compression test what next?
Thread Starter
|
Cross-Country
Joined: Jun 2004
Posts: 68
Likes: 0
compression test what next?
My truck has 290,000 on it and I started looking at injectors but decided I would check compression first. All cylinders were 425-450 except #5 and it was 300. I am not having any running issues, truck runs like it always has. Just thought I would check things out before making that purchase.
Since this is more than 25 psi off from the others, how can I check to see if this a ring or piston issue or a valve issue?
Since this is more than 25 psi off from the others, how can I check to see if this a ring or piston issue or a valve issue?
Laughing Gas
Joined: Nov 2013
Posts: 868
Likes: 1
From: SoCal
Rotate #5 to TDC on the compression stroke and put some air pressure to it and look/listen for air coming from the intake or exhaust. If you don't hear any, then it's probably rings. You'll probably need a way to keep the crank from spinning as the air pressure tries to push the piston down. Another thing to do is add some oil in #5 and see if the compression is any higher. That'll point to rings also.
Laughing Gas
Joined: Nov 2013
Posts: 868
Likes: 1
From: SoCal
What type of compression tester are you using? Can you use the glow plug adapter and put shop air to it? I'm not sure how much pressure, but I would guess around 15-20psi. The proper way is to do a leak down test which usually consists of 100 psi supply going through a a metered orifice and a gauge on the other side to measure % leak down, but in your case, you know you have a weak cylinder, you're just trying to find the fault.
Thread Starter
|
Cross-Country
Joined: Jun 2004
Posts: 68
Likes: 0
Well redid compression test, got 350 psi. Put about a tablespoon of oil in cylinder and got 400 psi. Really not what I wanted to find. I put air in cylinder and could hear it but not thru the exhaust or intake.
Now I have to decide what path to take. Long block, drop in ready or rebuild mine. Another problem is we are supposed to take a trip in 2 weeks with the fifth wheel, about a 2,000 mile trip. I'd like to wait until I get back to do anything. Like I said truck I'd running ok so I'm tempted to just go ahead and drive it for now. Any thoughts, should I try and do something before the trip?
Now I have to decide what path to take. Long block, drop in ready or rebuild mine. Another problem is we are supposed to take a trip in 2 weeks with the fifth wheel, about a 2,000 mile trip. I'd like to wait until I get back to do anything. Like I said truck I'd running ok so I'm tempted to just go ahead and drive it for now. Any thoughts, should I try and do something before the trip?
Trending Topics
Lead Driver
Joined: Jun 2004
Posts: 6,311
Likes: 577
From: Amarillo, TEXAS!
I really don't think I'd be too concerned about it, honestly. I've been driving mine with one cylinder with lower compression than that for quite a while now. I think it was down around 270 on cylinder 7, last I checked.
FTE Stories
Ford Trucks for Ford Truck Enthusiasts
AEV FXL Super Duty - the Super Duty Raptor Ford Doesn't Make
Brett Foote
Lobo Vs Lobo: Proof the F-150 Lobo Should Be Even Lower!
Michael S. Palmer
Ford's 2001 Explorer Sportsman Concept Looks For a New Home
Verdad Gallardo
10 Best Ford Truck Engines We Miss the Most!
Joe Kucinski
2026 Shelby F-150 Off-Road: Better Than a Raptor R?
Brett Foote
2027 Super Duty Carhartt Package First Look: 12 Things You NEED to Know!
Michael S. Palmer
10 Most Surprising 2026 Ford Truck Features!
Joe Kucinski
Top 10 Ford Trucks Coming to Mecum Indy 2026
Brett Foote
5 Best / 5 Worst Ford Truck Wheels of All Time
Joe Kucinski
Fleet Mechanic
Joined: Nov 2010
Posts: 1,408
Likes: 249
From: Ringgold, Ga
Enjoy the trip as if you didn't know.
Pull the dipstick often to keep oil level in check.
As long as it's doing its job roll with it. Research after you get back. I get in trouble when I work on something while out with travel trailer. LOL
She says can't that wait til we get home?
Pull the dipstick often to keep oil level in check.
As long as it's doing its job roll with it. Research after you get back. I get in trouble when I work on something while out with travel trailer. LOL
She says can't that wait til we get home?
Thread Starter
|
Cross-Country
Joined: Jun 2004
Posts: 68
Likes: 0
Thanks for the replies. I'll probably just go with it for awhile. I am probably using about 3 quarts between changes. It really just started using some in the last 6-8 months so I haven't tracked it that close. I change oil every 5,000 and just did a change so I'm going to keep track this change.
Thread
Thread Starter
Forum
Replies
Last Post
cbass139
Y-Block V8 (239, 272, 292, 312, 317, 341, 368)
2
Jul 9, 2012 10:08 AM
Johnblagg
1987 - 1996 F150 & Larger F-Series Trucks
2
Oct 14, 2010 04:17 PM
ernesteugene
1999 - 2003 7.3L Power Stroke Diesel
25
May 8, 2007 07:06 AM
jwalker
Explorer, Sport Trac, Mountaineer & Aviator
3
Sep 22, 2003 11:34 PM