325i - not starting (electrical)

[TriggerFish]

Hi all,

I've got a problem with my 325i not starting.

I had some rust on the bulkhead by the loom grommet, so I removed the loom from the car. Sadly, the POS 1990's immobiliser/alarm/RCL was too big to fit through the hole, so I had to cut it out of the loom. (I just cut all the wires leading into the box.)

The time has come to rebuild the car, starting with the wiring/engine. I've got it all bolted back together, and tried to start it today, but nothing happened - just an alarm siren started (which I think is a different siren to the one I removed? Been so long since I heard it though, I couldn't say for sure), no starter motor or anything. Before my butchery, it would start, and then cut out if the immo wasn't happy.

So, I guess I have two questions really. Firstly, there's this box under the bonnet - I've seen one other E30 with the same box in the same position. Is this an OEM/factory option thing, or is this more of the aftermarket crap?







(Ignore the mess!)

Secondly, what wiring is needed for the car to start? So far, I've connected the engine loom/ECU, the battery, and the three plugs from the steering column to the main wiring loom (I'm guessing these are mostly for wipers/lights though, but I guess the starter motor/ignition wiring is in this), and the round plug by the fuse box, but that's it.

I'm guessing this is going to be a case of tracing the wiring of that old alarm system, but I'd like to know what I'm working with before I go too far with it all.

Thanks for any help!
Joe

[Grrrmachine]

There is a flowchart to help you work through this:

http://www.e30zone.net/e30zonewiki/inde ... oubleshoot

To clarify: you removed the loom from the car. Did you also disconnect the whole engine loom from the engine, or just unplug it from the C101 plug on the bulkhead? We need to know if you've messed around with the connections on the starter motor.

[TriggerFish]

Thanks - flow chart looks useful Seems to suggest it's likely green wire related.

I left the engine loom in place (apart from the C191, which I did disconnect so I could refurb the injectors) - I just removed the ECU from the cabin so the interior could be sprayed.

Nothing on the starter motor/in the engine bay has been messed with by me, and it doesn't look like the body shop have disturbed it at all either, apart from the aforementioned C101.

[Brianmoooore]

That alarm looks like it might be a Scorpion, which (if painted black, rather than orange) was one of the BMW approved alarms, available as an alternative to the BMW branded unit. This unit is totally self contained, so if you've already ripped boxes from under the dash, it looks like you have (at least) two.
The Scorpion has two sets of immobiliser connections, as far as I can tell from my very confused twenty year old notes, with red/yellow and purple/black (the two left end connections on the larger plug) being one of them.
If you have no starter motor action, then there is a break in the black wire that runs from the ignition switch, through a multi pin plug and socket clipped to the steering column halfway down, changes to black/yellow, runs across behind the dash, through a plug and socket above the glove box area, then goes up through the duct that leads to the fusebox, passes straight through, and ends up in the C101.
Similarly with the green ignition wire, which follows the same path, and also has a plug and socket above the glove box, but this time a double socket which, in OE form, was fitted with a plug with a loop of green wire linking the pins.
The immobiliser connections should have been made at the connectors above the glovebox, but there are no guarantees.

[TriggerFish]

Fantastic, cheers Brian - I don't think I could have hoped for a more helpful answer!

I'll give those a try over the next few days and see where I end up.

Do you know what sort of fob/key/code/thing was needed to allow the Scorpion to start? All I've got is an oval/oblong fob that was part of the last system, and had a copper induction loop thing hidden the steering column cowling. There's nothing else with the car that I'm aware of to deactivate the Scorpion (assuming it's still wired in, of course).

Thanks again
Joe

[TriggerFish]

Right, an update to this.

I've now realised how pointless an alarm on an E30 is, having managed to default my old one in under a minute of troubleshooting. Although that's better than the BMW fitted affair (turns out the second alarm was a dealer fit), which could be overridden by unplugging it and shorting two wires.

I've now got it crank from the key, and power to the ECU, ICV, fuel pump, spark etc. Although it's still not firing - I think due to the injectors.

There's 12v going to the common injector power source (red/white wire) with ignition on, and there's continuity between the injector pins on the DME (16/17) and the wires in the inlet manifold loom. When cranking the engine though, there is no power being sent to the injector feed wires, which I assume there should be?

So, I guess I've got a few questions there (also posted on E30zone, but I know there's E30 knowledge here too):

1) Should I be able to detect a voltage on the feed cables to injectors 1,3,5 and 2,4,6 with a multimeter?
2) What could be preventing the injectors from firing? (I've tried a spare ECU, just in case. I assume as there's a spark, the ECU must be working?)
3) Is the fuel pressure regulator a one way valve? (Just checking I've plumbed the fuel lines up right - there's fuel in the line leading to the FPR, and if that's one-way only, then it stands to reason they're on the right way round.)
4) Under the throttle body is a plug which doesn't seem to reach anything. Any ideas what it's for? (ICV, AFM, TB are all connected)
5) What's this plug coming off the ECU loom in the footwell? (I recall, vaguely, that there was nothing plugged into it when I took it out? I can't see anything on the loom that looks the same anyway...)





And the aforementioned plug (two pin) under the throttle body:






Cheers for any help
Joe

[Grrrmachine]

(also posted on E30zone, but I know there's E30 knowledge here too):

eh?

1) Should I be able to detect a voltage on the feed cables to injectors 1,3,5 and 2,4,6 with a multimeter?

No. The injectors will pulse in a square wave, so the multimeter won't react in time. Pull off an injector plug and wire in a test bulb.

2) What could be preventing the injectors from firing? (I've tried a spare ECU, just in case. I assume as there's a spark, the ECU must be working?)

You need to confirm the injectors aren't firing first. Are the spark plugs soaked with fuel after half a minute's cranking?

3) Is the fuel pressure regulator a one way valve? (Just checking I've plumbed the fuel lines up right - there's fuel in the line leading to the FPR, and if that's one-way only, then it stands to reason they're on the right way round.)

This is probably the cause of your problem. FPR connects to the return hose, not the feed hose. When the rail gets over pressure (3 bar) the FPR opens and allows fuel to flow back to the tank, lowering the pressure.

4) Under the throttle body is a plug which doesn't seem to reach anything. Any ideas what it's for? (ICV, AFM, TB are all connected)

It's for the carbon cannister (check the Wiki) and has nothing to do with any of your problems.

5) What's this plug coming off the ECU loom in the footwell? (I recall, vaguely, that there was nothing plugged into it when I took it out? I can't see anything on the loom that looks the same anyway...)

Idle speed controls if you have aircon fitted.

[TriggerFish]

eh?

My bad - I copy and pasted most of that from another BMW forum. Not as not on E30s as this place though

No. The injectors will pulse in a square wave, so the multimeter won't react in time. Pull off an injector plug and wire in a test bulb.

Ah, explains it. (This is where I wish I didn't have the stupid injector loom where all connectors are in one metal rail, rather than a plug per injecotr)

You need to confirm the injectors aren't firing first. Are the spark plugs soaked with fuel after half a minute's cranking?

No, bone dry.

This is probably the cause of your problem. FPR connects to the return hose, not the feed hose. When the rail gets over pressure (3 bar) the FPR opens and allows fuel to flow back to the tank, lowering the pressure.

That's all I can think it is, or the injectors. I'll check them with a bulb first, and reverse this if they're working.

It's for the carbon cannister (check the Wiki) and has nothing to do with any of your problems.

Thanks - I've seen these mentioned, but not seen one on mine. I'm guessing the PO removed it.

Idle speed controls if you have aircon fitted.

I don't, explains why it was empty. Thanks

Cheers for the help, hopefully that should be enough to get me up and running. I'll update either way though (always annoying to come across a thread without a definite answer!)

[TriggerFish]

Oh, so the fuel flows out of the FPR, back to the tank? I'd assumed (based on no knowledge), that it went into the FPR and then to rail. That's embarrassing!

I'll swap those during the week and see if it splutters into life!

[Brianmoooore]

FPR is a pressure release valve. It keeps the fuel rail at the correct pressure by allowing excess pressure to leak back to the tank.
As said above, you won't see any signal on the injector control wires with a meter. At cranking speeds the pulse is very narrow, so won't register.
With no fuel reaching the fuel rail, then the spark plugs are going to be dry, whether the injectors are working or not!

[TriggerFish]

Right, so fuel lines swapped so it feeds into the rail, out of the FPR.

Checked the injectors (well, one set) with a bulb and a length of wire, and they're being told to fire (up until the plug on the inlet manifold anyway). There's still a spark, but there's no running still.

On Saturday, I removed the fuel line to check that there was fuel (forgetting it was pressurised), and sprayed fuel everywhere, so the pump is clearly working.

The injectors were sent away to InjectorTune, but this is the first time I've tried to start the car since then, and it seems unlikely all 6 would come back defective. Is there any way to narrow down if the injectors themselves are working (preferably without removing the inlet manifold again).

[Brianmoooore]

listen to the injectors while cranking. If they are firing, you will hear a regular tick. You can use a screwdriver/ plastic tube/ automotive stethoscope to listen.

Are the plugs wet with fuel after cranking?

[TriggerFish]

Sorry. Shoulda said. No, bone still dry.

I've got a spare set of injectors/manifold loom to hand if that's of any help in troubleshooting. Apart from confirming again the ECU is working, I don't know what use they'll be though.

[Brianmoooore]

There is a round plug and socket fitted to the metalwork under the inlet manifold, where the injector loom joins the main engine loom (facelift looms only). The lower half of this connector has a rubber boot on it, which traps any moisture that gets into it, and promotes corrosion of all the wires in there. Check under this boot to see if there is any problem there.
A TIS was issued by BMW that this boot should have a small part cut out of it, to allow water to drain out, but I've seen very few that have been done.
A face full of fuel when you disconnected the line is not proof that the pump is working. A failing fuel pump can work for a short time, but stop working under the greatly reduced voltage when the engine is cranking.

[TriggerFish]

Yes, the PO had clearly had problems there as they'd used some nasty bullet connectors on it, which had fused together. I've replaced these with better quality parts.

I was thinking about the the fuel pump, and then remembered that the Scorpion alarm was plugged in still (dunno why I reconnected it!). I then unplugged it and shorted purple/black + yellow/black and it fired into life (although it doesn't idle, but that's another problem!).

So, as usual, it was user error in the end!

Thanks for all your help though, massively appreciated