Nostalgia season is upon us. There are carburetors all over my shop. Life used to be so simple. Maybe. Maybe not.
Many a customer after seeing our current collection of old time automobiles laments. “Those were the days. I could fix one of those with a hammer, pliers, and a screwdriver.”
How come I can’t? I have a shop full of screwdrivers, hammers and pliers. The VW Beetle is still not happy, nor the Porsche, nor the MG. I hope my customers are patient. Old cars get old problems. My old car diagnostic routines are a little rusty perhaps.
When a late model vehicle comes through the door and there is a problem with the way it runs after that quick look under the hood the first thing I do is plug in a computer to the diagnostic port on the vehicle. That computer is a close friend. “Running rough” says the customer. “Not all the time.”
A quick perusal of my computerized diagnostic tool data says. Cylinder number two is missing when the engine is at 20 per cent load at 2,000 rpm while travelling at 20kilometres per hour. The outside air temperature was 20 degrees Celsius. The engine temperature is 50 degrees Celsius. The vehicle is adding extra fuel on one bank of cylinders.
The vehicle is already warmed up. A road test reveals perfect running and perfect numbers on the computer. I know what is up. The intake manifold gaskets have shrunk. As the engine warms up they leak but once fully expanded they seal again. Cylinder number two goes a little bit too lean and misses. Solution: replace intake manifold gaskets.
One of those nostalgia pieces (Porsche) shows up at the shop. “She’s running rough.” “Intermittently.” No computer port on this baby. No history. I guess I have to make my own history. Road test number one. Runs perfectly. Road test number two. Runs perfectly. Road test number three (gotta drive a little further). The vehicle acts up. It feels like an ignition problem.
Back to the shop. No obvious issues under the hood. Time to rig up some test equipment.
Back on the road. Road test number one. Runs perfectly. Road test number two. Runs perfectly. Road test number three. Runs perfectly. Ready to give up! Road test number four produces the symptom. Test equipment shows a problem with the primary ignition circuit. Move the test equipment from the primary side of ignition system to the logic side. Time for more road testing and data recording.
You now know the drill. Road test one, two, three, four, five. Got it. Ignition module dropping out.
Time to find an ignition module. Do they make those anymore for that old thing? Found one in Germany. A couple weeks and we will have that thing back on the road again.
Ahh …. nostalgia!
Trail’s Ron Nutini is a licensed automotive technician and graduate of mechanical engineering from UBC. E-mail: firstname.lastname@example.org