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I was wondering if anyone had any experience doing a cylinder leak down test on our 6.9l/7.3l IDIs? I'm thinking about testing the spare 7.3l IDIT I've had on an engine stand for years and years. It rotates freely with a ratchet, but the salvage yard I bought it from said it was no-good. FWIW, I once put the spare 7.3l IDIT injectors in my 6.9l and they made the engine KNOCK so bad I never got it running (maybe one was hanging open)!
I know the firing order of our IDIs is 12734568. I had thought I could run each cylinder to TDC, loosen the intake/exhaust valves, and apply compressed air through the tester.
I was thinking I could use nylon rope fed into the combustion chamber of another cylinder so the engine wouldn't rotate due to the compressed air. On second thought, I don't think this would work. The combustion chamber of our engines is probably too small to accommodate the nylon rope at TDC. Plus, which other cylinder would be close enough to TDC that I could test another cylinder at TDC? Am I thinking correctly in asking this, or am I way off base?
I figured I would also ask everyone's opinion on which cylinder leak down tester to buy?
I bought the OTC leak down tester and evaluated the spare 7.3l IDIT I have. I suggest to anyone doing a leak down test on our IDI engines to buy the OTC tester over the one from Performance Tool. I read on OBs that you actually have to use a GP hole adapter from the Horrible Freight compression tester to get the Performance Tool leak down tester to work.
To do the test all you have to do is loosen the rocker arms on each cylinder with the leak down tester in the GP hole and an injector torqued down in the pre-chamber (35 foot pounds). Make sure you rotate the engine around so the lifters are on the heel of the cam before you tighten the rocker arms (24 foot pounds).
I tested each cylinder at the bottom of the power stroke. Here are the results. The engine is bad.
I tested the leak down gauge disconnected. I got 90 psi on the left and 12 psi on the right. I hope some of the cylinders that failed horribly don't have damaged pistons. The engine rotates freely.
We'll see what I do next. Maybe I need to rebuild that Banks turbo and install it on my 6.9l.
I did the same test on my powerstroke engine and got similar results. After the tear-down, I found the low-cylinders had a huge taper and a large ridge on the top. The block had to be bored 0.030 to clean it up.
Interesting, I'd rather the cylinders were tapered than having catastrophic engine damage. I suppose I should remove the heads from the engine to see what condition the crank and pistons are in.
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