Anti-run on solution

[steveg]

I've been plagued by run on for years, including after my rebuild. Ran across an article in Norm Nock's book re adapting an MGB/TR6 anti-run on valve (ARV) to Healeys.

It works!

On engine shutdown, an always-hot relay activates the timer, which powers the valve for 10 seconds; the valve opens and allows engine vacuum to connect to the carb overflow tubes, resulting in immediate shutoff of fuel to the combustion chambers. During normal running the path for the overflow tubes is open to the atmosphere and the engine vacuum is sealed off. Servo operation - while engine running - not affected.

Had to get rid of my PCV valve, though, as the ARV requires all the engine vacuum in order to work.

Nock used an MGB oil pressure warning light switch to operate the ARV, but I replaced that with an inexpensive delay timer.

Details at: https://www.pbase.com/stevegerow/healey_tech

 

[Keoke]

Now that is cute, I had to ditch the PCV unit also it created crank case pressure.

However, a simpler fix for Run on is :
1 push in clutch
2 Press brake pedal
3 shut engine off
4 ease clutch out


Stop it every time --LOL

 

[steveg]

I was looking for a more advanced solution so I could do plug cuts to check my supertuning without worrying about the engine running on or even backwards.

Not sure how evacuating the crankcase with a PCV would contribute to leaks. Mine seems to have sprung a valve cover leak since removing the PCV.

With the stock vent tube setup, no concerns over leaning out the mixture, though.

 

[Michael Oritt]

Steve--

That's an interesting way of dealing with the problem of running on, though it does not investigate or cure the cause which can be hard to find and remedy as it may be due to one of several things (or multiples thereof) ranging from a hot spot to a fouled plug to an air leak, etc. But don't you think that this "fix" might be masking something that will prohibit you from achieving the high state of tune that you seek through supertuning? In other words, if this valve allows you to "tolerate" an air leak or a fouled plug how will you know of that issue's presence and repair/eliminate it?

 

[andrea]

Hi Steve
Also my car suffered the same symptoms - use of 100 octane fuel cured it perfectly
Bad green fuel are the actual problem on all country

 

[Keoke]

Hi Steve
Also my car suffered the same symptoms - use of 100 octane fuel cured it perfectly
Bad green fuel are the actual problem on all country

Andrea:
I think you may be right, when traveling my first fill up is with leaded fuel not sold at the pumps here in CA, from then on I can usually find leaded fuel across the USA.

 

[steveg]

Andrea - you may be right. I won't get out of state with my car until summer of 2019 and like Keoke have to be satisfied with the Calif-brew gas/ethanol until then.

Michael - it must have been part of normal running in the '70s or British Leyland wouldn't have equipped all kinds of MGs, Triumphs, Jags and Sprites with it.

 

[Michael Oritt]

Steve--

I sent you a PM.

 

[steveg]

Steve--

That's an interesting way of dealing with the problem of running on, though it does not investigate or cure the cause which can be hard to find and remedy as it may be due to one of several things (or multiples thereof) ranging from a hot spot to a fouled plug to an air leak, etc. But don't you think that this "fix" might be masking something that will prohibit you from achieving the high state of tune that you seek through supertuning? In other words, if this valve allows you to "tolerate" an air leak or a fouled plug how will you know of that issue's presence and repair/eliminate it?

Michael -
I would argue that run on is a more-or-less common condition, not necessarily indicative of a larger problem. My newly rebuilt engine has only 2500 miles on it and runs very strong, so I think probems such as described are unlikely, although I'll conduct plug cuts to check things out.

Supportive anecdotes:
Back in the 50s & 60s, air cooled VWs had an anti-run on solenoid on the carb.
Norm Nock's original article (Nock Book, Pg 157) was dated 1996. He stated that he built the solution because at tech sessions people would ask him how to stop run on, and in fact his car exhibited it. He also discusses various methods factories used to fight this common problem.

 

[mgtf328]

Keoke, If the PCV gives excess pressure in the crank try fitting a restrictor in the line to the inlet manifold. It worked on my MGTF. All I did was drill a small hole in an inch long piece of steel rod and rammed it into the pipe. You may need to play around with the diameter of the hole before you get it right.
AJ

 

[steveg]

Have relocated anti run-on valve to more inconspicuous position on lower fender.
More photos at: https://www.pbase.com/stevegerow/healey_tech