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Tach ?

1twisted1

1twisted1

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Location
Garden City,Michigan
Hi guys I really hate doing this but it seems like if I do not post my general 6.2/6.
5 questions over here in the 6.5 section they do not really get seen.

So here's the question from my post in the 6.2 section with a quote from J.Peal


Originally Posted by J.Peart View Post
Some 6.2's had a vacuum pump with a speed sensor that a normal teach would hook up to.

thanx guys

Does anybody have any info on this???

What years to look for or even better Pics of one!!!
 
In 6.5, in my case 95, the tach is hooked up to the alternator. One of the wire to the alternator senses the tach.

I am not sure what would be the answer for 6.2.
 
x2,

but as far as i know.. and im in NO way a guru here..

the tach needs to receive a generated electrical pulse to spin the needle accordingly to how much of a "generated" signal its receiving. i dont see how the vac pump would supply a voltage signal? ok,maybe an isolated voltage send and retreive system , but why would it be designed to?, with an alternator right next to it to do that exact job...
 
I guess I should have put a little more info into my first post. What I'm trying to accomplish is not having to buy a new tachometer, seeing how i just bought all new autometer cobalt gauges (oil,water,trans temp,volt,tach) right before the gasser blew up and I decided to go diesel. So I've all ready bought the Pyro & boost in the same gauge and now I'm finding out being new to diesels that the tach will not work.

So does someone out there with there infinite powers know how to make this work???

Does one of the vacuum pump with a speed sensor that a normal tach hooks up to exist???
 
I also would like to hook a tach up in my old 6.2 military truck so I will know how bad im abusing it running it on the road with 4.56 gears.
 
Has anybody tried to attach a tach wire to the Engine Speed Sensor/Oil Pump Drive for all 92-93 6.5's with Automatic transmissions. This sensor mounts in the "distributor" hole in the back of the engine. It acts as a drive for the oil pump off the camshaft gear, and measures engine RPM to feed the transmission controller???

Would this work????
 
I think I would find a really cheap tach and see if it will work on one of the newer alternators with the tach output. If it did it would be alot easier to cange the alt.
 
1twisted1 said:
Has anybody tried to attach a tach wire to the Engine Speed Sensor/Oil Pump Drive for all 92-93 6.5's with Automatic transmissions. This sensor mounts in the "distributor" hole in the back of the engine. It acts as a drive for the oil pump off the camshaft gear, and measures engine RPM to feed the transmission controller???

Would this work????
Click to expand...

I don't know the answer, but I do know the 6.2 vac/ess combo would be puting out the same signal as the 92-93 6.5 ess. So, if one will work the other would also.
Both ESS's pulse 8 times per RPM.
 
Burning oil said:
I don't know the answer, but I do know the 6.2 vac/ess combo would be puting out the same signal as the 92-93 6.5 ess. So, if one will work the other would also.
Both ESS's pulse 8 times per RPM.
Click to expand...

IS this the one used on the Humvee ???

Or is there some oddball vac/ess pump out there that mounts to the front of the motor??
 
1twisted1 said:
IS this the one used on the Humvee ???

Or is there some oddball vac/ess pump out there that mounts to the front of the motor??
Click to expand...

The one I am thinking about is the oil pump drive/vac pump/ess combo. It mounts in the same place as the 92-93 6.5 ESS. It looks just like all the other 6.2 oil pump drive/vac pumps I have seen except they also have a ESS mounted on them as well.
 
1twisted1 said:
I guess I should have put a little more info into my first post. What I'm trying to accomplish is not having to buy a new tachometer, seeing how i just bought all new autometer cobalt gauges (oil,water,trans temp,volt,tach) right before the gasser blew up and I decided to go diesel. So I've all ready bought the Pyro & boost in the same gauge and now I'm finding out being new to diesels that the tach will not work.

So does someone out there with there infinite powers know how to make this work???

Does one of the vacuum pump with a speed sensor that a normal tach hooks up to exist???
Click to expand...


You need to see (read) the out put of the speed sensor you are trying to use. What is the input spec on your tach that you have now, the manual should give you the trigger values. It is either digital or analog, then we can figure out how to trigger it if you can't use the feed from the alternator signal generator, or the engine rpm sensor off of the oil pump drive.

There are plenty of ways to generate the correct signal as long as we know the values we have to work with.
 
If you are trying to use the gasser tach on the diesel, there is a way to convert them, you have to make a a signal converter so that it will run off of the alternator signal. I don't have the instructions, but they are included in the book sold at the diesel page. If you want to pay their price for it. Someone here might have it. Can't believe I just remebered this, and your right you don't want to have to waste that nice gauge you bought, I bet those are expensive.
 
Check with the oem mfr of the tach B4 you do anything else - they may have a module for the interface

Tachs for gasser (patooie!) ignition are looking for a sharp voltage spike per ignition pulse, which signal is available in the electronic ignition systems - Diesel engines, not being spark-infested, of course, have no such signal available in the mech-injected systems, nor in the primitive EFI systems, such as the 6.5 - herein, we must needs punt

The ESS on the 89-93 vacuum pump puts out a raw ac signal for the TCM and emissions, not even suitable for electronic tach circuitry - some oems offered a converter module for use with their tachs in that era

Those oems that offered a tach for the 6.2 engines used a photocell to be mounted on the timing cover and a strip or several of adhesive-backed aluminum foil to be stuck upon the harmonic balancer - the shiny strip(s) generated the required pulses by reflecting rays into the photocell, thenst to the converter module or directly to the specially-circuited tach

Some offered a magnetic sensor and a sticky magnet or several to be stuck upon the hb - the magnets generate the pulses amongst the mag pickup, thenst to the converter module or directly to the specially-circuited tach

Other mfrs supplying tachs to the 18-wheeler industry used a mag pickup mounted on the bellhousing flange, adjacent the starter ring-gear on the flywheel - the gear teeth generated the required pulses amongst the mag pu, thenst to th.........well, you get my drift, eh

So, those are your choices, each involving a signal-conditioning module to interface with the tach

I removed the 0-5000rpm tach from the factory rallye-pak out of a 305-equipped early '80's blazer, grafted it into the oem fuel-guage location in the quartz-speedo equipped cluster from an EFI '90-'91 'Burb, grafted-in the rallye fuel guage in place of the oem clock, modifying the mylar printed-circuit sheet to accommodate the alterations, engineered an fet signal-conversion module to adapt the output of the (primitive) EFI 6.5 CPS to the gasser (!) tach - the revamped instrument cluster residing in my GMC since Y2K looks oem stock, works fine, lasts a long time

And, that's yer choices amongst yer options - choose well, grasshoppers, and yer good to go............

FYI, I designed a simple single-bipolar signal-conditioning circuit to interface the ESS to a tach designed for spark-infested systems, but had been using fet's for too many years and had forgotten that bipolars require totally different biasing than fet's - the good Dr Lee revised the resistor values and posted the resulting circuit on the Diesel Page, suitable for installing a gasser (!) tach in a 6.2-equipped truck - converts the isolated ~6vac signal to the ground-referenced ~12v pulse that the tach is expecting
 
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