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Robert Thornton

elect fuel pump saftey switch

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the safety switch has 3 wire plugs, one to switch,  one  to pump, other to solenoid.  on my 52 dodge b3b i have a stomp starter no solenoid so where do you run the wire to run pump when starting. I Thought i might try to wire it to negative side of push button on top of starter. or just not use that solenoid wire pump will come on when oil psi goes up when starting. just wont start as quick.

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So is the purpose of the switch to not pump while the truck is on, but not running?  I've just always had my pump wired to the key in the on position 

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wire the pump from the starter switch and run to a toggle switch. then from the toggle switch to the electric fuel pump.  Thus way the pump is always turned off and then you can switch the pump on by flipping the toggle to the on position and then prime the carb or leave it on to feed the carb.

 

Buy having the this setup you control the electric, some people put the switch on apulse switch so as long as you push the pulse button the electric pump will push fuel but this makes it harder to drive if you need to use the electric as a backup pump.

 

Rich Hartung

desoto1939@aol.com 

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this is why you need to know just what switch/module the man is using...some need the third wire for ignition pulse..it one shots for a few seconds at key on, if no signal from the distributor it will not continue to run....others will swing the pendulum and disconnect the pump but a third wire is there to automatically trigger a warning light or even tie into the emergency flashers.  Then you have a few designs of the OEM retrofit.  So, you truly need to know just what style/model the man has on hand in order to answer his question.

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Yes I agree that we all need to know which model or specific electric FP the gentleman is going to use. The ones that you see on Ebay and also at the swap meets are mostly two wire units and are the AIRTEX model for 6 volt positive ground units.  So in that case the man only has two wires to worry about. One to supply power the other for grounding. So therefore one wire from the ignition switch when the swithc is hot to the toggles switch on the dash. then when the toggle is on then the power will turn on the Electrci fp. Very simple setup and works just fine unless the owner has some other setup that we dont know about.

 

So why does he need a safety switch? He has not stated the reason for this type of switch. Most owners use the electric pump as a primer pump so the use of the toggle switch is the main cutoff for the power to the pump.

 

Feel he needs to provide more information on why a safety switch.

 

Rich Hartung

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many folks with electric and especially the high pressure fuel injection fuel pumps have a pendulum switch that will interrupt the power with a roll over and a collision impact of x magnitude.  One either used the OEM from the donor system installed/retrofitted or go with an aftermarket.  They vary by design and purpose...but yes, they are a valid safety device.  

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the pump is in line close to fuel tank. model after market GZYF 12S universal micro 12 volt 2 wire self priming. The pump is low psi  4-7 lb  for carburetor . the problem is I have safety oil psi switch that has 3 wire connectors one is for pump feed, one is for ignition key start the third is to a solenoid. I do not  have solenoid, trucks have foot starter that is mechanical. the wire to solenoid is used to prime pump when starting. PUMP WILL NOT RUN IF THERE IS  LESS THAN 15PSI OF OIL psi THIS KEEPS PUMP FROM RUNNING IF MOTER IS OFF IN AN ACCIDENT. I CANT DECIDE TO JUST LEVE 3 RD OFF WHICH CAUSES LONGER CRANK TIME or try to put a dummy solenoid wired to key switch or just let pump come on with switch and wate a few seconds to start. it starts very quick now when pump is on.   I hope this a better explanation  I appreciate your help and knowledge   ROBERT T

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I forgot to add I have third wire hooked to starter right now which is hot all the time this causes a feed back , but it will turn off with switch.     the safety switch looks just like a oil sending unit with 3 wire plugs

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the number you listed was for the pump and that shows just two wires, positive and ground.  The switch is the regulating device for control of the pump in accordance to the preset pressure conditions of that device.  What brand/type/part number 3 bladed oil pressure safety switch are you using...there are a number of schematics on the internet with proper wiring of the safety oil pressure switch.   

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MR GASKET 7872 fuel pump safety switch        I can find plenty of instruction on wiring with solenoid but nothing if you have mechanical starter which has no solenoid. I appreciate your help  thanks Robert t

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  in you case where there is no solenoid to connect to..you must then connect to the output of the stomp switch, the lead the goes into the starter itself..therein you will have the voltage to run the pump while turning the starter and hopefully your pressure rise will be quick enough to switch internally to continue to run the pump.  If you should stall, the pressure subside and at below 15PSI the switch contacts open and shut down the pump.  

 

http://documents.holley.com/mr_gasket_instructions_fuel_pump_safety_switch_7872.pdf

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55 minutes ago, Plymouthy Adams said:

  in you case where there is no solenoid to connect to..you must then connect to the output of the stomp switch, the lead the goes into the starter itself..therein you will have the voltage to run the pump while turning the starter and hopefully your pressure rise will be quick enough to switch internally to continue to run the pump.  If you should stall, the pressure subside and at below 15PSI the switch contacts open and shut down the pump.  

 

http://documents.holley.com/mr_gasket_instructions_fuel_pump_safety_switch_7872.pdf

 

Couldn't you wire the pump power from the armature output of the generator (between the generator and the cutout built into the voltage regulator). Then the pump would only be powered if the generator was producing electricity (i.e. the engine was running). A SPDT switch on the dash, possibly momentary push button style, could be used to power the pump manually to fill the carb bowl if the car hasn't been run in a while.

