Engine cut out while slowing down....

[Mtl-Diesel]

OK. New gauge. Consistent results:
1 - 105
2 - 75
3 - 60
4 - 60
Did leak down with no change. Rebuild time? :-(

 

[Mtl-Diesel]

Reminder, this is with the rebuilt head already.

 

[nola mike]

So assuming your "leak down" test consisted of pressurizing the cylinders? Did you hear air escaping? Did you try a wet compression test? You mentioned testing compression warm. Did you try to start it? Those numbers are pretty crappy. Your engine was running, and then had some sort of failure, presumably the head. Now it has numbers that won't let it run. So a failure of the block as well? Worn rings wouldn't have numbers that low in a running engine (I don't think...certainly not an engine that could get you moving). I didn't see any significant piston damage. I'm thinking that you're losing compression between the block and head. Warped block? Incorrectly torqued HG? Incorrect valve timing/timing chain issue? IDK, something sounds off here. Curious as to what the smart guys think.

 

[Mtl-Diesel]

So assuming your "leak down" test consisted of pressurizing the cylinders? Did you hear air escaping? Did you try a wet compression test? You mentioned testing compression warm. Did you try to start it? Those numbers are pretty crappy. Your engine was running, and then had some sort of failure, presumably the head. Now it has numbers that won't let it run. So a failure of the block as well? Worn rings wouldn't have numbers that low in a running engine (I don't think...certainly not an engine that could get you moving). I didn't see any significant piston damage. I'm thinking that you're losing compression between the block and head. Warped block? Incorrectly torqued HG? Incorrect valve timing/timing chain issue? IDK, something sounds off here. Curious as to what the smart guys think.

My bad. I did a wet compression test. I did NOT do a leak down test. I have not been able to start the engine, it's still in indoor storage in the garage.
When I installed the head I followed the manual. Torqued down to 93ft/lb.
My piston walls are really nice. No scoring or marks what so ever. I want to make sure I've done everything before pulling it out and sending it out for rebuild, but also don't want to wait too long as I want to have a season!

 

[alldodge]

Agree with Mike, and with compression that low I would be looking at the head again

 

[alldodge]

When I installed the head I followed the manual. Torqued down to 93ft/lb.

In manual 3 shows it to be torqued in 3 passes to 130 ft lb
Passes 55, 90 to 130

Unable to find it in manual 10
Manual 13 list 90 ft lb

In any case, if the head was flat within .003 and the correct gasket was used, it would be higher then what your seeing.

Measure the height of the valve springs when their closed. See if they are the same height

 

[Mtl-Diesel]

In manual 3 shows it to be torqued in 3 passes to 130 ft lb
Passes 55, 90 to 130

Unable to find it in manual 10
Manual 13 list 90 ft lb

In any case, if the head was flat within .003 and the correct gasket was used, it would be higher then what your seeing.

Measure the height of the valve springs when their closed. See if they are the same height

Ok. I used manual 3. Page 6A-1 says 93
Page 6B-1 says 130
Stupid question. Which engine do I have? 1984 Mercruiser 140 s/n 6777639

 

[alldodge]

I would use the 93, the 130 would be over torque so it has to be a misprint
Your serial number comes up 1982 to 1984 3.0

 

[Mtl-Diesel]

I would use the 93, the 130 would be over torque so it has to be a misprint
Your serial number comes up 1982 to 1984 3.0

Phew! Thanks for the confirmation!
OK. Bare with me. Measure literally from bottom of the spring to top? I assume I should do this at TDC to ensure they are closed?

 

[Mtl-Diesel]

Another question. During compression test, should the throttle be wide open? If so, why?

 

[alldodge]

Yes at TDC, I'm thinking there is either the valves are still to tight or there not seating. Could loosen the rocker to see if the spring comes up further

Yes, run test at WOT to allow maximum air to be drawn in. Your numbers are so low, not doing WOT would not be the issue currently

Could bring each cylinder to TDC and use a air compressor to listen where the air is coming out, the head or rings

 

[Mtl-Diesel]

Could bring each cylinder to TDC and use a air compressor to listen where the air is coming out, the head or rings

How do I use a compressor to introduce air? Would this be at WOT?

 

[nola mike]

I would use the 93, the 130 would be over torque so it has to be a misprint
Your serial number comes up 1982 to 1984 3.0

Didn't you say that in #3 there was a 3 pass sequence to 130?

Another question. During compression test, should the throttle be wide open? If so, why?

Yes, open. Just to allow air into the cylinders. It will probably end up close with it closed, but will take more cranking. You also won't be able to truly see how quickly it pressurizes. It should increase quickly for the first two or three cranks, and then level off.

How do I use a compressor to introduce air? Would this be at WOT?

Either see if you can rig up your compression tester, or use a leak down tester. Doesn't matter at wide open throttle or not for this test, but the valves have to be closed (tdc).
You can also just loosen the rockers all the way to make sure that the valves are as closed as they're going to get. (Maybe repeat the compression test quickly at that point)
Seems important to figure out the correct torque for the head... @Scott Danforth ?

 

[Mtl-Diesel]

Ok. So managed to rig together a few adapters to pressurize each cylinder. I hear air escaping into the block. I assume that points towards rings?

 

[nola mike]

Yeah. Weird. If that's the only place it's going. If it gets into the head it could make it back to the block, but you'd hear leaks in the head too (and that's a stretch). Still not sure how you'd be running with those numbers. Wonder if you have broken rings? Again, odd in 4 cylinders. But I guess you're out of options.

 

[Mtl-Diesel]

Yeah. Weird. If that's the only place it's going. If it gets into the head it could make it back to the block, but you'd hear leaks in the head too (and that's a stretch). Still not sure how you'd be running with those numbers. Wonder if you have broken rings? Again, odd in 4 cylinders. But I guess you're out of options.

Just for clarification. It's not running. It hasn't run since it died back in August. Then I had the head redone.

 

[nola mike]

Yeah, but it was running. Usually compression loss from worn rings is very gradual.

 

[alldodge]

If each piston was at TDC when air pressure was connected and most all came out the block, then its the rings

 

[Scott Danforth]

or holes in the pistons

 

[Mtl-Diesel]

or holes in the pistons

Definitely no holes in the piston. Unless they are microscopic.