Re: Re: Re: Hard starting propane engine

Posted by Jon Hagen on December 23, 2005 at 17:46:56 from (69.26.18.11):

In Reply to: Re: Re: Hard starting propane engine posted by grabatire on December 23, 2005 at 14:04:52:

Thanks for your good description of how each part of the fuel system reacts,it makes it easier for me to visualize what is is going on to cause the hard starting.

1 the fuel lock sounds fine,It opens quickly and if it flows the full capacity of the line/fitting,then the internal filter is clear.

2 The vaporizer/regulator is working as it should. No propane should come from the secondary stage untill a slight vacuum signal from the mixer/engine sucks the secondary diaphram in and opens the secondary gas valve. One thing to check here,the secondary regulator diaphram must be very soft so the slight suction from the engine can open the valve and feed propane vapor to the engine. Oil heat and age will harden up the diaphram and cause hard starting.

3 I assume the IMPCO mixer is an air valve type model 300 or 445 ? The air valve is an aluminum cone that fits into a seat machined into the base of the mixer. The air valve is lifted off it's seat by a diaphram in the very top portion of the mixer housing. You can test this valve for free operation by placing a couple fingers under each side of the top diaphram housing and lifting gently. You should be able to compress the diaphram and lift the air valve off it's seat aprox 1/2 to 1 inch. When you release it,it should close smoothly and completly. If a hard diaphram or sticky air valve slide prevents tight closing of the air valve,then no vacuum signal will be generated in the 1 inch fuel hose,and no fuel will make it's way to the engine.

One last thing to check,IMPCO mixers have an "economizer" valve in the mixer vapor passage where the 1 inch vapor hose attaches. This should be adjusted to the full open/rich position for over the road use. It will be a threaded hex screw with a spring over the shank on a model 445 mixer,it is located in the side of the mixer housing opposite where the 1 inch vapor hose attaches. Turn this screw counter clockwise untill the plug is totally backed out of the gas passage ( 10 turns ccw or visual through the big gas passage. On a model 300 mixer,it is a little barrel valve in the fitting where the 1 inch vapor hose attaches,set it to max rich(the valve has a R and L mark).

Please post back what you find,we can get this beast working right. The 445 mixer is by nature a bit of a slow starting beast,but not nearly enough to kill the battery.

Try cranking 5 seconds with the throttle closed to open the fuel lock,then wait 10 seconds for the fuel to vaporize,then press the primer button and after 5 seconds crank the engine at 1/4 to1/2 throttle while continuing to hold the primer on untill the engine starts. It should not take more than 10-15 seconds cranking time to start.

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