rcboxer

OKay, im not sure why my lst will not prime. my hoses are good, i dont think the primer leaks, no exhaust leaks, and my truck does not like to idle and i have the carb settings correct. Can anyone think of anything else to look for? thanks

bentgear

How new is the engine? Is it still breaking in?

Now much info to go on but I would look at the glo plug or the low speed needle settings. If its new you may have to lean the low speed needle from the factory settings to get it to idle.

And if it truely is lack of prime, ie. no fuel getting to the carb then make sure the fuel filter is screwed together tightly.

Ed M.

jon2

Check your fuel filter for any debris. You may have some stuch in there. Remove the line before the filter and try priming it. If you have fuel coming out then try it after with the fuel filter on. Let us know what happens.

rcboxer

the engine has almost 2 gallons through it. i have tried a couple glo plugs. i"ll try to mess with the low speed settings a little more. the fuel filter i actually took off because i thought that it was the problem but i guess not. could anything on the engine have a leak to stop it from priming. thanks

offrdmania

When you are turning over the motor with the starter, put your finger over the exhaust outlet, that will casue vacuum in your fuel line

DaveG55

I bet there's a leak in the fuel preasurization system somewhere. That's most often the cause of priming problems.
The most common problem is the rubber seal at the tank lid. Other areas to check (I know you've already checked some) are the block to header gasket, the header to pipe seal, the preasure and fuel line, fuel filter and the tank itself (primer/fittings/cracks/holes).
It could also be a blockage somewhere like the fitting in the pipe where the preasure line attaches.
Find your leak/blockage and the truck start easier and idle better but you will probably have to fine tune the engine again as an air leak anywhere will affect the engine tune across the board.

bentgear

Lets think about this a minute. If everything from the tank to the engine and the engine itself is in good shape then even with the tank lid held open the engine will draw fuel and will run. Not good, but it will crank and run.

You have ruled out the filter and the line. Is the oring on the end of the primer swollen up not letting fuel pass into the line. Easy to check. Unhook the line at the carb and hold it below tank level. You should have a good stream of fuel coming out. If you don't the problem is in the tank.

There are three possibilities at the carb. Is the carb seated fully on good orings and is the pinch bolt tight? Is the banjo fitting held in place tightly with no leaks, air or fuel? Has something passed into the carb blocking the fuel flow between the high speed needle and the carb venturi? Plugged off air filter, remember that first an engine is just an air compressor, no air in, no vacuum.

That pretty much covers the fuel system and if its none of these then we get into possible engine problems. Front crank seal gone out not allowing the piston on its upstroke to develope a vacuum to pull fuel into the crankcase. Backplate of engine loose or gasket/oring bad not allowing piston to develope a vacuum, could also be from a large amount of slack in the starting system.

Now for the bad part. Bent rod not allowing full piston travel. Worn piston/sleeve not allowing vacuum to form on upstroke. Hole in piston. Something else amiss in the engine causing problems.

That should keep you busy checking for a while.

Anybody think of anything else?

Ed M.

rcboxer

well thanks for the replies everyone. i found the problem, i took my motor apart and the piston had two BIG gashes on each side of it along the sleeve. there were metal chunks inside of my engine and i had no compresion AT ALL [].oh well mabye its time for a MACH .28

SublimeJason

Did you find what Caused the Gashes?
Theres no way your Engine should only last 2 Gallons....I have 10 gallons on one of my Mach 26s and it Still Run Good...

bentgear

Almost be willing to bet if you check you will find a wrist pin keeper missing, maybe both................

Ed M.

DaveG55

Give Horizon/Dynamite a call. One of my Machs barley lasted 6 tanks. They replaced it for free. They did not ask for recepit, just had me strip the motor down and send it in. Even if you decide to put a different motor on it never hurts to have a spare. The new Mach seems to have more power and run better too.
Check out this thread to see what my engine looked like.
http://www.rcuniverse.com/forum/m_3436397/tm.htm
Here's the info for Horizon
Horizon Hobby, Inc.
4105 Fieldstone Road
Champaign, IL 61822

Main Phone: (217) 352-1913
Toll-Free: (800) 338-4639
Support Phone: (877) 504-0233
Sales Phone: (800) 338-4639
Fax: (217) 355-1552

rcboxer

yep one of my wrist pin clips is missing.

bentgear

I better go find a good high stakes poker game latter on tonight!!!!!

Ed M.

SublimeJason

Yea that was a Good Call!