Magnetic tach sensor?

[Number21]

My '83 6.9 F250 has no tach, and I want one. Don't want to spend very much money, this is just an old beater. Not having a factory tach it does not have a tach sensor either. Ebay has lots of cheap digital tachs like this one:
http://www.ebay.com/itm/4-Digital-R...-Sensor-NPN-/291122353744?hash=item43c83e9650

They require a small magnet to be placed somewhere to read RPMs. Has anybody used something like this, and if so, where did you put the magnet? Would it throw off the balance if I put a tiny magnet on the crank pulley? Is there a better place to put it?

 

[riotwarrior]

Never seen one of those. Suppose you could by it and try it.

Crank is THE place to install magnet. Maybe some epoxy and small magnet hopefully it clears the timing tab.

I wonder if the GROOVE that the kent moore meters read would work. Hmmm got me thinking now on testing this theory.

 

[IDIoit]

what does the stock magnetic pick up read off the cam gear?

 

[snicklas]

what does the stock magnetic pick up read off the cam gear?

Brian,

I think it is just the teeth going by.... a simple Hall Effect Sensor......

 

[icanfixall]

what does the stock magnetic pick up read off the cam gear?

Nope.. The tach sensor reads off the injection pump gear teeth.... No need to feel silly or dumb for not knowing this either. BTW the cam gear and the injection pump gear have the same number of teeth. And thats twice the number count of the crank gear.

 

[Greg5OH]

regarding OP link...its a hall effect sensor, so can you just place that into the pump cover housing where the factory sensor is? Using an appropriate thread adapter...I too dont have a tach since i dont have a factory dash anymore.

 

[riotwarrior]

As I said and I suspect that this unit reads a single pulse so placing pickup to read harmonic balancers notch that we already use provides a single pulse per revolution.

This would be the same as the magnet on the harmonic but in reverze.

Betcha a lil bracket a d set as I suggest would work.

Someone buy one and try it!

 

[icanfixall]

Reading off the injection pump gear is taking half the rpm of the crank. So please take that into consideration when deciding on a pick up point.

 

[riotwarrior]

Reading off the injection pump gear is taking half the rpm of the crank. So please take that into consideration when deciding on a pick up point.

That was point of reading crank...

 

[OLDBULL8]

The one on Amazon the OP is wanting to use is a Hall effect pickup but does not contain a magnet within it, hence a magnet has to be used to upset the 12 VDC field in it, the signal output drives a Digital meter. The Tach sensor we have mounted on the IP gear tower contains a magnet, each tooth on the IP gear upsets the magnectic field, that said in a laymans terms, IP gear Tach sensor drives a Tach much like a speedometer.

 

[OLDBULL8]

The one on Amazon the OP is wanting to use is a Hall effect pickup but does not contain a magnet within it, hence a magnet has to be used to upset the 12 VDC field in it, the signal output drives a Digital meter. The Tach sensor we have mounted on the IP gear tower contains a magnet, each tooth on the IP gear upsets the magnectic field, that said in a laymans terms, IP gear Tach sensor drives a Tach much like a speedometer.

Now if you want to get real technical, have at it.

 

[IDIoit]

Nope.. The tach sensor reads off the injection pump gear teeth.... No need to feel silly or dumb for not knowing this either. BTW the cam gear and the injection pump gear have the same number of teeth. And thats twice the number count of the crank gear.

i did mean IP gear, my IDIocracy!

 

[F350camper]

If I have a free moment, I can take a pic of how I rigged up an aftermarket tach for my 4bt. I'd think you could to the same with an IDI.

 

[F350camper]

Ok, here is the setup on my 4bt. its a crank position sensor from a 96 vw golf 2.0L.

I bolted two metal tabs to the crank pulley, they have about a 1/8th inch clearance above the sensor as it spins around. This produces two pulses per crank rotation which is what a 4 cylinder engine would have. So I just set my aftermarket tach to be in 4 cylinder mode. For it to work, the metal tabs needed to be really skinny at the tip like it is. I just used trial and error. My tach is steady as can be, and appears to be dead on balls accurate.

As far as the sensor goes, I cut the connector off. It has 2 wires and a shield. I grounded the shield and one of the wires (didn't matter which one), and connected the tach "input" to the other wire. I drew a red square around the sensor in the pic, its a little hard to see.

 

[Number21]

Ok, here is the setup on my 4bt. its a crank position sensor from a 96 vw golf 2.0L.

I bolted the metal tab to the crank pulley, it has about a 1/16th inch clearance above the sensor as it spins around. This produces one pulse per crank rotation which is what a 2 cylinder engine would have. So I just set my aftermarket tach to be in 2 cylinder mode. For it to work, the metal tab needed to be really skinny at the tip like it is. I just used trial and error. My tach is steady as can be, and appears to be dead on balls accurate.

As far as the sensor goes, I cut the connector off. It has 2 wires and a shield. I grounded the shield and one of the wires (didn't matter which one), and connected the tach "input" to the other wire. I drew a red square around the sensor in the pic, its a little hard to see.

Thanks for the info! If that steel tab doesn't throw off the balance surely a little magnet won't. I'll order one of those tachs, we'll see how long it takes to get here from China.

My timing gear cover doesn't even have the hole for the tach sensor, thought that was odd they didn't just put a plug in there for the base model.