Wiring diagram for a petrol generator required

[RonOz]

I’m looking for the wiring diagram for a petrol-driven electric generator. My web searches have yielded little. Possibly, someone on this forum has a source.

My little generator has lost its spark and consequently won’t start. It’s possible I can fix this by fumbling around. I’d rather locate some technical documentation if available – a technical manual. Which could be useful to have should other problems arise.

It’s an “Atomic” 700 watt generator. Model Ai700x. https://www.vektools.com.au/atomic-...-item-please-contact-us-for-alternatives.html Web searches for atomic tend to return the wrong kind of results.

The generator is probably Chinese and may sold by a variety of names. Here’s an example of a different generator that looks identical: https://www.amazon.com.au/GenTrax-Inverter-Generator-Portable-Camping/dp/B07NVKVT2D?th=1

If it’s the case these small generators are all the same except for their names, the manual to any small inverter generator may well suit my needs.

 

[waross]

Take it to a small engine repair shop.

 

[RonOz]

Too late for that. I have it in pieces. Do you have any documentation?

 

[waross]

Take the pieces to a small engine repair shop.
If you can't diagnose a small engine not starting, diagrams won't help.

 

[LittleInch]

The engines for those units tend to be the same, but are seen as simple blocks. Take the spark system apart and try and identify th parts then buy spares.

Or buy one on eBay and replace the engine.

 

[Mark_Markus]

To be safe, I'd better take it to a repair shop. The spark model might be CMR6A(TORCH).

 

[RonOz]

The engines for those units tend to be the same.

Chances are they all come from the same factory, but get different brand names stuck onto them as they leave the factory. I'm hoping that's the case. A good suggestion about eBay. I've had been looking on Facebook. Seen nothing to date.

Waross, if someone came to me with a box of disassembled parts I'd laugh and tell them to piss off.

Circuit diagrams are like a road map. They avoid guesswork. They provide some insight into how things work. A simple example: These machines often have a low oil cutout. That could be the reason there is no spark. So, will the switch be normally open or normally closed? Will it be hooked up to the ignition circuit side of things or simply a switch to earth? Or is it simply a warning lamp and has no impact on the ignition circuit? There may well be other things a circuit diagram could help me with. I won't know until I see it.

 

[RedSnake]

I found a user manual but I am guessing its not what you where looking for.

ATOMIC AI700X User Manual | Manualzz

Download the user manual for the ATOMIC AI700X inverter generator. Learn about the features, specifications, operation, maintenance, and troubleshooting of this product.

manualzz.com

 

[RonOz]

Thanks for that RedSnake. It was good of you to look. I found that one too. Though, I already have a paper copy as well. I got excited when I spotted the web address on the last page of the manual, but when I checked it found that address is dead.

I'm really surprised I couldn't find the Chinese factory's web address. All I get is sites from companies wanting to sell products; not any that manufacture them.

You can still buy Atomic generators. Just not the one I have. I think I'll email the service dept of one of the retailers to see if they have anything they can send me.

 

[BrianPetersen]

So the ignition doesn't work?

These small engines are mostly the same in terms of their ignition circuit. There's a magneto coil (usually installed outside the flywheel), which goes to the spark plug, and there's a bypass circuit that goes to the "on/off" switch and sometimes to a low-oil-level switch. The bypass circuit just grounds the magneto output circuit to kill the spark when the engine is to be stopped.

The first test is to remove the spark plug cap, put another known-good spark plug into it, lean that against the side of the engine, and pull the starter cord to spin the engine over, and see if you have spark. I take it that you've done this and the answer was "no".

So. Find the magneto. Find the wire that leads from the magneto up to the on/off switch (and possibly the low-oil module). Unplug it (so that there is no longer a way for the on/off switch and/or the low-oil module, if present, to kill the spark). Repeat the spark test. At this point the ONLY things in the circuit should be the magneto coil and the wire from that to the spark plug.

Spark works when the low-oil module is unplugged? Problem in low-oil switch or module. (which could be, that it's low on oil ...)
Spark works when the "on/off" switch is unplugged? Bad switch.
No spark no matter what? Bad magneto coil.

I'm aware of some newer ones that have a CO-detection module. Same deal. Its function is to kill the spark if the CO-detection module detects too much CO present. Same situation. Same diagnosis technique as for the low-oil module.

 

[RonOz]

Thank you for the detailed notes, Brian. It was good of you to take the time. I have certain skills that led me down the path you described. However, there were a few surprises and stumbling blocks. Hence my request for a circuit diagram.

I suspect the ignition coil is the problem. It has a reasonable resistance in the secondary windings, but the primary windings show zero. An internal short. eBay shows some possible replacements, but it’s annoying that I can’t find any that are an exact match.

