Dead Tacho

Neil · Jan 19, 2002

In a previous post (still open and ongoing) I mentioned problems with my tacho not working. Schematic, you said to check the volatage and gave me wiring options. 4 Wires, gnd, live, ignition and AC. My tacho only has 3. Gnd, live and AC. When I switch on the ignition the (live zero) moves the needle to zero. When I crank the needle wavers around 100 RPM, when it fires - nothing. I checked AC and couldn't see an thing. I don't know what make the tacho is. There are 4 wires going to the tacho. One of them (black) has a terminal ring on it but it is not used and taped back. I presume this is a ground but I can't see where it would go. The tacho only has 3 connections. The tacho also has a setting 1,2,3,4. It is set to 4. Electrics are all working OK as I have just about completed a re-wire. Charging circuit also works. I have no idea where the ac output comes from. Engine is an Evinrude 140 built in 1980. Any advice on this puzzle. Thanks NG

petryshyn · Jan 19, 2002

Re: Dead Tacho

Hello again Be sure the tach has: >ground (it bothers me that there is a wire taped back) >live with key on >a/c signal when running >power to internal light(optional) The signal coming from the charging stator is usually a grey wire. It originates at a terminal strip where it mates with the yellow wires coming from charge stator. >check for a/c at the terminal while idling to verify stator voltages.(set DMM to a/c volts) This grey wire goes to either a three pin pan plug or through the engine harness plug and terminates within the control box. Another harness may plug into the control box and connect to the tach. Probably easiest to follow wire from tach through to engine terminal strip for troubleshooting. >Remember, a missing ground will bugger you up. >The sensor or signal terminal on tach should have a/c present when running. Be sure to have one meter lead to a known good ground, and the other to the sensor or signal terminal when checking for tach signal. How do you know the charging system works?

Neil · Jan 19, 2002

Re: Dead Tacho

Scematic, Thanks for the prompt reply. The tacho definately has a ground. I need to check just how good though. There is a grey wire connected to AC and the live is from the ignition and it works. 12 volts is available across the pos and neg so I assume my gnd is good. AC is a greyish wire. I think I will need to do some wire tracing as it is in the harness. How do I know the charging works. I ran the engine with voltmeter across the battery terminals. This is someting that pussles me and I think I mentioned it before. With the meter across the battery I see a dip as the current is drawn by the starter. Then the voltage slowly increases the original level and then continues to increase. The opposite to a car though. Alternators push out over 13 volts and slowly decrease as the battery charges. I think this is because of the coil charging system on a 2 stroke ?? Anyway, is that what you wouold expect to see on an engine like mine ? I do have a complete electrical system for the engine should I need to swap and test. Just knowing what to test. NG

Trent · Jan 20, 2002

Re: Dead Tacho

As Schematic was saying... If it aint charging the battery the tach is not going to work. Double check to make sure battery voltages go up after engine has been started.

petryshyn · Jan 20, 2002

Re: Dead Tacho

1)turn ignition on 2)measure for voltage from the gauge ground to ign. terminal = 12-13v 3)start engine 4)measure for a/c voltage from gauge ground to sensor terminal = 6-17vac pending on speed of engine and type of meter used *battery voltage should rise over 13v when engine reved to 2000 for a few seconds *a bad rectifier can result in no tach signal, even if the stator is good... *if one neg. diode fails in the rectifier, you will still have 50% charging, but no tach signal... >>>Words to Live by when trouble shooting....<<<< "Give it what it needs, then, if it don't work, pitch it" It needs ground, batt+ and signal..... now get out there and fix that puppy!!

Neil · Jan 20, 2002

Re: Dead Tacho

Schematic, I haven't checked yet but I have a feeling it could be the rectifier. I know from pervious battery problems that the battery voltage does not increase significantly when I rev the engine. It does rise but only slowly as if it is a trickle charge. I put this down to 2 stroke charging systems as I didn't know any better. Now the fun part, checking out the rectifier. I think it is a small board that sits inside a black housing on the very top of the engine. The circuit board is sealed in epaxy or something. If it is not this I have no idea. My big problem is getting a workshop manual. You wouldn't believe the trouble I am having getting one in Oman. NG

petryshyn · Jan 20, 2002

Re: Dead Tacho

Is this what you have? Or do you have just a rectifier? I'm not sure what year you have...

Neil · Jan 20, 2002

Re: Dead Tacho

Schematic, No, not quite. There is a box close to that position though. The black box that is on the side (I presume its plastic) is more like it, except it is in the position you marked. It has a two bolts holding on the cover and when you peer inside there is a cct board ant its completely sealed. NG

Trent · Jan 20, 2002

Re: Dead Tacho

It should look like this... for that model? I think??

