I have put an om617 in a Scout 2. I have purchased Isspro gauges and have them working. I am trying to figure out how to wire up the tachometer. The motor still has a magnetic sending unit on the crank. The wire coming off of it has 3 pins. Anyone know how to make this work or a direction to take?

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1984 300D

Well, I have a pretty rudimentary understanding but that wire should plug into a tach amp and then it travels to the gauge on the W123. I would imagine if you don't have a tach amp on you conversion then you won't be able to connect it to your gauge cluster. Just a thought

http://carinstructions.com/wp-content/uploads/2010/01/w123-connecter.jpg

That black plastic canister looking deal is the tach amp and is where the cable from the sending unit plugs into into it (underneath).

Not sure how to help you from the tach amp to the gauge cluster though.

Guide: How to get the tach working in a w126 gas to diesel conversion

It will not work with a non MB gauge (most likely) though.

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General George - 1967 Land Rover 2a SWB 1983 OM617 Turbo

Your aftermarket tach is almost certainly designed to take a signal from the ignition of a gasoline car. Your challenge is going to be to emulate that signal using some rotating component on the engine.

You might be able to use the existing pickup and wire it into a MB tach amp and then use the 123 tach movement with a custom gauge face emulating the Isspro style (the sweep graduations likely won't line up)

Some have used the alternator as a signal source and coupled that with a tach display, others have used a photo tach using a reflective strip on the pulley and a compatible display module. You could also make your own using a Hall sensor on the pulley or a piezo on an injector line, and then use an Arduino and an LCD display.

Whatever the course you take, it's not going to be easy.

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Current Stable

• 380SL (diesel)
• Corvette C5
• Manx
• Baja Bug
• F350 Powerstroke
• Auburn Boattail Speedster replica

The pickup on the front crank damper pin is probably a "variable reluctance" type, which is simply a 2-wire coil with magnet. The 3rd wire is probably a cable shield. I doubt you could get that to work with a tachometer meant for a gas engine ignition system.

OM617A Tach Amp for Engine Swap Applications
Anyone know how to get a hold of these guys? I tried email. Btw Isspro brand gauges are for diesels.

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1984 300D

I 'spect your isspro rpm gauge is supposed to connect to a sensor on the alternator. pretty simple but needs to get calibrated since the crank and the alt spin at different rates.

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General George - 1967 Land Rover 2a SWB 1983 OM617 Turbo