Compression check out of truck

Joined
Oct 22, 2013
Messages
258
Hey all, hopefully an easy pair of questions...

Background (this is not the question - just info): My 1991 FJ80 has an undiagnosed knock and power loss I want to sort out. Could be bad, but with close to 250k the engine, was planning a possible rebuild anyway.

Today: I was gifted a 3FE. The owner told me that the guy he got the engine from said it was running when it was pulled and that the truck had less than 100K miles. Story went that the engine was pulled due to body damage. Spark plugs actually looked great.

Question 1: Flex plate is in place, can I check compression by jerry rigging a starter with spacers, or is there another, more clever way?

Question 2: I'm considering that this engine could possibly be a drop-in for my knocking one. I'd do a refresh... clean, main seal, oil pump, water pump, gaskets and such... but aside from compression are there other critical checks I'd want to do before I try to go down that road?

Thanks in advance for any thoughts!

IMG_20211009_112522_01.jpg
 

baldilocks

Battle Ground, WA
GOLD Star
Joined
Jan 29, 2014
Messages
7,476
Location
Battle Ground
A leak down test will provide more information about the condition of the valves and piston rings/cyl walls. With the valve cover removed you will be able to see if there is sludge build up. I would also pull the oil pan to inspect and plasti-gauge the the main and rod bearings. Of course a thorough cleaning and reseal job before dropping it into the chassis where access is not as good.
 
Joined
Oct 22, 2013
Messages
258
A leak down test will provide more information about the condition of the valves and piston rings/cyl walls. With the valve cover removed you will be able to see if there is sludge build up. I would also pull the oil pan to inspect and plasti-gauge the the main and rod bearings. Of course a thorough cleaning and reseal job before dropping it into the chassis where access is not as good.

Nice!

So evaluate with...
  • Compression test
  • Leakdown test
  • Check valve train for sludge
  • Pull oil pan
    • Inspect
    • Measure main & rod bearing clearance
Then clean/spruce & reseal all the stuff that's going to be way easier on the stand.

So, am I thinking about this starter thing backwards? Starter actually mounts to the engine side of the flex plate facing the rear, not the tranny side, so maybe there's no spacers or cleverness needed at all?
 
Joined
Oct 22, 2013
Messages
258
You could crank the engine with the starter but it would have to be bolted to some sort of stand.

All makes sense, appreciate the input! I was already going to pick up a 2-ton stand for the check & refresh process. And a 2t crane.

I was just confused about mounting the starter from watching a Youtube. This guy had to kluge up the mount because the starter on his Honda bolted from behind the flywheel through the transmission bell housing. I've rebuilt my starter and removed my dang transmission, so you'd think I'd know better that the 3FE starter was mounted from the engine side. :oops:

In fact, it mounts through that big round hole that's clearly visible in my picture, lol. Anyway, I'll nab a spare starter, mounting stud, nut, and bolt, get this big hunk of iron inside and on a stand and see what I'm in for. Fingers crossed I can get on the road with a nice clean, leak-free 3FE without a full rebuild. If not, well, rebuild was original plan A.

[EDIT: Part numbers I'm picking up because I want spares but mainly because I don't want to pull them from my running truck until I'm ready to pull that engine.
1 x 29362-87701 - Mounting bolt through starter
1 x 90116-12005 - Mounting Stud
1 x 94115-41200 - Nut for starter stud
2 x 94512-01200 - washer for starter mount
End Edit]

I'll post back to this thread with outcome, but it may take some weeks between getting parts, work, travel, and general slowness.

3FE Starter mount duh.PNG
 
Last edited:

Users who are viewing this thread

Top Bottom