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Actual builder now!
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Discussion Starter #1
I dont know how to explain this. Last year I had a new fuel pump installed. Since then I have noticed that the pump runs with the four way flashers. It pulses with the lights. 5.0 with EFI and Chuck's rebuilt harness. What is going on? It didn't used to do this and seems to run fine otherwise.
 

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Bad ground?
Always start by checking grounds.


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I have seen exactly this issue before. With the ignition off and the hazard lights on, power will track back through to the ignition circuit if the indicator switch is in either the left or right turn position. It will power the ignition circuit briefly with each pulse of the indicator lamps.
Problem can be solved using a double pole hazard light switch along with some rewiring, or installing some blocking diodes.

Cheers, Nigel in South Oz
 

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Discussion Starter #4
Thank you! Good to know it is not unique. Or I guess I could put a fuel pump switch on the dash to use in emergency and just make it more difficult to steal
 

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Discussion Starter #5
Nigel: Where would I install the diodes? Power to the self canceling indicator module?
 

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If it didn’t do this before you changed the pump then the issue is related to the pump, not the flashers.

What was the reason for changing the pump?


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Without knowing the wiring layout, I will say that is likely to work. 20 amp diode will do the job, or 2x 10amp in parallel.

Best of luck, Nigel
 

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Discussion Starter #8
If it didn’t do this before you changed the pump then the issue is related to the pump, not the flashers.

What was the reason for changing the pump?


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Pump failed leaving me stranded but looking good on the side of the road. The old pump always sounded sickly compared to the new one. Think it had been on it's way out for a while. Not sure how it could be related to the pump since that is remove two wires change pump and replace two wires.
I did also install a self cancelling module for the indicators since I kept forgetting to manually cancel the turn signals with the provided toggle switches. I know, I could have done like everybody else on the road and just not used the indicators. Seems maybe more likely that it is related to that module? The module has power and so does the 3 way momentary switch it uses. I didn't notice the problem for a while since I don't often use the four ways.
 

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Official OLD GUY
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Not to rub salt into the wound but those turn signal flasher units are notorious for causing electrical gremlins. They are known to have issues with "marginal grounds" and are internally powered/activated by triacs, which bleed current if pushed too close to threshold current values . . .
Any chance you only have one dash indicator for TS function? If yes, install diodes in the power lines (left and right) to the indicator, that will isolate the backfeed. Stripe on diode toward the lamp.

My guess isn't the pump install but rather the TS module.

Doc
 

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Discussion Starter #10
Not to rub salt into the wound but those turn signal flasher units are notorious for causing electrical gremlins. They are known to have issues with "marginal grounds" and are internally powered/activated by triacs, which bleed current if pushed too close to threshold current values . . .
Any chance you only have one dash indicator for TS function? If yes, install diodes in the power lines (left and right) to the indicator, that will isolate the backfeed. Stripe on diode toward the lamp.

My guess isn't the pump install but rather the TS module.

Doc

No salt taken Doc and thanks for the reply. Yes I suspected the module too. Other than this problem it has been functioning well. OK I'll try the diode option. Cheap and not too difficult to do. I do only have one indicator for the TS on the dash as is provided by the kit. . Did not occur to me to isolate that with diodes.
 

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Discussion Starter #11
Quick update for anybody who might be following.. After a chat with the manufacturer of the self cancelling module we traced the problem to how I activated the fourways.. I was still using the Mustang wiring for the fourways. The module will activate fourways by itself if both left and right turn signals are pressed at the same time. Since I have a 3 way momentary switch for the signals he suggested I run wires from left and right triggering wires to one pole of a momentary switch with power to the other pole. Diodes are installed in the triggering wires (Doc) to prevent them backfeeding each other. Then abandon Mustang fourway wires. Presto, Problem fixed.
 
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