Fuel pump Live

[JonJon]

Hi All,
I've been striping my Elan ready to do an inventory before the rebuild can start. I think its safe to say the fuel pump is one item that is going on the list. My question is, what would cause the pumps power supply to be permanently live when keying the ignition on?
I'm hoping the ECM isn't at fault, if it is, does anyone sells replacements or am I looking at a re-map?
Cheers Jon.

[Brit-Car-Nut]

Where are you measuring the power to be on all the time? At the relay? Are you sure you are testing the "switched" connector instead of the ignition power feed?

I bought a cheap NEW pump for a Buick Riviera off eBay for less than $20.00 since my car is still sitting waiting for a lottery win so I can have it painted after all the body repairs. So far, it has worked well every time I start it to make sure the injectors flush and don't get gummed up from sitting. I also have the same pump in my suburban and I drive it every day and after almost 2 years, it is still working fine.

In the US there are a lot of sources for pumps since that same pump was used in a lot of GM cars in the 1990s. Rock Auto has low cost pumps listed under the GM car listings.

[epipete]

Failing that option, then Merlin can supply as per: https://www.merlinmotorsport.co.uk/s/fu ... lotus/elan

[JonJon]

Unread postby Brit-Car-Nut » Sun 20.10.2013, 20:54

Where are you measuring the power to be on all the time? At the relay? Are you sure you are testing the "switched" connector instead of the ignition power feed?

I'm testing the wire at the tank plug (3 wire)
GB 7/8 volts
WG 0 volts
B
I'm told the GB wire is for the sender, should that not be full time live?

[Brit-Car-Nut]

Funny, I ordered a replacement Voltage regulator from Lotus and they sent a 5V chip but looking at the instrument wiring diagram, it says it is a 10V regulator that is wired like a variable regulator?

The unplugged GB wire should read 10V? which it gets from the ignition, through the voltage regulator (behind the facia) through the fuel gauge to the sender which provides a varying ground (earth) to make the gauge read. If you ground the GB wire (short it to the B(lack) wire in the plug) and the fuel gauge should read Full. If you leave it plugged in, the voltage will vary based on where the float is since it is also providing a ground for the gauge.

On my car, the variable resistor and ground connection inside the actual sender were gummed up, so I cleaned the gum with carb cleaner and verified the float arm had a good connection to the structure which is what gets grounded.

Basically, you are at the far end of the circuit if you are looking at the fuel pump and tank unit. See Sheet 24 in the Electrical Manual for the fuel gauge wiring and sheet 5 for the fuel pump.

[Simon_P]

2 things.

1. There is a fuel cut-off trip switch
2. The ECU cuts the power to the pump after 2 seconds of inactivity
edit- that is 2 seconds of sensing the engine not running.

[Brit-Car-Nut]

fuel cut-off trip switch = inertia switch. Best to use the same names, words and descriptions that are in the Lotus Manuals. Gotta start conventions somewhere...

[Simon_P]

fuel cut-off trip switch = inertia switch. Best to use the same names, words and descriptions that are in the Lotus Manuals. Gotta start conventions somewhere...

Yes! that is the one - Didn't have the manual to hand

[JonJon]

Sorted
It was the immobilizer as I suspected!

Dead Alarm System.JPG

[HJ2]