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9 minutes ago, TodFitch said:

 

Couldn't you wire the pump power from the armature output of the generator (between the generator and the cutout built into the voltage regulator). Then the pump would only be powered if the generator was producing electricity (i.e. the engine was running). A SPDT switch on the dash, possibly momentary push button style, could be used to power the pump manually to fill the carb bowl if the car hasn't been run in a while.

What would the voltage out of the generator be when running? 

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49 minutes ago, maok said:

What would the voltage out of the generator be when running? 

 

In general, it should probably be in the range of 6 to 8 volts. The regulator should be holding at the proper voltage for charging the battery. Except possibly at idle where the voltage will drop some, the amount probably varies based on generator condition, idle RPM, etc. You probably want to check the idle voltage on the armature side of the regulator to verify it is high enough.

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4 hours ago, Plymouthy Adams said:

  in you case where there is no solenoid to connect to..you must then connect to the output of the stomp switch, the lead the goes into the starter itself..therein you will have the voltage to run the pump while turning the starter and hopefully your pressure rise will be quick enough to switch internally to continue to run the pump.  If you should stall, the pressure subside and at below 15PSI the switch contacts open and shut down the pump.  

 

http://documents.holley.com/mr_gasket_instructions_fuel_pump_safety_switch_7872.pdf

thanks Robert t

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 thanks this gives me some imfo to think about I am running a12 volt single wire alternator with internal regulator will see what output is I can not connect to starter button It is hot all the time. if I could take it apart and put a wire to open side of starter button then when you push starter it would be hot.  I do like the alternator idea it could work.  I knew I could get help here you always come through. I will let you know what works thanks to you all Robert T

Edited by Robert Thornton

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9 hours ago, Plymouthy Adams said:

IF you connect the safety switch to the alternator output it would continue to pump as long as the engine is running and you have defeated your original intention of shut down with low oil pressure....

 

If the goal is to stop the electrical fuel pump when the engine stops (e.g. in an accident), then either an oil pressure operated switch or powering from the armature side of the external regulator wiring on a generator will do.

 

If you have an alternator, especially a one wire alternator, then I don't think there is a place you can pull the DC power from that is on only when the engine is running. In that case, as Plymouthy Adams notes, an oil pressure activated switch is probably your best option.

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3 hours ago, TodFitch said:

 

If the goal is to stop the electrical fuel pump when the engine stops (e.g. in an accident), then either an oil pressure operated switch or powering from the armature side of the external regulator wiring on a generator will do.

 

If you have an alternator, especially a one wire alternator, then I don't think there is a place you can pull the DC power from that is on only when the engine is running. In that case, as Plymouthy Adams notes, an oil pressure activated switch is probably your best option.

 

oil pressure control of the pump was the man's original desire and reason for the question....just tried to stay on point with the man...

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1 hour ago, Plymouthy Adams said:

 

oil pressure control of the pump was the man's original desire and reason for the question....just tried to stay on point with the man...

 

Yes, and I veered away because on my '33 the oil pressure relief mechanism is different than on late '33 and up engines where the flow through the oil filter is shut off when the pressure drops too low. End result is that hot idle oil pressure on my engine is low enough that I'd end up with the fuel pump being shut off. So my immediate thought was to offer something that might also work on my car. :)

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If I followed this thread correctly and you are installing an oil pressure safety switch in line with the electrical supply to your fuel pump, then all you will require is a momentary push on switch in parallel with the oil pressure safety switch when starting. Keep in mind as Tod Fitch pointed out, should your oil pressure drop below the safety switch limit when your engine is hot your engine will die because of fuel starvation. 

 

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A push button would act  like solenoid. That might be my best bet  the third wire to solenoid was just to prime pump. I could do the same with a  push button . With a car type starter you would put 1 wire to pump 1 to  switch 1 to solenoid and add a push button to start your car or truck. unless you have a starter switch with a start terminal.        thanks for your time  helping me with this. Robert T 

 

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Why not use an electric fuel pump inertial switch like this: http://www.rockauto.com/en/moreinfo.php?pk=941751&cc=1122028&jsn=501

This one is for a 1992 F150 4.9L. Use the inertial switch to cut power to the fuel pump relay coil during a collision. Should be a little safer than the oil pressure switch.

Wire from ignition switch to inertial switch, then from inertial switch to relay coil, then from relay coil to ground. Run a power wire from a source of fused battery voltage to the normally open contact of the relay, then from the other side of the normally open relay contact to your fuel pump. When you turn on the ignition the fuel pump relay will energize sending power to the fuel pump. In case of an accident the inertial switch opens, de-energizing the fuel pump relay and shutting off the pump. 

 

Scott

Edited by cavisco1
Add more information.

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To good minds thank alike. I just ordered one yesterday. I had been thinking about it and thought it a good idea to have. new was pricey found a good used one with wiring $18.00. I also found  my oil safety switch was bad. it would run every time switch was on . might just do both would not heart to be over cautious if one might fail. i will add a push button to prime if necessary. I already have ordered a new oil psi safety switch. pluming is there might, as well use it. inertia switch was a good call I wish I had thought of it earlier.  Thanks so much for your help and time ROBERT T

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