My boss recently purchased a gp25 with a SOHC 4g63 Mitsubishi LPG engine. The lift ran fine when we got it but was dumping coolant into the oil and oil onto the floor from the head gasket. We pulled the head and sent it out for work and replaced the gasket. Once everything was ready to go the engin ran like crap and sounded very "bogged" down at idle. Hot or cold you can stall it by operating the lift or steering wheel at idle. For us to run it we have to keep it alive with the pedal constantly being feathered but it still doesn't run correctly. The engine acts like the timing is out but I've checked the timing multiple times and I can't get it any better than what it is now. The compression is 150 cold on all cylinders. We have tried a different LP tank too. The plugs are good with a gap of.030 and on my tester I'm getting a nice arch at.25". We disconnected the hydraulic pump and it still runs rough. The engine only starts when the throttle is opened at 50% or more. I have tried running the engine on starting fluid and gasoline and still runs like crap. I have even tried putting very small amounts of starting fluid in the intake while running and if a drop makes it in the engine falls on its face like I'm pouring water into the throttle body. I am at my wits end and can't figure it out. It seems like it's running rich but my knowledge of LPG systems is slim. I've checked the LPG filter and lockout and everything works and seems peachy with that. The system is a impco model 100 mixer, a cobra 101025 regulator, and a cobra model n-vff-30-2 w/p 312 psi fuelock. Any help is appreciated thank you.
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Alright I think that was it. Now at the 740-750 rpm range this thing isn't stalling for operation anymore. The rpm's dip to about 600 at idle while going lock to lock on the wheel. Thanks for your help guys.
740 rpm.
Vff30 is just a vacuum lock off. Liquid on or off.
I just hooked up my inductive rpm meter to the engine and its running around 500 rpm hot. When I take it up to 700-750 rpm it starts better (when hot so far) and doesn't die when turning or going forward. You wouldn't happen to know the rpm spec for idle. That may help.
Yes I have checked the timing and I have installed the distributor multiple times. All of the markings line up. I plugged the vac line to the vff and nothing happened. At the moment I'm cleaning the filter in it. It didn't have too much crap in it so I believe the fuelock works properly. I'm waiting to find something stupid that I missed but I have been unlucky on that adventure. is the vff just an on and off valve or does it have some influence on the flow rate when working properly.
Have you checked the cam belt timing AND the ignition timing? With it starting only with the throttle half open points towards it being too rich. Either the cobra has a problem and the pressure is too high or the vff has a internal leak and propane is being drawn into the manifold through the vacuum line that's connected to it. You can test the vff by starting and running the motor and then taking a pair of pliers and squeezing the vacuum hose. If you notice a differance, bad vff.
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