Humming noise from the LPG converter

[dom14]

Hi Guys,
I had to replace the LPG converter(Impco model L) on my GQ RB30 Patrol.
The converter has been giving trouble for a while and I had it replaced with a used one for the time being.
Old converter was making a humming kind of noise for first few minutes and then it goes away.
Now the same thing happens with the "new" one.
I had a close look and found out that vibration noise sort of comes from supply line between the lock off valve-filter and the converter.
This line is only about 6-8 inches long.
I could feel the vibration from the LPG supply pipe between the lock-off valve and the converter.
When I touch the converter, I couldn't feel the vibration of the humming noise.
This is why I think it's coming from the line(some issue with the lock-off valve?!), rather than the LPG converter.

I'm about to upload a youtube video as well.

Can you guys please give me some advice on where to look and what to replace?

After running poorly on LPG for a while, it stopped running on LPG completely before I replaced the LPG converter.
Now, it's running fine on LPG, but the noise bothers me, because I know it's not right, since the same thing had been happening before the old converter died.
I'm wondering whether the LPG lock-off valve-filter is faulty and it damaged the converter as well(by letting in partly filtered LPG into the converter).

Any help would be great.

[threedogs]

One I think the lock off valve is upside down, have you bleed the water system correctly.
For gas vehicles you need to park up hill and use a cut off coke bottle to fit into the radiator neck.
even crack that conection on the converter as air will be trapped there trust me.
To make the system more efficient "Y" pieces instead of "T" pieces help stop cavitation
and assists in water flow,
Put a reco kit through the converter

Edit turn the tank on then back off half a turn too

[dom14]

One I think the lock off valve is upside down, have you bleed the water system correctly.
For gas vehicles you need to park up hill and use a cut off coke bottle to fit into the radiator neck.
even crack that conection on the converter as air will be trapped there trust me.
To make the system more efficient "Y" pieces instead of "T" pieces help stop cavitation
and assists in water flow,
Put a reco kit through the converter

Edit turn the tank on then back off half a turn too

Thanx mate. It has a T piece. I'll replace it with a Y piece. The noise vibration, sort of comes from the gas pipe, according to the way I hear and feel it.
That's what bothers me a lot. I'll put a kit through the converter. I was suppose to do it last time, but was running short of time, so replaced with a used one quickly.

When you said, "crack that conection on the converter" on the converter, what did you mean by it?

Thanx.

[threedogs]

Just loosen the hose clamp a tad, you'll see heaps of bubbles before water starts to flow.
Air always get trapped there. when the bubbles stop nip it up again

[dom14]

Just loosen the hose clamp a tad, you'll see heaps of bubbles before water starts to flow.
Air always get trapped there. when the bubbles stop nip it up again

Ok, cool mate. I'll do that. Just uploading the video. I checked it this morning again. humming vibration is definitely coming from the LPG pipe as in the picture.
I can't say for sure whether the humming noise is coming from the converter or the pipe+lock off valve, but the vibration is definitely from the pipe as in the picture.
thanx

[dom14]

I also closed the vent on the converter to see if that makes any change to the humming noise, but it didn't

[threedogs]

Is your tank fully open ?

[dom14]

Is your tank fully open ?

I think so. It has two tanks. One under the chassis, which should be open(I think), because I haven't touched it for years.
The auxiliary tank is inside. I had it closed for a while, but it's open now again. I closed it, because I haven't been putting any gas anywhere near the capacities of the two tanks.
I had the auxiliary installed for long trips, but later realized LPG is not readily available in the outback, so it's not getting used much.
The bottom tank had to be lowered for me to access the tap. But, I think it should be fully open. I know, it's worth a check anyway.

[dom14]

Here is the video.

https://www.youtube.com/watch?v=0gZA5gazskE&feature=youtu.be

It's not that clear, but you can still hear it. The engine noise overcomes the "trumpet noise" of the converter+LPG pipe. But, it's really loud in real.
Hard to produce it clearly with the video camera. I think I need an external microphone with filtering technology.
I added a better photo as well.

BTW, I forgot to mention, the noise only lasts for few minutes and then goes away after warm up.
Which I think is a good indication, it may have something to do with the converter.

I'm about to bleed any air bubbles trapped in it by loosening the water hose.

[mudnut]

It must be just about icing up, then the water thaws it out. It's could be something silly like a piece of crap rattling around inside the pipes and partially blocking it.

[dom14]

It must be just about icing up, then the water thaws it out. It's could be something silly like a piece of crap rattling around inside the pipes and partially blocking it.

Yes, mate. I was suppose to open up the piping and clean it up with compressed air. I didn't have enough time(excuse excuse).
Main reason for my slackness was that lowering the tank & disconnecting the plumbing is a bit a of PITA job. Now, I think I have to get off my rear end and do it properly this time.
I even had a replacement lock-off valve that I was going to replace with. I forgot to do it or rather didn't think it was needed when the things started going smoothly after
replacing the converter. Now, I won't have a choice but doing things properly, including the putting a kit through the converter.
The old converter had a brand new cold start primer fitted, which the "new" one didn't need at all.
Now, without the cold start switch, engine starts with two rounds of crank when stone cold. So, I thought it was all good to go. Apparently not.
I've never done a converter rebuilt before, but I reckon it's not a tough job. The kit comes with all the instructions.

