my vp sucks on gas now can anyone help

[rob drag racer]

ok my vp sucks on gas now when i take the foot off wile under 80 km per hour the revs drop to stall out it only happens with gas and its not the converter it flows well enough to rev threw the range it just stalls when going threw roundabouts and slowing for granny drivers anyone got any ideas of what it could be

thanks in advance :thumbsup:

 

[Gosling1]

Rob - this has happened on our VN a few times, and can be caused by a couple of things......

#1 - Poor-quality gas. LPG from Woolies should be avoided like the plague - its crap. The car just ran like a dog with this stuff - stalling, backfiring etc. Only thing you can do is go on a long drive and use it up.....

#2 - Overheating. If the engine temps are up, the LPG mix just doesn't work properly - had some issues with this only recently, and the radiator pressure-tank was bone dry. Filled it up, and the problems dissapeared straight away. Same problems as yours - only happens on gas, stalling at lights etc....Check your cooling system, maybe could have a stuck thermostat or temp. guage not showing correct temp ??

The other issue with temperature is that if it is really cold in the mornings, if your gas kicks in a bit early (say <1500rpm), then you will get these symptoms. Up here, last week we had a couple of 0deg mornings, and one at -6deg ! Just run the car on petrol for short trips early in the morning when the temps are this low. If your gas kicks in a bit higher (say 1800rpm and up) - then you may be able to get some temp into the motor before the gas kicks in, which will stop the problem happening in the first place.

Hope this helps - there will be a lot of LPG converts here with some tips as well.....:thumbsup:

 

[rob drag racer]

well thanks for the reply im sure its not number 1 because i refuse to use (cheep ) crappy lpg

i thought it was number 2 but my overflow reservoir is pretty full unless i have an airlock or like ya say a bugged thermostat

i also thought it was a dfi issue until i tried it on fuel all i can say is i think Thursday this week will be a long foul language filled day

:bang: :bang: :bang: :bang: :bang: :bang: :bang: :bang:

 

[blownba]

Great response but unfortunately barking up the wrong tree.

I take it you have a mixer ring LPG conversion??
What you are describing is classic balance line problem. The balance line is required for a mixer ring conversion to allow the LPG converter to balance according to ram air effect on the mixer from the air cleaner.
When you are at low speeds there is not that much air being forced in to the air cleaner but at higher speeds (and especially if you have a clod air intake or ram pod) air is being forced into the intake and therefore air speed in increased through the LPG mixer.
Because the secondary diaphragm is open to atmosphere (when no balance line is run) it has no way of knowing that extra air is being introduced so the fuel mixtures go out of whack and when you take your foot off the throttle it will be to lean and it will stall every time.
To fix it you need to firstly check that your system has a hose running from the air box to the back of the LPG converter (the side opposite the gas outlet to the engine)
If it does have one then check it has NO leaks at all, even a tiny leak will affect balance.
If you don't have one you need to fit one.
The practice is to fit a barb to the air box, usually before the air filter so it can get the best reference of ram air entering the air box, usually directly opposite and with the fitting opening facing the ram air flow. then run the biggest size fitting (at least a 10mm barb but 16mm is best) and then at least 10 mm I.D. hose (16mm or heater hose size is better) and run it to the fitting on the rear of the LPG converter (some just have a hole there with thread that you have to screw a fitting in to)
I will bet my bum that this will fix it if you have a mixer ring system cause as I said it is classic balance line problem you are describing.

P.S. If you run a pod you will need to place the fitting into the air duct just after the pod filter to get it to work.

Hope that helps.

 

[Gosling1]

thanks for the tips blownba - I am pretty sure that the LPG setup I have is a mixer-ring - its got that large circular fitting just before the throttle body ?? The LPG lines from the converter run to it.....the whole shebang is run from a small ECU.

I will check if that balance line is fitted - not sure at all if there is any line running from the airbox back to the converter......(and I have fitted a CAI to the VN, all stock GMH stuff from the local dealer, it was about $60 for OEM parts :thumbsup

When I had these problems recently and went and asked the installer about the stalling issues - he pretty much said overheating will do it everytime ?? I will drop past and ask him about the balance line solution tomorrow - it sounds like a pretty easy fix to me, something that can be knocked over inside an hour at home....

