Fuel Pump Not Running

Hi All

I have just recently purchased a 1994 Xj40 for parts. The PO says it will not crank. They have installed a new fuel pump, crank sensor, rotor button, wires, plugs. After checking it over I have determined it is in too good of a condition to part out.

I have determined that it is not getting any gas to the fuel rail. Also, the Fuel pump is not running at all. I have checked all the relays and fuses and they are good. What could be causing the fuel pump to not run?

Have you checked the inertia switch (if there is one)

no…wasn’t aware that it had one. Where is it located

On a RHD car its in the drivers footwell below the bonnet release.

These seem to be incongruous statements - does the engine turn over, but not fire off? If this is the case the inertia switch is not the problem.

Good point on the inertial switch, doesn’t the heated o2 sensor have something to do with supplying power to the pump as well?

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Correct. The power sequence is:

Ignition switched power–>EMS main relay–>Oxy sensor heater relay–>Fuel pump relay

sorry bout that…the engine turns over but will not start

Cha Cha …

So you’re sure that the fuel pump is not running when you crank over the engine. How did you check that?

You said that you checked all the associated relays. Did you check for 12v on the load side of the fuel pump relay while you crank over the engine ? If you ARE getting 12v then it’s either a bad wire/connection going from the relay to the fuel pump or the fuel pump itself has failed.

The fuel pump relay on your '94 is the one in a black base near the right rear bulb failure module (BFM) in the trunk.

The first way I checked it was at the fuel pressure regulator before it gets to the rail. I loosened the nut while I had someone to try and crank the car. There was no fuel at the rail

The next thing I did was to have someone turn the ignition on while i listened in the boot for the pump running and did not hear anything running. I will not be able to check the voltage until Monday…weather is bad.

Cha Cha …

I believe that you only get a 3 second run of the pump (a prime) when you turn on the ignition. The fuel pump doesn’t start to run until you’re actually cranking over the engine. At least that’s the way it works on my '89.

Give the tank a bloody good smack with an axe handle. If all the electrics test out good and you determine the pump is not impulsing, the bang-on-the-tank method usually jars the pump motor enough to move it off the dead spot and it will spin up (temporarily)

I have checked the voltage to the harness wherein the Fuel pump relay is plugged in in the trunk. It is getting 12.5 volts to the relay plug. I swapped the relay out just to make sure. The pump is still not running.

I next checked the inertia switch and it is in the down position but I can’t say for sure that the switch is good.

Lastly,I checked for voltage to the wire that runs to the top of the evap flange which connects to the fuel pump and It has no power to the plug or the wiring at all. any ideas/help is greatly appreciated

Have you tried jumping #30 and #87 in the fuel pump relay base (key in run position) to force the pump to run?

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no yet I will try and report back

Check ground wires in trunk, no ground = pump not working

ok…I just checked the fuse box on the passenger side and the entire fuse box has no power. The fuse box on the driver side has power. Also there are two relay sockets out of the 7 under the hood on the firewall that has no power. The white relay (Petrol Injection Ignition) socket and the violet relay socket Automatic Transmission Power).

I will check the ground and report

I disconnected and reconnected all of the grounds I could find in the trunk and now the passenger side fuse box has power and all the fuses checked out good. I still do not have power to the violet and white relay plugs under the hood. Can someone tell me if they are supposed to have power and could this be the source of my no fuel pressure-pump not running issue

OK, let’s get back to some basics. Re: driver side / passenger side - let’s refer to ‘left’ or ‘right’ side because in some parts of the world the driver sits on the wrong side. :grin: Do you have the ‘lightning bolt’ warning on the instrument panel indicating a fault with one or more fuses? In any event fuse C1 (20 amp) in.the LEFT side fuse box feeds the ignition on relay (white base on firewall) which in turn feeds the oxy sensor relay which then feeds the fuel pump relay. So yes, with the key in the run position you should have voltage to these three relays. Or so I believe.