first, let me introduce myself. My name is Danilo, I'm from Slovenia and this is my 2nd LPG converted car. The first one was also a Subaru, but with a 'factory' conversion with a BRC system and a 2.0 4-cylinder boxer engine. When I bought it (used, of course), the LPG wasn't working and I had to fix it myself and in that process, I gained a bit of basic knowledge about how these systems work (in my case, the gas pressure sensor didn't give a signal, so replacing it made the LPG system switch over, but then the injectors were stuck and I had to help them a bit with a couple of light taps with a hammer).
Now I have a Subaru Legacy 3.0 H6 with a Zavoli Alisei S LPG system, installed in 2017. It has a lube system and I've done about 50k km with LPG since. About a year ago I started noticing that going slightly up-hill, the engine sometimes cuts out, but just for a moment. Didn't think much of it as it was a pretty rare occasion. At the time, I didn't even blame the LPG system.
However, as the frequency of these cut-outs increased, I also noticed that a cut-out is accompanied by an audible click from the LPG tank solenoid and a change of LED status on the Zavoli switch - the green LPG LED turns off while the yellow petrol LED turns on (I do have a video here where it happened a couple of times in a row). Sometimes, the LPG system seems to turn off completely and then comes back as if it was restarted (video here).
I took the car back to the installer, they had a brief look at the computer and there was an error code and based on that, they replaced two coils, but that did not fix the issue.
Although these cut-outs at first appeared random, over the year of living with them I did notice a pattern - (most of the times) it happens with moderate acceleration, at about 1/3 throttle valve opening and only around the 3000 RPM mark (give or take 500). If I accelerate softer or harder, it doesn't happen, it just pulls right through that rev range. It is possible that it's happening under different conditions as well, but for an even shorter amount of time, so that there is no click and I can't have my eyes on the LEDs all the time.
Recently I found a way to pretty much make it happen 'on demand' - the car has a sort-of ECO drive mode, which softens the throttle response and limits the throttle plate opening and in this mode, accelerating from 2000 to 4000 RPM in 3rd, 4th or 5th gear pretty much guarantees one or two cut-outs.
Also, if I try the same on petrol, nothing unusual happens under the same conditions.
When I presented all that to the installer, they seem to be pretty clueless. They thought it could be a bad electrical connection, but I don't believe that (just) a bad connection would be as consistent with regards to the amount of acceleration and RPM range.
Since the Zavoli system is still under warranty, I am inclined to leave it to them, but I'm not really that hopeful and I'd much rather have a working car than a car in their workshop.
I had a few ideas, but ruled them out already:
- LPG tank level - at first it seemed as this only happens if the tank is about 1/2 full - but with the 'on demand' method mentioned above, it happens regardless of the amount of LPG in the tank
- the switch-over button - I mounted that button so that it is flush on the centre console and afixed it with hot glue, so I thought that maybe some glue got somewhere it shouldn't, causing problems - but I have a spare new one, connected that one and nothing changed
- temperature / heat - the Zavoli ECU is mounted in the engine bay, very close to the engine, so I thought maybe the ECU overheats (though this would not explain the acceleration / rev consistancy) - but again, I can make it happen pretty much as soon as the LPG turns on, so can't really be heat soak.
To finish off, here's a list of components used in this conversion (according to the paperwork):
- LPG tank Atiker 650x250 67 L
- multi valve Zavoli / Tomasetto AT-02
- LPG level sensor AEB1050
- reducer Zavoli Zeta S
- injectors Zavoli Pan Jet
- pressure sensor AEB025 (LPG pressure, manifold pressure)
- ECU Zavoli AEB2568