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Discussion Starter #1
I have a 1989 900
VIN : Ys3ac46d4 k3021909
B202,I,4-CYL,4-CYL I,PETROL

with the ENGINE CONTROL UNIT / MODULE, Jetronic (LH 2.4)
Bosch 0280000564 / Saab 7487135

I replaced 2 broken capacitors in this unit.
I was thinking the unit was the problem and just had reset.. or so.

When the engine is off. It wlil sometimes start but most of the time i have to wait long.
When it not starting i can see the Fuel pump and ignition is not turned on (either Engine control unit of the Bosch ingition system)

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If the fuel pump isn't running when the engine is cranking, either there is no tach signal (Hall Effect sensor has failed, the ICM has failed) or the ECM has failed (no fuel pump relay engagement). The latter is a common problem on some LH 2.4 ECMs.

Here are a bunch of threads on starting c900s:

https://www.saabcentral.com/forums/showthread.php?t=728020&highlight=start
https://www.saabcentral.com/forums/showthread.php?t=723250&highlight=start
https://www.saabcentral.com/forums/showthread.php?t=721992&highlight=start
https://www.saabcentral.com/forums/showthread.php?t=708273&highlight=start
https://www.saabcentral.com/forums/showthread.php?t=669434&highlight=start
https://www.saabcentral.com/forums/showthread.php?t=693113&highlight=start

The second to last one hits every single bullet point about starting a 16v c900.
 

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....yep......usually, when 1989 and C900 are mentioned in the same sentence, Fuel ECU is usually a hot topic.
For what it's worth, the white ceramic hybrid chip is the item that performs most of the fuel calculations and fuel relay control.
The most efficient use of your time would be to source another ECU and swap it in to see if the behaviour of the issue changes.
Otherwise, as Jvanabra has kindly highlighted for you - many long hours can be wasted chasing all sorts of imaginative thoughts on the suspect fuel pump relay control.
There have been a few instances where the fuel relay control might have been impacted by some other condition but with MY89 cars, the fuel ECU is a simple fix......replace it.

And, this condition is not a Saab thing....Volvos of the same era suffered the same issue.
 

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Discussion Starter #5
Thanks guys. Very helpful to know I am going in right direction.
Swaping out ECM ICM or Hall sensor would be right way to find this problem. As I am probably the only one in this country with a Saab I need to investigate further. The linked in threats are very useful.
Thanks.
 

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Hello guys. Thanks a lot. I was able to get a replacement Bosch EZK (176 in diagram) and this solved my engine off problem.

Ps I also have a same year 1989 LH fuel module (200 in diagram) for a 9000 B202.. Can I use this on my 900 or do I need to swap the eeprom?
 

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If they are both the same engine (displacement, aspiration) it will probably run, but maybe not exactly right. Best off getting the right ECM.
 

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The 1989 LH 2.4 ECU's were known to have problems with the PCB tracks etc. for the fuel pump relay circuit, and also with the idle control loop in the firmware. I don't know enough about them to go deeper into the technical side. When I had my old 89 3ck n/a hatchback I replaced the 89 ECU with a 90 version and that sorted out some problems.
 

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Discussion Starter #9
Thanks for the input.. i am sorry to report that after a long test drive... the problem came back. (engine off)
I will now replace the hall sensor (while also replacing crack shaft oil seal and oil pump O-ring.. (quite some oil leaking there)
I will open up the 9000 ECU and compare.. as electronics engineer i try to look past the broken capacitors this time. ;-)
 

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Last action to fix this was replacing the crack shaft hall sensor. (and oil seal, that came off with the pulley....)
It all was very dirty due to leaking oil seal and leaking power steering system.
I was not able to remove engine but removing the Aircon pulley give enough space to work.

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