Another newbie with another dumb question!

[WarpedCue]

By way of introduction,my name is Bruce,and I drive a 1984 D100,with a Slant 6. Yeah,it's got a Slant 6. This is my 3rd Dodge truck.My first was a 1964 D100,with a 361.My second was a 1941 half ton,with a flathead 6. Unfortunetly both of those are gone.(If you're the guy who bought my 1941,I'd like to talk to you about getting it back) A long time ago my Dad told me"Boy,never touch anything under 18 years old" I didn't realise until much later he wasn't talking about machines. So I guess that's why all my stuff is so old. I am a lifelong Mopar guy. My first one was a 1971 Duster 340,which I still have.

I have been in the auto repair biz for over 30 years, so I may be able to help answer some of the questions here,but this one has me,and some very experienced mechanics, stumped. I have been trying to hook up an aftermarket tach on my truck. Very simple wiring. Red to power,black to ground,white to dash light,green to negative side of the coil. It don't work. It's hooked up correctly. At first,I spliced into the wire going to the neg side of the coil.When that didn't work,I hooked it up directly to the coil. When it still didn't work,I spliced directly into the wires from the distributor,first one,then the other. Still no workee. I checked,with a test light,to make sure I was getting voltage everywhere I was supposed to. The only thing that works is the backlight.

Defective tach,you say? Ha! That's what I thought too,so I took it back and got another. Same results. Here's the really weird thing. I get constant voltage on BOTH sides of the coil. At least,as near as I can tell with my little test light. It seems like it should at least flicker on the negative side. I get this voltage with the engine running,or not. I should be getting voltage on the positive side,key on,engine off,but no voltage on the negative side,until the engine is being cranked,or is running,correct? How does the field in the coil collapse,unless it is being switched?
What am I missing here? It's driving me crazy!

I have installed several tachs over the years,on my Mopars,but they all had points ignition. This thing has the Elecronic Spark Control module mounted on the air filter housing. Does anybody remember how to work on one of these? Is there somewhere on here to hook up a tach lead, like GM has on its distributor?

Any advise,comments,biting satire,denegration,or downright insults,would be welcome at this point.
Thank you.
Cheers!
Bruce

[75K30]

Good story:
Two things that come to mind when you mentioned the install of this tach in your ride. How old, or new is this tach? New ones require a small internal jumper configuration change to operate correctly.
Now here is where I think the problem is. In 74, Mopar changed all of the ignition systems to electronic just like the bow-tie boys. It was similar to the very popular HEI, and had its own method of wiring. Some were a series configuration, and some required an ignitor to operate tachs.
A company called Pertronix makes on for you, and the part# is 1281. This should cconvert your ignition signal to something that your tach can read.

[WarpedCue]

Thanks for the tip 75K30, but the Pertronix 1281 is an electronic ign replacement for the points in V-8 Fords.While I'm sure I could probably make it work in my 6 cyl Mopar,there's got to be an easier way. Maybe you got the numbers transposed?

I hope you are not suggesting that I switch to an aftermarket ignition system.I am no fan of those.I would sooner retro-fit a points distributor.While the stock Prestolite EI is quite reliable,and parts are plentiful,that is not generally the case with aftermarket EI set-ups.They may be reliable enough,but if you do have a problem,are you going to be able to find parts in,say,East Boondocks,Wyoming? Even though this truck is 23 years old,I would not hesitate to jump in it,and drive across the country tomorrow.

What do you mean by an internal jumper? Got any kind of schematic,or picture?

This is a brand new Super Pro tach,from Carquest.It was not a cheapie either.I think the retail was somewhere around $70.00. It is similar in appearance to a Sun tach,if you are familiar with those,although I do not know the manufacturer.Like I said in my first post,this is the second one,because I suspected the first of being defective.Could be two in a row defective,it wouldn't be the first time! I have a little,hand held, tach/dwell meter somewhere. I'm going to find it this weekend,and hook that up to see if I can make it work.If so, I know I have a defect on my hands. If I can't get the hand held to work,it's back to square one.

