Thread: fuel/gas problem

Have a 86 classic 3.5 efi on gas . Gas system is only 6 months old ive been told that the fuel pump relay when cranking the car over is not triggering the system to work like thers no power

any help thanks steve

I've just rewired mine, and whoever did the original job, well, was all over the place. Without pics, I can't comment on how your's is wired, but I can tell you how they wired my RR. It's a simple venturi system - no ECU.

On the fuel pump relay ( the one under the drivers seat) , they spliced a feed (fused) to the LPG switch, and then cut the coil signal feed to the EFI at the relay ( in a 4CU system - flapper - the relay under the MAF) and added a delayed cut off relay controlled by the LPG switch. ( A normally closed relay, and when you change over, the relay 'delays' for a couple of seconds before it turns the EFI off - it is wired with the solenoids) Then, all the cut off solenoids were wired together driven through the LPG switch. Then, because the wiring sometimes didn't supply sufficient power, they added a 2nd switch to boost the solenoids in case one of them stuck.

I was able to figure out the wiring colour code a little on my 'Landi' brand switch, it appears that other switches go by similar methods:

Red - power from fuse
Black - ground
Yellow- supply for a petrol cutoff solenoid ( not used by me yet )
Blue- gas supply solenoids
Brown - coil negative ( tells the switch that the engine is running)
White- Joined with green (weird??)
Green- LPG fuel gauge

This should at least point you in the right direction to diagnose what isn't working.