Hard to start when warm

[Suprglf]

It has been very interesting on my trx 3.3 to learn how to tune nitros. When i bought this tmaxx it was ready for the graveyard! Well I've brought it back to life (mostly) and it is running great, except......
When I get it up to running temp it will not restart if it dies until it cools for a minute or two. I've tried all spectrums of tuning from too lean to too rich and still have the same issue. It seems to have good compression even when warm and the glow plug still glows bright. I'm out of ideas.
Anybody know what could be going on with it?

 

[Martinoffi]

It has been very interesting on my trx 3.3 to learn how to tune nitros. When i bought this tmaxx it was ready for the graveyard! Well I've brought it back to life (mostly) and it is running great, except......
When I get it up to running temp it will not restart if it dies until it cools for a minute or two. I've tried all spectrums of tuning from too lean to too rich and still have the same issue. It seems to have good compression even when warm and the glow plug still glows bright. I'm out of ideas.
Anybody know what could be going on with it?

Hello, Suprglf. I have experienced this a few times with my Team Associated RC8.2. What would happen to me is if my engine decides to stall or if I shut it off after getting it to operating temperature, I would need to wait a few minutes for it to cool down before re-starting it. Just as you have experienced, otherwise it would not start. I doubt that it caused by a worn engine as my engine has about 2 gallons through it. Instead, I think that it is due to vapor lock. Basically, while an engine is running the fuel going through the carb cools it down a bit. As soon as the engine shuts off, and the fuel stops circulating, the temperature of the engine and carburetor will rise. This temperature increase will often pass the boiling point of the fuel causing it to vaporize/evaporate/or boil in the carb. Since there is so little fuel getting into the engine if it vaporizes, the engine will not start until the carb cools and the fuel re-liquifies. Trying to re-prime the hot engine may make it start, but sometimes even this wont work.

What I'm trying to say is; don't worry about it, because it is normal for this to happen with some engines, especially to those with full metal carburetor bodies, or ones that aren't designed to shield as much heat away from the carb.
-Peace

 

[Suprglf]

Guess I'll just deal with it, oh well.
Funny thing now is I tore down the carb and engine to the point the only thing left in tact was the rear bearing and, well I got it all cleaned and put back together and now it runs good but idles way high and the idle screw does nothing to slow it down, even with the slide almost completely closed. Even stranger is if I try to raise the idle with the screw, it bogs out and dies.

 

[cbaker65]

Guess I'll just deal with it, oh well.
Funny thing now is I tore down the carb and engine to the point the only thing left in tact was the rear bearing and, well I got it all cleaned and put back together and now it runs good but idles way high and the idle screw does nothing to slow it down, even with the slide almost completely closed. Even stranger is if I try to raise the idle with the screw, it bogs out and dies.

Leave it at the first setting you had with the idle ,an just richen the HSN a little to see if it
calms the idle down!...

 

[Suprglf]

Driving the ole tmaxx around yesterday and all of the sudden it lost all power and sounded like it was bogging from an overly rich setting. Pretty sure I need a rebuild along with engine and clutch bearings and several other things I've been neglecting for a while. Figured up over 200 bucks worth! Thinking about holding off for a while and considering getting into the 1/5 scale world.

 

[olds97_lss]

Cheaper just to get a new 3.3 and throw in it.

The traxxas engines tend to run hot, but with the composite carb, they are less likely to vaporlock. However, I never had great luck with the ez-start, at least on it's own. I used a normal heater with the ez-start. Eventually, I just do away with the ez-start and go pull-start.

When hot, try giving it WOT and pull the cord quick a few times with the heater on. Usually they come to life and you let off the gas.

 

[Suprglf]

Yeah you're prob right about just replacing it. I've got a clutch bearing thats shot and potentially a front engine bearing thats leaking so I'm gonna try those and a new glow plug as a last effort. At least those are cheap and can keep for later if it dont work. Thanks yall.

 

[2revo1maxx]

If you can't get it to idle down with the idle screw chances are you have the lsn set too lean. If the rpms kind of 'hang up' then drop a few seconds after a wot run chances are the hsn is lean.

Always try to tune the hsn on a warm engine by first turning it out until you notice it slowing down on a wot run. That is the easiest way to get it right.

Starting a hot engine is as easy as giving it some throttle.