Early Griff third fuel pump relay

[Russell Mc]

Can someone help me shed some light on this please. In my cars handbook in the fuses section there is a relay for the fuel pump. I thought this could of been at fault causing my recent starting problems. I went to a well known TVR specialist in Sussex to try and get one of these. I was pretty much told straight up there is no fuel pump relay on the fuse board and there is only the two on the loose bit of loom in the footwell. Despite my explaining about my handbook and the fact that removing the relay while the car is running cuts the fuel pump the "expert" just wouldn't have it.
is this relay something thats just fitted to the early pre-cats?

[davep]

The 'TVR' expert is no expert, there is a fuel pump relay at position 8 on pre-cat Griffiths that have the original fuse/relay panel fitted. Both relays (R8 on the panel and the floating Bosch) are required for the fuel pump to function. The R8 relay is switched by the ECU. The R8 relay is not used for the fuel pump circuit on 500s.

Following the circuit through, the R8 relay sits between the metal-cased Bosch Fuel Pump relay O/P feed and the Inertia Switch. The relay is where the ECU controls the timing of the fuel pump priming function and acts as a fuel cut-off control in addition to the Inertia Switch so is an important safety feature. To fault-find the fuel pump feed circuit on a pre-cat both relays need to be checked.

Edited by davep on Friday 2nd December 20:10

[Russell Mc]

Thanks for clearing that up. Don't think I'll be going back there again

[kabaman]

For anyone referring to this thread for info. As part of the postings here: http://www.pistonheads.com/gassing/topic.asp?t=131...

I've just discovered that although my Griff 4.0 has a relay for fuel pump in the fuse/relay panel. Removing the relay had no effect. When I later removed the fuse/relay panel the fuel pump wire had been cut and soldered to bypass the relay - presumably from the factory although I can't be sure.

Neil

[davep]

If anyone wants to fault find the pre-cat 2nd fuel pump relay circuit the following might prove useful (it's my attempt at following the circuit through so there may be errors):

Relay R8 – Fuel Pump Control

Pin out Connections (refer to Bible Circuit Diagram and Fuse panel block annotations)
Cable colours in brackets.

Relay Pin 39
+12 V circuit to energise coil with ignition switched On:
Ignition switch – Block D 58ar (WR) – Block C 56ak (W) – Block H 50w – relay 39

Relay Pin 37
Ground circuit for coil:
CDL3 and RISTS12 (BW) – Block F 50z (BW) – relay 37

Relay Pin 38
+12 V feed control from ECU to relay contact:
ECU – Block J 58 (Y) – Fuse 14 - Block I 58D (Y) – Block E RS (Y) – relay 38

Relay Pin 36
With relay energised and contact made supply +12 V to Inertia Switch, and if closed circuit to Fuel Pump:
Fuel pump – Inertia switch (Y) - Block F RL (YB) – relay 36

Relay Pin 59
Not used.