Electrical Non-Start HELL - SORTED!!!

[Royalratch]

Quite simple I hope - but bear with me.

Car started fine before I removed the factory (Phillips) alarm. I didn't know it was also an immobiliser as now it won't start. I removed the control box, loom and siren from the engine bay. But 2 things I could not remove and remain:

1) These 3 wires coming from the fusebox which I assume are 12v feed and earth.


2) 2 wires coming from the bulkhead relays and I suspect these affected the fuel/starter relays?


3) On trying to find a 12v feed for my sunroof I used one of these blue green sockets, I think the ignition wire lives here - did I disrupt anything?


After removing those items, I turned it over and heard a loud pop and then the power went out across the car - I assumed it had drained the already weak battery. All electrics are fine - did I blow a fuse / relay somewhere? Do I need to join some of those wires?

[jenad]

The accessory plug delivers ignition. The wiring of the sunroof is simply plugged in. A relay is usually mounted between the plug and the wiring of the sunroof. Disconnecting here would only affect the function of the sunroof.

The wires in the first picture are from the retrofit. Use a circuit tester for knowing what they are for. Disassemble the fuse box and remove them completely.

I would check the usual suspects: fuel pump is running? Spark is at hand? DME/ Fuel relays have some voltage?

[Royalratch]

No. No starter motor at all and battery is on full charge.

I think I've interrupted the ignition between key and starter by stealing the feed for the sunroof...?

The fusebox wires I'm sure are just power for the siren / alarm controller.

The wires from the bulkhead relays are probably also causing some kind of trouble.

[Brianmoooore]

The two relays in your first pic. are the main DME relay and for the fuel pump. Neither has any effect on the starter system.
The socket with the two green wires i your third pic. must be fitted with a shorting loop, otherwise no ignition switched live will reach the coil or the ECU 'switch on' terminal.
The starter motor circuit is fairly simple, and should be easy to sort.
First of all, link together pins 11 and 14 of the diagnostic socket, which should engage the starter motor and crank the engine.
Assuming it passes this test, you will have to trace through the entire length of the start signal's path, to see where it's been 'got at'!
The start signal leaves the ignition switch on a plain black wire, passes through a plug and socket, which should be clipped to the steering column, about half way down, where it also changes to a black/yellow wire. This wire goes across behind the dash to a single pole plug and socket above the top of the glovebox area, which is where the starter inhibitor circuit connects in on autos.
The wire then goes up through the large duct at the back of the glovebox area, and into the fusebox. It should pass through the fusebox without any connections or joints, and go on to the C101 engine loom socket, on the bulkhead next to the fusebox.
The white/black and red/yellow wires in your third pic. look like they may be the ones that go to a blue relay mounted in the rear left area of the glovebox. A green/blue wire comes from this relay, connects to a green/blue that feeds the sunroof, then loops on to another green/blue that feeds the windows.

[Royalratch]

Cheers very much - I will try the C101 thing and see what happens.

The yellow and red wires in the first pic are from the alarm loom.

I'll also remove the sunroof feed and return that area to normal.

Thanks all.

[Brianmoooore]

I will try the C101 thing

Sure you don't mean diagnostic socket?

[Royalratch]

Where's the diagnostic socket - I thought that was also done at the C101 lol.

[Royalratch]

So!

Connecting Pin 11 to 14 cranks the car so I assume it HAS to be the two wires coming from the bulkhead relays. They are both red/white and were connected to each other before being split to accept the alarm/immobilser...?

[Brianmoooore]

Start signal wire is black/yellow, and is NOTHING to do with the two relays on the bulkhead.
Open up the fusebox, and check that the black/yellow makes it through unmolested.

[Royalratch]

Opened up Fusebox to find a scotchblock fest.



Two yellows tap into blue/purple and blue/red. Red goes to the red of the main + from the thick battery cable.

The fuse holder near my finger housed a 15amp fuse which had blown - it's wired directly into the main fusebox feed from the battery - would this have any affect on ignition...?

But the 3 wires that leave this fusebox led to the alarm / immobilizer before I cut them so I can't see how they would...

