Did a compression test today.
Thread Starter
|
Cross-Country
Joined: Aug 2012
Posts: 83
Likes: 2
Did a compression test today.
93 F150 L6 XL. ODO says 308,000, though engine is supposedly no original. No way to confirm either way.
Plugs were clean, and all cylinders were +/- five percent of 120lbs / 800kpa.
Another thread suggests this is on the low side. Any thoughts?
Plugs were clean, and all cylinders were +/- five percent of 120lbs / 800kpa.
Another thread suggests this is on the low side. Any thoughts?
Fleet Mechanic
Joined: Jan 2011
Posts: 1,709
Likes: 4
From: 8600 ft in Colo
It's usually more important that the cylinders are close, than the actual number.
The test procedure matters a lot...
Did you test it warm or cold? Have the throttle wide open? Let it turn over through 5 or 6 compression strokes?
The test procedure matters a lot...
Did you test it warm or cold? Have the throttle wide open? Let it turn over through 5 or 6 compression strokes?
Cargo Master
Joined: Mar 2010
Posts: 3,342
Likes: 294
From: Laramie, WY
Air pressure makes a big difference too. I've tested my snowmobile at 800 ft and seen 155psi, that same motor at 7500 ft was 115psi. Air pressure drops, to a rough approximation, 3% per 1000' of altitude. So guys at sea level will think a guy in Leadville, CO (10k ft) has a trashed engine if they see his compression test results.
An oiled cylinder will also seal much better. Some gauges leak too.
The fact that all your readings are within 5% says the motor is doing fine. Now use those readings as a "health baseline", so if in the future you suspect something is wrong, and measure compression with the same gauge, and find lower readings, you know the motor is going south.
An oiled cylinder will also seal much better. Some gauges leak too.
The fact that all your readings are within 5% says the motor is doing fine. Now use those readings as a "health baseline", so if in the future you suspect something is wrong, and measure compression with the same gauge, and find lower readings, you know the motor is going south.
Thread
Thread Starter
Forum
Replies
Last Post
c2z4s9
1980 - 1986 Bullnose F100, F150 & Larger F-Series Trucks
73
Feb 29, 2016 07:14 AM
MONAVIERONJON
Pre-Power Stroke Diesel (7.3L IDI & 6.9L)
3
Oct 15, 2009 11:50 PM
tractoman
1973 - 1979 F-100 & Larger F-Series Trucks
11
Feb 19, 2006 02:18 PM
