Cylinder compression is unusually high and locks up.

[Squerl101]

Hey guys, i have a Revo 3.3 and i'm going to junk it if i can't figure out what to do or have to buy a whole new motor.

So i was out a few days ago doing some high speed runs and tuning it for the 90 degree weather. I had a good time and i went through a few tanks like normal. Then, one tank, i forgot to fill it up when it got low so it ran dry out of gas. I filled it up, then tried starting it. I put the glow plug heater in (its a pull start), but the glow plug didn't respond on the indicator. I took out the glow plug and saw that it looked normal, but it just wouldn't light up when i applied the glow plug heater. I went out and picked up another glow plug. I put it in and forgot to fill it up so it ran dry out of gas again. I filled it up and applied the glow plug heater to try starting it. The glow plug didn't respond. I toook it out, and instead of it looking normal, the filament inside the plug was completely gone . So i put another plug in and tried starting it the glow plug responded (why wouldn't it it's brand new) and I pulled the rip cord, but the engine wouldn't turn. I took the head off to see the cylinder and found that there was a bunch of metal in the cylinder and on the piston (pieces of the glow plug filament melted). It was pretty attached to the piston sleeve and the piston. I cleaned it off and put the head back on. I then tried starting it. The glow plug heated like normal, and i could turn the engine. I started it, then got a few feet down the street, and it cut off again. The glow plug didn't respond when I checked again. I took out the plug and noticed that thew filament was still there, but the engine wouldn't turn. I took the head off again and saw that there was more melted glow plug fragments in the cylinder. I cleaned it, put in a new plug, and tried cranking. It did turn, but it was very hard to because the compression in the cylinder was unusually high. The piston slid up and down in the sleeve very smoothly. The only think i did notice was that after the piston gets to the TDC, it would normally want to go down, but as I turned the flywheel just a bit more, it kind of locked there as if there was a physical object preventing the piston from going down. I tried pulling harder. It then came out of the lock and went down. This happens every time the piston goes up. I have to pull pretty hard to give the piston enough momentum to get past the lock and go back down. The lock isn't very hard, but there are also no more pieced of melted glow plug in the cylinder. My current thought is that when the engine siezed because of there being melted metal in the cylinder, it might have damaged the crank or the rod or something.

For now, I really don't have the time to disassemble the whole engine to see what's wrong. If you guys could give me an idea of whats wrong and what needs replacing, that would be great. I don't have the money to buy a whole new motor or a new car.

Thank you for your help.

 

[rc 66]

it sounds to me like that glow plug fillament went down in the motor you will prob need a new sleeve and piston for the most part

 

[Squerl101]

NO KIDDING! I just took out the piston, and the whole bottom half is gone (cracked off somehow). The bottom half is sitting in the crank case. Ill just get a new piston and sleeve. Hopefully all will be well after. Thanks for the suggestion!

 

[Snook Man]

The glow plug failure was most likely not the cause, but a symptom of the internal damage.

 

[Metalhead Matt]

Probably running it lean. I'd pick up some quality bearings while the engine is torn apart.

 

[Punisher]

You have run lean when you ran the tank dry.

First time the Revo let you off and only burnt up the glow plug - second time you lunched the engine.

 

[2revo1maxx]

Was running lean the entire time. Running out of fuel one time should not kill a glow plug.

 

[joshman1204]

Was running lean the entire time. Running out of fuel one time should not kill a glow plug.

Exactly what I was thinking ... I run my revo out of fuel all the time and have never burned up a plug just simply by running out of fuel. I do run McCoys plugs instead of traxxas so that may have something to do with them being a bit more durable.

 

[Bkyd Basher]

wouldnt u notice in the way the motor ran that u were that lean to keep smokin glowplugs?

 

[Zdragon71]

I was burning up a plug every other tank till i realized the tank seal leaking bad was causing it to run lean all the time and kept having to tune the hsn constantly. Actually snook told me that seal was causing it. Fortunately i never ran it long enough like that to kill the piston or rod. But this guys saying he replaced all lines the tank and sealed everything up good and would lean up on mid tank and he was richening for the other half till empty. I think maybe the piston was worn already before he started his learning process and replacing parts. Its just part of the hobby for us all at one point. A learning curve so to speak.

 

[2revo1maxx]

I've seen many people make the mistake of tuning their engine before it warms up, which causes it to run lean.

 

[Zdragon71]

My father is bad about doing that. Tuning it before its warm and i keep telling him your just gonna have to richen it back up again soon as it gets going.

 

[D arrow]

For $30-40 more I would do the trade up programs if, you want to stay with 3.3 engine. $110 you get a new 3.3 & all you have to do is drop it in, your all ready going to have to brake in the new sleeve & piston when you change them out with new ones. You do not have to have the old engine put together to trade it in, just have all the parts, keep your CB,FW,Air Filter, they don't come with new 3.3 hope these helps you & good luck.

 

[Bkyd Basher]

Or u can go on ebay and pick up a new 3.3 with no carb for 90. I have bought 2 now and both have been great so far..