[Royalratch]

Another issue now - wanted to drive this thing out today

Engine cranks when C101 pins 11 to 14 are shorted but it will not catch.

Have I screwed up the ECU somehow?

[Brianmoooore]

Pin 30 of the fuel pump relay (red wire) should have battery voltage on it at all times. This comes from one of smaller wires connected to the battery + terminal, so check these are all making good contact.
The thick red wire in your pic. feeds the fusebox, and goes on to the ignition switch, where it becomes the purple auxiliary feed, the green main ignition feed, and the black/yellow start signal. There are no fuses in any of these wires.
I can't identify your blue/purple and blue/red wires! There are no wires of these colours associated with the engine or the fuses, but the whole wiring loom to the front of the car passes through the box. You'll have to pull the top half of the box up further (I've never broken one yet!) and give some idea of which direction these wires come and go from.

[Royalratch]

I'll try and check all for relevant junctions 12V tomorrow.

I don't get it, it ran fine before and removing redundant hardware has shut it down.

[Royalratch]

I can't identify your blue/purple and blue/red wires! There are no wires of these colours associated with the engine or the fuses, but the whole wiring loom to the front of the car passes through the box. You'll have to pull the top half of the box up further (I've never broken one yet!) and give some idea of which direction these wires come and go from.

The blue/red and blue/purple are door wires I think, activating locks I think as the alarm also went into both doors.

[Royalratch]

Okay - did a lot of troubleshooting today and have a theory.

+12V @ DME Relay - YES
+12V @ Fuel Pump Relay - YES
+12V @ Ignition Wire behind glovebox - YES

+12V @ Fuel Pump on Ignition - NO
+12V @ Ignition Loop - NO
Spark on Ignition - NO

To retrace exactly what I did right before I tried to start the first time and it didn't:

1) Removed old alarm/immobilizer which was redundant as it didn't go anywhere as I removed the control box years ago.

2) Plugged sunroof motor into what I thought was a +12V feed at the glovebox but could have been an ignition interrupt loop.

Current sunroof is plugged in here - is this okay:




What's the single loop on the left?:




I then started the car, starter kicked in then loud pop from the engine bay area. All fuses and relays seem okay with continuity on the DME between the two horizontal pins here:




My theory is I have blown the ECU as only this cold affect fuel, coils and ignition. I have a spare but can I check the ECU is okay visually or with a multimeter? Is my theory sound?

[Brianmoooore]

The blue/red and blue/purple are door wires I think, activating locks I think as the alarm also went into both doors.

No blue/red or blue /purple associated with the doors, and the wiring loom doesn't go anywhere near the fusebox.
One of the indicator wires is blue/red, and passes through the fusebox, but the other indicator is blue/black, not blue/purple. In fact, the only blue/purple I can think of in the whole car is the windscreen washer level.

[Brianmoooore]

+12V @ Ignition Wire behind glovebox - YES

Where, EXACTLY?

+12V @ Fuel Pump on Ignition - NO

There shouldn't be, unless the engine is turning.

+12V @ Ignition Loop - NO

If you mean the green plugged in loop, then concentrate on finding our why not. This wire leaves the ignition switch as a thick green wire, goes through a plug and socket clipped half way down the steering column, then goes into the loom where it splits at a soldered joint, with one wire going straight to the green loop.
Have you checked the complete path of the black/yellow yet?

[Royalratch]

Thanks for replying Brian!

The Black/Yellow is getting +12V right between the head unit and the accessory panel, directly under the factory ground point to the right of the accessory panel.

I will try and trace the entire Black/Yellow from that point to fusebox an beyond.

Is my ECU theory BS?

[daimlerman]

You have found the black/yellow behind the glovebox(cubby in NZ)Is it black/yellow BOTH sides of the connector?

[Royalratch]

Both sides of what connector? It leaves the ignition plug housing as black yellow and stay that way until it enters the firewall. Have to see what happens to it once it enters/exits the fusebox.

Is that what you mean?

