If you don't have a source for a leakdown tester handy, and your cylinder compression gage has the spark plug adapters with the quick disconnects, you can try this:

Since you already know you have a problem cylinder, just use the plug adapter and put shop air straight to the cylinder at TDC without the gage, and, as steponmebbbboom says, listen for where the air is escaping, intake valve (carb), exhaust valve (tailpipe), rings/pistion hole (oil filler/crankcase) and cracked block/headgasket (bubbles in coolant)

I've also been known to break out the porcelain and tap the shell of an old spark plug to install a quick disconnect to make my own adapter. (My leakdown gage adapter is for the 7/8" aviation plugs)

But, of course, the most fun thing to do is use this opportunity as an excuse to buy a cool new tool!

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'81 D150 with "Lean Burn"

I think a new tool is in order!

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Chuck Rivers, Webmaster

that is correct, the leakdown tester uses two gauges and an air regulator to display pressure differentials so you can quantify the amount of leakage but being able to listen to escaping air from either your oil fill cap, air horn or tailpipe is its most important function. you will quickly determine whether you need rings or pistons, or a head job; for the home mechanic the amount of leakage is mostly immaterial. if it leaks, and it's obvious, it's time.

don't forget to index the cylinder in question to BDC power stroke for the test to work correctly. it wont do much good with a valve yawning wide open.

good luck~

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I've been calling it as i see it for my entire life and that's not about to change. Take it or leave it.

Problem fixed!

My buddy Dan came over with what I call his can of "do-attitude". He got the lifter installed in 15 minutes, then we slowly turned over the engine. We were rewarded with a loud SNAP when the valve stuck and popped back up.

I then got out the trusty valve spring removing tool and removed all the parts from the top of the valve stem. After turning the engine to get #6 up to TDC to prevent losing the valve in the cyl., I tapped on the valve stem, driving it down a bit. I have never seen a valve so stuck that wasn't completely rusted in!!

I tried WD-40 and PB (Parts Blaster), but ultimately has to use carb cleaner to free up the valve! We had to pry it back up with a screwdriver in the keeper grooves and repeat. We worked on that for a good half hour.

After a preliminary valve adjustment, it fired right up, and after a complete adjustment, it is running better than it has in years!!

So the general opinion was right. These things are tougher that one might think.

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Chuck Rivers, Webmaster

Great! I hope you got rid of all the old gas! Old gas will completely ruin an engine. I'm glad it didn't ruin yours!

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Joshua