Diagnose a Bad Fuel Pump

Got Bad Fuel Pump?

PaulM850R-960 » My 850R wagon would not start at the airport after returning from a flight at 11pm (argh!) I suspect the fuel pump or relay. Happened once before but eventually started and ran fine for some time. How do I check both of these items, are there 2 fuel pumps with this vehicle and I assume you have to drop the tank to replace if it is the pump. Please advise and thank you in advance for your help.

erikv11 » Does the car have pressure at the fuel rail, with the key turned on? If it does, then look elsewhere for the problem e.g. cam position sensor or crank position sensor (check if the wires are getting spark), or ignition parts.

Only 1 fuel pump on an 850R

Fuel pump is accessed through a port under the rear boards, pretty easy, no fuel tank moving required.

• Checking the relay: If the relay is good, does the fuel pump hum? When you turn the key part way, does the fuel pump hum? It should. If not, pump is bad.
• If the relay is bad
• …and see also: A paperclip as a Fuel Pump Relay bandaid?
• If the pump is bad: search the Repair Database for the DIY on fuel pump, not a bad job.

One last thing: if the pump is bad, then you will not hear it hum when you turn the key to position II (where the dash lights up, but the starter does not crank). Just turn the key and listen carefully. Better yet, kneel on the rear seat passenger side with your head leaned over toward the floor of the cargo bay, and have someone else click the key. If that pump comes on, guaranteed you will hear it hum. If you don’t, then it’s time to get a new fuel pump.

The Volvo pump is more expensive than the aftermarket ones. I went with the Volvo branded one. A lot of people go with Walbro brand they work fine but are noisier. You only need the insert. If you have the time, first remove and take apart the bad fuel pump, then you will understand exactly what you need and can get it.

1997 850R Fuel Pump Diagnose