Monday, August 9, 2010

Engine Compression Testing

This summer has been busy with traveling and so I have not been able to make the most of the weather to work on the Triumph as I would like. It has been months since I really worked on the car, but I finally got around to doing an engine compression test on the car this past weekend.

Engine compression testing was something that I had put off because I thought it was going to be complicated, but it turns out it isn't so bad. First, I labeled the location and corresponding cables to make sure I put them back correctly. I unplugged the cables going into the spark plugs and used a special socket (it has a rubber attachment to pull the spark plug out) to remove all 4 spark plugs.

One by one, I hooked up the engine compression reader to each socket. With the help from Chris, he connected jumper cables to a car battery as I read the compression value - no need for a remote starter switch. The only minor problem was that the original Triumph's car battery was dead, so we moved my daily-use car close to the garage and left it idling while we ran the test on all 4 sockets.

The trickiest part of the whole process to get access to the two central spark plugs. The distributor was in the way, so we temporarily took the distributor out of its mount. Friction made it a bit stubborn to remove, but the most difficult part was putting the distributor back in. After referring to the Haynes manual, we had to make sure the first cylinder was in its end of compression phase (took a flashlight shining into the socket and observing the pistons while Chris hand turned the crankshaft) before aligning the distributor back in.

Engine compression readings after one or two turns of the engine.
1. 70 PSI
2. 70 PSI
3. 52 PSI
4. 70 PSI

Cylinder 3 had some issues with its compression. Whereas the other 3 cylinders had no problems hitting 70 PSI immediately, cylinder 3 slowly crept up in compression pressure. Not a good sign I'm assuming.

1 comment:

amy said...

Feedback provided from various people have told me that we did not do the engine compression test correctly. We were suppose to turn the engine until max compression is reached. The comparison reference given was that a 1930s Ford Model T's compression was 60 psi.

Also, to better diagnose cylinder problems, it was recommended we do a wet engine compression test as well to the dry engine compression testing we had done. The wet engine testing involves dropping a bit of oil in each cylinder to see if there is any improvement in numbers. This will help us understand better if something is not sealing in the cylinder since the oil will help seal the cylinder and improve compression numbers.