Argh, Mondial quit with a new different bug

1984 Mondial QV. I spent the last 8 months sorting out my FI issues. finally got that all done, car running good, take a few drives. Few weeks ago, it leaves me stranded. runs barely, but at least it starts and goes a bit. found the FI too lean, and richened it up just a touch. Smelled right sounded right, and I'm getting ready to go for a drive.

Dies. No sputter, cough, popping, just - off. Hmm, that sounds like ignition. I do a brief check of the FI, it's getting gas. Pull a plug wire from front and back bank, and hook up a few spare plugs. No fire! Both banks done packed it in. So, I'm looking at the wiring for the ignition and everything is separate but the TDC sensor.

Do these go bad with regularity? Is there a bench test for the TDC sensor? I have an oscilloscope, and know how to use it. other potential culprits that would halt ignition on both front and back bank?

Thanks

Doc

 

Anyone? bueller, bueller?

 

Thank you. Yes I did mean RPM sensor not TDC. My FI issues were long and painful. I had the WUR refurbished and it hasn't had much milage on it. The car died before running too lean, the plugs were almost white. I only added a very small touch to the mixture set to get it running smooth again. I can't check the charge voltage until I get it running again. Thank you for the wave forms, that's exactly what I need. I"ll report back on what I find.

 

1983 CIS(K jet) no Lambda circuit. Wish I had it.

 

Thanks Hetek. I did notice from the schematic in the reapir book that the B+ from the batt goes directly to both the coils, and the modules. I assume there's a fuse in there, but it does show the keyswitch very clearly. I'll check that as well. I'm in CO skiing this week so it'll be a bit until I can test.

 

Checked for +12 at pins on ign modules, no soap. Check at coils B+, no soap. Jiggle keyswitch and bounce back and forth from run to start, and 12V shows up. It looks like intermittent 12V from the keyswitch back to the ign area. I'll pull the switch, clean and verify, but pretty sure that's it.

Thanks again,

Doc

 

Well, heck, I just got back to work on this, and I can't figure out how to get the ignition switch out of the steering column. It is obviously a security part, and won't come out easily, but I can't see how to get it out unless I start drilling the pin on te side.

Anyone know how? Thanks.

 

Okay, I was on track for the 12V at the ignition switch. I rigged a temp wire and lamp from the B+ side of the ignition, and another from the switched side, and both are working well. Conected my Oscilloscope probe to pin three of the digiplex and can see the waveform well when the engine starts, and runs on the cold start circuit. Just after the engine comes out of cold start, and idle goes down to around 900, the engine dies and sputters.

HO! I'm watching the O-scope, and just as the engine dies, the waveform disappears. Nuyk, nuyk, nuyk. Try cranking and no waveform from pin 3. I bought a set of Marelli crank position sensors and swapped one in for my RPM sensor at the back of the flywheel housing under the rear dizzy. Crank it up, let it run, gets warm, idle goes down to 900, and it keeps running. I adjust the CO for about 1% on my cheap little meter, and go for a drive.

Oh, yeah! That thing must have been slowly failing for a long time. I had a stumble at high revs before, and it's gone. Maybe the combo of the slight enrichment, and the new sensor, but it's mucho bettero now.

Thanks to this forum again for the assist.

I now have two used but working TDC/RPM sensors left over. I will keep one as a spare, but one is for sale for $30 + a bit of shipping. PM me if you NEED one. They are $96 from Ferrari, which isn't too bad for a new one.