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T-Maxx 3.3 - Trouble firing up

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exilestudios

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Hello,

A couple weeks ago I had finally got my T-Maxx back together and ready to run. My dumb ass didn't think to lube it all up after having it sit for a while. Well I ran it for about 10 minutes and then it suddenly cut off. My EZ-Start was smoking, which highly concerned me. I assumed the EZ-Start was shot and I needed to replace it, as it wouldn't kick the motor over and had the smoke rolling out of it. I got to checking it out and found that it seemed to be seized up.

After tearing everything down I noticed the piston would move when I had the head off, but would appear to be seized again when I had it on (couldn't turn it over by hand). So I ended up having to tear off my EZ-Start and discovered the piston rod was split down the center and detached from the piston. Well after another week passed I had finally got around to getting a new piston rod. I ended up replacing it with aircraft alloy piston rod.

After putting it all back together (and making sure it was all good and lubed up this time :P) my EZ-Start seemed to be turning the motor over, but there's another issue with this which worries me. When running the EZ-Start for about 2 mins I notice sparking inside the EZ-Start motor, but initially when I use the EZ-Start it doesn't do this. I'm wondering if this is normal and I just never noticed it or if something is seriously wrong with it. It concerns me a lot because if that sparking causes a little spilled fuel to ignite it would really be screwed, as the EZ-Start essentially lays on the fuel tank. I am thinking about replacing this with my next pay. Anyways, the main topic of this thread is that I am having trouble getting it to fire up. At first I figured well maybe I just need to retune my carb, so I set it all back to default settings. It still would not fire up, but it acts about half like it wants to every so often. I got to thinking and thought well maybe my fuel line is pinched some where or it's just not getting the fuel some how. After looking all of that over it didn't seem to be the problem. There was fuel coming up to the end that slides on the carb. I'm leaning towards thinking it's something to do with the EZ-Start. However, I wanted to get another individual's opinion about it before I go fork out around $20 for a new EZ-Start.

Thanks for taking the time to read this if you made it through all of that!

Edit - Hmm...Does the way the piston rod faces make any difference in the firing? Not like top or bottom as there's only one way it'll fit that way, but like the two sides? I wouldn't think it would...
 
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exilestudios said:
Edit - Hmm...Does the way the piston rod faces make any difference in the firing? Not like top or bottom as there's only one way it'll fit that way, but like the two sides? I wouldn't think it would...
Click to expand...

Absolutely it matters. There is also a cutout portion on the piston skirt that must face the carb side of the engine or it will not run correctly.

There is also a very good chance that the piston and sleeve are scoured from the split connecting rod and you are down on compression.

I don’t know what aircraft aluminum rod you replaced the broken rod with ( the only aftermarket rod I know of for the 3.3 is the Davis diesel rod) but there should be a oil hole in the bottom. That hole should also face the carb side of the engine when installed properly.
 
Snook Man said:
Absolutely it matters. There is also a cutout portion on the piston skirt that must face the carb side of the engine or it will not run correctly.

There is also a very good chance that the piston and sleeve are scoured from the split connecting rod and you are down on compression.

I don’t know what aircraft aluminum rod you replaced the broken rod with ( the only aftermarket rod I know of for the 3.3 is the Davis diesel rod) but there should be a oil hole in the bottom. That hole should also face the carb side of the engine when installed properly.
Click to expand...

That's the aftermarket rod I'm talking about. Thanks for telling me this I'll tear it all back down and double check this. What about the EZ-Start sparking the way it is?
 
Even a brand new ez start will spark/arc if you continually run it and get it hot.
You should not run the starter continually for more than approx 5 seconds at a time. Often you will get better starts with just a couple bumps of the starter button rather than continual turning .

Nitro fuel is not that easy to ignite, it’s possible but improbable that an arcing ez start motor would ignite it.
 
AAAA+++ on what the Snook Man says.
1) You need to pull off the blue wire to your plug and use a glo plug ignitor instead of the EZ start for ignition.
2) You might have damaged your sleeve or piston during this event. I cooked off a rod a while back and put a new one in it and now for some reason I have to idle it high to keep it running. The stock rod in this engine is junk and it's a shame that we have to spend $40 to get a good one. (Shame on Traxxas!)
3) The starter motor will overheat if you crank it too long. The way I start my engines might help you. I do not prime my engines by putting my finger over the exhaust and forcing fuel to the carb by pressurizing the tank. (because I always do it too much and flood it). I disconnect the fuel line from the carb. I then hook up a piece of tube to the top of the tank and blow into it to fill the fuel line and then hook it back up to the carb. I use an eye dropper and put 4 or 5 drops of fuel right into the carb. This eliminates flooding for me and the engine usually fires right up. It should do the same for you "IF" your engine is not damaged. If your pinch is gone on the sleeve, or you have damage from the rod breaking, you're not going to get it to start and stay running. You need to take it back apart and have a real good look and see if you find anything.
 
