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Discussion Starter #1
Hi

I'm new to the forum and Saabs so apologies if I'm going over old ground. (I've done a search and can't find anything that helps).

On Sunday I bought a 1984 900 Turbo S. It's done 120k miles and is in pretty good nick but was stood in the pub car park up the road from my office. It's been there six months. I finally convinced the owner to sell it and towed it home. The story is that he spent a load of money on the brakes for the MoT then it just refused to start one day. It's sat there ever since.

A new battery had it turning over and a spark at the plugs. However, there's no power to the fuel pump and none to the fuel pump fuse. I managed to get the pump running by running a live to it (and smacking it with a hammer several times) and there's fuel at the fuel rail – I know becuase I cracked a union and covered myself in it. But it still won't fire.

I took the plugs out and they're bone dry so I don't think the injectors are firing.

The car has an old alarm on it, judging by the siren under the bonnet. I suspected this might be the cause but bearing in mind that every alarm I've ever seen disable the ignition circuit (usually the starter too) and that I have a spark, I'm not so sure. Despite this I'm going to remove it - when I've found the damn thing.

So, any ideas?

Thanks

Will Holman
 

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Will,have you checked the fuel pump relay? There are 2 relays above the ECU, the one on the right is the fuel pump relay, the one on the left is the main system relay.


Dan.
 

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willholman said:
Hi Dan

No - I didn't know they were there. That's inside on the driver's side A-post, yes?
Yep, but they are a pig to get to. Easier if you remove the knee roll (lower dash panel) 1st. Later Turbos had the Fuel Pump relay relocated to the fusebox .
 

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I recomend buying the previous owner a few pints at the pub, and find out if there is a hidden kill-switch or some other device at work here.
 

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grif900 said:
I recomend buying the previous owner a few pints at the pub, and find out if there is a hidden kill-switch or some other device at work here.
Reminds me of only last week when I was at a petrol station in one of my 9000 Aeros. The car wouldn't start. Queue of cars behind me. 1/2 hour of trying this and that before I remembered it has an imobiliser ;oops: Pressed the button hidden on the dash and drove home!
The moral is - don't have so many different Saabs that you can't remember how each one starts :cheesy:
 

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I have purshaced many old 900s (sixteen I belive), I'd say half of them had a mysterious switch that would disable something, like fuel pump power.
 

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Will, taken from the dealer service manual #2.3 Fuel system, injection engine M 1981-93 page 240-193:

Main relay: (on left)
30 = 559a red (RD) = battery
85 = 548 yellow/white (GL/VT) = to control module pin 21
86 = 559b red (RD) = battery
87 = 538 brown/white (BR/VT) = to control module pin 9
87b = 557 brown/white (BR/VT) = Hot Wire (fillament) burn-off function

Pump relay: (on right)
30 = 559 RED (RD) = battery
85 = 545 violet (VL) = to control module pin 17
86 = 560A brown/white (BR/VT) = to pressure switch pin 15
87 = 561 blue/red (BL/RD) = to injector and
558 blue/red (BL/RD) to auxiliary air valve or idle air control valve
87b = 261a grey/red (GR/RD) = to fuel pump and
564 grey/red (GR/RD) = LIMP-HOME socket.


BTW, Will from PPC ?

Dan.
 

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Discussion Starter #10
Hi Dan - yes - Will from PPC magazine here. My quattro's in bits and the Merc has no heater so I needed another car quickly. Preferably one that worked but you know how it is...

I saw this black three-door 900 and decided I had to have it. It's absolutely filthy inside and out but I reckon it will clean up well. First things first though - I need to get it running and throw it at the MoT man. Am I right in deducing from the above that if this relay's failed the injectors won't fire?
Thanks for your help - much appreciated.

Will.
 

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I think you need 5 posts before you can receive pm's. Which you have now, Dan will just have to send it again.
 

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Discussion Starter #15
Brilliant - thanks a lot. And the two relays you refer to are the ones hidden under the carpet on the A-post on my car?
 

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Welcome aboard, Will :)

Must be a very early 16v you have there. And in the right colour! If you don't get it started, at least it'll look good :cheesy:

Can't help you I'm afraid. Too many valves and it has electronicy gubbins, so all lost on me.
 

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Discussion Starter #17
Thanks. Yes - it's an S too, whatever that means!

I thought it would be an 8v but was pleasanly surprised when I opened the bonnet.

Will.
 

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Hi Will - hopefully this 900 will make it into your magazine :)
If you can get a lend of a decent multimeter ( with a setting for duty cycle ), you can connect it to one of the injectors and see if its firing. The fuel pump relay won't affect the injectors, so if they aren't firing maybe the main relay has failed ( and the ecu isn't getting power ). Check if the ecu is getting power.
 

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And the two relays you refer to are the ones hidden under the carpet on the A-post on my car?


Yep, remove the door sill trim and the upright metal trim (J-shaped) that hold the carpet in. The ECU is behind the carpet and the relays are above and a bit to the left. You can just about reach up with your hand if you know where they are but a lot easier to remove the knee roll 1st - and essential to remove it if you want a close look at the connections or want to put a tester on the connections.


To remove the knee roll:
http://www.saabcentral.com/forums/showthread.php?t=113525

Dan.
 

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The power to the injectors is controlled by the relays. If you jumped the fuel-pump to supply fuel that will have only run the fuel pump and nothing else.

I don't think the alarm is causing the issue but if you run out of options then it might be a line of investigation for later. Often those alarms have all of the circuitry built into the box containing the siren so may not need to look for any other boxes. You can tell by the thickness of the cable comming from the back of the siren. If it's more than 1 or 2 wires then you know its more than just a siren and it probably contains the alarm system as well.

With an electrical fault like this there are a range of possible causes. As Dan has already pointed out the fuel relays are one common point of failure. Another thing worth checking is that this problem isn't caused by a dodgy earth strap between the engine block and the front cross-member at the bottom of the engine bay. Don't bother looking at it. Just by-pass it by connecting a jump-lead between the battery earth pole and a metal part on the engine such as the lifting hook or fuel rail. If the car starts and runs then have a look at the earth strap and clean or repair as necessary.

In the bentley manual for the Saab 900 T16 there are detailed instructions describing how to troubleshoot a fault with the Bosch LH 2.2 injection system.

These are all the components involved in the running of the fuel system. Perhaps if none of the above advice is of any use then maybe you can work through the different connectors to look for power, earth and signals.

- Fuel pump
- Fuel relays
- Fuel ECU
- Air Mass Meter
- Throttle position sensor
- Coolant temperature sensor
- Injectors
- Ignition key switch
- Earth connection required for most components (if not all)
- Ignition Module

Save you buying any manuals I had a little hunt around looking in all the usual places and I found the wiring diagram from the proper Saab workshop manual. I think it might help.

http://townsendimports.com/Web/electrical_system_folder/Electrical_900_89-90/064-71.jpg

It's from the website http://www.townsendimports.com He publishes lots of pages from the Saab manuals. Very useful website if you've not got access to any of the manuals. Haynes manual for these cars is a joke so don't waste any time looking in there and if you've not got the manual then don't bother buying it. Best all-rounder is the Bentley manual from Bentley Publishing.
 
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