Moyer Engine Wiring Diagram

[ndutton]

What would this category be without some of the great contributions by Don himself? Judging by how frequently it's viewed, this drawing is legendary.

[Laker]

Ah , yes. That graphic image was the primary source of information I relied upon when I rewired my A4 2 winters ago. Even a horticulturist can follow it.

[JOHN COOKSON]

Another Wiring Schematic

Here's the A4 wiring schematic from my A4 owner's manual. When I rewired my engine, gauge cluster, ignition, blower, so on I was able to use these schematics as a guide so I can say they worked for me.

Since getting the firing order correct causes me to wig out I keep figure #7 beside me every time I attach the spark plug wires.

TRUE GRIT

[jpian0923]

In this diagram of the DC power distribution, Does anyone know the direction of flow of the current? I'm talking about all the wires in the diagram.
If for some wires the direction is both ways please mention how that affects the flow in other wires.

Am I asking too much?

[kiskadee]

Current flow or circuit path...

You've asked a question that could take pages to answer. Current flow is seen by some (mostly engineers) as the flow of the positive charge, therefore starting at the battery's +ve terminal and ending at it's -ve terminal. Others (mostly technicians) see current flow as electron flow, since electrons actually flow from the negative to the positive. Technicians refer to the flow of the positive charge as Hole Flow, as the holes left by the electrons are displaced in the opposite direction. (This is where most people's eyes glaze over except for us nerds who can waste hours arguing about true flow direction.)

Don Moyer's diagram is a pictorial circuit diagram, which is intended for layout and installation. To more accurately follow either type of current flow then you'd need a detailed schematic circuit diagram.

The diagram may be easier to understand if you imagine the internal connections at the ignition switch. When OFF nothing is joined. When ON only BATT and IGN are joined, providing power to the gauges and ignition coil. When momentarily turned to start, the BATT and IGN remain joined and power is also provided to the ST terminal. This energizes the starter solenoid while the key is held.

To follow the flow you'll have to add in items to complete their circuit. i.e. The oil and temperature senders are variable resistors leading to ground. Remember that the engine block is grounded so items attached to it are grounded as well, which completes their circuit even though they don't have their own ground wire.

No parts of the circuits shown have current flowing in more than one direction. To trouble-shoot just think of what it takes to make a complete circuit from one side of the battery through things and back to the other side of the battery. If the route cannot be completed then the circuit is OPEN. If the route takes a short cut and bypasses the intended components then it is a SHORT circuit.

In 33 years as a Naval Electronics Technologist I've found it less important to worry about either convention of Current Flow and more important to simply ensure the correct circuit continuity. I hope this helps.

Dana

[jpian0923]

Thank you dana.

Let me see if rephrasing my question would clarify my delema in understanding the flow of electricity in the engine, and it's parts.

If I was to take each engine parts as an individual (to work in conjuction with each other part of the engine, and cost of wire was not an issue, and space was not an issue, and voltage and amps was not an issue) how would I wire my engine to work?

I hope this makes sense.

[rigspelt]

Jim, I am not sure I understand your question, but it might be easiest to think of current flowing from the positive post of the battery through the red cable to the various engine circuits and then collecting in the black cable back to the negative post of the battery (ground). There are important design and product choice rules for wire sizes, wire types, wire colours, fusing and methods of making wire terminations, depending in part on the voltage required for the device at the end of each circuit. Is that anywhere close to the information you need to start thinking about this, or did I start off too simple?

Kiskadee's advice is very helpful, and his expertise a most welcome addition to the forum, but maybe I'll take another tack on it from an amateur boater perspective.

The red to black current flow idea gets wobbly thinking about how alternator current recharges the battery, because the alternator output is wired continuous with the positive (red) post of the battery, but the red-to-black idea helps think through individual circuits within the engine.

Appliances on an A4 engine that need electricity are:
- starter motor.
- condensor or electronic ignition module in the distributor, and through it the coil then the spark plugs.
- fuel pump safety switch.
- temperature sender.
- oil pressure sender.
- ignition panel gauges.

Engine circuits gets their electricity from:
- the battery, via a large red cable attached to the starter motor and then distributed downstream to other engine circuits.
- the alternator.

The ignition key throws people at first, so it pays to think it through. In Don's diagram, current flows from the starter red battery terminal through the red wire to the ignition switch, then from there to:
(1) the starter motor (yellow-red wire), coil and gauges (purple wire) when the key is turned to "start", and to the coil and gauges only (purple wire) when the key drops back to "run".
(2) the gauges (purple wire) and then to ground either directly (voltmeter, black wire), or through the senders (oil pressure light blue and temperature tan, then black) and the coil ground (tachometer grey).

