cummins driver

My Feedback: (31)

The first time I started it, it was REALLY,REALLY lean, and went wide open for about 5-10seconds, and every since then it never had any power, and always died if you tried to take off fast.Now i cant even get it to start, and it is getting fuel, has a good glowplug, and is cranking over plenty fast, but it wont even hit.It also has good compression, which is what blows my mind if there is something wrong with the motor. I have not run it in probably over a year, but would like to get it going so i could drive it if i knew what was wrong. Like i said, i hadnt even broke it in yet, and it was way to lean the first time i started it, so im wondering if that did something? But like i said, it DOES have good compression?

miserynitro

My Feedback: (8)

it could be either
a) plug isn't getting hot enough... signs are, not all the coils glowing bright... maybe 2 or 3 of the bottom coils not even glowing
B) Too much fuel in the engine..... signs lots of fuel coming out the exhaust... maybe prime less, or turn the needles in slightly to get it started then back them out...

If the motor has compression then it should be fine...

teamsquirreltail

If it was really lean from the factory, I bet it has an airleak, that is unless you messed with the needles before break in?

Nitroaddict

what u have described sounds like a classic example of blow by. this is usually caused by what u stated happening, running WOT in too lean of a condition. although it may have decent compression when cold, once it heats up, it all goes away. i would take the piston/sleeve out, and check to see if it still pinches about 1/2 inch from the top. if it doesnt, then u know its worn, and will need to do a rebuild, or purchase a new engine

hairnutz

Even if it was very lean, the engine shouldnt be damaged by only running it 5-10 WOT. I stress the shouldnt.

If it stalls right away when you give it the gas, it sounds like your tuning is off. You need to see if it is sluggish right before it stalls, or if the RPMs go up very fast and it stalls very quickly. You could have your needles set too lean still on the high speed.

It helps to know the brand / model of engine you have - you should be able to get the factory needle settings from someone or the web and start from there.

Also, make 100% sure your glow plug starter battery is fully charged and that your plug glows bright when connected to it. Also make sure your starter box batteries are fully charged if you have one - sometimes it may sound like its turning fast enough when its not. The faster it turns, the easier it is to start.

dbow

My Feedback: (1)

I have never seen an engine die from what you describe, I have seen cars go WOT across the subdivision and down the street the first time they were started. While this does not help the long term life of the engine, it should not have damaged it to the point of it not running, and should run fine, it just may not last a very long time.

I suspect tuning issues or something other than a piston and sleeve problem. Check everything and re-set your needles.
If all else fails take to the shop and let the gurus get it going for ya.

Dbow

cummins driver

My Feedback: (31)

Thanks for all the info guys. It is a tower hobbies nitro st-15 with the factory engine(bought before i knew much about hobby r/c's). The stop screw in the carb fell out, and i put in a homemade replacement that does pretty much nothing but close the hole it fell out of. The motor always seemed to run VERY rich when i had it running; even with the needles almost all the way in. If i remember right, it wouldnt run with the needles out very far at all. My pull starter messed up, so i made a homemade drill starter to replace it, and the drill was on high turning pretty fast, so im sure it was spinning fast enough to start. The stock tires got wore out from just driving slow on black top, so i bought some masher 2000's for the back, and they have practically no use on them, because thats about when it quit running.When i first got it, i messed with the needles because it was spewing gas out around the head, and wouldnt even start. Finally i figured out it had a loose head bolt, so i tightened them up, and thats why it was so lean when i first started it. It did run for a little while, but it never had the power it should have had. I drove a 2.5 nitro rustler, and the difference was night(pitch black) and day(blinding sun). A new motor is $80 for a stock replacement, but id probably get a better one if i bought a new motor. I would rebuild this one if i knew it would run right then. Thanks for all the help guys. I may pull it apart in my spare time someday, and check it out.

dbow

My Feedback: (1)

Sounds like this motor has a little more history than I thought initially. If I were you I would buy another one and make sure to take care of it properly. A failsafe of some sort or a spring on the throttle would not be a bad idea.

Dbow