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Anti-run-on Valve in a '71

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KLUTZ

KLUTZ

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I have a problem with the car running on for about 5 seconds when I shut it off, if the engine is hot. I was thinking of installing an anti-run-on valve, and I have been offered one from another member, who doesn't need his. The idle on the car is a little fast, 1400 and I imagine that would contribute a bit to it, but what I am wondering is... Would the wiring for the ARV be on the harness for the '71? I don't think they had them origionally, did they? If so, I will put it on and see if there is a differance, if not... Guess not.

Thanks

Paul
 
To install an anti-run on valve in a car that did not come with it would be a major undertaking. Even the ignition switch is different. Only a few techs even understand how the system works. And every component must work perfectly for the system to work properly. One of the red-cover Bentley manuals describes this ingenious system.

Alan T
 
Paul - For a good description of how the anti run on valve works, go to Paul Hunt's web site, The Pages of Bee and Vee at: https://www.mgb-stuff.org.uk/ Click on Spanners, Fuel, then running on. Paul describes what causes run on and how the anti run on valve works. Your fast idle is definitely contributing to the problem and is probably set that way because the car doesn't idle poperly due to less than perfect tuning (particularly if the timing is retarded too much, requiring a higher idle setting). The anti run on valve can be made to work on cars without the proper wiring and ignition switch with the use of a single pole, double throw relay if you wish to persue the project.

You can also get a print of the wiring for your car and the later cars with the ARV installed so you can see the difference at: https://www.advanceautowire.com/ Click on Stock Schematics.
Good luck,
 
If your idle is at 1400, that is most likely the cause. Can you not set the idle to 1000 or lower?
 
My idle is near to the 900 mark, and it seems to be too high. My anti-run on system isn't functional right now as the tab for the lug on the wiring harness for the oil pressure sensor is broken off, and the connections to the valve itself are broken. I'd like to get it working, but those parts are kind of expensive and I have other, more pressing concerns to repair on the car.

You're far more prone to run-on with improper idle speed, overadvanced timing, and carbon deposits in the head. If your engine is idling too high to conceal a tuning issue, you could be prone to any of the above problems.
 
I agree with William....adjust the idle down to around 900....Then start tunning to get it to run properly at 900....Make sure you have no air getting into the intake from the carb mounts or other areas.
 
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I agree with William....adjust the idle down to around 900....Then start tunning to get it to run properly at 900....Make sure you have no air getting into the intake from the carb mounts or other areas.

[/ QUOTE ]


Ron,
The fast idle screws are both set out as far as they need. I sprayed Carb. cleaner around the mounts and detected no leaks, and the choke cable is not too tight.
How can I drop the idle?

Paul
 
Can't really think of what exactly would be keeping your idle so high, remove the air cleaner(if you haven't already) and look at the butterfly valves...at correct idle they should be almost closed,with only a slight tilt...if adjusting the screws out does nothing, then maybe it's as simple as something not allowing the throttle to fully release.
 
Check that your throttle disks are properly centered. Often they can look fine, but are off center just a bit and that will keep you from adjusting the idle ddown to the level it should be. You may have to remove the carbs, but you need to loosen the screws holding the disks and rock things around and back and forth to insure that the disks are cenered and allowing everything to close properly.
Good luck,
 
Something just dawned on me. ~sheesh~

When I had the carbs off to clean them, I noticed that the screw thingy on one of the butterfly valves was not on. I had intended to look into replacing it of going a different route, (I have read about plugging it up), but I guess I was in such a state to have it on the road, it totally slipped my mind.
Could this be a major issue with the idle? And.. what exactly does the screw do, and how can I "Plug" where it used to be?

Paul
 
Are you talking about two screws that go thorugh the butterfly valve itself? If so that could be your problem...as described above by Dave.
 
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Are you talking about two screws that go thorugh the butterfly valve itself? If so that could be your problem...as described above by Dave.

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YUP
 
I believe that maybe your problem, the butterfly is probably not seating properly in the body.
 
& could be vibrating around.

Luckily, when the screw came loose, it didn't do any damage to the engine! Has it showed up in your oil pan yet?
 
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& could be vibrating around.

Luckily, when the screw came loose, it didn't do any damage to the engine! Has it showed up in your oil pan yet?

[/ QUOTE ]


I wouldn't really know Tony. I changed the oil in the fall before putting it in storage, and wouldn't have even known about it. It may have been off for years for all I know. Right now though, I don't think I will worry about it; It's 30c right now and sunny. /ubbthreads/images/graemlins/thumbsup.gif
I will take them off when we have a run of rain and fix them up.

Paul
 
Hmm, same kind that vacume leak. Chewing gum won't work but a small bolt or screw would I expect.
 
[ QUOTE ]
[ QUOTE ]
& could be vibrating around.

Luckily, when the screw came loose, it didn't do any damage to the engine! Has it showed up in your oil pan yet?

[/ QUOTE ]


It's 30c right now and sunny. /ubbthreads/images/graemlins/thumbsup.gif


[/ QUOTE ]

I love this weather...I just calculated the mpg on SWMBO's MGA...26mpg..."Look at all the money we'll save if you let me drive it to work" /ubbthreads/images/graemlins/driving.gif ....Lets just say I am still driving the Caddy. /ubbthreads/images/graemlins/nopity.gif
 
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