Quick question - would it matter if the fuel pump relay is also a diode relay like the main one?

I'm on about my third attempt to get my xj-sc up and running, determined life wont get in the way this time - it cranks on the key, but with no sign of firing up, so working through the Grant guide (very helpful, thank you). The fuel pump isn't running on turning the ignition, but the spade connectors on the battery positive look good, so I'm working from there through the guide. Before i start changing parts or going through the wires, i wanted to check if there's any problem in both relays having the diode (like the main one)?

Many thanks,

 

Never tried that way.

I have NO diode in both sockets, no issues 20 years now.

With a helper, have them turn ON the IGN, and you "feel" the pump relay and "feel" if it clicks when the Ign is ON. Remembering that the Main Relay powers up the Fuel Pump Relay.

Very few issues with relays in any of mine, just replaced with new as an age related thing.

That Orange wire earth via the ECU is 98% of the relay NOT clicking/pump not working.

OR


Volt meter on the +ve wire of the pump, fiddly but doable, and the helper again turning the key, see what reads out for 3 seconds.

 

Thanks, that's really useful.
So, I had another go at it today:

1. No relay click or fuel pump on ignition key.
2. Fuel pump works with a 12v supply from battery (thanks to the cherry blossom thread for the video), so the fuel pump works.

I didn't get a chance to ground the orange wire, but I did test the relay out of the car - no click when 86 and 85 are energised. I tried the same on the main relay and no click there either - after a 10 year layup, how likely is it both are bad, or I wonder if I'm testing them wrong?

Any how, need to order some relays - is it as simple as getting a Bosch 12v 30a relay with the pins in the right places, or does it need to be specific?

Thanks again

 

Standard CUBE relay, 5 pins with TWO #87 terminals, NO "a" or "b" for the centre terminal.

When inserting onto the sockets take a peek at the wires, and ensure they do NOT push out of the sockets as you insert the relay, RAERE, but it does happen, and the beer intake to sort it is HUGE.

#85 and #86 should get activity.

Probe the #85 (now thats memory haha) with Ign ON, and there should be 12V. If not, probe #86 just in case I screwed up, one of them, MAIN RELAY, will have 12V, or should, with Ign ON.
The pump relay will remain DEAD if the Main does not do its task.

 

Thanks for the flag on 87/87 not 87a - quite hard to find a 5 pin which isn't a change over relay and not sure I'd have realised.

Relays now ordered - will report back when they arrive later in the week.

Thanks,

 

Fuel at the rail! (small wins, but they keep you going!)

In case its useful to anyone in future, the fuel pump wasn't running on the ignition, but worked when connected to a battery. Turned out that both the main relay and the fuel pump relay were dead (when tested out of the car). For anyone (like me) who is not so used to older cars, the fuel pump is really obvious when it runs for a few seconds on ignition, and I found it hard to find a 5 pin relay with 2x 87 (most were changeover relays), but Grant had highlighted the difference.

So, onto the next challenge - I don't think the injectors are clicking on turning the throttle, so I'll carry on following the guide - a couple of questions if you dont mind:

- to clean the EFI plug, contact cleaner and a toothbrush on the wiring loom plug and the socket on the box?

- probing an injector wire, just take the plug off an injector and black probe to earth, red probe on each pin in the plug one at a time should show 12v?

- TPS - looking to measure voltage between the red and yellow wires while it's plugged in and the ignition is on?

Sorry, for the simple questions, just dont want to break anything!

Thanks, much appreciated.

 

Well sorted,

You need to move down here, "a" and "b" relays are hard to find, Twin 87 everywhere.

The rest will keep you warm in the cold you currently have.