Engine Missfire

Old forum posts ending on Oct 21 '09

Moderator: TechMOGogy

Locked
HOOPS PINZ
Posts: 105
Joined: Sat Dec 20, 2008 3:45 pm
Location: UNITED KINGDOM

Engine Missfire

Post by HOOPS PINZ »

Hi Guys I have a missfire on No 2 cylinder with the plug oiling up and oil leaking out of the exhaust manifold on that cylinder, but no smoke out of the exhaust. The engine runs fine till its under load then drives on 3 cylinders.
I had just replaced a bad civy dissy cap which had cracked internally and I had to run the vehicle for 100 miles like that with it backfiring to get me home. Also just replaced the batteries.
Before I pull the head off any ideas
Also can you pull the head and barrel off in situ on one cylinder if I need to replace a piston:(
psychoman
Posts: 161
Joined: Sat Jun 21, 2008 3:25 am
Location: Isle of Man - UK

Post by psychoman »

Obvious first questions (forgive me if too obvious):

1. Have you tried changing the offending plug?

2. Are you sure its oil at the exhaust manifold? I would have expected this to smoke like a bee atch if it was blowing oil through the rings...
It aint what you drive, its the way that you drive it...
HOOPS PINZ
Posts: 105
Joined: Sat Dec 20, 2008 3:45 pm
Location: UNITED KINGDOM

Post by HOOPS PINZ »

Yes I changed the plug, thats what surprised me no smoke and yes its oil I thought that a piston might have gone but it runs sweet as a nut until its under load and the oil drips out down the manifold and the plugs wet. Might be a cracked head but I cant see any cracks at the moment
Middlebury_Pinz
United States of America
Posts: 121
Joined: Wed Aug 13, 2008 2:00 pm
Location: ELkhart, in

Post by Middlebury_Pinz »

Before you do anything, check the basics and make an informed decision. Check the valve adjustment and make sure they are adjusted correctly. Then do a compression check and see what that tells you. All of the readings should be +/- 10% of each other. After you do a compression check to determine if there is a mechanical problem, do a cylinder leakage test.

It requires that you pull the spark plugs and bring the engine around to TDC on each cylinder. You then basically pressurize that cylinder at TDC and see where you have air escaping.

The CLT test will read out in percent. The higher the percent of leakage, the greater the blowby from somewhere.

Put your ear to the exhaust, if you hear air leaking you have a problem with an exhaust valve.

Put your ear to the intake/ carb(pull air cleaner), if you hear air leaking you have a problem with an intake valve.

Pull your oil filler cap and listen, if you hear air leaking, you have blowby past the rings.

Always, always, always, check the basics first before you tear anything down. The obvious always bites you in the butte and it's usually the simple stuff that causes problems.
HOOPS PINZ
Posts: 105
Joined: Sat Dec 20, 2008 3:45 pm
Location: UNITED KINGDOM

Post by HOOPS PINZ »

Yes I will do the compression test next. I will have to buy one in the next day or so.
I spent some time scatching my head over the truck today checking things out. I did the following
1/ Adjusted the carb float needle on front carb as the 2 front cylinders were wet this morning when I pulled the plugs.
2/ Checked out dist and coil connections I found the coil to dist lead faulty which I have replaced this has certainly improved things
3/ Retimed the vehicle to 10 BTDC when warm (Is this too far ) no pinking
4/ Found the oil leak problem seems the rubber rocker box gasket had failed on No 2 cylinder I replaced that with the old style cork gaskets. Thats 2 rubber gaskets that have let me down now. I thought that the head might have cracked.

the Pinz drives quite well now but pops back a little not sure yet if its through the carb or exhaust its a bit muffled. I wonder if its the dist or coil The previous owner fitted Pertronix ignition on it but had not filed the end off the rotor arm so the arm was not fitting on the dist shaft like it should.

Any more ideas
Locked