Low voltage at fuel pump?

[KeithL]

For the first time ever our Traveller refused to start today. It was turning well on the starter and there was a strong spark at each plug. However the fuel pump didn't seem to be pumping as there was no clicking. It is a relatively new electronic SU pump which has given no problems up until now so I checked the voltage between the cap and the earth and it was only 11.9V. The battery was a healthy 12.4V.

Is such a low voltage to be expected and should the pump work at this voltage? If not would it suggest the regulator is faulty as I assume the power to the pump comes via the regulator?

I'm not a motor technician but since I need to get the car started before it goes anywhere (i.e. a garage) I am going to have to sort this myself. What tests should I now be carrying out to try and isolate this problem? The regulator is a Lucas RB106/2. As a start I will tomorrow disconnect the fuel pipe to the carburettor to see if it is in fact pumping anything.

Thank you in advance for any help.

[StillGotMy1stCar]

The voltage at the pump isn’t that low, you get voltage drop though connections the ignition switch and the wire itself, also the circuit is partly shared with the ignition coil that if isn't electronic ignition will draw current through the points that will most likely be closed.
If you can’t hear the pump ticking there is a good chance it has failed and may be drawing current causing an additional voltage drop. No need to touch the voltage regulator.
So your next step is correct to remove the pipe at the carb and see if it is pumping preferably into a suitable container.
Good luck and take care.
Regards John

[Nickol]

The fuel pump has a set of contacts which switch themselves off and on as it pumps. That is the clicking sound you normally hear. Sometimes the points stick. Give the pump a good hit ( do not overdo it) with a spanner or small hammer whilst it is switched on.

[ManyMinors]

I also had an electronic SU pump fail inside 12months and reverted to the traditional contact type after that........

[KeithL]

Thanks everyone.

I checked with Burlen and the pump should work between 9.5V and 13.5V so the voltage isn't an issue.

I have disconnected the fuel pipe from the carb and the pump is pumping as expected. I didn't measure flow rate but I very quickly filled a 1/4 of a large coffee jar with petrol.

Just for fun I tried jump starting the car in case it was the battery. That made no difference either.

Under normal operation the carburettor obviously tells the fuel pump to stop pumping at some stage so has that mechanism stuck / broken / failed in my carburettor?

[Nickol]

If the pump is working as you say when disconnected from the float chamber but otherwise not then suspect the float needle in the float chamber and that the float itself is working properly. The needle (valve) may be clogged with dirt or broken .....

[KeithL]

I took the top off the float chamber and gave everything a good clean. It is the newer type with the plastic float which presses directly onto an aluminium plunger with a rubber seal on the end. I gave Burlen a call and their technical department said that if the car has been sat unused for a while, like ours has, then lacquer can build up on the rubber seal and make it sticky. As instructed I gave it a good clean with petrol and it seemed to move much easier. Once everything was put back together the car fired up. Result.

Thanks Nickol.

[ManyMinors]

That's a good result. You hadn't mentioned that your car had been standing unused.

[KeithL]

That's a good result. You hadn't mentioned that your car had been standing unused.

It's only been 2-3 months since it was last driven but it hasn't been driven must since October so I guess that was enough to cause this problem.

[myoldjalopy]

Nice easy fix - we like them!