor started fine and power was o.k. Having the advantage of hind sight. Should have started with the injector pump and injectors. What do you think? Thanks.
- Thread starter jsp5755
- Start date
Bern
Well-known Member
- Location
- Mount Vernon, WA
Two comments about your reply:
1) I think you mean 200 RPM, not 2000
2) I'm questioning where you got that 420-510 PSI figure from. You say it's a Ford manual, but I really doubt it. The last time I looked up specs in a Ford manual for that engine, it was 350-375 PSI, with 290 being a minimum.
1) I think you mean 200 RPM, not 2000
2) I'm questioning where you got that 420-510 PSI figure from. You say it's a Ford manual, but I really doubt it. The last time I looked up specs in a Ford manual for that engine, it was 350-375 PSI, with 290 being a minimum.
Ultradog MN
Well-known Member
- Location
- Twin Cities
I&T FO-31 says 420-510 @200 rpm.
Edit:
I've never checked one - don't have a diesel tester - so can not speak with any authority.
Edit:
I've never checked one - don't have a diesel tester - so can not speak with any authority.
Verify compression specs, even if they are low they are close to equal or within a few % of each other. Most of the time it takes at least 10 if not 20% difference in compression to feel or notice a misfire, vibration or weak cylinder. If you decide on a rebuild or not is up to you but I would be looking for the problem somewhere else.
Bern
Well-known Member
- Location
- Mount Vernon, WA
Even the 420-510 PSI spec is wrong. Later manuals have compression listed at 350-375. I've compression tested many Fords over the years. Getting over 400 PSI is tough to do unless there's a lot of carbon in the cylinder.
I think the error in the 5000 manual has more to do with the fact that originally, they had you check it with the engine running.
I think the error in the 5000 manual has more to do with the fact that originally, they had you check it with the engine running.
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