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Testing an LPG Petrol start control module. (Parnell PPSM5) 

 

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 Post subject: Testing an LPG Petrol start control module. (Parnell PPSM5)
Posted: Sat Oct 02, 2010 3:30 pm 
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Hi all,

I'm trying to find the problem with the gas system in a car I'm rebuilding (EF 6cyl swagon). At first that was just a case of just tracing all wiring to make sure it's all connected correctly, testing that the power from the p/g switch was getting to the relevant places and making sure all earth points etc are connected.

All of the above tests passed with flying colours, so I'm looking more closely at the actual modules.

Power is running from the petrol/Gas switch down to PMSM5 module (red wire), which should allow the car to start on petrol, then delay it for a predetermined period before switching to gas (I think)

If I manually trigger feed 12V to the gas safety valves (by the grey wire on the PPSM5 that goes out the firewall to the valves), all three open and gas flows, so the lines/valves etc themselves are fine. In addition the relay hooked up to the ECU wiring (which near as I can tell cuts off the power to the fuel pump when gas is running) also triggers. So that side of it is correct also.

My confusion is with regards to what the system should do if the car is already running on petrol and up to temp when it is switched to gas, the start control module should do essentially nothing right? just feed power to the valves kill the fuel pump and let the lambda module run the show.

That doesn't appear to be happening, when switched to gas, while running and warn on petrol, it just dies, the module doesn't feed a continious voltage out of the grey wire to the valves it has a tiny pulse and then drops to zero (as measured by my fluke mm)

How does the module know that the car is good to switch to GAS? does it have a temp pickup I've not found? or does it just work out the car is running based on the injector pickup it has and start a timer on that?

Anyone got any tips or knowledge they'd like to impart, I'd certainly love to hear it.

Once I get it running, I am taking the whole car to a gas fitter to have it checked over and the tank re-stamped, but it will be massively cheaper for me if the system works when I get there and he doesn't need to diagnose it.


ta

Frank
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 Post subject: Re: Testing an LPG Petrol start control module. (Parnell PPSM5)
Posted: Sat Oct 02, 2010 4:11 pm 
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Temp pickup for most gas conversions happens at the bottom of the thermostat housing, where they tap into it for a converter water feed.

Cheers

ToranaGuy

 

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 Post subject: Re: Testing an LPG Petrol start control module. (Parnell PPSM5)
Posted: Sat Oct 02, 2010 4:26 pm 
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Hi ToranaGuy, thanks for jumping in.

yeah, that was the first place I looked but nothing is split in.

I don't think this module is as smart as that. Looking at the front panel the terminals are identified somewhat and this is what I see. In brackets I've put what I know about them.

-- Injector simulator.
-- Injector simulator.

-- LPG SW. (RED, positive feed from petrol/lpg switch)
-- VLVE. (Grey, feed out to all relays/valves)
-- GND.
-- TPS.
-- Injector (relay)
-- Crank Inhibit (relay)
-- Fuel pump (relay)
-- Points (updated, split into pink/blue wire at ECU, tacho wire?)

The last couple of things are a TPS adjustment pot and a couple of LED's labelled TPS and RUN.

I am going to follow the points wire and see where it goes as obviously an EF has none. (UPDATE, turns out points runs to pink with blue trace at the ECU.. looking that up now.)

I also took the module cover off thinking that perhaps the circuit board micro relay on the grey wire was dead, but manually tripping the relay resulted in a very good and solid connection between the LPG switch in and the grey power out, so the relay is fine too. I am now thinking that perhaps whatever method this module uses to determine the engine is running is not getting a signal.
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 Post subject: Re: Testing an LPG Petrol start control module. (Parnell PPSM5)
Posted: Sat Oct 02, 2010 5:32 pm 
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frankieh,

Your welcome dude. That's what the forums are for.

Your lpg system should have a temp sensor of some sort or a signal from the factory one, if it knows to kick over to LPG after a certain temp is reached.

It should also be using a signal from the coil to work out the engine is running. Have you had a look at the wiring at the coil? If not there, check at the firewall where the LPG loom would have been spliced into the injection loom.

Cheers

ToranaGuy

 

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 Post subject: Re: Testing an LPG Petrol start control module. (Parnell PPSM5)
Posted: Sat Oct 02, 2010 7:28 pm 
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That is the weird thing.. there are two modules, one is the lambda module for normal lpg running, and the other is the petrol start control module.

That has an adjuster on it that says:
"Petrol Start Time Adjust" "Factory set to 1.0 sec"

Looks like it goes from 1 to 2.5 seconds adjustment time.

This module definitely has no temp sense wire, and yet it is the module that would need it since it is the one feeding the power to the gas cut off valves and triggering the relay to cut off the fuel pump and injectors.

I found a schematic online for a Parnell PCM2000 in the tech area of their site (requires login) which has similar wire colours etc and it has no temp sense I can see either. The instructions list only:

TPS Green w black trace pin 89
OXY lt blue w green trace pin 35 ecu
Tacho Pink with blue trace pin 45 ecu
12 Volt stay alive wire (white w black trace at pin 55 on ECU)

Other than that, it just has the injector wire (which I have found in the engine bay it has been cut and joined to the two orange wires from the start control module, the start control also has a wire in the idle control valve. but I couldn't find a temp wire. I did find a blue and white pair going from the lambda module into the engine bay and down into the vicinity of the coil, but they run up the back along the gas line to the tank so they are probably a +ve for the tank cutout and a gas level wire for the guage...

From looking at the layout and working backwards, when the start control has no power, the relays fall back and power goes to the fuel pump, injectors etc and no power goes to any of the gas stuff.

When you switch the unit to gas, the power goes to the start control module which eventually (after cold start delay or whatever) cuts the power from the fuel pump and injectors and powers up the cut off valves so the system runs on gas.. at that point the lamba module (a DEG-103) takes over the normal gas stuff.