What sort of solvent should I use to clean interior of the converter?

BTW, I have two converters, the old crap one and the "new" one. I'm thinking rebuilding the "new" one.

Thanks mate

[threedogs]

Carbi cleaner works a treat

[threedogs]

Not familiar with the RB30 but is it possible to fit sequentiual injection far more efficient
Gas is always a PITB, electrics need to be spot on, 99% of the time you have a problem with
gas its an electrical issue

[dom14]

Not familiar with the RB30 but is it possible to fit sequentiual injection far more efficient
Gas is always a PITB, electrics need to be spot on, 99% of the time you have a problem with
gas its an electrical issue

Yep, I corrected few electrical issues. Some of them were bad earth issues.
Yes, it's possible to fit sequential injection, but the LPG rebate is gone now and I'm not sure sure whether all the trouble's worth it.
EFI conversion+new LPG setup as well. It's a big job for me.
I was onto the job of converting to EFI while ago, but had to put if off for a while.

[threedogs]

still the impco is reliable enough I had it feeding my 350 chev troopy for 250Ks and 200Ks on the original motor, dont ask
bugger all problems really, Mind you gas was only 18c I think when I bought back in 92

[dom14]

I get around 5 - 6km per litre of gas. So, it's not that bad for a 4WD. Not much power, but just enough to go anywhere.

[garett]

before u overhaul the converter and if you are sure the noise is from the lock off, take the solenoid off it and open the top, it should have a spring in there (could be part of the plunger ). then open the bottom and check the filter is intact. that converter is a easy as one to overhaul.

[dom14]

before u overhaul the converter and if you are sure the noise is from the lock off, take the solenoid off it and open the top, it should have a spring in there (could be part of the plunger ). then open the bottom and check the filter is intact. that converter is a easy as one to overhaul.

Ok, cool. Thanx for the tip mate. I'll get to that tomorrow morning.

[dom14]

before u overhaul the converter and if you are sure the noise is from the lock off, take the solenoid off it and open the top, it should have a spring in there (could be part of the plunger ). then open the bottom and check the filter is intact. that converter is a easy as one to overhaul.

BTW, when I was replacing the converter, I didn't have the red thread sealant stuff to apply on the threads of the connections. So, I used the plumbing teflon as you can see in the picture.
Was that a good idea?! Should I get the proper stuff and redo it?
BTW, what is the red sealant stuff they use for the LPG pipe connections?
It can't be the loctite red, can it(that stuff is too tough)?!

I found these stuff on ebay.
http://www.ebay.com.au/itm/LPGas-LPG-Propane-Butane-Natural-Gas-High-Pressure-Gas-Thread-Sealant-Tape-/331045572210?pt=LH_DefaultDomain_15&hash=item4d13da8e72

http://www.ebay.com.au/itm/TL-242-Thread-Locker-Sealant-Medium-Strength-/301364601100?pt=AU_Toys_Hobbies_Radio_Controlled_V ehicles&hash=item462abae10c

http://www.ebay.com.au/itm/LPGas-Natural-Gas-Steam-Oil-Hydrocarbon-High-Pressure-Gas-Thread-Sealant-/330955930060?pt=LH_DefaultDomain_15&hash=item4d0e82b9cc

Which one would you guys recommend?


Thanks mate

[threedogs]

IT would be RTV sealant of some description I'd imagine
a bit pricey but worth investing in a tube of it.
They used to use a product called Stag but not anymore.
Plenty of sealents that will suit the job

[garett]

the gas tape should be ok, but the lp gas sealant would be better don't use a thread locker. i think i use loctite 572. same sort of thing as the last one on your list

[dom14]

The yellow tape is the cheapest. so I wouldn't mind it and it's only about ten minutes drive where they sell it. The red sealant stuff already on the threads looks like loctite red.
But, I know it can't be. I wouldn't have been able to undo it if that's the case. From memory, loctite red need some good heat to break it down.
I think I go for the yellow tape. I reckon I stay away from loctite. I have no idea about their strength levels.
I think I did a cheap ass job with plumbing tape, but I didn't have anything but loctite red, and I knew loctite red is a bad idea. :)

[mudnut]

The use of a thread sealant (not locker) is recommended over the use of tape in situations where there are solenoids and valves so that the tape doesn't get lodged in components and jets.

[dom14]

The use of a thread sealant (not locker) is recommended over the use of tape in situations where there are solenoids and valves so that the tape doesn't get lodged in components and jets.

Ok, cool mate. That makes sense. I thought I could get away with $4, but looks like I'm gonna have to spend bit more. :)
A thought just crossed my mind. The rattling hum from the pipe/converter can be from plumbing tape pieces accidentally getting lodged inside the pipe or the lock off valve.
I had it removed, but haven't had a chance to have a close look inside. Just about to clean them with compressed gas though.