Compression test on the stand
Thread Starter
|
Mountain Pass
Joined: Oct 2011
Posts: 218
Likes: 0
Compression test on the stand
Can I do a compression test on the 7.3l while its on the engine stand? i've only ever done them with a starter but I was thinking if I pulled all the GP's I might be able to spin the motor with a breaker bar. I just didnt know if I could spin it faster than it would leak down.
Cargo Master
Joined: Jun 2010
Posts: 2,771
Likes: 3
From: Louisiana
No way can you spin it fast enough with a breaker bar! Like Matt said, ahh, just thought about it. It's on a stand by the bell housing. You'll have to take it off the stand and bolt the trams adapter on it. I personally would not bolt it back to the stand. Seems like to much stress on the bolts and housing. Maybe I'm just paranoid. I tested mine hanging from my tractor, but a hoist will work as well. Now two things for sure is make sure everything is torqued down and filled with oil or well lubricated. Then pull all glo plugs and spin the engine a few rounds to clear out the cylinders and make sure everything is freed up. When I first tried to spin my block over I used a good set of jumper cables and my tractor running. It made me look like a fool. I thought the starter I was using was bad but it turned out to be low amps. I ended up bolting up the batteries from my truck with some pre made cables to ensure a good connection. Then began to test each cylinder. Take note of how quickly each cylinder climbs. By the fourth or fifth turn it should be at max compression. Good luck. Is this an old motor? Rebuilt? Your original? I'm curious of results and milage "if any".
Thread Starter
|
Mountain Pass
Joined: Oct 2011
Posts: 218
Likes: 0
Its the motor out of my 205k mile truck. I had to part out the truck in a hurry so I didn't get the compression test done beforehand. I'm cleaning up the motor to install in a v10 excursion but would have liked to know if it needed rings. I'll have to pan off so I'll get a good look at the bearings at least
Laughing Gas
Joined: Apr 2007
Posts: 1,238
Likes: 2
From: North Port, Florida
I am curious of the correct procedure of doing this in the truck. Is there by chance a write up on this???
This is all good info for later when I get my spare motor built though.
thanks
This is all good info for later when I get my spare motor built though.
thanks
Trending Topics
Elder User
Joined: Feb 2011
Posts: 518
Likes: 0
From: west sacramento ca
couple small squirts of oil for a wet test.
kurt
99 7.3 4x4 cc drw
FTE Stories
Ford Trucks for Ford Truck Enthusiasts
Top 6 Best Deals Available on New Fords & Lincolns Right Now
Brett Foote
This Hennessey Takes the Expedition Tremor's Off-Roading Capability to the Next Level
Verdad Gallardo
Top 10 Fords at 2026 Carlisle Ford Nationals
Joe Kucinski
3 Best / 3 Worst Parts of Modern Ford Ownership
Brett Foote
10 Amazing Upgrades That Solve Common Ford Truck Owner Headaches
Pouria Savadkouei
Every 2026 Ford Engine Explained
Brett Foote
10 Ugly Ford Trucks That We Still Kinda Love
Joe Kucinski
10 Things Every Truck Owner NEEDS (2026 Edition)
Michael S. Palmer
Rezvani's Latest Post-Apocalyptic Monster Is a Ford F-150 Raptor Underneath
Verdad Gallardo
Hotshot
Joined: May 2005
Posts: 13,484
Likes: 42
From: Stevens Point, WI
I'd use the truck starter, even with using the vehicles starter I have seen motors that need to turn over up to 10 times to get an accurate reading. I would think turning over anything less than 100rpm would result in fluctuations in the readings.
Post Fiend
Joined: Nov 2007
Posts: 9,549
Likes: 14
From: Payson, AZ
Thanks for the input.
I think it would work. I've hand cranked at the damper pulley with the GPs out and it's not that difficult.
Post Fiend
Joined: Nov 2007
Posts: 9,549
Likes: 14
From: Payson, AZ
It wasn't easy, but I've hand cranked a 7.3 with only 2 GPs out.
I have a 425 lb/ft air ratchet gun that I would try before hooking up a starter to an engine on a stand.
Cargo Master
Joined: Jun 2010
Posts: 2,771
Likes: 3
From: Louisiana
Yea but how fast does that impact turn when it's putting out that 425lbs? The 7.3 is alot of rotating mass. Sure the motor is easy to turn when it's turned slow. The valves will bleed down enough to allow you to turn. Same reason you can spin the motor when trying to break the crank pulley bolt or hpop gear bolt. Try it. I would be supprised if it works. I'm not arguing that I know cause I don't. I just can't get my mind wrapped aroun it working with the trouble I had spinning it with the starter. Think about how much gear reduction you have with the flywheel. Like a 10 speed bike.
Post Fiend
Joined: Nov 2007
Posts: 9,549
Likes: 14
From: Payson, AZ
David,
I understand all you are saying and agree.
I just think it's worth a try.
You never know till you try.
If I ever have a 7.3 on a stand I will give it a shot.
I'll let you know if it works.
I understand all you are saying and agree.
I just think it's worth a try.
You never know till you try.
If I ever have a 7.3 on a stand I will give it a shot.
I'll let you know if it works.
Duct Tape Tech.
Joined: Jul 2009
Posts: 2,381
Likes: 1
From: San Antonio Tx.
Robin, I think you may do more harm than you think, I believe the impact wrench will over torque the crank bolt and damage the threads or berak the bolt.