Bad cylinder
Thread Starter
|
Mountain Pass
Joined: Sep 2006
Posts: 157
Likes: 0
From: Plain City Utah
Bad cylinder
Hello everyone I have a 1994 f-350 4 door an my #2 cylinder had only 150 psi, the rest of then have 300 or just over 300 psi I am woudering if the 300 psi is good for the 7.3 IDI an also can I just repalce the #2 piston . thank you . Rick
Posting Guru
Joined: Mar 2005
Posts: 1,701
Likes: 0
From: KY
300 is low. A motor in great shape will be around 500 PSI.
You probably just have a very tired cylinder. Broken ring or a cylinder starting to score.
If you open this motor up just be prepared to a good overhaul.
How does it run?? You readings could be off. Hope they are.
You probably just have a very tired cylinder. Broken ring or a cylinder starting to score.
If you open this motor up just be prepared to a good overhaul.
How does it run?? You readings could be off. Hope they are.
Elder User
Joined: Aug 2007
Posts: 728
Likes: 0
150 psi means it didnt drop a valve , it could be a broken valve spring , a broken piston ring or it could have a valve that is not seating properly you can perform another compression test but first put about 5-10 drops of oil in the cylinder spin it over a few times to distrbute the oil then install the compression tester if the compression increases dramatically it has a bad ring if it stays the same it is one of the valves
Post Fiend
Joined: Nov 2004
Posts: 5,638
Likes: 1
From: Manitoba
How did you perform the pressure test....... hot/warm or cold engine... warm is required at a minimum and crank for at least 5 pumping strokes on each cylinder. This ensures a good test of all cylinders equally. Record highest compression and # of strokes to obtain. There may be some worn valves....... at around 160K the 7.3 does experience some wear in the guides which can lead to cocked/non seated valves.
Thread Starter
|
Mountain Pass
Joined: Sep 2006
Posts: 157
Likes: 0
From: Plain City Utah
The dealer where I took it said ther tested it warm an that all my cylinders were at around 300 or or just over 300 psi but # 2 was at 150 psi an they also said I am getting lots of blow bye into my crank case . So when I got it home I did my own test an #2 was at about 130 to 145 psi the rest of them were at 300 or a little more. I have not done a leak down test yet from what I have found out is , if I am getting lots of blow be into my crank case I have a bad piston or broken rings . it sounds like I need to motor .Thank you Rick
