Posted by JDEM on March 02, 2018 at 12:23:18 from (174.230.9.47):
I have a 4WD Suzuki there that is driving me nuts. Actually -I have two in my shop with problems - but I will stick to one that has me most perplexed.
1995 4WD Suzuki King Quad 250 cc. Four-stroke-cycle engine. Ran fine when I pulled it into my shop last Fall. I did a lot of mechanical drive-line work and NO engine work. I made one change to the fuel system by changing the fuel-valve under the tank.
Now - it will not start. At this point - I refuse to believe the fuel-valve is the problem. But like I said - I am beginning to lose my mind on this thing.
Here is how the basic fuel system operates. Fuel valve that I changed has two positions. "Run" and "Primer." It has a vacuum-gas-shut-off-valve. So when in "Run" position - no gas can flow without engine vacuum. When in "Primer" position, that valve is bypassed and gas runs out freely. I tested the valve and it works. From there - the fuel delivery line goes to what Suzuki calls a "vacuum fuel pump." My factory service manual gives NO info on it other then " if it fails, replace it."
I guess I do not understand how this pump is supposed to work. I have worked on similar looking pumps on two-stroke-cycle engines that worked off of crankcase impulses. This is however a 4-stroke-cycle. The port on the intake manifold it hooks to provides a steady 6-7 inches of vacuum and no pulsing I can perceive.
I took the fuel-pump apart and all looks fine. Diaphragms are soft with no holes. Two check valves look fine. Put it back together and tested it with a hand-held vacuum-gun. A steady-vacuum and it pumps no fuel. A on-and-off pulsing vacuum and it still pumps no fuel. BUT - I then tried blowing air into it, off and on with pulses. This way it pumps lots of fuel.
So I am almost at the end of my rope. Seems I never had to think this hard before about a pump like this. I am very temped to put on an electric pump but it is hard to find one that really runs at low pressure. I have tested a few rated at 2-4 PSI and they ran higher. Likely too much for this carb.
I stuck a gravity feed tank on top of the engine and it starts and runs fine. The built-in tank sits near at carb level and needs a pump. So - I am getting a mental fog here. Suzuki does call it a "vacuum" pump and not an "impulse" pump. It hooks to the intake manifold and I cannot figure how there should be any impulse there anyway. Just a steady vacuum.
Somebody here got an idea about what I am missing here?
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Today's Featured Article - Hydraulics - Cylinder Anatomy - by Curtis von Fange. Let’s make one more addition to our series on hydraulics. I’ve noticed a few questions in the comment section that could pertain to hydraulic cylinders so I thought we could take a short look at this real workhorse of the circuit. Cylinders are the reason for the hydraulic circuit. They take the fluid power delivered from the pump and magically change it into mechanical power. There are many types of cylinders that one might run across on a farm scenario. Each one could take a chapter in
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