Fuel not getting to engine

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sleeper341

RC Newbie
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Location
UK
RC Driving Style
  1. Bashing
Ok, I just picked up a secondhand truggy. I've got 4 other nitro's so have a bit of experience but I just cannot figure out what is going on with the one I just got. Here's whats happening:
Blow down fuel line to prime carb ok, engine fires up and runs for about 20 - 30 seconds then dies. It would appear that the exhaust is not putting enough pressure in to the fuel tank to push the fuel round to the carb.

If I put my finger partially over the exhaust then the engine will tick over great but after i remove my finger it dies again.

I tested for air leaks around the fuel tank, exhaust, manifold, carb etc but can't find any evidence of an air leak.

Compression is ok, not the best, but I've run engines with less.

Any ideas what could be causing this?

Thanks in advance for any help.
 
when you say fuel tank, do you mean, lines and the cap? the cap may need a rebuild if its and older car.
 
when you say fuel tank, do you mean, lines and the cap? the cap may need a rebuild if its and older car.

Sorry, the whole fuel tank is well sealed. Tested lines, cap and the seal where the top of the tank is joined to the bottom.

It seems that either the carb isn't sucking in enough air in comparison to what is 'blown out' from the exhaust or the exaust 'nipple' where the fuel line attaches to put pressure in to the tank isn't outputting enough pressure unless i partially cover the exhaust.
 
Every RC can react differently from losses of compression. It sounds more and more like your just not producing enough backpressure to keep the engine fed. How much fuel has the motor seen and what nitro %?
 
What about when you open the throttle? Is your idle gap set at 1mm? How old are the fuel lines? I've worked on a few trucks where the line seems fine but I have to replace them to get the fuel flowing.
 
Same here did all that and still nothing. A quick question if i pour a little nitro in the carb it should at least fire and burn what i pour in right?
 
It seems that either the carb isn't sucking in enough air in comparison to what is 'blown out' from the exhaust or the exaust 'nipple' where the fuel line attaches to put pressure in to the tank isn't outputting enough pressure unless i partially cover the exhaust.

Most nitro engines have a cutout on the piston skirt that affects the timing of the engine.
If perhaps someone had it apart and installed the piston backwards during re-assembly
The port timing would be way off and the intake/exhaust ports can not do their job. The exhaust pressure out the exhaust port to the pipe, and thus to the fuel tank is reduced and the fuel mix in the crankcase is pushed backwards for a short amount of time and will blow back out through the carb creating an impossible to tune and hard to start engine.

It may not be your problem but I would have a look see. Pull the backplate and with the piston at BDC there should be a cutout on the piston skirt that if present must face the front (carb side) of the engine.
 
I didn't get a chance to look this weekend but I'm going to try some narrower fuel line plus I have a spare exhaust that I'll try to see if its that. If both still fail to boost pressure or feed the carb with fuel then I'll strip down the engine and clean it up. It could be as simple as gummed up needles in the carb. I'll let you know if i have any success.

Thanks for all your advice guys.
 
id check the nipple on your pipe to see if its plugged.
 
I've got the same problem with my thunder tiger ssk just got it and can't get it to start its not pulling any fuel thow any ideas????
 
maybe the carb is gummed up a bit ...happens to me sometimes when i dont burn all the fuel out of the carb ....unhook the fuel line from the tank and blow in the carb while its open to full throttle ..air should go through it ..if not , then you have a clog ..lol..clean the carb
 
Hi I have a problem I've got my ssk running but the wheels dont spin any ideas??
 
I always get a giggle from these
 
That is too funny. I never looked at the date.LOL I just have to remember new posts. Upper right hand side. I must have been bored. I'm still looking for my resonator tube and need a couple of tires.
 

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