Hi, I thought I had a fuel pump or filter problem because of non starting. I removed the filter, it was clogged and I changed it but car still wouldn't start. I changed the external pump next. After changing the filter and external pump I noticed the fuel pump relay won't click anymore when I turn the key on. I changed it with a spare, I knew both relays to be working. Now there is no relay clicking when the key is turned to on position. I know when you turn on the key, the pump relay is supposed to click for a few seconds which tells you it is working and good. After I wired in the new pump the relay won't click anymore. I am sure the polarity is correct. What might cause the relay to stop working after installing a new pump? Thanks

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Inspect and clean fuses 4 and 6. Check for +12v on terminals 30 and 85 of the fuel pump relay when the key is in the on position.

Since I installed the new pump the fuel relay won't click any more (I tried two known to be good) instead when I turn the key on there is a constant fairly loud clicking coming from under the engine hood. Besides the negative and postive terminals on the fuel pump itself, are there any other electrical connections that I may have missed or forgotten to put back on? what might clicking from under the hood be when the key is on the :on" position? I checked fuses 4 and 6 in the fuse panel and also the 25 amp fuse which hooks up to the positive terminal of the battery.

I would inspect/clean all of the fuses, then try to isolate where the clicking is coming from.

having similar problem with 88 240. and had problem a couple of years ago, which was a loose connection at the coil. the ecu needs tachometer type input to complete a ground circuit in the pump relay. follow the test procedure for the relay in the Bentley manual. best thing would be the official Volvo manual. does anybody have official volvo wiring diagrams? the common trouble points for no current to pump(s): fuses, relay, ecu, coil connection.
good luck, volvoocrunch

Here are two diagrams for both the ignition and fuel systems. These only generally apply to US model 240's from 85 to 88 ...

Thanks Robert, My car is a 1990. You say these are for '85 through 88. I think the Haynes manual has these diagrams. I wondering if a bad ECU 0 027 400 169 if bad could cause there to be a clicking sound from the engine when the key is in the on position. Also I noticed that my battery is fairly weak. After charging it I only get a few good cranks out of it before it starts cranking slower and slower. Could a weak battery cause strange things to happen? Can the ECU be tested if removed? Thanks

Definitely a weak battery could cause these issues, clean-up the cables and have the alternator tested to make sure its charging.

thanks for wiring diagrams
volvoocrunch