His diagram also shows electricity produced by the alternator flowing through the orange wire to an ammeter in the ignition panel and then to the battery terminal of the ignition key, where it meets up with current from the battery. See my other post in this thread for another way of handling the alternator output that many of us are using because it is shorter.

Electricity returns to the battery via:
- a heavy black collector cable attached to the engine block, collecting current from appliances that bolt directly to the block (typically alternator, senders, fuel pump).
- and black wires directly from appliances that need a ground wire (typically distributor, coil, gauges), usually collected on a bus off the engine then wired to the negative terminal of the battery with a properly sized collector cable.

Did I get that right, everybody?

[rigspelt]

Don's wiring guide is brilliant, but many of us have made a key change to the old style of running a long hot wire from the alternator to an ammeter in the ignition panel and from there all the way back to the battery. We shortened that sub-circuit by running a short cable from the alternator output to the battery post on the starter, and instead mounted a voltmeter back at the ignition panel to check on the alternator's output. This reduces some problems associated with such a long run for the alternator output as well maybe as excessive load on new (lighter and less well made?) ignition switches, and is discussed in several threads in the archive.

An alternative using that method is discussed here:

http://www.moyermarine.com/forums/showthread.php?t=2727

and there is a lot more discussion here:

http://www.moyermarine.com/forums/showthread.php?t=214

Caution: I am not a professional electrician or engineer.

Neil, I seem to recall that you posted a nice schematic showing this alternative too, and if so maybe you could repost it here?

[ndutton]

Neil, I seem to recall that you posted a nice schematic showing this alternative too, and if so maybe you could repost it here?

I have a few such drawings, not sure which one you're thinking:

• The same Moyer drawing except with an electric fuel pump
• My engine electrical system with a whole bunch of stuff like electric FWC pump, engine alarm, electric fuel pump with OPSS and filter purging/fuel polishing system (and voltmeter rather than ammeter)
• Engine instrument panel with voltmeter
• and loosely related, engine wiring harness - voltmeter type

Any of these ring a bell?

[rigspelt]

Neil, thought you had one that among other things showed alternator output direct to battery terminal on the starter, instead of long way to the ignition panel and back.

[ndutton]

Okay, here it is both as an attachment and a pdf. There's a bunch of stuff unique to my engine wiring system that you may choose to ignore but the battery and charging path with a voltmeter rather than an ammeter is represented. I also have a far more detailed instrument panel drawing if wanted.

[jpian0923]

I guess my real question is, was my boat wired correctly/optimally by the previous owners.

I have some dead end wires that I'm not sure where they should go...or if they should just be pulled.

They seem critical but things are working fine and I don't want to screw it up...or burn my boat down.

I thought the best place to start thinking about re-wiring would be with the Moyer DC distribution diagram. Mine is not wired that way though.

I'm raw water cooled. Mechanical fuel pump. Mechanical tach. Mechanical oil pressure guage. No ammeter. No Volt meter. No OPSS. Delco-Remy SI series alternator.

I'm almost thinking that if it aint broke don't fix it but the PO's installed a car stereo sytem that is shorting out sometimes and seems to have wires that have been jeri-rigged to other critcal wires in my rats nest of wires.

I don't know what to do.

[ndutton]

I had trouble-free engine wiring unadulterated from the factory, still ripped it all out and started fresh with new everything. I figured it served its useful life at 34 years, why wait for problems? Plus, I'd added an oil pressure safety switch, an engine alarm system, an electric coolant pump, a tachometer and a fuel pump override (polishing system). Had I not done the harness replacement mine would have looked home brewed and half baked.

If you decide to go this route I have a harness and the previously mentioned instrument panel drawings available. I could rework them deleting the stuff you don't need if it helps.

[jpian0923]

Wow, appreciate the offer! Seems like a daunting task though. But I'm sure you are right. I just have to prepare myself mentally for the task. I'll ad that to my projects list...somewhere at the top of course. I guess the first task (that would ease my mind) would be to separate the car stereo from critical engine wires. Any advice on that? There has to be 5 or 6 wires coming from the stereo, maybe more.

I mean, I spent alot of money (and time) getting the engine right, I want to feel safe (electrically) on the boat as well.

Thanks

[ndutton]

As it turns out . . .

Jim,

The stereo has at most two power wires (one switched and one unswitched) and a ground, the rest are speaker wires (up to eight of them) and an antenna.

If you'd like an extra pair of eyes (or hands) on the situation, I'm in San Diego on Thursday, Sept. 1 for the Charger - 49er game. I could come down in the morning, wear my electrical hat for the day and make it to the game in the late afternoon. Your call, just say the word.