[Solved] 1983 628 start and stall!!

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andreszgz
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[Solved] 1983 628 start and stall!!

Post by andreszgz »

Hello everyone.
I have a problem with my 1983 628 csi I bought last winter. This is my first bmw and I'm not mechanic. The car wasn't been drived for many years. The last ITV, MOT, was in 2001. I want to get it back to the road.

First, I have changed fuel filter, fuel pump, spark plugs, ignition module, rotor, distributor cap and spark plug wires. Also changed coolant temp sensor and something more I dont remenber. The car now starts for a few seconds and then stalls. I think the Cold Start Valve is working but not the main injectors. I test it and have no pulse in the injectors. Bridged the fuel main relay and the same happened.

I thought it was the afm, because the ats readings were too low, 196 ohms. Then I bought an used one and the car still does the same. The ats resistance is near the same, 194 ohms. After this I read this ats is especial low resistance, different to other bmw's. So I don't know if two afm's are bad and need to buy a new one or it may be other thing like ecu.
Any help will be apreciated.
Last edited by andreszgz on Tue Jun 06, 2017 8:41 pm, edited 1 time in total.
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tschultz
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Re: 1983 628 start and stall!!

Post by tschultz »

Could be a failing ECU...
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andreszgz
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Re: 1983 628 start and stall!!

Post by andreszgz »

Do you know how to test it?
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MVX11V
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Re: 1983 628 start and stall!!

Post by MVX11V »

I've had this starts stalls thing on three occasions over the last few years. The cures:

1) A failing main relay, eventually it won't start at all, could take months or even years to completely die, you may also smoke your starter motor trying to start the car repeatedly. Temporarily replace relay with bridging wire to see if symptoms persist. Remove wire to kill engine. This can also make the engine cut out whilst driving and then it will start up fine again and work fine for weeks leaving the owner totally baffled.
2) A failing fuel pressure regulator. The engine may stay running once warm but idle will vary and engine will appear 'lumpy' in performance.
3) A loose battery or main earth. This is accompanied by many other, mainly electrical faults too.

As a note, always check for vacuum leaks.

I feel your pain during this frustrating problem and I'm still not completely over mine (the stalling has stopped, just re-tuning/ adjusting stuff to suit)

EDIT: My AFM had been messed about with before my time, tell tale is re sealing around the plastic covers. The sweep contact was completely leaving the track in several places and the air bypass screw was wound in tight. It ran for years like that!
'HAUNTED :evil: ' and playworn 1986 635 Daily.
andreszgz
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Joined: Mon Dec 12, 2016 1:36 pm
Location: Spain

Re: 1983 628 start and stall!!

Post by andreszgz »

I bridge the main relay and the car does the same. So I think it's ok. Also checked fuel pressure and seems to be ok. I will try to tighten the battery connections because only put it without tight the nuts.
andreszgz
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Re: 1983 628 start and stall!!

Post by andreszgz »

Well, the car does the same after tighten the battery connections. I have checked the ecu pinouts and found that pin 4 only has 8,5 volts when cranking and running until stalls. Is it normal or should be higher?
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Brucey
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Re: 1983 628 start and stall!!

Post by Brucey »

first thing is that the 628 runs L.E.-Jetronic which is completely unlike the engine management used on any other 6er.

The one thing it has in common with other 6er engine managements is that it uses a cold start injector, driven from a separate circuit to everything else. This means it can get enough fuel to fire when cranking even if the main injectors are not working properly.

Also note that the ignition system is also entirely separate except that it provides the timing signal for the injection ECU; this means you can have a healthy spark even if the Jetronic ECU for the injectors is broken or not powered up.

So yes I'd be suspicious that the Jetronic ECU is doing something peculiar. The other bugbear is that you could have a massive air leak and/or a bad AFM (AFMs don't like to be left standing)

IIRC if the AFM wiper starts to go bad, it defaults the other way (lean running IIRC) vs a motronic one.

cheers
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andreszgz
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Re: [Solved] 1983 628 start and stall!!

Post by andreszgz »

The shark is running again!!! Finally I have changed the ecu with a new one and goodbye problems. Thanks to all for the help
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MVX11V
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Re: [Solved] 1983 628 start and stall!!

Post by MVX11V »

Congratulations. The words 6er and solved don't go together in my world. =D>
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