Vanguard 31hp problem

[ssande]

I am using this engine on a custom vehicle and have run into a problem where I am apparently running on only a single cylinder. We noticed the exhaust note was different (running dual exhaust) from one side to the other. Upon closer inspection the exhaust from one cylinder was cool all the way up to the header pipe. That side is getting spark and sparkplug is working. Also checked compression on both cylinders and both are at 120 psi. So it appears there is some sort of fuel issue in the carb. I am still using the anti-diesel valve in the carb and am using an external electronic fuel pump. Is it possible the carb could be blocked so that fuel only flows to one cylinder?

Thanks for any insight before I tear into the carb.

Scott

 

[ILENGINE]

Do you have a single or two barrel carb. That would determine if it is a fuel issue. The other thing is the Vanguards on occasion like to bend pushrods for no apparent reason. So also check the push rods.

 

[Tinkerer200]

And check that there is spark at each cylinder. It has a coil for each cylinder. IF no spark on one cylinder, unplug the kill wire from the base of BOTH coils. IF you have spark now, problem is in the Kill Wire Harness, bad diode.

Walt Conner

 

[ssande]

Do you have a single or two barrel carb. That would determine if it is a fuel issue. The other thing is the Vanguards on occasion like to bend pushrods for no apparent reason. So also check the push rods.

Thanks for your response!
I have compression, so I would think a bent pushrod would be unlikely to keep it from firing at all on that cylinder. Not sure whether the carb is a single or two barrel carb. It is a single air inlet, but there appears to be some symmetry on teh carb that may suggest a 2 circuit design? Anyone have a service manual with a break down of the carb?

 

[ssande]

And check that there is spark at each cylinder. It has a coil for each cylinder. IF no spark on one cylinder, unplug the kill wire from the base of BOTH coils. IF you have spark now, problem is in the Kill Wire Harness, bad diode.

Walt Conner

Thanks for your response!
I have spark at both cylinders and the plug on the side that is not firing is dry.

Scott

 

[Tinkerer200]

I can send you a Service Manual for your engine IF you like. Address below, put in proper format and remind me engine model number and what you want.

Walt Conner
wconner5 at frontier dot com

 

[bertsmobile1]

Pull off the rocker covers and check the valve operation.
Something like a bent exhaust pushrod will give good compression reading but won't allow fuel into the cylinder

 

[ssande]

I finally had some time to post an update regarding the engine issue. Turns out that one of the orifices in the carb was plugged. After disassembling and cleaning everything out it runs like new. In fact, this engine never started easy and ran rough. It is likely that the carb was plugged from day 1. The material I pulled out almost looked like some sort of adhesive. Thanks to everyone for their responses - much appreciated! Here are some pics I took which show the culprit. Also, the float inlet needle also had the same material in it.

Scott