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Discussion Starter · #1 ·
I have a 1994 900s and it died on the way home from work, ive torn my dash apart and found the relay box and now im having problems finding out witch relay goes to the fuel pump. Ive looked on the back of the fuse box and found the wires that go to the fuel pump and relay box and swapped relays out with one another hoping to figure out what one is blown but that has not worked. All of the relays but one gets power but it doesn't seem to have any wire that goes to the fuel pump. So any ideas or better yet a detailed pic of the relay box and what relays do what function. thx
 

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It runs to the top connecter of fuse 32, the bottom connecter of fuse 32 (well technically the holder) then runs to the fuel pump.

The most likely cause of lack of power to the pump is a bad CPS (especially if it wasn't replaced in the last 60K), double check this by connecting a multimeter between the top connector of fuse 32 holder and a known good ground, check for ~12V while cranking. 0V normally means that either the relay or CPS is at fault, since you have swapped relays this would point to the CPS. Lastly connect a wire from the top of fuse 4 to the bottom of fuse 32, you should hear the pump run if it's good.
 

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Discussion Starter · #3 · (Edited)
i don't have a volt meter but i do have a ground test light and everything but fuse 32 gets power, I connected a wire from fuse 4 to the bottom of fuse 32 and tried cranking it over but it still didn't start. the fuel pump is about to be a year old so i dont think it could possibly be the fuel pump. And the fuel pump is a completely new part form bosh cuz i worked at the dealership so i spent $350 instead of $550.
 

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Discussion Starter · #4 ·
So I decided to play around with it a bit more and figured out what relay was my fuel pumps because when i poked a connector with the test light i herd the fuel pump turn on so i got excited and tried starting it while having the test light connected but still no start. SO if it is a CPS problem why would my fuel pump still not get power?
 

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The FP relay gets the 'on signal' from the ECU which relies on the CPS to know that the engine is turning over and needs fuel. If the CPS is faulty then the ECU doesn't know the engine is turning over and in turn cant provide the signal to the FP relay.
 

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Discussion Starter · #8 ·
Where can i find the cps? i found something that seems to look like it and its located on the bottom half of the block under the exhaust manifold. I talked to one of the techs at my old work and he believes it may be the crank shaft sensor so i looked around the block some more but i couldn't find anything that looks like the sensor i looked up.
 

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If you are going to do a resistance test on the CPS, you need to find it and trace the cable back to it 's connection point.

The CPS is the only unit on the drivers side of the front of the block near the flywheel (not the head) with a cable on it and secured by a single bolt. If you trace the cable, it should be terminated with the front and rear O2 sensors. You want to test the resistance between pins 1 & 2 (pin 1 is the yellow lead and pin two in the middle is black)... Ron
 

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Just had an identical problem on 1994 900S 2.3. Quit while running and fuel pump would not turn on. No power to fuel pump fuse either. Checked all the wiring and relays for days. Ended up being bad CPS. Even if you get fuel pump running by jumping connectors (I did), the car WILL NOT run because the ECU knows it's not getting a signal from the CPS. Mine was original and had 160K on it, believe it or not. The resistance measured somewhere in excess of 800 ohms I believe. It took like 5 minutes to change it and haven't had an issue since.
 

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Look, if you directly sent power to the pump via the bottom connector of fuse 32, and the pump did not run, don't blame the cps.
The chances are your pump is bad, whether it is one yr old or one day old, altho there could be a break in the wiring or a bad connection at the pump.
The next step is to uncover the electrical connector on top of the tank under the rear seat and hot wire power to the pump from there. If the pump still won't run, dang it, its time to cut the hole, if it aint already cut
PS If you have decent hearing, you should be able to tell if the pump is running by the sound.
PS2 It is possible, though quite unlikely, that the pump is making sound but not moving fuel. But first determine if it is making the magic sound. If it isn't, it's time for the tin snips.
 

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Discussion Starter · #12 ·
thx for all the help, ima do the test tonight with my multimeter but it will still take about a week for me to get the new cps since i am kinda broke and wont get paid for another week. get back to everyone then
 

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thx for all the help, ima do the test tonight with my multimeter but it will still take about a week for me to get the new cps since i am kinda broke and wont get paid for another week. get back to everyone then
Shop around for the CPS, the prices vary wildly..The labor cost is the killer, DIY really pays off.
I do champion the oscilloscope but they are costly, so, using the multi-meter take a cold and warm ohms reading, if this works not and with over 100K on the clock, I'd just re-new it....After all, if we drive the vehicle to 200K, and then to the junque yarde.... I see no real difference in changing the CPS , or anything for that matter, early...
 
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