I've got a 1993 F-150 with the 5.0, and its either got a cracked block/head or some sort of hole in the piston. #1 cyl has zero compression and I have gas getting into the oil. It is the only truck I have to drive and I was wondering if it would be possible to unplug the injector for the dead cyl and run it? The only thing i was thinking was would oil come in through the crack and go into the exhaust?

 

It sounds more like you might have a stuck or bent valve. Maybe a busted piston ring. I would at least pull the valve cover and check the rocker action to see if they're moving as they should. As far as unplugging the injector, I guess that's something you would just have to try and see how it works. It sure wouldn't be helpful to the situation, especially if somethings broken because you will just make it worse if you continue driving it without fixing anything. You can either do without a truck now and fix it cheaper or do without it later and spend a bundle.

 

put a cylinder leak down tester on it and that will narrow the problem down real quick. that will tell you whether its a ring, piston, valve, crack ect.

 

Agree with the leak down test. Need to find out what the problem is. After that then we can proceed with the repair. With a dead cylinder having the injector continue spraying fuel will do more damage. Sean could be correct with the bent/broken valve idea. Did this cylinder go flat quickly?

 

Yep, it died quick. Ran perfectally fine for 210,000 miles, then I go to start it one morning, and it starts fine, then dies a few seconds later. I started it again and it wasent running quite right and the exhaust didnt smell right. So I smell the oil and it smells like gas. Thats when I took the compression tester out and found zero compression on the #1 cyl

 

I've never done a leak down test before, I don't even know what's involved. I have heard of it though. If someone wouldn't mind telling me how it's done and what is needed to do it I would appreciate it. I like to learn new things sometimes.

 

a leakdown tes can tell you a bunch of info, you have a cylinder with 2 gauges and you hook it up to the spark plug hole just like a compression gauge. you pressurize the cylinder with the one guage and then watch the other gauge "leak down". the best part is, because your pressurizing the cylinder, if you start getting bubbles in the radiator you know you have a head gasket or a crack, if you feel air coming out of the intake the you know your intake valve isn't sealing, if you have air out the exhaust, you know your exhaust valve isn't sealing, and if you have air coming from the valve cover, then your rings are probably done. But with that, thats the reason you have a second gauge to monitor the "leak down" because your are going to leak some air through the rings its just shows you how much is acceptable, and what isn't. Very informative tool

 

Thank you for the info. It sounds like a very helpful test. Now I need to go buy another tool.

 

well worth it

 

Didn't see the suggestion while quickly scrolling through - perhaps a failed valve spring?