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S12 Technical Areas => Engine Tech => ENGINE (OEM): VG30E Tech => Topic started by: mikey on 10:27:32 AM / 12-Jul-19

Title: SE will sporadically cut ignition power
Post by: mikey on 10:27:32 AM / 12-Jul-19
I have an '88 SE with the VG30E engine.  The car sat for a while before I purchased it.  It would start and run fine and then shut off without warning.  It would not sputter and die, as if being starved of fuel, it would shut off as if someone literally took the key out of the ignition while driving.  When this happens, it will not restart.  However if you wait 15 minutes or longer it will restart no issue and run fine again.  Sometimes it will shut down within 10 seconds of a cold start, sometimes it will run for 30 minutes without issue before shutting down.  But it will always shut down in the form of an ignition cut.

What I'm asking is, are their known "weak points" regarding the VG engine that I should start with?  I know that if I run down the list A-Z, this is going to get very time consuming and potentially expensive, and I'd rather start with the most common known issues and work down from there.  I am completely new to the VG engine, so a lot of this is foreign to me.  I do have a factory service manual at my disposal which will help, but again with the time consuming part.

Any ideas?!
Title: Re: SE will sporadically cut ignition power
Post by: rednucleus on 08:00:00 PM / 12-Jul-19
When my CA did this is was due to failing solder joints on the main computer board. Thought I had a failing fuel pump as the symptom was intermittent loss of pump power. I opened the metal box and carefully pushed on different components and found on one section of board I could consistently replicate the problem. So I removed the circuit board and re-heated all the original solder joints and have not had a problem in a few years now. Here's the link to my thread on the problem.
https://club-s12.org/forum/index.php/topic,38038.msg403344.html#msg403344
Title: Re: SE will sporadically cut ignition power
Post by: mikey on 02:23:28 PM / 22-Jul-19
When my CA did this is was due to failing solder joints on the main computer board. Thought I had a failing fuel pump as the symptom was intermittent loss of pump power. I opened the metal box and carefully pushed on different components and found on one section of board I could consistently replicate the problem. So I removed the circuit board and re-heated all the original solder joints and have not had a problem in a few years now. Here's the link to my thread on the problem.
https://club-s12.org/forum/index.php/topic,38038.msg403344.html#msg403344

This is pretty interesting.  I did swap out the ECU for a spare I had sitting around.  This did not affect the problem at all.  It still caused the same symptoms, so I'm relatively confident (at least at this point) that it is not the ECU.  So far I have ruled out a bunch of sensors with the service manual test procedures and a multimeter.  Tonight I have to dive a bit more into the ignition system.  Thanks for the input!