elec. fuel pump relay wiring diagram

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terry

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does anyone know the wiring for a 5 wire relay? wire colors are black, red, white, yellow and blue. I currently just use a ground and hot wire/fuse for the pump. seems like I have seen one here but cannot locate it now.
terry
 
30 main power in
87 power out
85 switch in
86 ground

Lots of times 85 and 86 can be swapped without issue as it's only a trigger circuit turning relay on.

Look at your relay, should be numbered, or google relay wiring.
 
87a can be ignored.

pumpmod.jpg
 
Agree. If a 5th wire, it is usually "87a", which is "normally closed". But, you might have a special fuel emergency shut-off relay. Photos help when asking such questions.

Be careful about polarity for 85 & 86 since it can matter. Sometimes the relay base will have a clamping diode, and many relays do. Sometimes they use a resistor instead, in which case polarity doesn't matter. Seems like I have seen "86" as ground in some documents (Radio Shack's bubble pack?). The numbers are a Bosch standard, that applies to many electrical devices besides just relays. You can find the list online. You can also find tutorials online. One discusses the coil polarity and some surprises they found.
 
thanks for the input. i'll just give it a try and see what happens. what could go wrong with switching # 85 and 86 ?
 
If you get it backwards, and there is a diode, the coil won't actuate w/ 12 V since the current will flow thru the diode. If you do it very briefly, you may not damage the diode. You can hear the relay click. To tell ahead of time if there is a diode, measure resistance w/ a multimeter, and you should measure low one way (<100 ohm?) and high the other way (>1000 ohm?). But, should be a symbol on the relay if it has a diode. When a diode fails, it usually fails shorted.
 
BillGrissom said:
If you get it backwards, and there is a diode, the coil won't actuate w/ 12 V since the current will flow thru the diode. If you do it very briefly, you may not damage the diode. You can hear the relay click. To tell ahead of time if there is a diode, measure resistance w/ a multimeter, and you should measure low one way (<100 ohm?) and high the other way (>1000 ohm?). But, should be a symbol on the relay if it has a diode. When a diode fails, it usually fails shorted.
Click to expand...
I do not agree with diode test with Ohm meter. Typical Ohm reading applied voltage, is less than a diode forward junction, so the diode appears invisible. The diode setting on a multi-meter is able to supply up to about 3 V open circuit, but the coil in parallel will block the reading, because of the current limit in force circuit. As suggested look at diagram on relay.
The suggestion to quickly test by applying voltage a short time is also unrealistic. The forward voltage maximum is only 1V, applying 12V will result in diode failure, before the relay clicks.
A current limited 12V supply of about 250mA, would enable safe testing. The correct current reading would be the lesser for correct polarity. Current varies, but most are between 75 and 150 mA. Incorrect polarity will hit the supply limit of 250mA, yet protect diode short term.
 
Don't forget to add a normally open pressure switch to your motor fed from the high pressure side of the oiling system that closes around 15 psi. This will obviously shut off the pump when the motor dies.

It's also nice to wire in a bypass switch (on/off), so you can prime the system with the key on & motor off. You can hide a switch too, so you have an anti-theft device.
 
jbc426 said:
Don't forget to add a normally open pressure switch to your motor fed from the high pressure side of the oiling system that closes around 15 psi. This will obviously shut off the pump when the motor dies.

It's also nice to wire in a bypass switch (on/off), so you can prime the system with the key on & motor off. You can hide a switch too, so you have an anti-theft device.
Click to expand...


hi folks
well currently I just have a toggle switch with a fuse that runs from the fuse box and to the pump of course a ground back at the pump itself. been like this for 10 years just thought I would step up the wiring since I am going from a holley blue to a mallary 140 pump.
 
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