Thread: Engine bay pics and questions - P38 inlet manifold and LPG

Assuming the back one is the crankcase ventilation the other is probably for a brake booster for non ABS ( for some different model?)

Funny my D2 Thor manifold (fitted to my RRC)has different plugs with only one large plug.
Regards Philip A
Although I don't have LPG, I agree that the mixer should be in series as per your drawing.

Excuse me if I'm wrong but by the look of your diagram you have to have the heater turned on for water to flow through LPG mixer ???

Originally Posted by 33chinacars

Excuse me if I'm wrong but by the look of your diagram you have to have the heater turned on for water to flow through LPG mixer ???

You can't turn off the water flow in a P38A.

My converter is Teed off the heater lines. I am also thinking of putting it in series (after) the heater core. The water will still be hot enough for the converter.

The set-up you have is quite adequate, your LPG converter doesn't need a huge flow. Normally if I use tees I use reducing tees and 10mm hoses to the converter. On some occasions where I have had to use 16mm hoses I have added a 6mm restrictor to the converter circuit to allow the heater to get adequate volume. Adding the converter to the heater in series is a mistake as the flow through many converters is too restricted. The heater system is also important to the cooling system, allowing a good flow to keep flow through the engine below thermostat opening temp. Where there is a bleed hose going via the throttle body to the radiator this has enough flow for a LPG converter.

Thanks Guys I've a few things too

Gary

BeeUtey you seem to know your stuff on all this (me virtually nothing!)... is it possible to stop a P38 with mixer from backfiring? Mine does it regularly on hot/warm re-starts. Especially on warmer days, but not exclusively. Is there a state of tune that can help or should I just be starting on petrol every time?

Originally Posted by DT-P38

BeeUtey you seem to know your stuff on all this (me virtually nothing!)... is it possible to stop a P38 with mixer from backfiring? Mine does it regularly on hot/warm re-starts. Especially on warmer days, but not exclusively. Is there a state of tune that can help or should I just be starting on petrol every time?

Two main things: plug leads and plug gap. Your leads should be the spiral core type and separated a bit more than the standard lead holders allow, ie remove them from their clips and space them a bit more, maybe use some cable ties. This reduces the amount of magnetic interference between the leads. Secondly the plug gap on GEMS engines should be 0.7mm, and the THOR engines 0.6mm. Any more and you will get regular backfires.
Lastly your petrol-start relay may not be wired properly so to give a shot of petrol on starting. It should operate every time you crank the engine.

Off the three Rangies I've had on gas, only one has every backfired. The first one, (87 3.9). I was told, when installing gas on the second one (93 3.9) that the secret to non backfiring Rangies was to relocate the hose that connects the rocker cover to the throttle body.

From the rocker cover it should go further up the air inlet track.

The 93 one had it inserted just after the air flow meter, as far from the gas ring as possible. It NEVER backfired.

My current 96 4.6 has an IMPCO 425 which has provision for the hose. So it is still a distance away from the throttle body. It has NEVER backfired...touching wood.

The theory is that the oily gasses accumulate near the throttle body and when you backoff any residual gas fumes join and you can have BANG!

Sounds good enough to a layman like me.

Theory aside, 3 LPG Rangies 2 plumbed as above those NEVER backfired.

That being said I also have taken all precautions as previously quoted in regard to plugs/plug leads, etc.

Just my experience, yours may vary.