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Long crank time, problem solved.

4081 Views 7 Replies 4 Participants Last post by  Okie
1986 Honda Fourtrax 350. After setting for several days especially in cold weather the engine had to be cranked on and off over several times and finally would hear the fuel pump briefly click few times and it would start. Would not ever start until the fuel pump eventually ran. The fuel pump normally only operates on this model unit when the engine cranks or is running. Choke is operating ok also, just not getting enough fuel pump prime to the carb.

I noticed if I applied 12v to the fuel pump run wire manually for a prime until the fuel pump stopped clicking the cycle would immediately start. I installed a fender mounted primer switch like this one (see ebay number below) fused at 10 amps and works great. Cycle will now set for long time and immediately cold start after getting the manual fuel pump prime.

Note this switch is wired to apply 12v to the pump hot wire only after the normal regular feed wire is disconnected. (no backfeed thru the cycles regular wiring)

ebay number 302323003823
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I'm not familiar with your model of ATV, but normally there should be enough fuel in the bowl of the carburetor for starting. Isn't that the case with your machine?
The fuel cannot evaporate out of the bowl of the carb because it is sealed in there by the float needle and seat. Here is what I think is causing the problem on these old machines with diaphragm style fuel pumps:

Diaphragm pumps have two reed valves that act as check valves so the pump can function. Also, when the machine is off, the reed valves hold the fuel in the discharge line and fuel bowl of the carb. Over the years, the reed valves get stiff, curl up, erode, etc., to the point where they don't seal well. This allows fuel to leak from the fuel bowl, through the reed valves and back to the tank when the machine is off. This is the root cause of the problem. With the fuel missing from the bowl and fuel line, the pump has to run for quite a while to restore that fuel during a cold start. This is made even more difficult because the pump isn't operating as efficiently as it would be with good reed valves in place.

The way to repair it is to either install a pump repair kit, which includes a new diaphragm and reed valves, or just buy a new pump. I don't know if either of those are available any more due to the age of the machine, though.
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