tach sender problems - Diesel Truck Forum - TheDieselGarage.com
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post #1 of 11 (permalink) Old 03-27-2007, 07:52 PM Thread Starter
 
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tach sender problems

i drive an '88 jeep wrangler that i put a 4bta cummins into and am trying to figure out how to hook up my tachometer. i have no engine computer, magneto, coil, or any of the other common places used to pick up a signal for the tach. the engine is all mechanical so i'm having trouble finding something for the tach to read off of. is it possible to make a vdo or autometer tach read off of the alternator? i'm not sure how tachs on 1st generation dodges were hooked up and if there is anything there i could use. does anyone have a suggestion?
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post #2 of 11 (permalink) Old 03-28-2007, 12:12 PM
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Do you have a factory built in tach?




Autometer makes a tach to run off the alt. I think the number is 2888. Many 1st gen guys with pre92 models use it. 92 and 93 1st gens came from the factory with built in tach provisions.

93 W350 w/duals, fuel pin turned, 6X.018" injectors, 4" exhaust, 3" air intake horn, HX40/16, G56 /SBC Con-OFE, 307's axles' 2" skyjacker lift, B&W flatbed
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post #3 of 11 (permalink) Old 03-28-2007, 08:09 PM Thread Starter
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i've seen the Autometer tach number 2888. i would like something identical to that but bigger than the 2 1/8" or whatever it is. all my other gauges are 3 3/4" but i don't know if anybody makes a gauge that size that will read off the tach.
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post #4 of 11 (permalink) Old 03-28-2007, 10:42 PM
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You can use any auto tach. Most tachs are looking for a square wave signal. Square wave is another term for on/off signal.

You would need to epoxy a couple of magnets to your crank dampner. Then mount a magnetic sensor to the engine. Then feed the signal to the tach. Set the tach on the 4 cyl scale and you would be set to go.

There are many types of sensors on the market. The big thing to watch for is you want a normaly open sensor. It needs to see a magnet to close it and trigger the signal.

Here is a site with some examples of whats on the market. Just pick the smallest package sensor for your needs and make sure it is weather proof. Make sure the sensor is rated for 12 volt operation. Your aftermarket tach will need a signal voltage of 9 volts + to work properly. That is why the later 1st gens have problems finding tach's. Our PCM only throws a 5 volt signal. So a regular tach can't read the signal with that low of voltage.


http://www.reedswitchdevelopments.co...ctcatalog.html

93 W350 w/duals, fuel pin turned, 6X.018" injectors, 4" exhaust, 3" air intake horn, HX40/16, G56 /SBC Con-OFE, 307's axles' 2" skyjacker lift, B&W flatbed
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post #5 of 11 (permalink) Old 03-28-2007, 11:04 PM
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This is probably not what you are looking for, but I had one on my old 1st Gen and it worked great.

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post #6 of 11 (permalink) Old 03-30-2007, 08:37 AM Thread Starter
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so as long as i can create a square wave signal the tach will work? what kind of signal does the alternator create? i'm going to go with the magnetic pick-up if all else fails but i would prefer getting a tach to read off of the alternator. how does reading off the alt work?
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post #7 of 11 (permalink) Old 03-30-2007, 01:38 PM
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I am not sure how they read off a alt. Call AutoMeter and ask them. I have had good luck with customer service with them over the years.

93 W350 w/duals, fuel pin turned, 6X.018" injectors, 4" exhaust, 3" air intake horn, HX40/16, G56 /SBC Con-OFE, 307's axles' 2" skyjacker lift, B&W flatbed
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post #8 of 11 (permalink) Old 04-02-2007, 05:18 AM
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don't think i would set the tach on 4 cylinder. if your reading off the balancer, isn't a revolution a revolution? doesn't matter if it is 1,2,3,4,5,6,7,or 8 cylinder a rev is a rev. my 1st gen tach works wonderful.

95 4X4 482 hp. 1096 tq. with Slick 50 treatment, and a Fram AIR HOG filter.
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post #9 of 11 (permalink) Old 04-04-2007, 01:47 AM Thread Starter
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what tach do you have for your 1st gen?
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post #10 of 11 (permalink) Old 04-05-2007, 04:26 AM
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whatever came factory mounted on the dash. i am second owner so i believe it is factory.

95 4X4 482 hp. 1096 tq. with Slick 50 treatment, and a Fram AIR HOG filter.
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