Loss of power to the fuel pump

[kingqa69]

HELP, i just drove my V8s down the lane to let everything settle, pulled back into my driveway & the engine cut out. And would not restart, it would fire up but not run. Checked power supply to fuel pump & nothing. No sound from pump, obviously.

Have replaced all relays with a new one & checked all fuses. No problems.

I do not want to miss out on all this weekends TVR S activities!!

I have ordered a new Ignition module and Inertia switch should be here tomorrow.

Any advice, recommendations please

[magpies]

if you can - remove the relay and bench test it. Mine was failing because it was getting hot

[GreenV8S]

There are several possible points of failure in the pump power supply, and I had just about all of them in quick succession a few years ago. I guess that once the wiring harness reaches a certain age it can suffer from continuity and contact issues everywhere. In my case the problems were intermittent and needed some detective work to track down, so I made up a small loom that connected between the relay socket and the relay with telltale lamps showing which circuits were active.

It may be different on the V6 but on the V8 the circuit is in two parts:

A fused supply to relay coil +ve which is earthed via the ECU.
A fused supply to relay common terminal which has one output earthed via the inertia cut-off and then the pump, and another output earthed via the lambda sensor heaters.

I think my problems started with a relay that was wearing out and started getting resistance across the contacts that lead to overheating, that made the contacts fail quicker and also damaged the relay holder terminals so that the replacement relay had a poor connection to the loom. I also had corrosion in the inertia cut-off, a loose connection at the pump and brittle wiring at the pump. In the end I ended up virtually rewiring the whole circuit before it worked properly.

While I was diagnosing and fixing it I found it very helpful to keep a length of wire with a croc clip at one end and the right size spade terminal at the other so I could easily hot wire the pump if it started playing up.

Edit: speling

Edited by GreenV8S on Wednesday 27th April 23:35

[kingqa69]

thanks greenv8s, all sounds about right, will be going through the same trials & tribulations tomorrow. There never is a quick fix with old electrical wiring.

Thanks for your response