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Junbug

71' 510 won't shut off with the key

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1971 datsun 510 with a 1979 620 l20b motor in it won't shut off with the key. The alternator has 4 wires, 2 on posts and 2 on a plug. Any ideas?

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Is it dieseling? Or just continuing to run normally?

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What have you done to it recently, change alternators?

Have you added a wire anywhere?

Did you add a radio, tack, clock, change any wires?

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You have an internally regulated alternator on a vehicle that should have an external regulator. '78 and on Datsuns were internally regulated.

 

What you can do is convert your harness to eliminate the regulator. It requires joining two pair of wires.

 

6alternator_ir.jpg

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has it been this way for awhile ot you just put this motor in with a later model alternator.

 

 

YOu can disconnect the volt reg ,

as above drawing will show. you can make 2 jumpers with male blade connectors and jumber the colored wires in the engine side of the harness. So no cutting of harness!!!!!!!!

or you can get a say a 75 610  50amp alternator(external volt reg type) to install on that a L20.

 

 

 

if this was running fine fine and it had a early model alternaotr in there already and just stsarted happening then the 510 volt regis bad.

 

 

need to give more infor. a 79 motor doent mean it has a 79spec alternator in there

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First, Thanks guys for all the info. 2nd, This is a new project that I am working on. Old 71' that has been with me for about 15 years with a motor and trans I just bought this motor and put it in. Just got the car running for the first time. Gonna try the jumper fix

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If you kept your old alternator, the jumper fix will do nothing.

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old alt might be a L16 tyep 35 amper and have the smaller hole size. L20 mounts use the bigger holes. I guess one could bore out the L16 alt if he still has it

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Or bolted the stamped steel mount to the L20B with his 35A ER alt.

 

Who knows until more info is provided.

 

 

Is the case of said alt all metal or us there a black plastic cover on the back?

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If you kept the 510 alternator you wouldn't have this problem

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Keep in mind that you have to unplug the regulator from the wiring harness and put the jumper wires on the end of the plug like in the photo below.

DSCN1040.jpg

 

This below is a better photo because it shows the jumper wires at the plug and the regulator deleted/gone.

wiring_diagram_IR.jpg

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old alt might be a L16 tyep 35 amper and have the smaller hole size. L20 mounts use the bigger holes. I guess one could bore out the L16 alt if he still has it

That's what I do. I drill the whole bracket to eliminate the two bolts and use one long bolt all the way through the alternator and bracket.

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If it's just dieseling, a fuel cutoff solenoid will fix you up.

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If an L20B it will have an idle cut solenoid already. If not connected, there won't be any idle fuel to cause dieseling. If the idle speed is turned way up to compensate for no idle it might diesel.

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Just finished the 2 jumper across the plug and she shuts off with the key now. Thanks again

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Whoo hoo easy fix.

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Check to make sure it is charging, the moment you unplugged the regulator it should have shut down, running it should show over 13 volts.

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