Dan,

Exactly right - this is a '88 harness, I have an un-ballasted 3 ohm coil, and the solenoid is wing-mounted rather than on the starter.  

The ignition relay is in the place where most have a flasher (mine in this harness is on the other side of the bay I believe).

I'm not 100% on the connections for the electronic ignition, so think I will put back the points to get it running, then do the swap, to reduce the variables.

I also appreciate folks not simply saying "buy the right harness for your car", as this is a bitsa, of my own doing.  MkII car, with updates to include reverse lights, third brake light, rear window defrost, later heater, center interior light, tach, radio, wing mounted turn lights....  It's been a fun challenge, and in the end, it'll be just the car I wanted.

So far, so good!

In doing research on wiring (not my forte), I stumbled upon this site, which others may find as useful as I have:  //www.mgb-stuff.org.uk/electricstext1.htm

Scott

Spectre1275:

From what you've written about wire colours and the yellow relay, your wiring appears to be similar to Hayne's "wiring Dagram 18 - 1988 onwards.

Components: 48 = Battery; 62 = alternator; 17 = starter solenoid (& starter if you had the later car/engine); 16 = ignition switch; 15 = starter relay; 14 = coil; 18 = ballasted ignition wire ( you don't have)

So, it should work like this:

Starting (cranking motor): Smaller brown wire feeds power to itgnition switch (always); switch feeds through white/red to trigger the relay: relay feeds through brown/red to energize the solenoid, closing the switch to turn the starter motor. Note the relay recieves unfused power in a plain brown wire from the battery terminal of the solenoid. The relay witches this power into the brown/red, avoiding a heavier curent through the starter switch.

Engine running: Smaller brown wire feeds power to itgnition switch (always); switch feeds through pink/white (the ballasted wire) to ballasted type coil. In your car, this should be the un-ballasted wire feeding your coil. The white/yellow at the solenoid isn't needed in your car because you aren't running a ballasted type coil.

So, the white red you see at the relay should be coming from the starter switch only. To verify, disconnect it from the relay, put your multimeter or test light on it and turn the key to "crank" - you should see voltage here but no cranking while it is disconnected.

This.  I always think of those movies where some poor slub is trying to disarm a bomb while taking direction from someone over the phone or radio.  "Cut the red wire".....clip..."after cutting the yellow wire"....boom.

The electrical systems on these little cars are about as simple as they get. If you take a little time to understand the circuits and how they function then the color of the wire becomes nearly irrelevant.  Look at the function or purpose of the wire.  Think about what the circuit needs to make it work and then connect the wires up to create the circuit.

To the OP, I'm glad you got it sorted eat least enough to build oil pressure.  Good luck on getting the ignition system sorted out. I think you will get there and you'll be up and running in no time.

I am glad you removed that fuse. Confirm that the wire you are triggering the solenoid with is in fact from that relay, and is properly triggered by the white with red stripe wire from the switch. As mentioned, the normal solenoid does not need a relay, since it is a giant relay.

This is where things get tricky: fancy high performance starters and later pre engaged starters will need a relay to trigger the solenoid to reliably start. I suspect this has been accounted for in your present wiring harness.

just the other day, like in the parking lot at mini meet, I re wired a solenoid trigger system on a mini with a fancy starter. The owner had recently spent good money having an auto electric expert sort some aspects of the car. Expertise can only get a fellow so far. 

I would spend more time on that solenoid wiring. Using very good tape, super 88 or 33 from 3M, I would tidy up those heavy cables on the solenoid and route them so that after an incident they will not shift and touch the inner fender. Do you have the factory style hoods for those cables? They are nice.

check to make certain the main +12V cable from the battery is clear of the header where it transitions from the tunnel to the firewall. I have seen many failures here resulting in melted battery posts.

Makes sense Ian - this is a new harness from a reputable shop, so hoping the colors are correct.

I think the hump I need to get over in general with wiring is making use of my multimeter - I get discouraged when a wire goes into a nicely wrapped bundle of wires, and I can't see where these wires go/branch from there.  Multimeter end to end does away with that concern nicely, and I just need to learn how to use it!

Scott

Glad this worked out.. 

However, I think people would have much more success with a change in thinking ..

