E30 Zone

Hey guys, I'm new to the E30 zone. I would've liked my first post to be an "about me" kind of thing but i guess that'll have to be the second one, as i need some help right now. I have a 1990 325i, it cranks but won't start. I was on my way home when the car started sputtering during running. I revved it a bit as it seemed like the engine wanted to die. Moments it did the same thing and the engine died completely. Cranked the engine but no start. I checked for spark, air, and fuel reaching the fuel rail. When i checked the fuel i noticed that the flow of it was considerably low as it seemed weaker than water from a half opened sink. The fuel pump is still working as i can hear the buzz when activated so i don't know what could be causing such low fuel pressure and ifbthat has to do with the engine not wanting to start considering it ran before that happened. Thoughts?

If you're sure that you have a good spark from the plug leads (or at the coil king post?), and you haven't had a major mechanical failure, such as a broken cam belt, then fuel problems are the most likely.
Pull out the fuel pump relay ( four pin, probably orange and under the cover on the inner wing beside the AFM ), identify pins 30 and 87 of its socket (marked on the relay), and connect the two together with a short piece of wire. This should make the fuel pump run continuously, which can e easily heard, and there should be creaking and turbulent liquid noises from the top of the engine bay, as fuel flows through the rail and pressure regulator.
Disconnect the fuel hose that goes straight to the fuel rail, and there should be a good flow of fuel from it, with several bar of pressure behind it if you try to block it.

Did the fuel test, the pump was heard and i disconnected the hose from the fuel rail and i got good flow of fuel. It still doesn't start.

Can a bad flowmeter make the engine die while running? How do i know if i have air coming into the engine since i already have fuel and spark? Can the bad flowmeter prevent the engine from starting? What else is related to the air entering the engine that could possibly affect it?

Welcome to the zone and I hope that you get it sorted soon mate

Mart.

Michael540 wrote: ↑

Sat Oct 26, 2019 1:24 am

Can a bad flowmeter make the engine die while running? How do i know if i have air coming into the engine since i already have fuel and spark? Can the bad flowmeter prevent the engine from starting? What else is related to the air entering the engine that could possibly affect it?

Short answer is no. Engine should start and idle normally if the big air hose between the AFM and throttle body is removed, allowing the engine to draw its air straight into the TB.
Having said that, an AFM that gives an incorrect signal can certainly upset the running of the engine, but this is normally felt as flat spots when accelerating. It would be a very unusual AFM fault that stopped the engine from starting.
Unplugging the electrics from the AFM should also allow the engine to start and idle almost normally. Almost, because pulling the plug also disconnects the inlet air temperature sensor which is built into the AFM housing.

Take out a spark plug after a good cranking session, and see if the end is wet with fuel.

Check the C191 connector.

https://www.e30zone.net/e30wiki/index.php?title=C191

Ben

Replaced the fuel pump since i could replace it for free, nothing changed. I changed the fuel filter cause i disconnected the line and the fuel coming after the filter was brown so thought that might have clogged up the system, but that didn't change anything either. Also i took off the spark plug and it looks dry with a brown color, they're less than 6 months old. Also i sprayed carburettor cleaner directly to the throttle body and the engine managed to turn on, so i believe that could result in it being a fuel problem. If the C191 plug is bad it wouldn't even start at all, right?

If the plug tips are dry after cranking, and there's pressurised fuel in the injector rail, then it's an injector problem. All the injectors aren't going to fail at the same time, so it likely to be an injector electrical problem.
This is most likely to be a failure of the red/white wire at pin 5 of the C191 or a duff DME relay.
DME relay is the 5 pin one next to the fuel pump relay, and can be checked by pulling it out, and linking together 30 and both 87s of its socket with two pieces of wire, and trying to start the car.
Note that the problems with the C191 do not normally involve the pins of the plug and socket. The problems occur inside the rubber boot under the lower half of the C191. Water gets into here, can't escape, and causes electrolytic corrosion of the copper in the wires. There was an official BMW mod. for this problem, which simply involved cutting a small nick in the lowest part of the boot, so that water can get out, but very few were 'modified'.

I did the DME Relay test with the wire and i heard a buzzing sound as it had been activated. I proceeded to crank the engine but it didn't start. Now I'm going to check the C191, so the water gets clogged up inside the boot itself?

Update:
Ok so i disconnected the C191 plug and the plug looks pretty clean, no traces of humidity or corrosion at all. Not sure if the water that accumulates in the boot would affect that. What options do i have left? It still has to be an injector problems since i got dry spark plugs after cranking.

If the plugs are dry after cranking, then it's definitely an injector problem, but that doesn't mean it's anything to do with the injectors themselves. In fact it's most unlikely that they are at fault. It could be electrics to them or their fuel pressure.
You did connect 30 to both 87s on the DME relay? Did you check a plug for being wet afterwards?
You've checked the weak points for the injector electrics, so I think its time to revisit the fuel supply by buying a £20 ebay fuel pressure testing kit, connecting it up, and proving that all is well there or otherwise.

Okay so i justed cranked while i had the dme plug wired and i still had no wet spark plugs. I did notice that it started cranked faster (kind of like it did normally did) since it had been cranked so many times it started to slow crank (not the battery, it's fuy charged and i just put it in).

