I think I have lost power to my fuel pumps and need some thoughts: Driving down the road and engine just stops. Car been running without issue every couple of weeks. Car cranks and sometimes catches for a second and then nothing. I do not hear the “ticking” of the fuel pumps for either tank. I added gas to the air filter directly and it fired right up without issue…and then died when the fuel ran out. Fuel pumps are 2 years old, again no issues with them. Wires to the fuel pump are the original with the car with no fuse I can see.
I am unclear the wiring layout, role of the fuel selector switch, and/or if there is a “fuel relay” under the hood that may need to be rehabilitated/replaced. Is there an in-line fuse someplace that may be blown (Where would i find it?)
Hi Jim welcome to the forums.
My S11 had a fuse bank in front of the drivers side (RHD) knees I’m fairly sure theres a fuse for the fuel pumps in there, (I might be wrong, its been a few years since I had the car)
It switches power between ‘left’ (switch ‘in’) and ‘right’ (switch ‘out’) pumps (white/green and white/purple wires). Simultaneously switching fuel gauge ground (tank units) the same way. The gauge should read levels on selected tanks (light green/slate and light green/red wires). There are no relays or fuses - no engine management functions are fused.
Do you have internal or external pumps? With access to connections at the pumps; check for power - then jumpwire power to verify if the pumps are in running order.
However, late Series 1 may have a fuel safety relay, fitted to the Series 2 - which may have failed. First step is to check that power actually reaches the pumps as intended…
I would think my '73 S1 would have the same layout. Those pumps should be easily accessible once you have spare wheel out and if you have a multimeter then just do a check on the pumps when they should be energised (try dashboard switch both ways, the LH may be wired to RH). Its also an easy power supply check on the back of the changeover switch.
Just take care while working on electrics in trunk/boot, my mechanic once had a vapour explosion in there due to poor working practice. I’d normally say disconnect battery but obviously thats not great while you’re trying to diagnose a power supply issue.
Even though they are suspect being new parts, because it affects both it must be power delivery. Make yourself a test lamp 10…50w and see if you get power to the wire to the switch that selects which tank.
The Series 1 wiring is pretty straight forward. There is no safety fuel cutoff relay like the later cars. The power for the pumps is derived from fuse 1, goes to the selector switch on the panel, which sends power to either the right or left pump. Check that you are getting power to the Fuel Selector switch (White lead), and then out of the switch (White/Green for right pump -White Purple for let pump). The other leads are for the gauges. Ignore them.
If you are getting 12 volts out of the switch for both pumps. It is time to check the leads at the fuel pumps. Open the trunk, lift the carpeting and remove the wood cover over the pumps. If there is any fuel leaks or strong odors, Take the car outside and let it air out. If there are any leaks, now is the time to fix them.
Once it is safe, check the power at the pumps. If you are getting 12v at the pump and nothing is happening, check the grounds. Most common problems on the older cars is bad grounds due to corrosion.
If you are not getting voltage at the pump but you are getting voltage out of the switch, you will have to trace the wiring which runs under the door sill plates on the left side, if I remember correctly. Start at the panel and work your way back.
Good luck.
Very helpful, thanks for taking the time to write this. The issue was not the fuel pumps (as they clicked away when I added power to them…and the switch had voltage. When i took the fuel line off of the carb inlet “T” we had pressure 9and the pumps clicked away. Se we took off the carbs this weekend and they ar enow rebuilt. Will work on the reinstall and “balancing” soon. I would say, being in my 50’s the kids find it amazing that “I know how to do this stuff.” Actually “I know how willing I am to do this stuff and where to go to get some help.”