Fiesta fuel pump - Zetec 1.25 2000

I assume that you have actually checked the fuel pressure? and found it is zero? the schrader valve on the fuel rail on the engine is the test point, mind the spray if you press in the valve. I use an old tyre pressure gauge to check.

you can check it is lack of fuel by spraying some carb cleaner into the air intake while trying to start it, if it splutters and tries to run then you are probably on the right track.

the relay is: under the bonnet, the fuse/relay box has about 9 relays at one end, a big bunch of fuses to the right of them and 4 relays in a square at the end of the fuses, the fp relay is the one closest to the end of the fuse box and nearest to the fuses.

you could just stick a pin in the wires under the seat to check for power, that way you don't have to solder in any joins.

I assume that you have actually checked the fuel pressure? and found it is zero? the schrader valve on the fuel rail on the engine is the test point, mind the spray if you press in the valve. I use an old tyre pressure gauge to check.

you can check it is lack of fuel by spraying some carb cleaner into the air intake while trying to start it, if it splutters and tries to run then you are probably on the right track.

the relay is: under the bonnet, the fuse/relay box has about 9 relays at one end, a big bunch of fuses to the right of them and 4 relays in a square at the end of the fuses, the fp relay is the one closest to the end of the fuse box and nearest to the fuses.

you could just stick a pin in the wires under the seat to check for power, that way you don't have to solder in any joins.

All sound advice. If you follow it you won't go far wrong.

Thanks to both.

I did not bother before as the fuel pump is always audible when ignition is turned on and was not. But I have now confirmed there's none.

Yes thanks - did that (with an aerosol of EasyStart which I think is

1980 vintage) and got a few firings before I noticed the lack of sound from the pump.

OK thanks. I am still not sure I've foudn the right one but I swapped them all around with no effect. And I am left wondering why the Haynes circuit diagrammes refer to relay a, relay c etc but then give no map as to which relay is which in an auxiliary fuse box which so far as I can see labels the fuses but not the relays?

I get a voltage when the ignition is turned on and when the engine is cranked. (Only around 10v but I think that's probably down to the other current being drawn on switch on or when cranking.) So I think the cure does require the tank dropped.

Thanks again.

[...]

You should get very near to battery voltage with the ignition on and not cranking. What does your meter read across the battery terminals?

Chris

After the cranking the battery was down to 12.4V. (I checked as I thought it might need recharging; it'll be on charge tomorrow.)

I was not surprised to see less than battery voltage across the pump given that power is supplied to the pump for only a second or so when the ignition is turned on, and that is a time when power is also being used for other stuff. I was also using an ancient Avo8 so there was not an instantaneous response from the meter! (My cheap digital multimeters' response times are probably worse and they don't offer peak readings.) On reflection though I realised I failed to verify I was using a good earth. I'll check that tomorrow.

I'd be suspicious of anything less than about 10% of battery voltage; other consumers live at the time the pump runs are not high current ones, so shouldn't cause the battery voltage to drop much.

You really need someone else turning the key for you.

Problems with fuel delivery are fairly common with Fords of the age. First suspect is the relay; most mechanics have a link to bridge the contact part of the relay socket for fault-finding. That way, you can prove or eliminate both the relay contacts, and the feed to the relay coil.

If the pump still fails to run, it's likely to be the pump itself. Replacement requires the tank to be dropped.

Chris

I would run power/earth direct to the pump, avoiding using the vehicle wiring as far as possible, before deciding the pump was dead.

I assume that you have actually checked the fuel pressure? and found it is zero? the schrader valve on the fuel rail on the engine is the test point, mind the spray if you press in the valve. I use an old tyre pressure gauge to check.

What should the pressure be out of interest ? also if it was low could you you use something like a bicycle pump to increase the pressure to see if it holds? .. what usually causes low or no pressure ?

The fuel pressure will drop as soon as the pump stops, but it should retain some pressure for a time. The only relevant pressure is that when it is runs. At idle the pressure should be about 40 psi (varies by car) if the throttle is opened there will usually be a temporary rise in pressure of a few psi. Pumping air in at the test point would not help in any way that I can think of.

The fuel pressure will drop as soon as the pump stops, but it should retain some pressure for a time. The only relevant pressure is that when it is runs. At idle the pressure should be about 40 psi (varies by car) if the throttle is opened there will usually be a temporary rise in pressure of a few psi. Pumping air in at the test point would not help in any way that I can think of.

I see, thanks for the explanation Mr C.