LPG help

kermit_rr · Jun 3, 2019

Hi
I have a multi point LPG injection system. When I turn the ignition on, but don't try to start the engine, 2 of the injectors are energising, ie. if I unplug then and turn the ignition off and back on, I no longer hear any clicks.
I presume this is related to why the system fuse blew, but is it likely an issue with the 2 injectors, the loom, or the ECU? Our something else entirely?
Cheers!

MJI · Jul 3, 2019

Do you have an interface cable?

From memory, my last car was LPG using a system from a previous similar car which was badly pro fitted.

Check all the wiring, look for LPG wiring near hot things, or snagged wiring.

Multimeter the injectors, they can burn out, usually go open circuit rather than short.

Finally may need to see if you can borrow an ECU, hence need for software and cable to read old and set new up similarly.

I had to replace an ECU when the injector drivers failed.

kermit_rr · Jul 3, 2019

thanks for the reply, I dont have a cable

was going to get one, but it died before I got engine sorted

I can try to check the rest,, the snake of wiring is just a bit daunting

MJI · Jul 4, 2019

kermit_rr said:
thanks for the reply, I dont have a cable was going to get one, but it died before I got engine sorted
I can try to check the rest,, the snake of wiring is just a bit daunting

Not that complex, well even LPG installers are able to fit systems sometimes.

SGI systems are fuel

Tank - liquid
valve
pipe
evaporator (I think)
now gas
Injectors

Water
Intercept heating pipes for evaporator

ECU

wires to tank for sender and valve
wires to vapouriser for temp and valve
wires to battery
intercept loom (forgot name usually in 4s) to intercept petrol injectors to cut them out and control the gas ones. 8 wires
injector loom to gas injectors 8 wires
loom to control switch 4 wires

There are other things available like pressure not sure as over 10 years since i fitted the kit

Does it run OK on petrol, if so intercept OK.

kermit_rr · Jul 4, 2019

There's millions of wires everywhere, like someone sprayed silly string in the engine bay
It runs fine on petrol, it used to run fine on lpg, but now if the lpg ecu is plugged in, it revs it's nuts of running on petrol, even with no power to the lpg ecu.

MJI · Jul 5, 2019

Does it run if not plugged in as the petrol injectors should not work if ECU removed?

Has anyone been working on it previously?

The LPG ECUs cut out the petrol injectors and the ECU has the drivers and is where the signal is cut. The injector signal is intercepted, either passed on to EFI or modified and sent to SGI.

Car ECU ---> EFI ---> Earth or ECU
to
Car ECU ---| | -->EFI--> Whatever
| |
|LPG|-->SGI

What make is the kit?

Can you see the SGI injectors?

kermit_rr · Jul 5, 2019

When the lpg (sgis) ecu is unplugged from its loom, car runs on petrol perfectly
I don't know any history prior to my ownership, just that it ran fine on lpg and petrol up to the point the fuse blew
I'm not sure on the brand, sorry! How can i find out?
The injectors are on top of the intake manifold

kermit_rr · Jul 5, 2019

I've just had someone look at it who knows what they're doing, wired it all back up and got it running on gas again! With the only issue it was running lean.
So i think now i need to go thru with a fine tooth comb and check for any chafing/broken wires!!

And get the lean mix sorted. Does LPG work on its own fuel trims?
And get the vapourisers fixed, one seems to be leaking

MJI · Jul 9, 2019

There seems to be a few brands of bits used by multiple companies, ECUs by 3 or 4 kit makers.

Most SGI systems are piggy back systems so take the petrol injector values and adjust them for gas. So their fuel trims are adjustments to the petrol trims, they also use the ability of the car ECU to alter its trims for lean or rich.

Mine was trimmed so that on full throttle it would not cut out on gas, so was a touch lean.

Do an image search on LPG injector, or whatever component you want to check.

kermit_rr · Jul 9, 2019

this looks suspiciously like the one I have.. bigas sgis - https://www.lpgparts24.de/Bigas-SGIS-3-8-Zylinder-Steuergeraet
its been suggested to me that I upgrade to a more modern system.. but that sounds quite expensive to me, but equally it can't be good running lean enough to throw an error code?
I wonder if the software etc is still available to fix/trim/adjust my existing config....

MJI · Jul 9, 2019

Looks like a generic Italian system standard ECUs generally.

Not really worth changing if it works OK

This looks usefull
https://www.lpgshop.co.uk/brands/BIGAS.html

These days people tend to DIY with cheap systems of OEM brands, Polish ones common.

May be worth finding the ECU looking for the model and searching for the lead and software.

LPG help

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