Neil · Jan 21, 2002

Re: Dead Tacho

Trent, Just rushed to check. It doesn't look like that. After some tracing this is what I have. Looking from the boat towards the top of the engine.Just under the flywheel is a large black plastic box, about 1 1/2 inches thick, and about 14 inches square (only its not squeare. It is longer under the flywheel. Under the cover are 6 terminal strops. Sitting on top is another box, about 4 inches square and 2 inches thick. This has a cable that goes to a connector just under the flywheel. This box has some identification. CD4/8-61L 582645 13IV-OA Other cables go to the terminal strip in the box it sits on. I think this could be the rectifier. If it is now what ?? Should I be able to measure battery output and Ac to my tacho somewhere? Thanks so far. At least I am learning what is where on the engine. NG

Trent · Jan 21, 2002

Re: Dead Tacho

The CD4/8-61L you see is your electronic ignition box which is a 6700rpm limiter. Look at this pic..top right #1133072.

Look on this box for a gray wire..this is your tach wire.

Neil · Jan 21, 2002

Re: Dead Tacho

Trent, I am in awe. Yep that looks like it. Will measure the output and revert. Should this baby also be pushing some output to the battery. Schematic said I should be pushing 13 volts quickly and I know that is not happening. NG

Trent · Jan 21, 2002

Re: Dead Tacho

You need to find the rectfier and check the voltages as Schematic described. Bad rectifiers will cause your problem. However we need to know if the yellow wires comming into the rectifier have AC voltages their. If not you could have a bad stator. Dont worry about the CDI box right now.

Neil · Jan 21, 2002

Re: Dead Tacho

Really appreciate this. Just to recap. Stator wires coming from the flywheel should have ac. They go into the CDI box than out into the larger box that the CDI sits on. I presume that this is the rectifier box ? I would have thought then that the stator output would go to the rectifier first and then to the CDI. Let me trace all the cables and put something down on paper. It should make some sence then. Thanks so far for the patience.

clanton · Jan 22, 2002

Re: Dead Tacho

This engine should have 2 power packs, 1 rectifier, and 1 voltage regulator(clipper module). I have genaric trouble shooting guide that says to remove and discard clipper module.

Neil · Jan 22, 2002

Re: Dead Tacho

Gents further info. First I measured the tacho again. 12v Dc twice. One on the ignition feed and the other on the ac. Something has gone somewhere. Checked battery voltage with engine running. I am definately getting a charge but not 13 vots. Once started the battery voltage went from 12.6 to 12.9 in a matter of minis and continued to rise. I didn't rev the engine though but it was on fast idle. I did some wire tracing as I have no clue what is rectifier and what is a clipper. I have a drawing but I don't know how to paste it into this message. I will try to descripe. There are two sets of leads coming from what I presume is the stator. A large connector with 5 wires goes into CD4.8-61L. From this one is earthed, and two sets of two wires go to the ignitiion coils. A further black wire disappears somewhere. Two yellow wires from the other side of the presumed stator go to the unit below (583486) (5-MoA). This has a row of terminal stip connectors. The 2 yellow go into the left side connectors. a wire from each post disapears into the resin covered circuit below. the 4th post has a wire that enters the resin and another that disapears somewhere. I think this is gry but I can't confirm. the 8th post has a red wire going into the resin. I don't know if any of this makes sense. The drawing helps though. The spare unit I have is slightly different. This one trent identifies as 1134041. There is no additional smaller pack with this. Confused now as what to do or where to start measuring. Hope you guys are still with me?? NG

clanton · Jan 23, 2002

Re: Dead Tacho

E-mail me drawing. Sounds like you are describing a square single power pack with 4 wires going to the ignition coils. This pack is not the orginal pack for 1980 engine, if this was changed the complete system may have been changed.

petryshyn · Jan 23, 2002

Re: Dead Tacho

NGRIFF1: you wouldn't happen to have a digital camera at your disposal? would you....

Dhadley · Jan 23, 2002

Re: Dead Tacho

I've been following this with everyone else. I too am a little confused about what we are dealing with but I did notice the tach is set on 4. I believe it should be on 6 whether it's a 4 cylinder cross flow or looper. It should still read, just not correctly, so I don't think thats why its not working at all. Just a thought!

clanton · Jan 23, 2002

Re: Dead Tacho

One post talked about VRO, could this engine be an early 140 looper?

Dead Tacho

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