Solenoids issue Dodge Ram [solved]

[postbus24]

Hi all,

I have a bigas setup with 2 solonoid valves. One on the tank and one before the evaperator.
When the truck is going to switch over to lpg, there normally is a 'ratteling' 'clicking' noise because both solenoids get a few 12v pulses before they finaly open. (I tested this with a testing light)
Is this normal ?


The real issue is: sometimes we don't hear the solenoids noise and the engine stalls when switching to lpg
When I bypass he coil of these valves to the battery, they seem to work fine. And after that the truck runs for a few days untill the next time it stalls on switchover to lpg.

Is this a valve problem ? Or the coil ? Both ?
Or something else ?

Of course when I took it to the lpg shop, it was running fine with no errors in the lpg memory. :-/

[LairdScooby]

Sounds like a bad earth/relay in the ECU that controls the gas solenoids, or possibly a bad 12V feed to the relay output from the ECU.

I wonder if you used the output wire for the gas solenoids from the ECU to power a relay coil to switch the solenoids in direct from the battery if this would eliminate your problem. It could be the relay contacts within the ECU are worn and could pass the current needed for another relay coil but won't pass enough current to operate the solenoids directly.

Using a standard 4-pin relay, take the output wire (for the solenoids) from your ECU to pin 86 on the 4-pin relay, an earth connection to pin 85 a 12V feed (via a fuse) from the battery +ve to pin 30 on the relay and take pin 87 from the relay to your gas solenoids +ve terminals.

That may solve your problem directly but it also may make the new relay chatter if the contacts in the ECU relay are badly burned.

[LPGC]

AEB ECU's (which include Bigas) of a certain era / firmware, do pulse solenoid valves repeatedly before finally holding them constantly open and changing to LPG. The design seems intentional, maybe to stand more chance of opening a sticking solenoid valve. So yes, the chattering is probably normal for your model ECU. You may be able to stop the chatter using different settings of 'tank valve with dedicated wire' and 'open valves in advance'. But might as well leave it as is, after all, the chattering currently tells you when the valve is going to open and when the LPG system will work, maybe handy for this stage of the diagnosis.

You're thinking along the correct lines. Fault could be due to sticking solenoid, intermittent faulty coil, intermittent wiring fault.

Sometimes little relevant knowledge can be a costly, time wasting thing... It's probably best to make lack of experience clear along with good intentions. Tip to astronaughts... Save time on re-entry, just come straight down vertically, but I'd like to make it clear I'm not an expert on space travel...

Simon

[postbus24]

Thank you Dave, The tought of an aditional relay to relief the ECU from relative high currents, also crossed my mind. But it sounded a bit overkill in my mind at that moment.

Simon, you have a point with the astronaut story. I have checked all the wiring, that seems ok. Measured the 'pulses' again, because I find it fascinating. they are so regular that they must be sent on purpose so your explanation is spot on. Thnx.

I cannot find exact matches to replace the coils and that is as about far as I want to go on fiddeling with the LPG system.
In the end I will simply 'demand' my lpg shop to replace both solenoids. (of maybe after I've added aditional relays )

regards,
Bart

[LPGC]

If your system is new enough to support LPG OBD and you fit the relays, then: You may need to disable on board diagnostics in software because solenoid coils generally draw about an amp and as they are designed for 12v the coil resistance will be around 12ohms. But relay coil resistance will be much higher than 12ohms, probably high enough that on board diagnostics will interpret a broken solenoid coil and therefore refuse to run on LPG. You would need access to an interface cable to disable the obd. After disabling OBD the system won't inform you if it detects any problem such as failing solenoid coils, injector coils, map sensor, reducer temp sensor, gas temp sensor, incorrect readings from petrol injectors. Shopping list may now be 2 relays, perhaps a separate fuse holder in the feed to the relays and an interface cable? But don't forget to find and repair the actual issue, as fitting relays etc unnecessarily won't effect a repair.

Simon

[postbus24]

fyi: I have managed to find a replacement coil which is working fine. -> problem solved

[LPGC]

fyi: I have managed to find a replacement coil which is working fine. -> problem solved

And the chattering still occurs...

[postbus24]

Yes, it does, but only when the engine is cold.

Both solenoids are connected to a different output of the Bigas ECU and they both get the 5 or 6 pulses after a cold start. (I've checked with a light bulb in stead of the solenoid)

When the engine is warm they just switch ON/OFF in one "click".

[LPGC]

That's right Bart.

Simon