Rather than "....large Brown/Red wire connected to where the White/Red wire would normally go.."  people need to think of it as connecting the "..alternator output to the solenoid live terminal.."  (just an example - I'm guessing the brown wire is the alt o/put - no idea what the white/red wire might be  

Wiring is just an exercise in logic...  You need power + a device + an earth.....  Relays are just remote switches and fuses go as close to the power source as possible.  Simple as...

The trouble with "remote" diagnosis (as per these posts) you never know when a PO has switched what used to be a red wire for a blue one.... so what right for my car is not for yours..

Cheers, Ian

Yay!  Success!

So, took the fuse off the ground from battery (yup, was blowing fuses with each crank, didn't realize the starter doesn't go through the normal fuse box).

Kept the large Brown/Red wire connected to where the White/Red wire would normally go (test light revealed this wire was only live when the key was in crank position, so this seems a reasonable thing).

Starter now cranks strong with the key, and within 5 seconds, had 60+ on the oil pressure gauge!  Woo-woo!

Next step is making sure coil (which is a 3 ohm, non-ballasted flamethrower), dizzy, carb and timing are adjusted for the basics, and grab some gas to start the ring break in cycle.

Thanks again for the help all.

Scott

Take the fuse away fromthe battery cable. The battery is probably capable of providing about 600 cold cranking amps, and the starter would probably draw well over 100 amps. You'd just be wasting fuses and your patience.

The starter solenoid is just a low current switch to control the high current starting circuit:   battery -> solenoid -> starter -> battery

It is triggered by a circuit that takes current from the main battery terminal on the solenid via a brown/blue trace wire to the ignition switch (no fuse). (If your car was built with a generator and voltage regualtor, a brown wire would go to the voltage regulator where it would be connected to the brown/blue. Some circuit diagrams show a plain brown going to the ignition switch.) The ignition switch has two outputs: one to power the coil and anything else that is supposed to run only when the ignition is "on" via white wires, and the other to control the starter motor, via the white/red trace wire.

That's the basics.

You have a "white/yellow trace" wire. That is used in later cars having a ballasted ingnition (like mine). so, your car may be wired like a 1977-onwards car.

If this is the case, the white/yellow should come out at the coil where it should be connected with a white/pink to the coil + terminal. The white/pink is the ballasted ignition wire - it has a resistance that reduces the coil normal operating voltage to about 8-9 volts, and you would have a ballasted-type coil.

On a ballasted system, the engine runs with the coil powerd by the ballasted wire fed from the ignition switch #2 terminal. But when cranking the starter, battery voltage drops and the spark gets weaker. To compensate, a white/yellow feeds a full 12V directly from a separate terminal on the solenoid to the coil. That boosts he spark while trying to start. Once the engine fires and you let go of the key, the solenoid releases, cutting power to the starter and the red/yellow at the same time.

So, if you have a ballasted system you should have, at the solenoid:

• Battery cable on a big 'battery' post
• several brown wires feeding live power to assored places (may be attached to the battery post)
• a white/red fed from the ignition switch "crank" position connected to the solenoid triggering terminal
• a white/yellow connected to a separae terminal fed only when the solenoid is triggered.
• a big cable going to the starter.

Spectre over time I have bypassed stuff in the harness I wasn't sure about.

I would do a yellow wire from the ignition start position straight to the solenoid.  If it gets hot you are coming in to the solenoid on the wrong terminal.  

If it blows fuses or gets hot I am guessing you are running the solenoid from the ignition 'run' terminal (wrong) instead of the start terminal.

Perfect guys, will try this tomorrow.

As for overthinking, really just wanting to protect the $400 investment in the new harness, and not really understanding the current path for the starter.    Appreciate the help, love this forum!

Scott

When i was putting humpty dumpty (the Moke) back together, I had a 35 amp fuse in line from the battery. This was done so I could check all the circuits exept the starter. It really worked well blowing on a dead short in the lighting circuit saving me some expensive Moke smoke.
When I was showing a friend what I had done, he tried the starter motor. Result? A big old POP from the fuse and not even a whimper from the starter.

