3S-F Camry fuel pump operation.


Asked by May 07, 2009 at 10:39 PM about the 1990 Toyota Camry

Question type: Maintenance & Repair

This is a slightly complex query. From Melbourne, Australia.
Does the fuel pump run all the time the ignition is on or is it controlled by something in the injector setup?
I've changed the head gasket etc. and I want to check the pump and piping before putting the whole lot back completely. All plugs and sockets connected. But no fuel being pumped up with ignition on.
I know that the operating current goes through a relay or two at least.
Perhaps they connect only when the engine is running?
Or perhaps fuel has to be in the feed line first - it's 'dried' out.
Can anyone help please?
(I have the Haynes manual.)

4 Answers


Most systems use a relay to prime the system usually for only two to three seconds then it waits for a high enough RPM signal to continually run the pump.If the fuel lines are empty you may have to cycle the key on and off four or five times before the fuel gets to the fuel rail.This should be able to be heard over you shoulder .. a buzz for a few seconds and then shut of ... If you do not hear the buzz you have a problem electrical or pump

1 of 1 people found this helpful.

That's a great help Michael. Makes a lot of sense. I have a hearing problem so I'll get a 'helper' to listen out. I go 'way back to the 50's Morris Minors and the tick, tick of the SU pump. So nothing really chamges - but it does !? Just gets more refined. Thanks again.


A few days later.. Unfortunately Toyota seem to not use that 'priming' technique. I got no results so went further searching on-line. I finally got the circuit diagram; the feed is tied to the starter solenoid supply via the ECU. The pump operates when the starter is used then held in by a transistor relay to keep running. So I'll disconnect the starter Battery positive and try again, turning the ignition all the way.

1 of 1 people found this helpful.

At the risk of becoming tedious but to wind up the subject. There is a 'service' connection block in the engine compartment near or on the firewall in front of the passenger position. It gives the facility of starting and running the fuel pump for testing or full 'priming' with the use of a 'jumper lead' between socket contacts. It was in my Hayes manual all the time - in the fuel section not the electrical where I had already looked.

1 of 1 people found this helpful.

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