Fuel pump power supply problem.

[Jake.]

Trying to get a 2001 Renault Clio started but the fuel pump won't run.
When I turn the ignition on I can measure 12v for a second or so at the fuel pump plug. But the pump doesn't prime or do anything. I believe it should run the pump for a second or so to pressurise the the fuel rail, and then run the fuel pump full time once the ecu detects RPMs.

If I bridge the fuel pump relay I can measure a constant 12v at the fuel pump plug - but the fuel pump still doesn't do anything.
I've bought another fuel pump and fuel pump hanger assembly but still the same problem.

With one wire going from the positive side of the fuel pump plug to the pump and one test wire from the Neg battery terminal to the pump; the pump doesn't run.
But the other way around; a wire from the negative side of the fuel pump plug and a wire from the Positive battery terminal = the pump runs.


So, does this mean that, even though there is 12.5v at the fuel pump plug, the positive wire has a bad connection or a break somewhere?

From my research on the internet I understand that the Fuel Pump Relay switches to connect and disconnect the negative side of the circuit. So if I run a new positive wire to the fuel pump should I be OK to run it directly from the battery, or is it more complicated than that?

Thank you !

 

[PEG]

Hi dude,what are you measuring your voltage with? Have you tried connecting something that draws a bit of current (55 W headlamp for example)?

I would not recommend bypassing the original circuit,without knowing what is wrong. You may introduce other issues,and divert around safety functions,such as inertial cut-offs,which kill fuel pumps,at impact,to prevent Hindenburg type incidents...

As you seem to be able to follow a wiring diagram,better to trace upstream from your pump,from crusty french multi-plug to crusty fr...you get the picture...:cool3:

 

[Marauder]

As Peg says, it sounds like you're not load testing the supply voltage. If there is 12 volts there but it disappears under load, as it seems yours is, on that year range Clio, it's usually corroded fuel pump relay connections in the triangular under bonnet fuse box.

 

[ruston]

I know it is an old thread , but the fuel pump will only run for a few seconds to prime with the ignition on then then power is removed ,then it will only run under cranking .When the engine stars the fuel system is controlled by the ECU.
This is briefly how the Bosch system operates , Renault will probably be the same.

 

[telectrix]

could well be the ECU stopping it. a diagnostic is recommended to see if any fault codes come up.even a faulty sensor on the exhaust/camshaft/whatever can cause the ECU to shut down the fuel pump.

 

[ruston]

Yes, if the fuel pump doesn't run under cranking or initial ignition on , the fuel pump relay is favourite.
It's a two man job though to get wherever it is to listen, or feel for it running.

 

[Marauder]

Only realised how old the original question was after I replied DOH!
But you're right, if the ecu isn't seeing an RPM signal, it won't bother running activating the fuel pump relay. Some basic checks need to be done before condemning the pump. I've changed a few crank sensors after another garage has changed fuel pumps, relays etc and then given up.