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mrbones said:
AAAA+++ on what the Snook Man says.
1) You need to pull off the blue wire to your plug and use a glo plug ignitor instead of the EZ start for ignition.
2) You might have damaged your sleeve or piston during this event. I cooked off a rod a while back and put a new one in it and now for some reason I have to idle it high to keep it running. The stock rod in this engine is junk and it's a shame that we have to spend $40 to get a good one. (Shame on Traxxas!)
3) The starter motor will overheat if you crank it too long. The way I start my engines might help you. I do not prime my engines by putting my finger over the exhaust and forcing fuel to the carb by pressurizing the tank. (because I always do it too much and flood it). I disconnect the fuel line from the carb. I then hook up a piece of tube to the top of the tank and blow into it to fill the fuel line and then hook it back up to the carb. I use an eye dropper and put 4 or 5 drops of fuel right into the carb. This eliminates flooding for me and the engine usually fires right up. It should do the same for you "IF" your engine is not damaged. If your pinch is gone on the sleeve, or you have damage from the rod breaking, you're not going to get it to start and stay running. You need to take it back apart and have a real good look and see if you find anything.
Click to expand...

Thanks for all of the responses guys! Last night I tore it all back down and noticed I did have the rod in backwards, so I switched it around so the little oil hole was facing toward the exhaust. Also I checked out the piston head and my sleeve and it didn't appear to really have any damage. I took steel wool to the piston and the sleeve the last time I had it all apart and first replaced the piston rod. I just have to remount the motor today and see how things go.

Edit - Well I got it all back together and tried firing it up. Acts about half like it doesn't want to fire up. Also the EZ-Start put out a little puff of smoke which smelled weird. I don't trust this EZ-Start one bit since it was smoking that one time, so I'm going to end up replacing it like I originally planned.
 
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mrbones said:
well, by the time you get all this straightened out you're going to be real good at taking that engine apart because that hole in the rod should be towards the carb side of the engine. (as per post #3). Here's a link to rebuilding the engine.
http://traxxas.com/support/TRX-Engine-Rebuild-Instructions-0
Click to expand...

Ugh..You're entirely right. I misread what the other guy had said...I had it right the first time. I'll just switch it back around when I replace the EZ-Start. Thanks for the help guys!
 
I just have to ask the question, sorry.

Why did you put steel wool to the piston and sleeve?
 
mrbones said:
Maybe it's like honing a cylinder when you install a new set of rings except without the rings. ??? At least it will be nice and shiney............
Click to expand...

Well it was suggested by my dad, in-case the piston rod did do any minor scrapes, it would smooth it up some. He's done this with quads before, but yeah I didn't really think about if it would make any difference being nitro. I mostly used it on the piston head to clean it up a bit. I didn't run the steel wool through the piston sleeve that much.

Edit - Hm...also he was suggesting me to use 3-in-1 oil to lube it all back up, which I did. Was that okay advice or are you guys cringing again? xD
 
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I use 3 in 1 for reassembling. I use WD40 for after run oil. When you had the piston and cylinder out did you check to see if the piston tightens up when it gets near the top of the stroke? If it does, your pinch might be OK. If not................ a new piston and sleeve is about $50 on Ebay. OR you can send it off and have it squeezed (resized). I have a mechanic in Detroit that will do it for $15 plus shipping BUT if you're going to spend $25 to get a squeeze you might want to just spend another $25 and get a new one. . And this project of yours has turned into one just like I had about a year ago. By the time I replaced everything, I could have just about bought a new one.

And yes the steel wool deal made us cringe a little because the inside of that cylinder is chrome plated and we try the best we can to not let anything but the piston come in contact with it.
 
Last edited:
mrbones said:
I use 3 in 1 for reassembling. I use WD40 for after run oil. When you had the piston and cylinder out did you check to see if the piston tightens up when it gets near the top of the stroke? If it does, your pinch might be OK. If not................ a new piston and sleeve is about $50 on Ebay. OR you can send it off and have it squeezed (resized). I have a mechanic in Detroit that will do it for $15 plus shipping BUT if you're going to spend $25 to get a squeeze you might want to just spend another $25 and get a new one. . And this project of yours has turned into one just like I had about a year ago. By the time I replaced everything, I could have just about bought a new one.

And yes the steel wool deal made us cringe a little because the inside of that cylinder is chrome plated and we try the best we can to not let anything but the piston come in contact with it.
Click to expand...

Yeah, it still tightens up at the top of its stroke thankfully. I'm leaning towards converting it to electric later on when it dies after I finally get it revived. With all of the money I've already put into it replacing parts I could have already afforded the conversion, but oh well. I do like the smell of the nitro and hearing it roar. It's just a pain in the ass sometimes. Anyways thanks again for all of the input! :)
 
i dont think i would do a rebuild without doin bearings also. Then ur about 10$ away from a complete new motor..
 

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