[daimlerman]

Both sides of what connector? It leaves the ignition plug housing as black yellow and stay that way until it enters the firewall. Have to see what happens to it once it enters/exits the fusebox.

Is that what you mean?

Before this wire enters the firewall,it passes through a connector seen here just under the main dashboard harness...

In this piccie,the black/yellow changes to black at this point,does yours?

[Royalratch]

No sign of that connector actually - yours Auto?

But it was all working fine and the loud pop I heard on first crank since my 'tidying up' MUST mean something...?

Anyway, the black/yellow makes it in and out of the fusebox in tact (does not go to a fuse) and has +12V on entry and exit. It comes from the bulkhead loom from the battery into the fusebox and over to the ignition barrel - correct?

My main issue appears to be at these ignition loops, if that's what they are - can anyone tell me what these 3 wires do, all are green with blue stripe:



Also, what can I do to check the ECU isn't fried?

[Brianmoooore]

There is no reason to suspect the ECU is fried! They are very difficult to damage.
You have already said that the starter motor works from the diagnostic socket, so if the start signal makes it intact through the fusebox and on as far as the C101, there must be a break in the black/yellow between here and the soldered joint in the engine loom, where the branch to the diagnostic socket tees off.
The green/blue wires you have circled are for the windows and roof - nothing at all to do with the engine. The wires to the circled two pin socket should be both plain green, and these have everything to do with the engine starting or not!
The next place this green wire appears is in the C101, and the furthest extremity it reaches is the + terminal of the ignition coil, so check that the power is reaching here.
BTW, how are you checking for power? It's essential that you use a a 12 volt bulb with a minimum of 5W, and not a meter on its own. If you've used a meter, then most of your results will be meaningless, and need to be done again with a bulb.

[Royalratch]

Lol! - why would it be useless?

I use a small digital meter but it's a very high quality one.

I understand the bulb being a good visual confirmation but why is a meter no good?

So I will check voltage to the coils - where do I get my +12V reading from - don't really want to strip the HT leads.

[Brianmoooore]

A meter isn't useless - in the hands of someone who knows its limitations! A meter connected to a 12 volt source on an unloaded circuit, and through a faulty connection with a resistance of several thousand ohms, will still read 12 volts, althoiugh there is no practically usefull voltage there a all!
It may be usefull to know exactly what model/age/engine we are dealing with here as well.

[Royalratch]

June 1990 M42 - totally standard.

[Brianmoooore]

June 1990 M42 - totally standard.

In that case, it doesn't have a coil with a marked + terminal; it has four coils, each with a multipin connector.
The green wire is present in each one, so disconnect a connector from the coil pack, roll back the rubber cover, and check on the green wire.

[Royalratch]

Awesome.

Should I get voltage on key ignition (Pos 3) or Position 2 also?

[Brianmoooore]

Green wire: positions 2 and 3.
Black/yellow wire: position 3 only.

[Royalratch]

I will report back tomorrow - many thanks again. I also have a new ECU on the way - just in case lol!

[Royalratch]

Ok.

I checked the black/yellow all the way from where it clips in at the ignition barrel to where it exits the fusebox and there is +12v.

The green/blue ignition loop at the accessory panel DOES have +12V despite my earlier check. Fuel and DME relays have +12V.

Ignition coils do NOT have voltage at any key position - I checked it like this, which is probably a cheat and I will do it as Brian pointed out to be sure:




At this point, I'm starting to think it must be the ECU. Surely only the ECU would affect spark, fuel and ignition simultaneously.

The question is, if I put my new one in, what's to stop that blowing too. I need pinouts for the ECU Connector to check that voltage is coming in and then I'll now for sure.

[beemerbird]

Don't overlook the fact that the point of a meter probe will cut through any crud on connections you are checking, rather than actually checking that you have continuity of voltage which the said crud could be stopping.

[Royalratch]

Are you talking about Meter Vs Bulb?

[beemerbird]

I am talking about Meter. I am an Electrician and total advocate of the Multimeter, but being no car electrics expert I am offering you the advice posted above as it has caught me out. Bulb has an archaic air to it, but is more reliable.