Hyster H50XM:
Poor running Mazda 2.0 LPG. Update.

Hello forum. I want to share my experience on a Mazda 2.0 LPG since I got a lot of help from this forum. This engine would seem like it was running out of fuel after a full throttle run but, if you let it idle for a short time, the power would come back. I rebuilt the impco regulator and lockout valve and cleaned the mixer( carb) but that did not help. I also could not start the engine after it sat for a while due to weak spark (yellow spark). I searched the forum and found some ideas to try and here's what I did. I read that someone had the same fuel starvation problem and it went away after he changed the head so I removed the head and found that the intake valve seals were leaking badly and had large amounts of carbon / oil deposited on the valve stems that were also making the valves stick. No doubt that the deposits were also affecting engine vacuum and the propane system needs good engine vacuum to work properly. I also found in this forum that there is an oil pressure switch that will kill the coil if your oil pressure is too low. Sometimes this switch goes bad. I ordered a new one from Hyster and found that the old one which was a single wire switch, had been replaced by a newer version which had two wires( external ground). I had to replace a bad starter ring gear so, I removed the engine and decided to overhaul the whole thing. Hyster parts were very expensive and just getting part numbers were a pain in the *** so I got most of the basic engine parts like gasket set, rings, crank seals, timing belt, and bearings from O'Rileys using a late 80's mazda 626 as a base. Certain other parts I like new radiator hoses, oil pressure switch,and ring gear I got from Hyster. Note, the piston rings were stuck in the grooves on three of the four pistons with the same sticky deposits that were on the valves. It seems like the same gooey stuff that builds up in the LPG regulator goes in the engine over time other wise, the engine had very little wear for the high amount of hours it has on it and was pretty simple to overhaul. I did not really have the replace the bearing as they were in good condition but, I replaced them anyway. I replaced the engine into the lift, filled the fluids,primed the oil system, checked the spark ( very nice blue) and, it started right up. After adjusting the timing, I took it for a test run/ break in and was very happy with the outcome. I feel I owe it to this forum to post this thread because there is a lot of useful information in this forum if you spend some time searching and some of my problems, like the poor engine vacuum, applies to all engines and LPG systems. I would like to thank the people who replied to my post asking how to remove the engine from the trans also. Very helpful forum. Thanks.
  • Posted 20 May 2015 17:48
  • Discussion started by Jamo
  • Hawaii, United States
Showing items 1 - 2 of 2 results.
NICE! Good feed back. I have one doing this with 1700 hrs on it. I will check the vacuum. Thanks.
  • Posted 11 Feb 2016 13:58
  • Reply by chuck_c
  • British Columbia, Canada
I had 2 of these Mazda motors, with high hours, have the problem with lots of carbon on the valves. They were hard to start and were miss firing. The carbon was this thick, black, sticky, sooty stuff built up under the heads of the valve. Pieces were starting to break off and getting stuck under where the valve seats. I've never seen a carbon problem that bad. They were LP powered and didn't show any signs of smoking. I'm not sure what caused it, motor oil or bad LPG. Anyway, cleaning and a valve job made everything right again.
  • Posted 21 May 2015 03:30
  • Reply by mrfixit
  • New York, United States

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