Switchover buttons leds go out when button pressed?

[pyro225]

I have a v10 bmw on two king kits (1 per bank) it has ran great for 12 (yes 12) years with little problem.

Today after a month with no gas at the station I filled her up, started on petrol fine and both switch buttons are on orange, however if I press one to put it on gas both of them all the leds go out until I restart the car and then the same happens? Occasionally it will beep like it’s out of gas for a second before the lights go out? If it was only one I’d have thought control unit but as it’s both any ideas?

Cheers

[hitman2]

Similar thing happening to me, have traced it to a dodgy map sensor, but mine only gives an issue with high under bonnet temperature, have relocated map sensor and wrapped in foam as temporary fix until new map sensor arrives.


I assume you have the king software and can check what the map sensor is showing?


Eta single aeb king ecu system...

[LPGC]

Suggestions for possible causes might depend on how it's been wired up... Since you say you can press either switch (to presumably run just one side of the engine on LPG) then that implies they've wired it so both ECUs can power the tank(s one or two?) and reducer(s one or two?) solenoids. The installer may have wired the ECUs in parallel straight to solenoids or through a relay.

Much the same with the 'ignition live' feed to the ECU's. A lot of BMWs continue to power petrol injector common positive and coil pack coil pack common positives even when the ignition has been turned off for a few minutes, so installers may wire the ignition live from the King ECUs (which tells them the ignition is on so they should be powered up) to somewhere else that gets powered up only when the ignition is on.... Classically this would be the actual ignition switch but it's been comon practice on BMWs to get the ignition live signal from e.g. a cig lighter socket that is only on when the ignition is on. The ignition on wires wouldn't need to be wired through a relay but an installer fitting 2 ECUs on a vehicle might have thought it a good idea to so.

It seems likely that: Both ECUs are wired straight to solenoids, so if the button on a single ECU is pressed to run on gas that ECU carries the full current to solenoids, or if both ECUs are switched to run on gas they both flow half the current to solenoids. Both ECUs are connected to 'main power' (battery live and earth) at the same points. Then, if there was a dodgy common connection to live or earth the usual current to power the solenoids could be enough to break a bad connection. Or, if there was a fault with a solenoid (shorted coil) a similarly dodgy connection to battery live/earth would be even more likely to break the connection.

Don't discount earth wires when looking for wiring faults - All the earths are wired together in the loom and on the boards so the symptoms you describe could be due to the ECUs getting an earth from, say, the thin wire that runs to the tank for the level sender, which would be a good enough earth to see the ECUs power up but not a good enough earth for the ECUs to still get close to 12v when solenoids are powered up and especially when injectors also start to run.

One test you could do is wait until it's cooled down (so it wouldn't switch straight to gas as soon as you press a button) and see if the gas light flashes as normal as though it's waiting for it to warm enough to switch to gas or if all the lights on both switches still go out. If 'it seems likely that' is correct then this test will show that it's when the solenoids are powered up that causes the lack of power.

Another one is: When King ECUs first get an ignition live signal they power up, but (depending on which version of firmware they're running) they might power down in a minute or so if they're set to pick up rpm signal from the brown wires and they don't see that RPM signal. This is unlikely, because it is more likely that you've tried pressing the switch at various intervals after starting the engine (so wouldn't just be coincidence that they powered down just as you pressed a switch button)?

[pyro225]

Thanks for the answers here - a few things to try - I can certainly dig the cable out and see if it connects and check map reading.

I can then also check the brown wire as I’ve tried it only within a minute of starting each time.

The leds go off as soon as they start flashing hot or cold.
I believe it’s all wired in parallel as I can run one bank on petrol and one on gas with no issues and doesn’t matter which way around

[pyro225]

Took the ground and live cables off both crimp connectors heavily corroded not sure how as they were tight trapped under bolts anyway cleaned them up and so far so good

All working as it should getting rpm and map readings - can only surmise that it was a bad ground as mentioned above

[LPGC]

Good, an easy fix then