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Discussion Starter #1
Well my beloved 84 900T died again today. I believe I traced the problem to the fuel pump relay...after the car is full warmed up, about 20 minutes, the engine dies like an on/off switch. The fuel pump relay is very warm to the touch and when i replace it with a jumper wire, she fires right back up and gets me home.
I replace the original relay with a german made KAE 3.307.100 and still have the same issue.
Questions: is that the correct relay? Is there something else going on here or did i get two bad relays?
Please help.
 

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I would guess (since I have no evidence) that you have a weak signal from your ignition pick-up or amplifier.
Put the old relay back, your replacement's not the continuous-duty kind that came with the car. That's why the fuel pump relay costs $50 instead of the $13 a fog light relay costs.
 

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Discussion Starter #4
Amplifier replace a few months ago.
Make and model number of proper continuous duty fuel pump relay please.
 

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Discussion Starter #5
I have looked online and have not found a concrete answer.

The failing relay is a KAE 3.307.100 and actually has "fuel pump relay" printed on the top for whatever that's worth.

I notice there are also KAE 3.307.110 for sale. Does anyone know the difference?
 

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.110 and .100 are probably the same relay. 100 is specified for 1985 and older cars, 110 is for 1986 and newer cars. The schematic is the same, so I'd suspect a supersession.

But, I doubt the relay is your problem too. Two relays with the same problem? Seems unlikely. I don't know what the inputs to the relay are, but I would be sure you test them... I know the old CIS relays interact with a few systems. I'd be sure those are all behaving.
 

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Discussion Starter #9
This is actually hilarious.

I jumped the fuel pump relay at the 12 and 9 o'clock pins and drove for about 45 minutes, well over the time when it usually would die, and it run great.

The hilarious part is that the radio that has been inop since I've had the car, started working! And loud and clear at that!

I have to do more research before I'm able to check the input voltages of each pin but was hoping this might shed a bit more light on what the heck is going on.
 

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It's been a long time since I've dealt with a CIS car, and my more recent experience is with even older c900s - '79 and '80. On those cars, the "fuel pump relay" is responsible for powering a fair amount of the chassis bits, and the fuel pump relay is triggered by the starter OR the ignition switch (independently) AND the tach signal. Those relays are susceptible to failure on the tach side, and then nothing works. Perhaps your situation is similar. These relays are NOT like regular old "Bosch style" SPDT etc. relays - just jumping across probably won't have the effect you think it will.
 

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Discussion Starter #11
Ive been sipping a little knob creek and listening to David Allen Coe so forgive some screwed up typing.

Anyhow this is what I finally found:

The '84, and probably other years, have a different fuel pump relay between the turbo and non turbo models. I have a non turbo relay in my turbo 900. The turbo models have a large rectangular shaped relay that takes two slots in the relay holder, slots F and G, part number 8579484 for the turbo 900's and slot G, part number 8539728 for the non turbo 900's.

I hope this helps anyonee having the same issues as described above. Information came out of the 1984 Saab 900T owners manual.
 

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The extra pin in the larger relay for the 8v turbo cars is to cut to fuel pump when the APC tells is to. Those relays are no longer sold, and you can pay 100+ for a refurbished one (or be lucky at a salvage yard).


My 1983 Turbo 8v is using a regular fuel pump relay, and it is working fine. As long as I don't floor it all the time, the risk is minimal.
 

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Discussion Starter #16
As posted above, the problem does go away when the relay is jumped.

I was "lucky" to find a NOS relay for $140.
 
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