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Re: Spark No Fuel
Posted by David Prantl (more from David Prantl) on Fri, 16 Aug 2002 23:19:22
In Reply to: , Kok Chen, Sat, 17 Dec 1988 12:00:00 

>  89 900 for
>  I have spark but no fuel.
>  I can turn the fuel pump on by a jumper wire
>  I can even fire the engine with these terminals jumpered.

Tom,

your car has the 16V non-turbo motor with LH2.4 fuel system.

The Bentley manual for SAAB 16V cars has the appropriate wiring schematic 
for you car's fuel system.  It has also been scanned and presented here:

http://216.78.172.244/electrical_system_folder/Electrical_900_89-90/072-77.jpg


For safety reasons, the ECU controls whether or not the fuel pump runs.  
When you crank the engine, the ECU receives a tach signal on pin 1.  When it 
sees this signal, it should ground pin 20, activating the fuel pump relay 
(component #102) and thus turning on the fuel pump.

There is a known/chronic defect in 1989 900 16V non-turbo ECU's, whereby the 
ECU loses the ability to ground pin 20 when it's supposed to.  Early on, 
Bosch used to have a repair kit available to fix this problem.  Soon after 
it became clear that this was a widespread problem, Bosch stopped selling 
the repair kit and started the much more profitable practice of selling 
'remanufactured' ECU's (for hundreds of dollars a piece).

So, here are some possible fixes:

1.  Obtain a used '89 900 16V non-turbo ECU (part #7 487 135), and hope that 
it works better/longer than your current one.

2.  Obtain a used '90 900 16V non-turbo ECU (part #9 119 447), which is less 
prone to the fuel pump activation problem, and with the relevant wiring 
schematics, verify that all it's wiring connections match up to the '89 
unit.

3.  Obtain a remanufactured '89 900 16V non-turbo ECU from SAAB for big 
bucks (part #8 826 026), and hope that it works better/longer than your 
current one.

If it was my car, I'd go for option 2.

David Prantl

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