will a stock tach dash wor with a diesel ? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

wbmoore · 10-01-2002, 09:43 PM

I just bought a '82 diesel crew cab dually and miss my tach. Will a stock tach dash cluster work for this ? Does anyone know how to wire it up ? Thanks a lot. brad moore.

**crossy** · 10-05-2002, 12:12 AM

well I have been labeled the tach guru for 73-87's ( not my term). and I had asked a few diesel guys about this before. they did ffere a tach in the heavier series trucks withthe same dash and diesel engine. I also have a diesel 4,000 RPM tach dash here but can't get it to work?/ , I will reprint here a reply I got from a respected diesel guy. thats the best i can do for you. DAVE .

Getting a tach signal on a diesel is not easy. As you know, there is no electrical signal to tap into.
There are three ways to get a tach signal: one is to locate a vacuum pump with a tach drive built into it. These are rare. On a 6.2L diesel engine, there is a spot in the back of the motor in the same place as a distributor on a gasser. The vacuum pump sits in this hole, and is driven by the camshaft. The vacuum pump then drives the oil pump, just like a distributor. Diesels produce no vacuum, so you have to have a pump in order to operate your A/C controls, cruise control, etc. Some pumps had a built in sensor for a tach, but they're hard to come by.
The other and more common way to get a tach signal is to glue a magnet onto the harmonic balancer, and a sensor onto the engine block. If you buy a tach made for a diesel, it usually comes with this type of setup.
The final way to get a signal is off the alternator. The late model factory Chevy tachs use this method. They are wired directly into the alternator to derive rpms. It's critical in this case to get a proper sized alternator pulley with a replacement alternator. Most aftermarket alternators slap on any old pulley then can use, and even a mm in size difference can throw off the readings. A few aftermarket tachs do use this method, but most use the crank sensor style.
If I were to get a 4000 rpm tach like we've been talking about, I would have to rig up a crankshaft sensor

10-01-2002, 09:43 PM	#1
wbmoore Registered User Join Date: Jul 2001 Location: Big Bar, California Posts: 136	will a stock tach dash work with a diesel ? I just bought a '82 diesel crew cab dually and miss my tach. Will a stock tach dash cluster work for this ? Does anyone know how to wire it up ? Thanks a lot. brad moore. Last edited by wbmoore; 10-01-2002 at 10:03 PM.

10-05-2002, 12:12 AM	#2
crossy Oh,you can't buy that new Join Date: Apr 2000 Location: Pennsville,N.J. 08070, USA Posts: 2,039	tachs well I have been labeled the tach guru for 73-87's ( not my term). and I had asked a few diesel guys about this before. they did ffere a tach in the heavier series trucks withthe same dash and diesel engine. I also have a diesel 4,000 RPM tach dash here but can't get it to work?/ , I will reprint here a reply I got from a respected diesel guy. thats the best i can do for you. DAVE . Getting a tach signal on a diesel is not easy. As you know, there is no electrical signal to tap into. There are three ways to get a tach signal: one is to locate a vacuum pump with a tach drive built into it. These are rare. On a 6.2L diesel engine, there is a spot in the back of the motor in the same place as a distributor on a gasser. The vacuum pump sits in this hole, and is driven by the camshaft. The vacuum pump then drives the oil pump, just like a distributor. Diesels produce no vacuum, so you have to have a pump in order to operate your A/C controls, cruise control, etc. Some pumps had a built in sensor for a tach, but they're hard to come by. The other and more common way to get a tach signal is to glue a magnet onto the harmonic balancer, and a sensor onto the engine block. If you buy a tach made for a diesel, it usually comes with this type of setup. The final way to get a signal is off the alternator. The late model factory Chevy tachs use this method. They are wired directly into the alternator to derive rpms. It's critical in this case to get a proper sized alternator pulley with a replacement alternator. Most aftermarket alternators slap on any old pulley then can use, and even a mm in size difference can throw off the readings. A few aftermarket tachs do use this method, but most use the crank sensor style. If I were to get a 4000 rpm tach like we've been talking about, I would have to rig up a crankshaft sensor __________________ "been there, done that, ruined the T-shirt". 2007 LBZ GMC Sierra, ECSB 2006 LM7 RCSB Silverado 98 Vortec project. 94,3500,6.5L 4L80 81 SWB GMC POS finally gone 73 Pinto, stock, w/CragarSS's-eww LOTS of Cummins trucks.



Register or Log In To remove these advertisements.

Register or Log In To remove these advertisements.