IDI compression loss

[Tbag3]

I bought the truck for a fixer it’s an 86 250 with an 94 7.3 T and all I was told was it will start sometimes with ether and dies after warming up. So it would barely start with ether so I did a compression test, driver side readings from rad to cab were 200,140,120,320 passenger side was 180,160,220,300. So I tore apart I’ve found a floppy lifter and a stuck open valve but all pistons and cylinders look good. So would a bad lifter and stuck valve cause the no start. I was expecting the cylinders and pistons to be awful but looked very good

 

[ihc1470]

I doubt they are all of your problem. Might make it harder starting and probably a miss. You are low on compression in 6 out of 8 cylinders. From this distance it looks like a tired engine.

 

[Tbag3]

I’ll post some pics of the cylinders in a few minutes. What else would I look for

 

[Tbag3]

Also what is the minimum compression tolerance per cylinder, is anything under 200 to bad for starting and running? and my results are from a cold engine if that helps. Just thinking of buttoning it up with new head gaskets and see if any changes. Thanks

 

[Tbag3]

I didn’t think it looked that bad, I’ve seen much worse

 

[DirtyWood]

I don't know what the minimum spec is but 200 is very low. Most compression test results I've seen for these engines are 300-350.

 

[DougBoy66]

How many cycles did you do on each cylinder when you checked compression? You have to crank the motor several revolutions to get a true reading for each.

 

[Tbag3]

Yea that’s what I was thinking. I fixed the stuck valve and bad lifter, hopefully that with new head gasket brings my numbers up

 

[Tbag3]

10 to 15 seconds on each

 

[Tbag3]

They climbed pretty slowly, I used a snap on brand it should be pretty accurate hopefully

 

[DougBoy66]

Looks like the valve kissed one of the pistons and on looks like it might have had something, maybe a failed glow plug tip bounce around in the chamber

 

[DougBoy66]

Look close between the valves. Mine were cracked in on both my old heads. I didn't see it until the machine shop found them

 

[Tbag3]

I bought the truck with the 7.3 in it and the original 6.9 that was running when taken out, so I could throw it back in there and try and rebuild the 7.3. Or just make one good engine from the 2. A young boy had it and wanted a turbo engine and was probably rough on it and put stupid looking 20’s on it. I’ll be going to 16in rim’s after it’s running

 

[Tbag3]

Ok I will thanks for your input

 

[ihc1470]

It might bring up the numbers on the cylinders those were in, should not effect others though. If you would have done a cylinder leakage test before pulling the heads it would have told you where the lose was. Tip the heads so valves are up and pour some solvent on top of the valves. Watch and see if you have any leakage into the ports. You can also blow air from the ports onto the back sides of the valves. If you can see leakage or bubbles you will have valves that are not sealing. Rings will be hard to tell without pulling pistons. They could be stuck or just wore out either way hard to tell without physical inspection.

Has this engine been sitting for a long time? Just wondering why the stuck valve. What do you mean by a floppy lifter. Both those issues along with low compression numbers still tell me a tired engine and I doubt new head gaskets are going to do anything for you other than making your pocket book a little lighter.