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  #1  
Old 06-23-2003, 12:26 PM
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Join Date: Mar 2001
Posts: 223
190e fuel pump relay and OVP

I have been researching my situation with the stalling 190e. Is there a difference between the fuel pump relay and the overvoltage protection relay on a 1988 190e 2.3?
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1996 E320
2000 C230 Kompressor
1988 190e 2.3 - 225K miles, owned for 7 years. I cannot say enough good things about this car. Very well built, even at 225 it ran like new.
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  #2  
Old 06-23-2003, 02:06 PM
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Join Date: Jan 2002
Location: Salt Lake City, Utah
Posts: 9
190e fuel pump relay and OVP

If you're asking, are they two seperate relays, the answer is yes.
The OVP and Fuel Pump Relay on my 1986 190E are located behind a plastic shield behind the batery.
I believe that the OVP is there to protect the Fuel Pump relay from excessive voltage.

Make sure that you verify weather or not you have voltage at the fuel pump when you turn the ignition. Also of note on my car when trying to determine my problem, is that on the Fuel Pump the negitive cable is Red and positive is Black. This caused me some confusion and lead me to believe that I also had a relay problem.
Start with voltage at the pump when the car stalls and then go to the relay.

Todd
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  #3  
Old 06-23-2003, 03:37 PM
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Join Date: Mar 2001
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Todd thank you for your reply. When you said confusion about the red and black cables on the fuel pump on your car, were they reversed?
When I check the fuel pump for voltage when the ignition is turned on but the car not started, am I l looking for 12 volts? Is there supposed to be voltage at that time when the ignition is on?
Thanks
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1996 E320
2000 C230 Kompressor
1988 190e 2.3 - 225K miles, owned for 7 years. I cannot say enough good things about this car. Very well built, even at 225 it ran like new.
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  #4  
Old 06-23-2003, 05:43 PM
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Join Date: Jan 2002
Location: Salt Lake City, Utah
Posts: 9
On the Fuel pump the Red (negitive) and Black (positive) were not reversed. Apparently this was not an uncommon practice on older European cars, or so I was told by a friend who worked as a mechanic when he was in school.
I was confused when checking the voltage because I assumed that Red was positive and Black was negitive, and hooked up my VM as such. Obviously when the ignition was turned I did not see any voltage, so I suspected the Fuel Pump Relay. After wasting time checking the relay I connected the VM correctly and verified that I had voltage and that the pump was faulty.

I was testing when the car would not start and if I remember correctly, voltage is only supplied to the Fuel Pump for one second when the ignition is turned, this primes the engine to start. If the engine does not start ( 0 RPM's ) either the Fuel Pump Relay or someother electronics module stops the voltage to the Fuel Pump - I believe, but did not confirm that if the RPM's are greater than zero (engine starts) then continious voltage is supplied to the pump.
(I also found a note about this on a schematic.)

I believe that 12V is correct for the pump.

Todd
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  #5  
Old 06-27-2003, 06:50 PM
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Join Date: Apr 2002
Location: Surrey, Uk
Posts: 254
When ignition is turned on, voltage is only fed to the pump for about half a second unless the engine is turning.

OVP failure shouldn't prevent that car from starting.
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  #6  
Old 06-28-2003, 09:55 AM
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Join Date: Oct 2002
Location: Toronto, Canada
Posts: 700
bypass fuel pump relay

See if you can bypass the fuel pump relay with a paper clip, then try to start the car.

As soon as you do this the pump should start working and will continue at all times until you disconnect it, but it will rule out the fuel pump relay for sure.

I forget what pins you have to jump, but I will try to draw a diagram for you, if memory serves, this is what the port for the fuel pump relay looks like


OOOOOOO
OOOOOOO

Not all pins are connected, I'll use X to show these

OXXOOOO
XXXOOOO

if the numbering goes like this

1234567 - top
1234567 - bottom

you will be jumping pin 4 from the top to pin 4 on the bottom.
The moment you do this the pump should go on, ignition won't count here. Start the car and see if it runs. If it does, then you just found your problem, if not, you still did

Please correct me if I'm worng. This procedure is listed in the service manual but I don't have it on me at the moment.

xp
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