 

[delcowizzid]

my mates falcon did the same thing stalling etc but ran fine when driving was wax build up in the tank, lines and mixer happens quite a lot when the systems age a bit.

 

[levymetal]

kummo took some pics of this for me once when i was having some issues. actually i still am having the issues, when i plant my foot on gas sometimes it acts as if it backfires, ie the engine just cuts out for a tic at high RPMs. yet it isn't a backfire, no bang, no blown up airbox, no damaged air filter... it's like the gas is just being cut off. i thought i needed the balance line because i run a CAI, but when i ran the standard air box the problem still existed so i decided that it's not the balance line that's causing my problem. btw it's a new gas system, gas installer doesn't seem to give a **** about my problem to be honest. i know where i won't be going next time. and where i will be, straight to blowba - a person that cares about their product (yeah i've called you up before )

now, on the topic of gas, i've just replaced my radiator and installed a 3 degree hotter thermostat (it's actually the correct one, my car was running a cooler one before). now my car idles lower, it's not too bad in drive but it almost dies in park/neutral on gas. my only idea is that it was running richer when it was cooler or something.

so can i tune the gas system myself? there are 2 screws on the converter, i was under the impression that you adjust the smaller screw (i think) to give you a good idle, then rev car to ~1050rpm and adjust it so it idles fine there. it *should* still idle well when the rpms drop, but this stop it from leaning out when you give it a touch of throttle. then the other bigger one is adjusted as far in as possible without affecting the idle. is this all right? there's also a full throttle one between the converter and the mixer, but i'm not too worried about that...

 

[rob drag racer]

Great response but unfortunately barking up the wrong tree.

I take it you have a mixer ring LPG conversion??
What you are describing is classic balance line problem. The balance line is required for a mixer ring conversion to allow the LPG converter to balance according to ram air effect on the mixer from the air cleaner.
When you are at low speeds there is not that much air being forced in to the air cleaner but at higher speeds (and especially if you have a clod air intake or ram pod) air is being forced into the intake and therefore air speed in increased through the LPG mixer.
Because the secondary diaphragm is open to atmosphere (when no balance line is run) it has no way of knowing that extra air is being introduced so the fuel mixtures go out of whack and when you take your foot off the throttle it will be to lean and it will stall every time.
To fix it you need to firstly check that your system has a hose running from the air box to the back of the LPG converter (the side opposite the gas outlet to the engine)
If it does have one then check it has NO leaks at all, even a tiny leak will affect balance.
If you don't have one you need to fit one.
The practice is to fit a barb to the air box, usually before the air filter so it can get the best reference of ram air entering the air box, usually directly opposite and with the fitting opening facing the ram air flow. then run the biggest size fitting (at least a 10mm barb but 16mm is best) and then at least 10 mm I.D. hose (16mm or heater hose size is better) and run it to the fitting on the rear of the LPG converter (some just have a hole there with thread that you have to screw a fitting in to)
I will bet my bum that this will fix it if you have a mixer ring system cause as I said it is classic balance line problem you are describing.

P.S. If you run a pod you will need to place the fitting into the air duct just after the pod filter to get it to work.

Hope that helps.

thanks for the low down well it wasn't that either it turned out to be a lose earth to the lpg computer i also found that the power valve that's run inline was connected until about 4 inches up the loom then went no where so i replaced the power valve and the wiring not its fine besides the fact i need to dial in the power valve i have an odd tic coming from the drivers side of the engine now its not there all the time it comes and gos and its not the injectors as it happens wile on gas any ideas i think i my have a bugged push rod or lifter or something by the way i do have a gas ring id like to get rid of it or mod one of my own spare throttle body's but i wouldn't know where to start

i wish there rep points system was still in place you would get the most i could get thanks again

and can some one sticky this the info blownba gave will be very valuable in the future i think :thumbsup: