M10 cold start issue

[goosiegander]

HI All,

For those of you that still remember the glorious M10 please help with the following.

April 1988 316 with a cold start issue,

Issue being that it wont, cranks over just fine and ran when hot when I bought it the other day.

No noise from the fuel pump/s on switch on,

A slightly bent 15a fuse was in no 11 so that trick has been tried and I also tried jumping the pins at the fuel relay to no avail...

As I said the car ran fine enough when warm and since then nothing has happened to it beyond a general poke about without disturbing any wires (so I am pretty sure)

Thoughts as to how to proceed would be appreciated,

Obviously I've already used the search function and considered the thermotime switch but I don't know if a duff thermotime will kill all power to the fuel pumps...

Thanks in advance

[daimlerman]

So the fuel pump refuses to run with 12v direct to it?

[goosiegander]

Have not tried to jump the fuel pump with 12v yet, nor have I had a chance to check the power supply at the pumps with a multi meter...

[Brianmoooore]

First thing to establish is what we are dealing with. OP says April '88 316, which is a 1.8 litre M10 carb. engine, with a carb. that may or may not be OE.
Is this what you have?

[goosiegander]

Mechanical distribution Brian, its fuel injected no carb, no apparent molestation to the injection relays on the nearside wing of which there are three Orange in centre, Tall block at front and large rectangular block at rear...

HTH - and thanks for looking at this guys!

[goosiegander]

Well perhaps I've solved it, the pin out schematic on the fuel relay is wrong, pin 30 to 87 has the fuel pumps running. How the hell the car ran on this relay when it was warm I have no idea, pins 31 and 30 were the wrong way round. Brian can you sense check me on this?

[Brianmoooore]

30 to 87 is the normal two pins to short to bypass a standard relay, but I presume yours is a multi pin device that has electronics to detect engine rotation.
If the engine runs when you short 30 to all 87 pins, then it suggests the relay is faulty.

[goosiegander]

and item 6 here: http://bmwfans.info/parts-catalog/E30-2 ... ump_relay/

[Brianmoooore]

Seems unlikely that the relay would be marked wrong. 30 comes directly from the battery, 87 goes to the injectors, and 87b goes to the fuel pump, so joining these three pins together in the relay's socket completely bypasses it.
All the other pins are associated with the electronics: 31 is earth, 15 is ignition live from the ignition switch, 50 is the starter motor signal, also from the ignition switch, and TD is the ignition pulse to the coil, that indicates the engine is running.
Your car is a 316i, BTW, not a 316. Very different cars, in the area in question.

[goosiegander]

Yes sorry Brian, I ran the fuel pump jumping pin 87 to 31 not 30 hence my confusion, positive and negative appear to be reversed at the socket of the relay or am i just being stupid??

[Brianmoooore]

It's 87b to 30 that should run the pump according to my circuit diagrams. 87 is the injector supply. Are you sure you're relating the layout on the relay case to the socket the right way around.

[goosiegander]

Now you say that yes i'm wrong, i'll ask our techs at work tomorrow to check the relay for me and order a spare in the meantime, any thoughts if the relay comes back as being ok?

[Brianmoooore]

Does the engine run OK with it bypassed? If so, leave it bypassed and see if the symptoms go away, but don't forget to remove the link when you're parked. Check (with a bulb, NOT a meter) that the start signal and ignition on signals reach their respective pins, and that the pins of these signals on the relay are clean and making good contact.
Unless the 'techs at work' have a special 30 year old rig for checking these ancient technology relays, then I don't see how they can fully test it.
I certainly wouldn't order a new one until it is confirmed faulty.

P.S. I've deleted one of your posts with a link - it was screwing up the page layout.

[goosiegander]

Thanks guys,

If I bridge the pins with fused wire should the relay be left in place or should I run the car for a few miles and reinstate the relay to see if the problem has gone away?

[Brianmoooore]

No fused wire required - just link the pins together, preferably with male blade terminals crimped onto two bits of wire.
You can run the car for as long as you like with this set up, as long as you pull out the blade to pin 30 when you are stopped, otherwise it is the equivalent of leaving the ignition switch on, and you will flatten your battery.
Apart from the inconvenience, the only thing you will have lost is the safety aspect of the fuel pump cutting off when the engine isn't running.

[goosiegander]

thanks Brian, shall do, should the relay just be left out?

Is there a down side to the speed input being left out?

[Brianmoooore]

If leaving the relay out and bypassed cures the problem, check that all control signals to it are present, as in my last post, and if they are, that pretty much confirms the relays guilt.
The fault in the relay is quite likely to be just a dry solder joint, but it looks like it is of 'potted' construction (filled with resin), so a repair is unlikely to be possible, and you will then need to order a new one.
As I said above, the ignition signal is only for a required safety aspect - ensuring that the pump doesn't continue to pump fuel out if a fuel line is severed in a severe crash.

[goosiegander]

OK the car will not run bypassed,

The polarities on pins 30 and 31 are back to front with continuity back to the battery terminals,

pin 15 and 31 will light a bulb with the ignition on or off totally

pin 50 and 31 will light a bulb when cranking

All other functions on the car are normal no fuses have blown so I'm totally at a loss...

[Brianmoooore]

If the engine won't run with the relay bypassed to give 12 volts on 87 and 87b, then it seems likely that the relay is OK, and the problem is a missing ignition pulse on TD.
This might also show up as lack of sparks from the plugs when cranking, so the next test is to check that.

[goosiegander]

No spark brian

[Brianmoooore]

This engine doesn't use a crank position sensor like most E30 engines, but relies on a trigger wheel and pick up in the distributor - just one step on from the ancient points and condenser system. The output from the pick up goes to an ignition amplifier module, so it appears there is a problem with either of these.
Your 'techs at work' may be able to check these out with an oscilloscope.
Only check you can do yourself, other than making sure everything is plugged in correctly, is to check that 12 volts reaches pin 15u of the ignition amplifier when the ignition switch is on. I would expect this wire to be green, as it is as far as the ignition coil + terminal, but the circuit diagram shows it as black. This is not the only black wire to the module, so care is needed.

[goosiegander]

No voltage at pin 15 of ignition amplifier at ignition on or off Brian, are there any other relays I can check?

[Brianmoooore]

Check at the + terminal of the coil with the ignition on.

[goosiegander]

there was some continuity from the pins on the plug to the positive terminal on the coil one was ok the other not, continuity to ground was poor and the coil has no continuity to ground at any state of ignition,

Bad ecu?

[Brianmoooore]

You are supposed to be looking for 12 volts on the + terminal of the coil (to earth, NOT across the coil) with the ignition on, preferably tested with a bulb.

[goosiegander]

Apologies Brian the is only .007v reading between ground and and the positive terminal of the coil with the ignition switched on

[Brianmoooore]

Connect a piece of wire directly from the + terminal of the battery to the + terminal of the coil, leaving all wiring connected and in place, then try to start the car.

[goosiegander]

Car starts and runs as per above post, had to disconnect wire to stop car. Battery light remained on whilst running but otherwise no issues,

So that's progress, what's next?

[Brianmoooore]

Search out and destroy the immobiliser you didn't know you had.
The + terminal of the ignition coil should come directly from the ignition switch, via the 20 pin C101 engine loom plug and socket. You've already said that there was 12 volts on pin 15 of the fuel pump relay with the ignition on, so the power from the switch should be making it as far as a soldered joint in the wiring loom, in the cabin, just to the right of the heater box. From here, the power splits.
One branch goes to the pump relay via the C103 and C104, and the other goes across the car, through the fuse box duct, and to the C101.
Most likely place to find an immobiliser is behind the glovebox, where you are looking for something connected in series with a plain green wire.

[goosiegander]

And if there isn't an immobiliser?

There aren't any hidden fuses that I don't know about are there?

I took the glovebox and cover down to look at the ecu wiring on the above basis and it looks like I was the first person in 20 years to disturb anything...

Not had the underdash panel on the left side down yet though...

Also can I drive the car to an MOT with the coil bypassed or is this a no-no?

[Brianmoooore]

No hidden fuses - there's only one hidden fuse on an E30, and failure of that will only stop the heater from producing completely cold air.
If there isn't an immobiliser, then there's something else breaking the wire. You may have to hunt for it - if it's DIY it could be anywhere.
You can drive the car with the bypass in place as long as you like - it's just the same as turning the ignition switch on, and shows you how easy it is to bypass the average E30 immobiliser.

[BenHar]

I took the glovebox and cover down to look at the ecu wiring on the above basis and it looks like I was the first person in 20 years to disturb anything...

Not had the underdash panel on the left side down yet though...

Is this car left hand drive?

Ben

[goosiegander]

Oh yes!

[goosiegander]

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