The solenoid directs electricity directly from the battery to the starter. There's no possibility of damage to the rest of the wires. The manufacturer didn't put a fuse in the battery ground so why should you. You're totally over thinking this.

Normally there is no fuse between the battery and the starter motor itself as it will draw a lot more than 35Amps especially if the engine is cold. You can fuse the circuit that is used to enagage the starter solinoid through the the relay. 

Image Gallery

Remove the fuse from the boot - I'm no expert, but I believe the starter motor draws more than 35A.

I doubt that you've a 'bum' solenoid and I'm dying to ask what function that yellow relay is suposed to have.  I recently did a big relay project; it started small and got really wild.  I've now got 8 relays switching things, not including the starter solenoid.  Lots of wires, even more connectors and meters of shrink wrap...  I learned a lot, Mur was my tutor.

I'm a big fan of going 'back to basics'.  If it were mine, I'd remove the yellow relay, connect the B- without a fuse, connect the red/white and everything else as standard.  Only then, would I try to add things and make improvements.

Edit:  Don't let the 850 diagram disuade you - it's a great diagram for cars w/alternator and rocker-type switches.

And more (plot thickens).

Confirmed the fat Brown/Red with a large spade connector only got power when the key was turned to crank (so, seems this is serving the same function as the White/Red wire in most schematics).

So, I moved this Brown/Red wire from the large spade connector on the +battery post of the solenoid, to the smaller spade connector on the solenoid that the White/Red wire would normally go.

Then, turned the key to crank, and....  the starter cranked!!   For half a turn, and then stopped.  Turns out the 35amp inline fuse in the boot blew.

So, next steps??

Scott

Progress!!!

The 35amp fuse didn't blow, and I'm now hearing a clicking in the starter relay - so, wiring is working from the back through the key switch and relay, and somehow getting stuck somewhere past that.

I took a grounded test light and touched it to the connection on the solenoid that the starter cable is hooked to, and turned the key to crank, and the testlight did not light up, so... power isn't getting from the one post to the other on the solenoid.  (I checked that power is going through that Brown/Red wire when the key is turned to crank).

So, seems I'm back to either that White/Red wire (where is it/should I have it), or a bum solenoid, which is new from this site.

Thoughts?  Any other tests I can run?

Scott

Thanks Jeg!  Used a 25, as I didn't want to burn up the harness, but will switch to 35amp and see what happens.

Also learned a few things in the last hour - the Brown with red tracer hooked to the +terminal side may take the place of the White/Red wire, and I may need to get a different relay.  The one I have is listed as "multiple use", and was purchased as it has the correct number of spades for the holder in the '88 harness I'm using.  Maybe there needs to be a change there.

Scott

I don't think that 25A fuse is going to be big enough to allow the starter to crank.  A 1970's era wiring loom isn't going to have that relay, so you'll probably have to do some tracing to find out what's connected to what.

A half-bad in-process photo of mine - can only see one side, unfortunately. 

The white/red is connected to the ignition switch -

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Hey all!

Background:  

Newly rebuilt engine, new mid-70's wiring harness, starter without the build in solenoid (I have this one, properly grounded on the inner wing:  //www.minimania.com/part/SRB335/Starter-Solenoid-78-On-Mini--Mini-Cooper).

New battery, lights/wipers/dash/horn all work when key is turned to first notch.

Have power to the battery side of the solenoid.  

Have the ground cable in the boot rigged with a 25 amp inline fuse, to save my harness if things go to custard.

Issue:

I'm trying to bring up oil pressure in my newly rebuilt engine (so coil wire's disconnected), but when I turn the key to crank, the 25amp inline fuse in the boot blows.

Haynes isn't great at the solenoid diagram, but I've got the + from battery going to the engine-side terminal, along with all the brown wires.  I have the starter cable going to the fender side, all by itself.  I have the White/yellow wire going one of the small spade terminals, BUT my wiring harness doesn't have a White/Red wire, which I believe should go to the other spade connection.

Up nearer the firewall is yellow relay, and that mysterious White/Red wire.

Sooooo.

1)  Should I expect to have a white/red wire down by the solenoid, and if so, why don't I have one?

2)  Why does the inline fuse keep blowing when try to turn over the starter?

Thanks!

Scott