Hyster H50XM:
Will not fire

The main problem right now is the engine will not fire. It turns over and sounds like it has compression. 1999 Hyster H50XM SN:H177B10160W Engine- 3.0GM propane.

Has new tank of propane, has spark (new plug wires), new carb/mixer diaphragm, charged battery, new alternator (with all new wires from battery to starter, fused, grounded and still not charging).

sounds like a fuel delivery problem. I do not know a great deal about propane air mixing assembly's. I see two units here between the LP tank and air intake. I have yet to troubleshoot them although I do know the one closer to the water pump frosts over while running.

Any tips where to start or a link to service or troubleshooting manuals. thanks in advance
  • Posted 23 Nov 2016 07:42
  • Discussion started by Vantech
  • Pennsylvania, United States
Showing items 1 - 7 of 7 results.
With those compression readings I would guess you had a backfire through the intake. Check the diaphragm in the mixer. It sounds like you have some sticky valves. This can cause backfire. See this quite a bit on the Mazda engines.
  • Posted 4 Apr 2017 04:25
  • Reply by BREWSKI
  • Nebraska, United States
The driver today heard a "pop-pop-BANG". the engine will no longer fire. after some troubleshooting I assume it is a fuel delivery problem. I would need some basic info on how to troubleshoot between the LP tank and the fuel/air mixer.

here is what I have so far:
motor turns
New plugs/Wires
New distributor/rotor
Ignition provides spark to each plug
new IMPCO diaphragm
-cylinder 1) 70psi
-cylinder 2) 125psi
-cylinder 3) 142psi
-cylinder 4) 90psi
-fuses good

now going to attempt to figure out the following fuel system:
LPG cylinder
adaptor through chassis
12V fuel light switch?
(regulator?) with vacuum line
into (vaporizer?) with coolant hoses
into 12v shut off switch
into mixer-throttle body (vacuum line)

I took the main fuel line off just before the shutoff switch and turned over the engine with no fuel present.
  • Posted 4 Apr 2017 03:31
  • Modified 4 Apr 2017 04:42 by poster
  • Reply by Vantech
  • Pennsylvania, United States
There is a problem with your charging system Normally idle voltage should be 13.2. Throttled max should be 13.8-14.2. 12.35 will not keep your battery charged.
  • Posted 24 Nov 2016 07:54
  • Reply by BREWSKI
  • Nebraska, United States
I changed out all 4 spark plugs with new. (one of the old ones had a smaller gap than the others) and now the motor fired up and is running more smooth than it has for a while. The plugs were only two months old and were taken out and wire brushed last month.

When I pulled the head off two months ago, I replaced the radiator as well as ran blue devil through the engine. This put a clog is the heater core coolant line and caused it to blow. I washed out the heater and replaced the coolant line. The lines to the radiator are in good condition and the thermostat is new after the blue devil. I will check the LP line into the truck for leaks.

Do you know at what voltage the alternator should be charging the battery? My battery says:
12.5 standing
10.5v starting
12.35v running Idle
12.35v running throttle up
12.35v with heater, lights, etc.
  • Posted 24 Nov 2016 01:59
  • Reply by Vantech
  • Pennsylvania, United States
It sounds like the regulator is frosting. There are 2 reasons for this. The first is low coolant level or plugged water lines. Second is an external leak of fuel at the regulator.
  • Posted 24 Nov 2016 01:12
  • Reply by BREWSKI
  • Nebraska, United States
The unit in line with the feed hose is not frosting. The second unit located lower towards the motor is the one in question.

also upon taking out the spark plugs today, there is a considerable amount of carbon buildup on the tips. I cant seem to find from where this buildup is coming, as we pressure tested the cylinders, as well as took off the head and checked that a few weeks ago.
  • Posted 24 Nov 2016 00:33
  • Reply by Vantech
  • Pennsylvania, United States
If you have spark and the truck will not start it generally is a fuel problem. The unit that is frosting, is it the first component in line from the feed hose?
  • Posted 23 Nov 2016 08:39
  • Reply by BREWSKI
  • Nebraska, United States

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