Hand held switch to run fuel pump

centerline · Jan 20, 2015

the wording of your post is kind of broken into less than full sentences so its hard to understand what you are asking....
my question is, what is the need for a "hand held" fuel pump switch?

but as for connecting a push button switch, which i assume is for bleeding the system, the following procedure will work well for you...

if you want to hook up a "momentary on" push button switch to an electric fuel pump without the power backfeeding to other electronics, you will need a diode in the fuel pump hot wire. this is as simple as joining two wires with butt connectors.

then you will need to connect a wire from the switch to the hot wire on the fuel pump, between the diode and the pump.

then connect a fused hot wire to the switch.... and MOUNT the switch... DONE!

now when you press the button, the power will pass thru the switch to power the fuel pump, but because of the diode in the main hot line, the power will not be able to run backwards up it to get to the other devices..

a diode is a one way electrical valve... current can only pass thru it in one direction.

Stu Jackson · Jan 20, 2015

centerline's right.

If your goal is to bleed your engine without the glow plugs running, you might be interested in noodling around the links here:

http://c34.org/bbs/index.php/topic,5078.msg41829.html#msg41829

KZW · Jan 20, 2015

If anyone has pictures of the electric fuel pump on the M-25XPB, showing the hot and neutral connections on the fuel pump, I'd like to see it!

I've noodled around the C34 listing Stu posted, and have not seen such. It is entirely possible I missed it.

Stu Jackson · Jan 20, 2015

KZW said:
If anyone has pictures of the electric fuel pump on the M-25XPB, showing the hot and neutral connections on the fuel pump, I'd like to see it!

I've noodled around the C34 listing Stu posted, and have not seen such. It is entirely possible I missed it.

IIRC, there are no hot and neutral wires on a fuel pump . Just a hot wire and a ground.

KZW · Jan 20, 2015

Stu,

Thank you for the correction, I meant ground. I should have been more specific.

I would still love to see a picture.

Stu Jackson · Jan 20, 2015

KZW said:
I would still love to see a picture.

OK, try this:

http://c34.org/bbs/index.php/topic,2515.0.html

KZW · Jan 20, 2015

Stu Jackson said:
OK, try this:

http://c34.org/bbs/index.php/topic,2515.0.html

Nothing in the reference or the branch threads within the reference that comes close to looking like the pump on the M-25XPB. I can go in with a volt meter and find the hot lead, but I really don't want to go splicing in diodes and switches without a good picture/diagram to ensure I won't hose up something else. There will be a bit of voltage drop across the diode (my guess would be 1 to 1.5 volts turn on voltage). One presumes that won't be a factor for the pump.

On the other hand, I would like the ability to bleed the fuel lines on my own and also not light up the glow plugs in the process.

woodster · Jan 20, 2015

if you hook the wires to the hot side of the pump and the other wire from you switch to a 12 v source that is all you need and everything else will work as before as long as you don't leave the priming switch in the on position and the best way to keep that from happening is to either use a no push button switch like a starter button or a normally open momentary toggle switch and if you don't activate it will not do any thing

centerline · Jan 20, 2015

KZW said:
Nothing in the reference or the branch threads within the reference that comes close to looking like the pump on the M-25XPB. I can go in with a volt meter and find the hot lead, but I really don't want to go splicing in diodes and switches without a good picture/diagram to ensure I won't hose up something else. There will be a bit of voltage drop across the diode (my guess would be 1 to 1.5 volts turn on voltage). One presumes that won't be a factor for the pump.

On the other hand, I would like the ability to bleed the fuel lines on my own and also not light up the glow plugs in the process.

if you have a mutimeter and a non destructive wire tap, you will be able to distinguish between the hot and the ground...

once you find them and can tell the difference, its as simple as i stated earlier. its been said that a picture may be worth a thousand words, but in this case a photo of what someone else may have done, wont show you how to do it, and it may or may not be any different that what you will do, but it possibly will be in a different location.

you just need to get the right supplies and then cut, strip and crimp...

SimiSAilor · Jan 21, 2015

Why not just remove the two wires from the oil pressure switch, make a short jumper wire.
Connect those two and turn the key on and the lift pump should run. We are talking about a Universal diesel?

njlarry · Jan 21, 2015

woodster said:
if you hook the wires to the hot side of the pump and the other wire from you switch to a 12 v source that is all you need and everything else will work as before as long as you don't leave the priming switch in the on position and the best way to keep that from happening is to either use a no push button switch like a starter button or a normally open momentary toggle switch and if you don't activate it will not do any thing

If I understand this correctly, sounds like all you have to do is hook up a normally open remote starter switch (like we used get at PEP Boys to use to tune our pre-emission cars) from the positive battery terminal to the positive lead coming off the pump. Every thing is close at hand and now we can bleed the XPB without burning the glow plugs.
Sounds like a piece of cake. Thank you.
(These engines are supposed to be self bleeding but after a filter change I usually will have the engine stall if not bled)

woodster · Jan 21, 2015

njlarry said:
If I understand this correctly, sounds like all you have to do is hook up a normally open remote starter switch (like we used get at PEP Boys to use to tune our pre-emission cars) from the positive battery terminal to the positive lead coming off the pump. Every thing is close at hand and now we can bleed the XPB without burning the glow plugs.
Sounds like a piece of cake. Thank you.
(These engines are supposed to be self bleeding but after a filter change I usually will have the engine stall if not bled)

that is correct