As I begin to think about prepping the Series 2 OTS for spring here in New England, I’m recalling how last season, while driving about, the engine quit after an half hour of touring on country roads. . It would then turn over but would to start. Hmmm, a fuel issue of sorts, I thought.
After 20 minutes or so, it started right up and continued flawlessly back home. Besides checking the fuel filter for possible sediment (I did and it’s clear), what else should I look at to trace down what I think is a fuel delivery issue?
Did you take a look at the inside of the top part of the fuel filter on the firewall. It may have a very fine brass (?) screen that filters the fuel going to the carbs from the bowl. That can get clogged and cause the problem you are experiencing. It did on my car. You need to get it out and see if you can see light through it.
When it would not start, was the fuel pump running? Usually it will run briefly with every ‘key-on’ when you are attempting to start.
Another possible source of trouble is an ignition part that fails when it gets really hot, then revives after it has cooled down. I have had a coil do that, others have reported a condenser that would do the same thing.
‘Spark or fuel?’ is the initial bifurcation in diagnosing a non-start issue.
Yes, Geo, the fuel pump was running when the key was on. Thanks for the diagnosis - given the engine quit when warm and then revived when cool could point to something in the ignition system getting too hot then cooling down.
The easiest way to access the screen is to remove the oval lid on the gas tank. What tends to happen is that debris fills the sump of the tank, and causes a restriction at the inlet. Pump suction then causes vapor lock. I’ve had this happen once or twice.
Since the coil is the simpler problem to identify and fix I would be tempted to start there. Everyone should carry (IMO) a spare coil so the easy check is to drive until it fails, then swap the wires to the spare (cool) coil and see if it starts. Have the spare coil ready so the swap is quick before any fuel problem (e.g. vapor lock) has a chance to resolve itself. It is not necessary to do a full coil replacement, just have the spare coil attached (bungees, duct tape, what have you) where the wires can be easily moved.
I actually mounted my spare coil in such a spot for an easy back-up (and one less spare part in the boot):
+1 on the coil overheating. Also check the fuel tank vent for clogging. If it runs fine for awhile, then quits and restarts fine 20 minutes later, the line may be clogged. Pump pulls a vacuum until the vacuum of the tank overcomes the capability of the pump. Fuel flow then stops. As it sits, the pressure slowly equalizes to where the pump can again draw fuel, and it starts all over again.
What actually happens is that the blockage causes pressure to drop in the pump feed line. The fuel will vaporize when line pressure drops below vapor pressue. The pump isn’t efficient when pumping vapor and it won’t hold prime. After sitting, the line pressure normalizes and function returns. It can seem intermittent, because the effect is temperature sensitive.
