Fuel pump relay
Discussion
Having problems getting the fuel pump to pressurise. Normally when I turn on the ignition the fuel pump can be heard to whirr into action - not now! I've powered up the pump , having first disconnected the terminals, from a remote battery and the pump buzzes into action so I've ruled out a defective pump.
I've checked the fuzes and they are all in tact. Just checked the fuel inertia switch behind the glove compartment and am not getting power to the device. I'm told this is between the fuel pump relay and the fuel pump therefore this would intimate a defective relay. (am I correct so far?). Problem is which of the relays is the fuel pump relay?
There are several relays - a bank of relays above the fuses, a couple tucked into the left hand side of the battery compartmenmt which are at the end of a wiring loom ajacent another couple of fuses, and 4 relays behind the dash which were only found when I took out the glove compartment...... help please..... any advice would be most welcome.
Regards
John
I've checked the fuzes and they are all in tact. Just checked the fuel inertia switch behind the glove compartment and am not getting power to the device. I'm told this is between the fuel pump relay and the fuel pump therefore this would intimate a defective relay. (am I correct so far?). Problem is which of the relays is the fuel pump relay?
There are several relays - a bank of relays above the fuses, a couple tucked into the left hand side of the battery compartmenmt which are at the end of a wiring loom ajacent another couple of fuses, and 4 relays behind the dash which were only found when I took out the glove compartment...... help please..... any advice would be most welcome.
Regards
John
There are two metal-cased Bosch relays on flying leads, on the loom to the ECU. One of these is the ECU main power relay, the other powers the fuel pump and lambda sensor heaters (where applicable).
On the fuel pump relay, terminal 30 is the fused power to the relay and terminal 87 is the switched feed out via the inertia cut-off switch to the pump. So you can pull the relay out, and with the ignition on you should find 12v coming in on terminal 30, connect a fused link wire between 30 and 87, and you should hear the pump. If there's no 12V you are looking for a fuse or wiring fault on the supply side. If 12V is there but no pump you can do a continuity test between the relay socket and the inertia cut-off, and between the cutoff and the pump, and see where the output is getting lost. It's quite common for the relay to fail intermittently (so it might be duff, but work for a while after you take it out and shake it around), and also for a failing relay to make the relay socket terminals overheat and relax so you get a poor connection.
On the fuel pump relay, terminal 30 is the fused power to the relay and terminal 87 is the switched feed out via the inertia cut-off switch to the pump. So you can pull the relay out, and with the ignition on you should find 12v coming in on terminal 30, connect a fused link wire between 30 and 87, and you should hear the pump. If there's no 12V you are looking for a fuse or wiring fault on the supply side. If 12V is there but no pump you can do a continuity test between the relay socket and the inertia cut-off, and between the cutoff and the pump, and see where the output is getting lost. It's quite common for the relay to fail intermittently (so it might be duff, but work for a while after you take it out and shake it around), and also for a failing relay to make the relay socket terminals overheat and relax so you get a poor connection.
Hi
Checked all the fuses - all in tact. Established which is the fuel pump relay The one with a variety of white and white/orange wires (as oppoosed to the ECU relay which hsa a number of thicker, mainly brown wires)and checked the voltage from terminal 30 absolutly no power from this. What next? any suggestions?
Regards John
Checked all the fuses - all in tact. Established which is the fuel pump relay The one with a variety of white and white/orange wires (as oppoosed to the ECU relay which hsa a number of thicker, mainly brown wires)and checked the voltage from terminal 30 absolutly no power from this. What next? any suggestions?
Regards John
GreenV8S said:
There are two metal-cased Bosch relays on flying leads, on the loom to the ECU. One of these is the ECU main power relay, the other powers the fuel pump and lambda sensor heaters (where applicable).
On the fuel pump relay, terminal 30 is the fused power to the relay and terminal 87 is the switched feed out via the inertia cut-off switch to the pump. So you can pull the relay out, and with the ignition on you should find 12v coming in on terminal 30, connect a fused link wire between 30 and 87, and you should hear the pump. If there's no 12V you are looking for a fuse or wiring fault on the supply side. If 12V is there but no pump you can do a continuity test between the relay socket and the inertia cut-off, and between the cutoff and the pump, and see where the output is getting lost. It's quite common for the relay to fail intermittently (so it might be duff, but work for a while after you take it out and shake it around), and also for a failing relay to make the relay socket terminals overheat and relax so you get a poor connection.
I don't know if this applies to the 500 but on the pre-cats I believe there is a second Fuel Pump relay at position R8 on the Fuse/Relay Board. Following the circuit through, this relay sits between the metal-cased Bosch Fuel Pump relay O/P feed and the Inertia Switch. The second Fuel Pump relay is where the ECU controls the timing of the fuel rail priming function and acts as a fuel cut-off control in addition to the Inertia Switch so is an important safety feature. To fault-find the fuel pump feed circuit both relays need to be checked. The other metal-cased Bosch relay provides the feed to the injectors and AFM.On the fuel pump relay, terminal 30 is the fused power to the relay and terminal 87 is the switched feed out via the inertia cut-off switch to the pump. So you can pull the relay out, and with the ignition on you should find 12v coming in on terminal 30, connect a fused link wire between 30 and 87, and you should hear the pump. If there's no 12V you are looking for a fuse or wiring fault on the supply side. If 12V is there but no pump you can do a continuity test between the relay socket and the inertia cut-off, and between the cutoff and the pump, and see where the output is getting lost. It's quite common for the relay to fail intermittently (so it might be duff, but work for a while after you take it out and shake it around), and also for a failing relay to make the relay socket terminals overheat and relax so you get a poor connection.
Had this on my 500 recently.
Swapped relays and the problem still there.
Eventually killed the battery by disconnecting and unplugged ECU.
When reconnected no prob. I have been told that ECUs can freeze and need a hard reset as sometimes PCs do.
Maybe talking out of my dump chute but it worked for me!
Swapped relays and the problem still there.
Eventually killed the battery by disconnecting and unplugged ECU.
When reconnected no prob. I have been told that ECUs can freeze and need a hard reset as sometimes PCs do.
Maybe talking out of my dump chute but it worked for me!
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