Go Back   Ford Truck Enthusiasts Forums > Performance, Engines & Troubleshooting > Ford Inline Six, 200, 250, 4.9L / 300
Sign in using an external account
Register Forgot Password?


Reply
 
 
 
 
LinkBack Thread Tools Search this Thread
  #1  
Old 07-02-2006, 01:27 PM
galaxiedan galaxiedan is offline
Senior User
 
Join Date: Apr 2003
Location: Citrus County, Florida
Posts: 103
galaxiedan is starting off with a positive reputation.
1990 4.9 300 dead cylinder?

I have an F-150 with the 4.9 six. Truck has 85,000 miles on it. I have just (less than 500 miles) put new plugs, wires, cap, and rotor on it. The first cylinder (from front of truck) does not fire. A local mechanic told me he could listen to it crank over and tell if it had weak compression in a cylinder. He heard it and said yes weak compression. The shop wants $100 to test compression. Is there an easy way to test to see if the injector on that cylinder is working? If the injector is working is there an easy way to tell if the possible weak compression is a head problem or a piston/ring problem? I really don't want to invest the amount of money it would cost for a complete rebuild on the motor but would consider head work if needed. Thanks
__________________
2003 F250 2wd 6.0 Powerstroke 5sp auto
1997 F250 2wd 7.3 PowerStroke 5spd
1994 Mustang 5.0 auto convertible
2009 Harley Davidson Night Train
Reply With Quote
  #2  
Old 07-02-2006, 01:39 PM
holland501 holland501 is offline
Elder User
 
Join Date: Jan 2004
Location: houston
Posts: 561
holland501 is starting off with a positive reputation.
A good mechanic can indeed hear if a cylinder has seriously low compression, just by cranking the engine over. If it is that low, it almost has to be a problem with a valve. Even bad rings would create enough compression for the cylinder to fire and run. Pull the plug, chances are you will smell raw fuel or it will be very black and sooty. Good luck.
Reply With Quote
  #3  
Old 07-02-2006, 02:06 PM
galaxiedan galaxiedan is offline
Senior User
 
Join Date: Apr 2003
Location: Citrus County, Florida
Posts: 103
galaxiedan is starting off with a positive reputation.
Would it be more common for a valve to be sticking or wore out? The plug seems wet but it is not black or sooty at all. I can't really tell if it is fuel or oil on the plug. Engine does not have blowby from pcv and does not smoke out the tailpipe. any advice?
__________________
2003 F250 2wd 6.0 Powerstroke 5sp auto
1997 F250 2wd 7.3 PowerStroke 5spd
1994 Mustang 5.0 auto convertible
2009 Harley Davidson Night Train
Reply With Quote
  #4  
Old 07-02-2006, 02:19 PM
galaxiedan galaxiedan is offline
Senior User
 
Join Date: Apr 2003
Location: Citrus County, Florida
Posts: 103
galaxiedan is starting off with a positive reputation.
I had an old 250 straight six in a chevy truck that had a habit of losing the nuts holding the rocker arms on. Does this motor have that problem? Is it possible to pull the valve cover on this motor (1990 4.9 FI) without removing the upper FI manifold? Would I be able to tell if it is a valve problem without taking the head off?
__________________
2003 F250 2wd 6.0 Powerstroke 5sp auto
1997 F250 2wd 7.3 PowerStroke 5spd
1994 Mustang 5.0 auto convertible
2009 Harley Davidson Night Train
Reply With Quote
  #5  
Old 07-02-2006, 09:03 PM
300I6VAN85 300I6VAN85 is offline
Senior User
 
Join Date: Jan 2006
Posts: 284
300I6VAN85 is starting off with a positive reputation.
You might have a stuck open valve. Bum a compression tester. I think you want at least 120 lbs. You might have luck with some snake oil. Marvel Mystery Oil. My friends Dad had luck with his sons 2 stroke dirt bike gas. Some people pour the snake oil right on the valve spring assy. 85,000 miles is a young 4.9. My 4.9, she's so fine. My 4.9.... Second thought, if you can't get a compression tester. NAPA #901, Air Holding Device, about 10 bucks. Get a hose fitting that will fit the part and buy some hose about 3 feet. Screw this into your bad cylinder spark plug hole at Top Dead Center when the valve should be closed. Blow into it. You are looking for that 120 lbs.
Reply With Quote
  #6  
Old 07-02-2006, 11:42 PM
pud pud is offline
Posting Guru
 
Join Date: Oct 2003
Location: Quesnel, BC, Canada
Posts: 1,948
pud is starting off with a positive reputation.
ive never heard of anyone blowing into a compression tester, I always just diconnect the coil and crank the engine over by bumping the starter.
__________________
1987 muteg GT T-Tops
Reply With Quote
  #7  
Old 07-03-2006, 11:50 AM
300I6VAN85 300I6VAN85 is offline
Senior User
 
Join Date: Jan 2006
Posts: 284
300I6VAN85 is starting off with a positive reputation.
Pud. You are missing the point. Dan is on the cheap and does not want to buy a compression tester. The tool I was refering to is used to hold the valve inplace when you want to replace the valve steam seal when the head is still on the motor. You get the valves closed, connect the fitting to the air compressor and that holds the valve inplace while you remove the rocker arm, valve keepers, spring and old worn valve steam seal. That is what the tool is made for. I was just trying to give Dan another cheap option to see if his valve was stuck open if he could not find a compression tester.
Reply With Quote
  #8  
Old 07-03-2006, 12:12 PM
pud pud is offline
Posting Guru
 
