Alternative Fuels

hi guys.. this is my first post on this account (have an old account from years ago but couldnt find it)

ill start with details of the car
2000 model Ford AU Falcon (australian)
all basically stock
L6 4.0 sohc 2 v/cyl EFI has DIS ignition
4spd auto

LPG system :
prins VSI 1 system.. running orange KEIHIN injectors
system installed 2008.

PROBLEM :
it is cutting out at high RPM/high load..
does not entirely cut out... more like hits a rev limiter..
starts to cut in and out at around 4000-5000 rpm..
will rev out to 5500 if u dont go full throttle..
runs perfect on petrol..

DIAGNOSIS so far :
(i do not have the cable or software so this is all done with multimeter and scope)
i have scoped the injector voltages and they are shutting of when the issue happens..

why?

POSSIBLE CAUSES :

i have adjusted the regulator pressure many times now and it seems to make a slight difference but i have no idea if regulator pressure out of range could cause this.. according to online info it should switch back to petrol when it goes too low or too high, but it is not doing this..

cheers guys thats all i have for now..

Check two items immediately for injector voltage issues.
1. All the grounds for the propane system. If their not grounded directly to the battery run a jumper from the existing ground to the battery ground.
2. Check the relays that switch the power from propane to petrol. There should be one or two five pin relays that control the injectors. They were typically mechanical relays with points and they could be failing or the terminals where the relays plug in were prone to corrosion. Just unplugging the relay and plugging it back in a few times may cure the problem.

seems like an issue with the lpg ecu..

the main earth was not connceted at all .. probably has caused damage..
also the rpm input should have been a sqaure wave signal of no more than 40V .. it was instead connected to ign primary seeing over 400v.. that is how the installer did it..

i want to try another ecu .. but am having a hard time finding one cheap enough locally.. they want $650 for a new one .. may not solve the problem..

i have managed to get it all running nicely now..

i adjusted several parameters in the ecu ..

main issue i think was the rpm signal was not wired in properly..

it now has a funtioning rpm signal..

it revs cleanly out all the way... actually it will keep reving way up if u let it..

it seems now it has no rev limiter at all .. hit over 6000rpm (these engines never go over 5000/5500

also go the regulator pressure correctly adjusted..

all of this is impossible to do with out a diagnostic cable and software which i bought off ebay

Nicely done, however you are correct about the rev limiter. Since the ECU is a slave to the OEM Petrol ECU it should start cutting out the injectors at the same limit as it would on petrol. That's kind of puzzling.

The AU come out with the Ford 4 litre Intech straight 6, these engines are capable of 6000+ rpm especially the VCT engine. If the petrol system is not capable of achieving >5500 rpm it has a problem.