7.3 idi compression test results

[Wrenchmonkey316]

130k miles. Clean truck. I’m losing a bunch of oil.. 4 quarts at 500 miles. So I had a compression test done. I’m wondering if this is enough loss to be concerned about? The truck rocks at idle so running kinda rough, could the compression issue I have cause it? All input is appreciated!

 

[Nero]

Good compression doesn't mean good engine. Could have a broken 2nd ring on a piston from someone in the past getting to enthusiastic with starting fluid.

 

[Wrenchmonkey316]

Good compression doesn't mean good engine. Could have a broken 2nd ring on a piston from someone in the past getting to enthusiastic with starting fluid.

The old timer who had it from birth took it in for regular service and kept records. He kept it out of the weather and at 130k I’m not saying nothing happened, but I’d bet it wasn’t starting fluid.

 

[Nero]

Heavy oil consumption could also be a stuck open CDR. Take it off and clean it with hot soapy water. Do not use any type of aresol, break clean, ect. You'll wreck the diaphragm in it.
There is a small pin hole in the back of it. Make sure it is clear, it's prone to getting blocked by sludge and crud over the years.

 

[The_Josh_Bear]

Those compression numbers are stellar!

 

[Wrenchmonkey316]

Good compression doesn't mean good engine. Could have a broken 2nd ring on a piston from someone in the past getting to enthusiastic with starting fluid.

So, would you say that’s good compression? I wasn’t sure on the 2 - 370s bing on the same side right next to each other.

 

[Wrenchmonkey316]

I’m really happy the low oil situation didn’t hurt the compression much. It’s got a little slump in its rumble. When it’s in D it bounces a little. In P it shakes less. At stop/start it feels like a tiniest load on the engine makes it shake like low power. Why do you think I would lose so much oil and get the big blue smoke puffs at heavy throttle? It’s clear, almost no smoke at lower half throttle range.

 

[ihc1470]

Do a cylinder leakage test and you will know where the compression is going, it may tell you about the side by side cylinders with same compression.

You will always have leakage past the rings. Intake and exhaust should show no leakage, you should not see air in the radiator.

General rule of thumb is high and low numbers should be within 10 percent of each other for compression and five to eight percent leakage would be typical on cylinder leakage test.

 

[Nero]

Also, engine lope could be caused by tired injectors, but before fixing them, if you're concerned aboht the engine health, a leak down will tell you a lot.

Did you check the CDR?

 

[WrenchWhore]

I agree, narrow down the easier stuff like @Nero said. CDR cleaning is routine maintenance in my opinion. I usually get some diesel fuel and slosh it around on the inside. Got a lot of black chunks out of it last time. Once it's clean test it by blowing through it. I forget what direction but you should feel the diaphragm inside move smoothly.

 

[Wrenchmonkey316]

Also, engine lope could be caused by tired injectors, but before fixing them, if you're concerned aboht the engine health, a leak down will tell you a lot.

Did you check the CDR?

I did the injectors and return lines. I also replaced the cdr very recently.

I still get blue smoke at takeoff from a stop if I don’t start off slowly and didn’t improve the rough running problem.

 

[Wrenchmonkey316]

I agree, narrow down the easier stuff like @Nero said. CDR cleaning is routine maintenance in my opinion. I usually get some diesel fuel and slosh it around on the inside. Got a lot of black chunks out of it last time. Once it's clean test it by blowing through it. I forget what direction but you should feel the diaphragm inside move smoothly.

Yeah I tested the new one. I blew in the tiny hole on the front of the can and it compressed a little and blew the air back out the little hole. If it works, you can feel it blow air back out the hole. Truthfully I did the same test on the old dirty one and the little hole was blocked. It tasted bad.

 

[IDIBRONCO]

I still get blue smoke at takeoff from a stop if I don’t start off slowly and didn’t improve the rough running problem.

How's the timing?

 

[Brian VT]

Where'd you get your injectors?

 

[Lumberjackchuck]

I agree, narrow down the easier stuff like @Nero said. CDR cleaning is routine maintenance in my opinion. I usually get some diesel fuel and slosh it around on the inside. Got a lot of black chunks out of it last time. Once it's clean test it by blowing through it. I forget what direction but you should feel the diaphragm inside move smoothly.

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