I can't find any sign of a temp pickup on this unit or in the specs of the PCM2000. Is it possible that Parnell setups didn't use them?


regards

Frank

Last edited by frankieh on Sat Oct 02, 2010 8:19 pm, edited 1 time in total.

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 Post subject: Re: Testing an LPG Petrol start control module. (Parnell PPSM5)
Posted: Sat Oct 02, 2010 8:03 pm 
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It could be possible that they didn't use them, and only run on a time delay function, start on petrol & switch over in 1 to 2.5 sec's depending on setting. That's how the setup on my mates EF falcon runs.

That cut wire for the petrol injectors, could that be causing issues?

Cheers

ToranaGuy

 

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 Post subject: Re: Testing an LPG Petrol start control module. (Parnell PPSM5)
Posted: Sat Oct 02, 2010 8:18 pm 
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OK.. I traced that other loom with the brown and white wires, (blue and white at the lambda module as discovered with continuity tester).
They both run all the way to the tank along the gas line. So they are not relevant to this either.

I don't see how cutting the injectors could be an issue, it runs fine on Petrol, it's gas that is the issue and presumably it doesn't need the injectors for that. :-)

Also, this gas install was working until about 10 months ago before I got it and the wiring hasn't been changed till I got it 2 months ago.

I took the petrol start module appart, and it's just 4 micro relays, a couple of IC's, a pot, and a couple of LEDs and resistors etc.. fairly basic.

I bought a pipe flarer from Supercheap for 7 bucks and a 5/16th pipe bender from Repco for 20 and managed to make a new temp line between the cut off and the converter... I tested for leaks and all good. I fed 12v into the grey wire that triggers all the gas cutoff's and a gentle flow of gas came out of the converter... so now that the new converter is in place, it looks like it's mechanically sound, I just have to find a replacement Start control module and I should be good to go. (I can't find any other problems with the install, so it must be the module, I have tested it and it doesn't feed out a positive on the grey line, but that test didn't take it's internal timer into effect.

Last edited by frankieh on Sun Oct 03, 2010 2:33 am, edited 1 time in total.

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 Post subject: Re: Testing an LPG Petrol start control module. (Parnell PPSM5)
Posted: Sat Oct 02, 2010 9:57 pm 
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Could the timer be dodgy on it?

Cheers

ToranaGuy

 

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 Post subject: Re: Testing an LPG Petrol start control module. (Parnell PPSM5)
Posted: Sat Oct 02, 2010 11:58 pm 
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I was kind of thinking the same thing, except in this case I was thinking that whatever wire "senses" the engine running, isn't doing so. I think it was using the pulse on the tacho/tps wire to trigger and for whatever reason it isn't detecting it now so it just doesn't start the timer and leaves it on petrol.

I really hope I can find a replacement module if that is the problem otherwise I'd have to replace both modules with a pcm2000 or something.

regards

Frank
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 Post subject: Re: Testing an LPG Petrol start control module. (Parnell PPSM5)
Posted: Sun Oct 03, 2010 12:44 am 
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I don't think it will be looking for a signal on the tps wire. Is it possible to run a new tacho signal to the module & see what happens then?

Cheers

ToranaGuy

 

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 Post subject: Re: Testing an LPG Petrol start control module. (Parnell PPSM5)
Posted: Sun Oct 03, 2010 5:08 am 
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yeah, I guess that is worth a try... there are two terminals on the unit labelled "simulate injectors". I'd love to know why that is necessary and how to trigger it.
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 Post subject: Re: Testing an LPG Petrol start control module. (Parnell PPSM5)
Posted: Sun Oct 03, 2010 2:01 pm 
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frankieh wrote:
yeah, I guess that is worth a try... there are two terminals on the unit labelled "simulate injectors". I'd love to know why that is necessary and how to trigger it.


Probably to keep the petrol ecu happy that it is still running the engine, when it's not supplying fuel to it.

Cheers

ToranaGuy

 

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 Post subject: Re: Testing an LPG Petrol start control module. (Parnell PPSM5)
Posted: Sun Oct 03, 2010 2:36 pm 
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I suppose if worse comes to worse while I am looking for a new petrol starter module, I can just bypass it and then i'll have to start it on petrol and manually switch it across. Only difference really is that it probably wouldn't start if I forgot to switch it to petrol.
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 Post subject: Re: Testing an LPG Petrol start control module. (Parnell PPSM5)
Posted: Sun Oct 03, 2010 4:11 pm 
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Wooohooo... I just hooked it all back up and warned the car up on petrol... and then swapped it to gas.. the car kept running this time around. (it used to die straight away.)

It doesn't idle, but I suspect that is due to having a new converter.. The new converter is also from a falcon 6cyl so it should be in the right ball back, but now I have to figure out how to get it idling.

Before anyone asks, yes the balance pipe is hooked up. :-)


Any tips to fixing idle on gas? I'm about to start googling the forum.
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 Post subject: Re: Testing an LPG Petrol start control module. (Parnell PPSM5)
Posted: Sun Oct 03, 2010 4:34 pm 
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wooohoo!

turned what I thought was the idle screw on the converter in about a turn and now it sits ever so smooth on LPG at 800rpm.

Now I can get it to a gas place and get the tank stamped and my home made 8 inch gas line replaced. (though I've checked it about 12 times now it it isn't leaking and the copper pipe was new, I just don't trust my flaring enough.)

Excellent. Many thinks to Mr ToranaGuy for talking me though. I still don't know exactly what I fixed, but in checking all of the connections and tracing most of them I apparently fixed whatever the problem was. (I think, I still have to start it cold and on gas to see if it correctly starts on petrol.)


cheers

frank
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