Starting woes..

[rpo83]

I’m hoping someone can help with any ideas how to get my RRC running again? I wrote a post a 7 months ago about the Rangie backfiring when i was trying to get her running on petrol, since then nothing, not so much as a whimper.

I had decided to simply rip the LPG out of the car and use her only on petrol, long story short, i couldn’t find a petrol tank and filler neck at a reasonable price, so i sort of gave up and got demotivated….

Last week i decided bugger it, let’s get it running on LPG, get it club rego’d then sort out the fuel in the future.. So i removed the 2 LPG tanks and had them retested and stamped as they needed to be done for a RWC. When refitting them, i noticed the earth wire that had been run for the solenoids were very dodgy, so a new earth lead was run, so now i’m confident they are opening, i get a nice loud click when i turn the ignition on :)

Unfortunately, i still can’t get her to start. This morning i had a mate come over to help diagnose the problem. Having 2 people really helped in fault finding, but still no go.

We discovered the coil lead to the distributor was cactus, so a new one was fitted… no help, we pulled a spark plug lead off and confirmed there was spark, so all good… Out of desperation we filled a spray bottle with petrol and squirted it into the flapper (as it was help open) no luck, so we removed the mixer from the plenum and sprayed fuel there… still no hint of trying to start…

So i find myself back here for help. Things i can confirm…

The fuel switch in the car works, we can hear and feel the supply solenoid switching.
LPG is getting into the converter, it is getting cold and the primer button locks up..
There is still no evidence of LPG getting out of the converter, no smell of gas at all.


I have 2 main questions, can the flapper have any affect on the engine starting even when we are spraying fuel into the manifold, does it have any impact on the engine running on LPG?

What exactly does the ECU do? The motor has a standard distributor with vacuum advance, so i can’t see how it can affect the ignition, so from my very basic understanding, does it simply modulate the fuel going to the injectors based upon how much airflow is getting to the engine which is measured by the flapper??? If this is the case, surely it can’t affect the starting of the engine on LPG???

There is a device between the converter and mixer, no idea what it is… but it has a vacuum line going to it. I’m wondering if this is some kind of valve that requires the engine to be running so it developes vacuum which will then open allowing the LPG to be used??

Please excuse me if i have the LPG components misnamed.. I’m using converter for the high pressure to low pressure conversion and mixer as the device that adds the low pressure LPG into the incoming air… Bee utey, as i have been unmotivated, i haven’t checked the mixer like you suggested yet…. :(

Here are a bunch of pics showing the components… Any advice would be greatly appreciated as this is doing my head in.

Switch
142023

Converter
142024

Mixer and unknown valve
142025

[bee utey]

The "unknown valve" is a "lean cruise power valve" which reduces gas flow when manifold vacuum is high. It should not prevent starting as there is always a gap through it. Adjustment is via a screw on one side and a nut on a thread in the small cap on the other side. With the vacuum hose off and capped it should give full mixture.

I'd be pulling the lid off the mixer (5 screws) and looking for a torn diaphragm. Don't lose the spring under the lid. A tear in the diaphragm will prevent it lifting and allowing any air into the engine.

The ECU does exactly one thing, adjust the fuel injectors on time. It won't affect the LPG.

Last thing, pull all the plugs out and dose each cylinder with some penetrating oil to make the rings happy, Crank it over to distribute the oil, then fit a new set of Bosch WR7DC plugs. I've experienced a number of sets of plugs over the years that just didn't want to start, replacement and away it went.

Oh and go easy on the petrol spray, these things are easy to flood. Starting fluids are better, e.g. start-you-bastard.

[rpo83]

Thanks bee utey,

if the weather clears, i'll go remove the mixer and pull it apart.

One other question, i had a new distributor built for a 3.9 10 years ago, which is just sitting around, it was rebuilt and setup for dedicated gas by Performance Ignition, would i be correct in thinking it will be worth installing in the 3.5?

Thanks for all your advice :)

[bee utey]

Nothing wrong with fitting the best distributor you have on hand.

[rpo83]

There was a break in the weather so i've just removed the mixer, the diaphragm looks fine, no obvious tears or holes, I've held it in front of a bright LED light and can't see any problems. The seal looks OK, there was a bit of oily residue on the engine side, but nothing over the top.

I was searching back reading some of your other posts, and you mentioned to check the surfaces to be true, so i'll do that when i get a chance, should i just replace the diaphragm to be sure? The mixer is an LG Motor brand, any knowledge of these, should i consider changing the whole mixer? They don't seem too expensive and if i'm already up for a rebuild kit, it might be something to consider.

Is there any thing else that could be responsible for the gas not getting into the inlet manifold? There hasn't been even the slightest wiff of lpg in the engine bay...

[bee utey]

With the lid off the mixer, turn on the ignition and subsequently press the button in the middle of the converter. If no gas comes out start pulling off hoses and look for a blockage. Also check that the solenoid next to the converter is opening at the same time as the tank solenoids, to let gas into the converter. There will be a filter before this valve that may be overloaded with iron dust from the tank insides, and has let some into the solenoid itself. The easiest way to check this solenoid is to disconnect the wire off it from the loom and hot wire it direct from the battery.

[rpo83]

Hi bee utey,

i only got a few minutes to have a look at the rangie today...

As i removed the mixer and MAF, to save time, i just tried what you suggested with just the gas line output from the convertor.

With just ignition on, nothing when i pressed the primer... i got my multi meter out and there was no voltage at the solenoid, so i got the mrs out to sit in the drivers seat and crank the engine over, there is only voltage at the solenoid when the engine is cranking, i pressed the prime button as she was cranking and heard and smelt gas... not sure what i should expect in regards to the amount of gas, but there was a hissing sound, not a massive amount of gas was released as we stopped cranking as soon as we heard the sound...

I hope this gives you enough info to help with diagnosis...

[rpo83]

Hi bee utey,

I've spent the day working on the ignition and re-assembling the mixer.

I can get it to start, but it only runs for a second or two before cutting out. I put my test light on the solenoid positive and discovered that it is only getting power when the key is turned to start, so as soon as the engine starts and you release the key back to ignition, there is no power at the solenoid! Would i be correct in assuming that there needs to be power there to allow gas to flow when the engine is running?

The thing i can't figure out is how this could change with a backfire! It was starting and running fine before the backfire...

As usual, any words of wisdom are welcome...

[rpo83]

After thinking about it, a backfire couldn't have changed the electrics, so i went back and thoroughly went over the engine bay, i discovered the flapper connector wasn't seated correctly, i played with the spring retaining clip and refitted it, hearing a nice snap when the spring retainer clipped into place.

I jumped into the cabin and hit the starter to hear the 3.5 spring into life :) Happy days

One last question, as there is now no petrol tank, what is the correct way to disable the low fuel warning light on the dash, do i simply short the wires, or does there need to be a resistor or something?