mercedes s320 problem?

[a11mcr]

hi i have a mercedes s320 v6 and im having trouble with it, i have just fitted a king system (brand new) and it runs fine on petrol but when you switch it to gas it looses a petrol injector signal (cyl3) after about 10-20 seconds, i have double checked the connections and there are fine so does anyone have any ideas before i hit it with a 14lb hammer! if i turn the engine off and restart it its fine again untill you switch it back to gas.

[Tubbs]

They shut a cylinder down if they log a misfire. And clear when you re start. As long as you have the wiring the right way round in the right plug. Green / injector plug c. And the trace goes back to the petrol ecu. Check the injectors check page that you are getting all the signals. Turn that cylinder back to petrol and see what it does then.
Swap b with c and see what happens then. Does it move ? If so its possibly an injector. If it stays its possibly a crimped hose. Or you have been a bit rough when putting the pipe on and got a flap of rubber restricting the flow. Or bent a pin when plugging them in maybe. Careful step by step diagnosis will sort it quicker than a hammer mate

[a11mcr]

Thanks Tubbs, will check tomorrow as its raining now, but i know all the electrical connections are fine so will check the pipes and maybe try swapping one around.

[Tubbs]

Double check the injector plugs for a bent or pushed back pin. Honestly. Have another look.

[a11mcr]

Just been back out and checked the plugs and they are fine (green to cyl3-inj-c) and took the hoses off and blown down them and they seem fine so could possibly be a dodgy injector but will swap one around tomorrow and see (im using bigas rails as its the only ones that will fit under the engine cover) the ones with silver coils and fly leads?

[Tubbs]

Are they new injectors ? The fly leads have been known to break over time, similar to magic jets, they suffer from the same issues.
Are you sure, sure the plug hasn't got a bent pin ? I can feel it in me water

[a11mcr]

I have double checked the plugs and no bent pins! so changed the coil on the top for another but still cuts off injector 3
is there any way of checking the output to the gas injector?

[Tubbs]

If you have a power probe you can check for a pulse at the plug, pull the pipe off and see if you get a phut, phut, phut.
Whats the diagnosis telling you, go and check your injector cut wiring, blue, red, green.
Make sure all the trace wires are going away from the petrol injectors. Red band on one of the two multiplugs is bank b. try a known good injector on that cylinder. If its already shut that cylinder off on petrol, it wont fire the gas injector. Or you have the wires the wrong way round, switch to gas and the emulator wire is firing at the petrol injector, the none traced wire is going back to the ecu and so the petrol ecu is seeing no signal. And shutting the cylinder down.
You have a wiring issue somewhere, bound to be your injector cut wiring.
So blue has to correspond with gas injector plug a, blue plug b,red plug c green. D is not used along with yellow.
Loom 2 the same e-blue f-red g-green h not used. Thats bank 2 red band.

[a11mcr]

Thanks, will try and take the pipe off and check for gas and a pulse at the plug, i am 110% the wires are correct (im an electrician by trade) all the ones with a black stripe go to the petrol ecu and the solid colours go to the injectors, i have bank 1 cyl-1 blue/black-blue to inj-a, cyl-2 red/black-red to inj-b, cyl-3green/black-green to inj-c, bank 2 (red band) cyl-4 blue/black-blue to inj-e, cyl-5 red/black-red to inj-f, cyl-6 green/black-green to inj-g. surely if any of these where wrong it wouldnt run on petrol? its only after about 20 seconds after its on gas it cuts off (the software reads it running correctly untill it just seems to loose the signal)

[rossko]

surely if any of these where wrong it wouldnt run on petrol?

It would, because while gas is off the wires are effectively shorted together i.e. polarity unimportant. Double-triple check that polarity.

its only after about 20 seconds after its on gas it cuts off

That's how long it takes the Merc management to decide it has a persistent misfire, and then shut the offending cylinder down.

Do Tubbs phut-phut test. Don't assume because you can blow through a pipe that putting it back on a nozzle won't re-lift a torn flap to obstruct it.

[Tubbs]

I've been gas converting 16 years and I still do it occasionally. Infact I did the other week. On a bloody car that it was a manifold off again job to get to the plugs. So I just swapped the wiring over on the loom instead. So you need to be 2 million percent sure. (Hopefully you will be less embarrassed to tell us it was wrong now, but honestly I did ! I know all the other installers do too)

[a11mcr]

all sorted now (i think?) it was down to a squased pipe so had to remove the manifold (two broken vacuum pipe later ) had to re-position the nozzles to a better place and it seems to be ok now but idles a little bit lumpy on petrol but ok on gas, now just three small questions?
1, i have a 0-90 ohm sensor so connected the white and green to one lead and the other to ground (as the book says) but wont show the level?
2, when the obd is connected it reads all the trims but the obd symbol is green but with an exclamition mark over it?,
3, what injector settings should i use as using bigas injectors there is no selection for them all i have is, matrix, matrix HD, matrix xs15, matrix xs20, valtek 34, valtek 2-3 ohm, rail 2-3 ohm, fast, magic jet or AEB at present i have them set to rail 2-3 ohm as this is what the coil restance measures but would like the best setting
thanks for all your help so far

[a11mcr]

Anyone?

[classicswede]

Have you set it as 0-90 in the software?

The injector setting should be ok as you have it.

[a11mcr]

Hi Dai, yes its set to 0-90 but just says empty if i change it to aeb it shows full?
Any idea on the OBD bit?
Mark

[classicswede]

Check the resistance with a mulitmeter. I've come acorss cheap senders marked as 1090 that were actualy 1050 senders

[a11mcr]

Faulty gauge! one of the resistors had burnt so will have to get another one but still cant figure out what the obd is showing an ! for as it seems to be working ( i have it set to auto) or should i set it to the ISO 9141 (as i think this is what it uses but could also be ISO 14230-4?).
Mark

[mercsl]

I dont know what year your car is so could be talking loads of @!## but isnt the mercedes star instead of obd2 systems?