2 replies to this topic

[Blatherskite]

Hi. For a while now I have been struggling to get our SPi to pull away; the engine starts and runs fine, but most times (not all) you try to pull away, the engine just dies. Out with the code reader, and eventually found thst, as you pull away and the engine dies, the reader gives the message "communication lost". There are no error codes. Just this afternoon, trying again in frustration, I used the code reade to operate the various items, and when it came to the purge valve, there was the same failure - loss of communication. I then unplugged the purge valve electrical connections, and the ECU won't boot up at all. Connecting the two wires to the purge valve together - everything works as it should.

The purge valve connectoon is frpm the ignition switch to pin 21 on the ECU, and seems to power it down when operated. There is direct power to the ECU to pin 11, so my questions are: Does the ECU need power at pin 21 to operate, or is a fault there causing it to "crash"? Also, will swapping out the purge valve for a new one fix the problem?

Man, but its complex! Give me mechanical stuff any time!

[xrocketengineer]

That is strange. As far as I can tell, pin 21 provides the earth path for the purge valve through the ECU. I would start with checking for a good earth connection on pin 28 (black). I am assuming that the earth path for the ECU is iffy and when needing to also provide earth for the  purge valve (additional current), it ends up with more than 0V and the ECU shuts down since it does not have any more a 12V differential between pins 11 and 28 to operate.

After that I would check for 12V at pin 29 (brown/pink) with the ignition switch on and the ECU connector mated. This is the same as the 12V feed for the purge valve.

 

Good luck,

Ivan

[Blatherskite]

Thanks for the advice! I'll have a go on Sunday.