'61 BN-7 Progressively Harder Starting . . . Now Won't Start

[mrunci]

Professionally restored dual carb BN-7 with about 200 gentle road miles on the clock has become progressively harder to start over the last couple of weeks. Yesterday starter turned over briskly as usual but it took a very long time to catch. Then it sputtered very meekly for a couple of minutes until it finally smoothed out and ran evenly, idling at about 800 rpm as usual. After a careful drive lasting about 20 minutes, finishing with a strong run to the top of the hill to my home, during which the car performed flawlessly with normal oil pressure and operating temp, the engine surprisingly exhibited some brief diesling (for the first time) at shut off. Today the engine just will not fire. The full pump runs as it should until the bowls are full, then stops. A short sputter on the initial push of the starter button . . . . then just cranking after that with no ignition.
There are no apparent problems with connections or signs of fuel leaks, nor have I made any changes in adjustments to timing or carbs.
My sense is that this condition has been developing and today is the tipping point.
Any suggestions as to where I start to troubleshoot?
Matt Runci

 

[Keith_M]

I would check two things: First, that your choke is operating correctly. Second, that your points haven't closed up.

The fact that the car ran well once warmed up argues for the choke, but if it's working right it's worth checking the points.

 

[andrewss]

Start at the back and work towards the front. 1) Check the battery and then check the voltage regulator. If the voltage regulator is not charging the battery when you are driving then it's charge maybe too low for the starter motor (even though it turns over). 2) fuel filter between the tank and pump... is it blocked or leaking.. 3) disconnect the fuel feed at the carbs (turn ignition on for a second or two) see if you have a regular fuel supply.. Next check the float bowl level.. check that the float lever (the arm that holds the float needle) is set at the correct height (use a 7/16 drill bit to check).. check for clean float bowls.... I could go on but this is a good starting point.. Its just a process of elimination until you find the problem.

 

[mrunci]

Thank you Keith and Andrew. I have my weekend project.

 

[Brinkerhoff]

Throw in my vote for points and or condenser.

 

[nevets]

I agree with the above...my guess would be ignition no fuel.

 

[Steve P.]

I've fought this battle a few times. Most likely first; points, condenser, coil, a fault in wiring
(special attention to ALL connections and connectors), fuel filter. I've replaced many condensers
and coils over the years that cause the symptoms you mentioned. Good luck!
Steve

 

[Patrick67BJ8]

Thank you Keith and Andrew. I have my weekend project.

When trying to read voltage remember that you can have a bad connection and still get your voltmeter to read but checking voltage with a 12 volt light tester will conform that you have a good connection because you also have good amps flowing through the circuit.

 

[mrunci]

Thanks to all who offered advice based on their experience.
The problem has now been solved - it was traced to a vacuum leak at the frieze plug on the rear of the intake manifold. Apparently it developed slowly, grew progressively worse, and finally blew out leaving a gaping hole. Hence the slow-to-no start problem.
It has now been replaced (thanks to Allen Hendrix) and the car fires up exactly as it should (and had).

 

[TimK]

Thanks to all who offered advice based on their experience.
The problem has now been solved - it was traced to a vacuum leak at the frieze plug on the rear of the intake manifold. Apparently it developed slowly, grew progressively worse, and finally blew out leaving a gaping hole. Hence the slow-to-no start problem.
It has now been replaced (thanks to Allen Hendrix) and the car fires up exactly as it should (and had).

This goes to show how difficult it is to diagnose problems remotely, and how many different ways similar symptoms can be caused. I appreciate the followup to explain what really happened.