Below is a scan of the hook up intructions.(click to enlarge) It's too small to read,but in the full size version,it clearly shows the tach lead connected to the neg side of the coil,as you are instructed to do in the text instructions.
scan.jpg

By the way,I answered my own question about voltage on both sides of the coil,after thinking about it for a while. Of course you will get volage on both sides,until the engine spins,and excites the magnetic pick up coil. Duh.

Thanks again for your help!
Cheers!
Bruce

[75K30]

Points in that six would be the worst thing you could do. The dist. location makes points adjustment very difficult to do.
I was looking at some numbers for a six popper chrysler, and I did use a combo of MSD, and pertronix parts to make up a great electronic ignition for it. Sorry for the confusion there.
That being said, can you confirm that you are running the solid state "EI" system found in the slant six engines from 72-83, or the later one with the lean burn system? Which electronic control unit are you using? That device is a solid state device that amplifies the low voltage from the pickup, and completes the 12VDC circuit from the coil. I believe you are having a low voltage pickup problem, that the new tach can't see. Knowing which ECU you are using will help me tell you which set of wires you need to obtain the correct voltage. Some were 4 wires, some 5, and others like the "Orange Box" could have been either too. Now if I recall the 4 wire can run a 5 box, but not the other way around, and some .5 ohm resistors had to be installed. Big old complicated thing, but I think I can remember back enough to recall what was what.
Now for your tach internal jumpers, these tachs can be used for 4, 6, 8 cylinder engines, but they have to be told ( via jumpers, or cutting a few wires) to move the needle accordingly. See if you have it set up for 8 cylinders, and you are runnig a 4 cylinder, the tach may only see 50% of the cycles, and will be fooled into giving you a reading of half scale, or twice the scale. That means you may see double the rpm.
Whatever, that is not the problem here, the problem is that the tach does not work. But I believe the problem falls into the "ECU". I will try to help as much as I can, but I am rusty with Chryslers, and very rust with the slant six, But I will do my best....

[WarpedCue]

Don't worry,I have no intention of reverting to points. I used to work on those things for a living. I know what a PIA points setting is on a slant 6. Besides,the emission standards on this truck are set artificially low,and it barely passes,as is. I dont need to screw it up with a different advance curve.

I have what is commonly known as lean burn,the ECU mounted on the air filter housing. However,it does not say "Lean Burn" like the earlier versions did. It says "Electronic Spark Control".I had pretty much hung up my wrenches,as far as working on cars professionally,by the time lean burn came on the scene,in the late '70s,so I never really bothered to learn anything about them. It's coming back to bite me in the a$$ now!

This tach has,like all the other ones I did, a little 4-6-8 switch on the back. Just for sh!ts & giggles,I tried it in all positions. Still no joy.

Don't know if I will get a chance to do anything over the weekend,what with the holiday,and family stuff,but I will get in there A.S.A.P. and report back with my findings.
Thanks again!
Bruce

[75K30]

Bruce:
Cool to know what system you are running now. I usually disable the lean burn system, and use a slightly different dist curve for this system. It increases throttle response, and cleans up under the hood. It is not too difficult, but does use a different ECU box like the chrome unit.
All that aside, I spent most of the evening looking through my old notes written on scrap paper, and even some old packaging material (gasket, or oil filter boxes) left over from some builds a few years before I had a computer in the shop, or the garage. In those days I wrote the important stuff on anything I could get my hands on, and it really was not a good method of retaining information. I will continue to look, and if I find the answer before you do, I will post up again. I look foward to finding, or remembering this solution, it has been a long time since I worked on one of these. Gotta get back to these old powerplants, they were a blast.
Have a happy holiday

[Dodgeramluvr]

Hello I'm a newbie also nice to meet ya I'm Brad.I've had four dodges and they all were pretty good

[Dodgeramluvr]

I have a 02 reg cab 1500 now that I am trying to fix back to normal from prev owner. I bought the truck with bottom leaf missing on each side.The truck was level and looked good but rode and drove like ****.I replaced leafs with a 04 reg cab set and now the truck looks like some old hot rod all jacked up hi in the rear.

[Dodgeramluvr]

if any one can help me with my problem or now what the height in rear is to be let me know

[75K30]

I have a couple of ideas for you Dodgeramluvr, how about starting a brand new thread, so you can get some opinions from others as well?
Your question has a better chance of being seen by others if you start a new thread.
I will reply to your new thread....