Not just another "Won't start" e30 m20 - BMW Forum -

3-Series (E21, E30) Chat relating to the BMW 3-Series from 1975-1983 and 1984-1991 line. Specific models: BMW 315, BMW 316, BMW 318, BMW 318i, BMW 320/4, BMW 320i, BMW 320/6, BMW 323i, BMW 320i. E30 Family models include: BMW 325e, BMW 325i, BMW 325is, BMW 325ix.

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post #1 of 5 (permalink) Old 04-26-2010, 04:03 AM Thread Starter
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Macaz is on a distinguished road
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Not just another "Won't start" e30 m20

Spark: yes compression: yes timing: yes fuel: yes ECU: yes

Hi guys. Need some brains here for what should be a "no brainer" .. if you read what I've done you and checked you will see my FRUSTRATION!!!

My 323i L-jetronic won't start except when i disconnect the fuel pump in which it will run (just) like a pig with rich grey exhaust fumes on what feels like 4 cylinders max. Yes .. fuel pump on = car will die. if I can get it idle and connect fuel pump (which should always be running when car is) it dies. I can rev it slightly so the ECU seems to be doing it's job.

Compression: All cylinders 150psi after 4 rotations.
Spark: Yes. Leads: All check out ok. Resistance is max 7 ohms. New coil
Fuel pressure: 2.5 -2.7 bar and stable when engine is started (connected between fuel line and fuel rail). Fuel Relay primed fuel and comes on when car is starting and I can hear fuel swishing past regulator.
Fuel tank: checked this. has external fuel pump but inside the tank all is clear, no blockages
Timing: I did this before it played up and checked again. Spot on. Spark Rotor, etc: Checked and cleaned. Spark plugs: re-gapped and checked. All clean spark.
Injectors: had these cleaned and flow tested. Came up good.
Injector leads: with an LED stuck in a harness for an example: all are doing their job. coming on for a split second with ignition start to squirt juice in the engine and led will flicker as I turn engine. this proves signal from ECU.
AFM: When I try to start and engine coughs a bit - AFM arm moves which means ECU is talking to AFM. When it runs (like a pig minus fuel pump on) afm top rotor thingy is dancing around.
Relay: This unit uses a 7 pin job but this is working. It is switching on fuel pump and powering the injectors upon ignition
Air leaks: Checked. Cold start valve: Doesn't have one but I checked the thermo-temp sensor in the back of the thermostat and it came up within spec. Harness to the thermo sensor has power.
Fuel: I even drained and put new fuel in case it was dirty. No luck.
Coolant: Looks clear. Oil: Looks clear.
Car has always used a little bit of coolant.
Flywheel sensor: Must be working since engine won't kick over if it isn't ??
Codes: Does car this dinosaur have codes? It aint Motronic and the connector is old school. Can I peg a led on two pins to get readings?. Note pedal method doesnt work outside of the US
So you see .. head case.

Gut feeling: Engine flooding - ECU???. 2) Coolant leak/ bad gasket. It is using a little and I thought this might be flooding the cylinder walls but this doesn't explain why it will run minus fuel pump pressure. If I take plugs out after I try to start they are wet.

Note I tried to start with the coolant sensor disconnected - i.e ECU thinks the engine is warm and I got a big arse backfire but again the coolant sensor is within spec. Again- this model has no extra cold start just tells the injectors to stay on a little longer

Temp here is 25c and dry so I'm not trying to start in very cold conditions.

Do you guys have any more suggestions? This is doing my head in. I have compression (4 rotations to reach 150psi not sure i this is normal), I have spark I have fuel to the best of my limited knowledge.

Finally - this car has no cats or O2 sensors so they can be ruled out.

Any advice from BMW technical lords would be appreciated. If there is internal engine damage compression readings aren't giving anything away.

Thanks guys .... and gals .... as you an see I'm not wasting time with dumb arse questions and have checked everything I can.
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post #2 of 5 (permalink) Old 11-29-2010, 12:21 PM
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follow up

Did you ever solve this?

Sounds like you went through most things, if you had a spark then the crank sensor should have been okay, but for reference check resistance at 500ohms +/-.

The engine will crank with this sensor bad, but not spark?

You shoud get 3.1barg of fuel pressure....

Will be interesting to know how you fixed it!

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post #3 of 5 (permalink) Old 12-27-2010, 03:17 PM
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remove cat converter ,, i would bet its clogged
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post #4 of 5 (permalink) Old 01-07-2011, 11:12 AM
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Originally Posted by sdenny140 View Post
remove cat converter ,, i would bet its clogged
Not sure on this, but from what he said about being L-Jet (meaning it's older) I wouldn't expect it to have cats on it. I though that was a facelift E30 thing... adding the cats and other redundant stuff.

If I just made myself sound like an idiot, forget what I said, been on the E30-only sites for a while...
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post #5 of 5 (permalink) Old 01-08-2011, 12:03 AM
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are you sure about the injectors part, sounds like the ecm is flooding the cylinders since you can start it with starting fluid but no fuel pressure. id recheck the injectors... the clogged exhaust part is possible but it would still run if it was plugged... another thing you might try is the mass air flow sensor (if it has one)... if not then i would try the ecm the bad thing about this is that you have no way to test this... the spark is controled by the crank sensor directly to the coil?? correct??? if so then more possibility for it to be the ecm...
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