I don't wanna celebrate yet but i just wanna thank you guys for all the help I'm getting, really wouldn't have known my way thorugh this if it wasn't for you guys.

Great news, the car started, turns out it was the DME relay. I connected the 30 and the 87s and went WOT and it started cranking faster until it catched up. I kept my foot on the gas kust in cased the engine died and eventually i lifted and it stayed on. Do i have to use am OEM relay? Do they sell those at rockauto or where could i get them?

"Bridge the DME relay by connecting pin 30 to both pins 87. This is to see if power to both the ECU and the Fuel Pump relay has been lost. If the car starts once bridged, it confirms battery power is getting to Pin 30, and that both 87 circuits are working (power to ECU and Fuel pump relay). It doesn't test the circuit that latches the DME relay, which therefore needs to be tested before condemning the relay.

That circuit consists of Ignition supply to the ECU, which latches and sends a ground signal to pin 85 of the DME relay. If pin 86 has a positive supply, the relay should latch. If it doesn't, then the relay is faulty and needs to be replaced."

What is it referring to as circuit? The plug where the relay goes or the relay itself?

So the car turned on with the old DME Relay, so i really don't know what was causing my troubles.

First test is to pull out and plug in the DME relay with the ignition on. There should be a 'click' which can be heard and felt each time. If the click occurs, then the switching signal i getting to the relay. If it doesn't, then either the relay's coil is open circuit (fairly unlikely) or the switching signal isn't getting there.
Pins 85 and 86 are the coil connections. One is permanently connected to 12 volts and the other is earthed by a wire to the ECU when the ignition is turned on. Can't remember which way around they are, because the circuit diagrams show it wrong, and it doesn't matter anyway.
Connect a 12 volt test lamp to 85 and 86 of the relay's socket, and see if it lights when the ignition is switched on.
The section of the ECU that controls the DME relay is switched by a plain green wire to pin 27, which should have 12 volts on it when the ignition is on.
I'm beginning to wonder if this is some kind of immobiliser problem, preventing this signal getting there. This would usually result in no sparks as well, but not all immobilisers are connected the same way.
Do you have an OBC in place of the analogue clock?

I have found the problem, and this time it's final: the fuel pump wiring was loose. Didn't even cost me a cent to fix it. Thank you guys for the help either way you have been of great support. I owe you guys a proper introduction and more pictures of the car (and a lot more considering how much i needed this car running). Right now there are some personal, what i could consider life changing moments that I'm going through (all for the better) that will be explained in the post.

Evening,

Rather than start a new thread, I thought I would bump this as I found it useful for initial troubleshooting.

Car is a 1986 320i Auto.

It has been off the road since 2010 and I am slowly recommissioning it.

After Timing Belt, Water pump, Service and other vacuum line replacements the car has been starting on the 1st turn of the key.

The running gear has been refurbed and after a 20m test run, a corroded pipe at the bottom of the Thermostat housing stopped play.

Housing since replaced and new brown and blue Temp sensors...

After the above work, I cranked it and it ran for 3 seconds (presumably burning what fuel it had in injectors) and now car wont start!

As Brian has previously pointed out, Early 320i are a bit different to later M20s and I note I don't seem to have the same relays as the above example.

Battery is fully charged and cranks strongly. I am getting good Spark. Spark plugs are dry and fuel line to regulator is dry. There is no buzzing from Fuel Pump.

As above, I bridged the 30 & both 87 pins on the relay and nothing.
I note the below fitting - is this my C191 equivalent?
Is there anything else I could be testing before replacing the fuel pump?

Thanks

Michael

Connect a 12 volt lamp in place of the fuel pump and see if it lights, or connect 12 volts from the battery directly to the fuel pump.
If the lamp lights, but the pump doesn't run when you reconnect it or the pump doesn't run when you connect 12 volts to it, then it's faulty.
Is your pump in the tank or external?

Brian,

Many thanks for your response, I will give that a go.

I should also point out that I can smell petrol after cranking; not sure if that is relevant.

RE the pump, I have the below set up in front of passenger side rear wheel
REAL OEM show below for my car
Do you have either No. 7 or No. 11, or do I have both?

This is view under rear seat

Thanks

You can tell whether you just have a pick up tube in the tank or the low pressure lift pump as well by looking at the electrical connections. The fuel level sender requires three wires, so if there's more than this, you have a pump as well.
Your high pressure pump is located in front of the rear left wheel, in the place occupied by the fuel filter on later models.
I should point out that the difference between the electronics on your car and the slightly newer one of the OP of this thread is not a small evolutionary change, but an absolute chasm. The difference between an abacus and a modern calculator, a penny farthing and a modern racing bike.
The electronics on a post '87 E30 is essentially the same as on the latest cars - a few more sensors and feedback loops now, but the same basic principals and operation.
There's no C191 on your car, or on early Motronic M20 cars. This was only introduced to make assembly and disassembly easier, but only succeeded in introducing a potential trouble point.
The item in your pic. is the ignition amplifier. Part of the ECU on later E30s, and every car since.