TheSamba.com :: View topic

Mon Sep 14, 2009 4:29 pm

I have a 1915cc with a single Weber on top. Very recently, I have noticed that the engine appears to be running extremely rich... It has started to run hot to the point of starting to burn the powder coat :shock: as well as spit out black soot so I'm pretty sure that there is some issue with over-carburetion. Fuel pressure regulator appears to be in spec. Around the same time, I also noticed that my fuel pump sounds like it is failing to prime correctly (just keeps running hard--never quiets down like it should).

I guess my question is whether or not a malfunctioning fuel pump could cause the engine to run extremely rich all of the sudden like I have described. Theoretically, I would imagine that if the fuel flow is never stopped after the float bowl fills that all the extra fuel would go right to the cylinder and cause a rich mixture.

Obviously, as you can see from the above post, I am still quite a newbie at all of this. Just trying to learn a little more about all of this stuff. Any ideas as to where to start to fix this issue would be of great help.

Thanks,

Mon Sep 14, 2009 6:01 pm

your checked your pressure regulator with a gauge? 2.5/ 3.0 lbs is max for an IDF
also, do you have heat to your manifold? if not, & the weather is turning cooler where you live,, that could start to give you tuning problems

Mon Sep 14, 2009 7:16 pm

I've had similar conditions suddenly occur when I got a bit of crap in an air passage in my carb. 34 Pict-3, but could be a similar problem.

Kyle

Mon Sep 14, 2009 7:28 pm

if it is getting hot it is probably running to lean, fuel cools the cylinder. at least that what ive been told, be careful you'll end up burning a piston. ramblings of a mechanic.

Mon Sep 14, 2009 7:31 pm

Sounds like you are running Lean more than rich, Rich mixtures cause the combustion chamber to cool, not heat up. Also, from what you said about the pump, they are noisey when they aren't pumping and running dr y, they quiet down when they pump.I have never seen a fuel pump Over pump fuel, especially if your needle and seat are working properly. I would definately check the Carb but make sure the Idle jets and emulsion tubes are clear. You may have other issues though..

Mon Sep 14, 2009 8:55 pm

Ed Carp wrote: if it is getting hot it is probably running to lean, fuel cools the cylinder. at least that what ive been told, be careful you'll end up burning a piston. ramblings of a mechanic.

That's 100% true. If it is running hot, it is running lean. Look at your spark plugs.. Black and sooty=rich, white=lean, brown=good. Unless you are running rich AND your ignition timing is wayyyyy off that could cause a hot condition too.

Tue Sep 15, 2009 5:15 pm

Thanks for the reply guys. I'll pull the plugs and take a look at those. Maybe that will give me an idea as to what is going on. I guess I'll pull the carb off too and give it a good cleaning and see if that helps anything. I don't think the timing is off. The engine runs great other than burning my powder coat and spitting out a bunch of black soot.

Tue Sep 15, 2009 5:38 pm

That's really weird. Look at your plugs for sure, but it sounds like a carburetor malfunction. Check your float level. Also, how long have you been running that powdercoat? If not for very long, you could just be getting a hot spot so to speak..