Join Date: Oct 2003
Location: Quesnel, BC, Canada
Posts: 1,948
pud is starting off with a positive reputation.
oh, my bad.
__________________
1987 muteg GT T-Tops
Reply With Quote
  #9  
Old 07-03-2006, 01:41 PM
Bdox's Avatar
Bdox Bdox is offline
Iconoclast
 
Join Date: Sep 2005
Location: Lake Tahoe, Nevada
Posts: 28,173
Bdox has a superb reputationBdox has a superb reputationBdox has a superb reputationBdox has a superb reputationBdox has a superb reputationBdox has a superb reputationBdox has a superb reputationBdox has a superb reputationBdox has a superb reputationBdox has a superb reputationBdox has a superb reputation
No problem is fixed for free. A compression tester and the proceedure are cheap and easy. Anybody can do it. You have to know that number before you know what to do next. This saves fixing things that aren't broken.
__________________
Bruce

corporations are not persons
.
corporations are not persons. corporations are not persons.corporations are not persons. corporations are not persons. corporations are not persons.
Reply With Quote
  #10  
Old 07-03-2006, 04:41 PM
galaxiedan galaxiedan is offline
Senior User
 
Join Date: Apr 2003
Location: Citrus County, Florida
Posts: 103
galaxiedan is starting off with a positive reputation.
Thanks for the help guys! I'm going to buy a compression tester tommorrow (the 4th). I will let you know what I find. If I did have a stuck open valve wouldn't I get a backfire into the intake or exhaust? I guess if it was backfiring into the exhaust it wouldn't be a backfire and I probably wouldn't notice it! Would that be considered front fire? I bought the truck for $200 as a second work truck/ loaner (eliminate people asking me to help them move, etc) and I have no idea of its background. Does anyone recommend an engine oil cleaner that might free up a sticking valve without taking the valve cover off? The fuel injection manifold along with a bunch of other stuff will have to be taken off first. I have no problem with changing an engine or head but just trying to slide by easy on this one. It runs and I can still drive it but I feel like a cross between Jud Clampett and chitty chitty bang bang.
__________________
2003 F250 2wd 6.0 Powerstroke 5sp auto
1997 F250 2wd 7.3 PowerStroke 5spd
1994 Mustang 5.0 auto convertible
2009 Harley Davidson Night Train
Reply With Quote
  #11  
Old 07-03-2006, 05:02 PM
Bdox's Avatar
Bdox Bdox is offline
Iconoclast
 
Join Date: Sep 2005
Location: Lake Tahoe, Nevada
Posts: 28,173
Bdox has a superb reputationBdox has a superb reputationBdox has a superb reputationBdox has a superb reputationBdox has a superb reputationBdox has a superb reputationBdox has a superb reputationBdox has a superb reputationBdox has a superb reputationBdox has a superb reputationBdox has a superb reputation
Front fire, I like it.

Have you pulled codes from this thing yet?

Again, run compression first. No point pouring in snake oil till you know what to fix. It could be anything from an injector wire to a flat cam lobe.

If you have low compression, put it on TDC, stick it in low, set the parking brake and blow air in the spark plug hole and listen to where is leaks out. If it's a valve you will hear it in the intake or in the exhaust.
__________________
Bruce

corporations are not persons
.
corporations are not persons. corporations are not persons.corporations are not persons. corporations are not persons. corporations are not persons.
Reply With Quote
Old 07-03-2006, 05:02 PM
 
 
 
Reply

Similar Threads
Thread Thread Starter Forum Replies Last Post
COMPRESSION ANDVICE truck crazy man 1987 - 1996 F150 & Larger F-Series Trucks 17 02-06-2014 08:50 PM
New 5.0 dead cylinder no compression Nally427 1987 - 1996 F150 & Larger F-Series Trucks 6 08-28-2013 05:59 PM
rebuilding a 7.3L motor turboboost 1999 - 2003 7.3L Power Stroke Diesel 4 11-04-2009 04:47 PM
351W HO Sudden Compression Loss in 4Cyl 2cyl in each Bank B. Abel Small Block V8 (221, 260, 289, 5.0/302, 5.8/351W) 11 12-01-2003 10:14 AM
HELP. sloth71 1987 - 1996 F150 & Larger F-Series Trucks 2 12-03-2002 06:38 PM


Go Back   Ford Truck Enthusiasts Forums > Performance, Engines & Troubleshooting > Ford Inline Six, 200, 250, 4.9L / 300

Tags
300, cylinder, dead, ford, inline

Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On
Trackbacks are On
Pingbacks are On
Refbacks are On

Forum Jump


Participate In The Forums

Create new posts and participate in discussions. It's free!

Sign Up »





All times are GMT -5. The time now is 08:50 AM.


Powered by vBulletin® Version 3.8.7 AC1
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Advertising - Terms of Use - Privacy Statement - Jobs
This forum is owned and operated by Internet Brands, Inc., a Delaware corporation. It is not authorized or endorsed by the Ford Motor Company and is not affiliated with the Ford Motor Company or its related companies in any way. Ford® is a registered trademark of the Ford Motor Company.

vbulletin Admin Backup