I contacted a retailer who services the generators they sell and they were generous enough to provide a diagram for a Gentrax unit (I've popped it should anyone else be interested). This was for a different brand of generator to mine, but as you noted, a lot of these units are similar. If different brand generators look identical, the internal components may be identical too. (That’s a big “may” but I’m grasping at straws here.) Anyway, the diagram hasn’t provided the detail I wanted. It also refers to connectors that are unmarked on mine. Such is life! Perhaps the labels are present but subsequently got covered.

Curiously, the coil is mounted some distance from the flywheel. Also curious is the fact that there is no magnet on the flywheel. That caught me off guard, I have to say. I wondered if that was the actual problem. A magneto without a magnet is not going to work.

There was a raised pad on the flywheel but it didn’t show even the slightest magnetic effect when tested with pieces of metal. Not even a pin would stick to it. That surprised me. Had the magnet fallen off, I wondered. However, I soon noticed that the magnet was part of the component that was mounted to the cylinder head, close to the flywheel. This component obviously had windings that appeared to be constructed around a magnet. The magnito. I presume that when the flywheel rotates and the raised pad (which was at TDC) passed near the magnet, it altered the magnetic field which induced a current in the windings. I could detect some voltage from it when I rotated the flywheel.

I’ve never seen one like this before. Every one I’ve seen has primary and secondary windings in the unit and the magnet is part of the flywheel. There was a single low tension wire leading away from this magneto that was lost to me as it disappeared into a circuit board.

Much of the circuit board was coated in a resin of some kind. No doubt to protect the components from vibration. Locking them in tight. A nice enough idea but it had the effect of hiding anything I might have been interested in looking at.

From another location on the board was another low tension wire that hooked up to the coil.

I was curious as to what was going on between the magneto and the coil. It’s a 4-stroke engine and the flywheel will rotate twice and needs to spark only once. We don’t want it sparking on every revolution, but maybe if it does spark at the top of the exhaust stroke, perhaps it doesn't matter. (I hope not.) I guess that issue will remain a mystery. I’m inclined to think there is some gearing behind the flywheel that tells the engine when to permit a spark to occur, but I couldn’t see anything.

I’ll wait for my new coil and try it out.

 

[GregLocock]

"if it does spark at the top of the exhaust stroke, perhaps it doesn't matter. (I hope not.) " It doesn't, it's called wasted spark and is benign. https://en.wikipedia.org/wiki/Wasted_spark_system

 

[BrianPetersen]

When that raised pad on the flywheel is passing the magneto, the clearance should be the thickness of a normal business card. The usual way of adjusting them is to slacken the bolts and slip a business card between the magneto and the flywheel (raised pad aligned with the magneto), let the magnetism draw the magneto in towards the flywheel, and snug the bolts with it like that.

A lot of those small generators use Honda clone engines. It's not unusual, but also not guaranteed, for parts to be interchangeable. Clones can be almost-but-not-quite the same.

Beware with magneto coils, that they can be direction-of-rotation-sensitive, so take note of which way the flywheel is supposed to spin.

The circuit diagram above is a little more complicated because it is for an engine in which the electronic controls can regulate the throttle as opposed to using an old skool mechanical governor, so they opted to bury some of the ignition control logic inside that circuit board. But, the circuit where it shows the "engine switch" is as usual: that switch is open in order to allow the engine to run, and grounded in order to stop it.

Briggs and Stratton, but they all work roughly the same: https://www.briggsandstratton.com/e...rowse/ignition-system-theory-and-testing.html

 

[waross]

I’m inclined to think there is some gearing behind the flywheel that tells the engine when to permit a spark to occur, but I couldn’t see anything.

It's called the camshaft.
That is also the component that prevents the exhaust valve from opening on the compression stroke.
I have seen the contact points mounted low down on the side of the block, far away from the flywheel and magneto.
The points were operated by a small push rod that extended to a cam on the camshaft.

 

[RonOz]

I’ve never heard of a wasted spark design. Thanks for bringing it to my attention. Interesting. The idea makes me smile! Only because I’m thinking of a situation of there being some unspent fuel in the cylinder at the end of the exhaust stroke or, in fact, as the cylinder is filling with air & fuel. But, hey, it’s being used, and it obviously works. (Still smiling at the idea.)

Brian, the business card idea is really good when there are two ends of the armature to adjust simultaneously. Easier than trying with feeler gauges. The magneto mount holes would be slotted to allow for adjustment. Curiously, this engine doesn’t have any adjustment provision on the magneto. Really! So that’s that. But the clearance seems reasonable.

Waross, I don’t doubt the engine has a camshaft. It’s a 4-stroke, after all. I was curious about it having breaker points, but I’ve seen nothing that indicates it has any. Unless it has a sensor somewhere that I haven’t spotted. Perhaps that’ll be my next task if the replacement coil doesn’t fix it. I’m inclined to think the wasted spark design that Greg suggested is how this engine has been built.