Hi
i have some problems regarding power to the fuel pumps. Both are new, bot has power when cranking, noen has power when i release the starter. If i hook up positive from the battery, the CAR starts . IT is SU carburated and has two pumps in the tanks.

anybody?

 

OK, from the memory, so watch out.

The carby cars had a "reverse polarity" oil switch, aft of the oil filter housing, I THINK is the location, OR the one UNDER the power steer pump bracket up the front.

Anyway, it earths the fuel pump relay when oil pressure of 8psi or greater is sensed.

Basically:

NO oil pressure, NO earth, NO fuel pump operation.

THEY FAIL, Lucas strikes again.

I simply fitted the wire under a local earth screw and moved on.

 

Tks for your prompt reply. Regarding the cable, i guess it is the black cable to the starter relay?

 

Dont remember the colour.

Moved from the switch to earth.

The fuel pump relay is on the bulkhead, near where the strut bars bolt up.

I will try and remember to dig out a wiring drawing tomorrow, and come back with the wire colour.

The one on the starter relay is the "by-pass" for pump operation during cranking, and that appears to be working just fine by what you said earlier, so dont mess with that one just yet.

 

If you could provide me with the scematick colour from the diode pack and fuelpump relay IT would hjelp me a lot.

 

Now I am confused.

Not aware of a diode pack on a S2 6cyl car with carbies.

Is yours a S2, or S3 3.4ltr?

1978, if that is the build date, would be a S3 from memory.

 

IT is a 1978 xj 6 carb 4.2

 

OK.

In all my 50+ years with Jaguar, the S2 wiring diagrams i have would be the worst, by a country mile, I have ever dealt with.

However,

6 hours later, and waaaay too much COFFEE.

The Ignition relay has a W (White) wire from terminal C2 that supplies the fuel switch in the dash.

That same relay has a GY (Green/Yellow) wire from terminal W1 that goes to the oil switch, and thus to earth as previously mentioned.

The Fuel Changeover Switch has the following:

WP (White/Purple) to one fuel pump
WG (White/Green) to the other fuel pump.
Which colour is which pump NO IDEA
LGR (Light Green/Red) to one tank unit.
LGS (Light Green/Slate) to the other tank unit.
Which colour goes to which unit, NO IDEA.
LGO (Light Green/Orange) to the dash gauge.

Based on that, the GY wire will on the RH side of the engine soewhere near the oil filter housing. That is the wire to earth, thus by-passing the oil switch mention before.

Good luck, beer and pizza is on their way, gotta luv the kids sometimes.

 

I have just gone through the same scenario on my 1977 xj6 c with downdraft webers. I have in tank fuel pumps. The car had been sitting for 18 years; took some doing to clean everything up, including the fuel system. But Howdy I know it now!



1. make sure your pumps work, test with 12V.

2. test the switch-over-switch. Continuity will do.

3. know Doug's relay info.



So what is really going on is the pumps don't get voltage until the engine, from cranking, generates enough oil pressure to enable the engine start relay ( Doug again). Use a jumper wire and skip this thing. The car thinks it should start because it has fuel left in the carb bowl from last time; except if you have let it set, it may not. You jumper out the oil pressure sensor by connecting it to ground with the key on for some seconds, then unconnected. The car will then start, provide pressure and turn on the pumps. Provided you are wired right on the starter relay. (Doug)



Hope something here helps you or someone else.



Geneo

1977 XJ6C & webers

 

I think you're intending to say "Grant" rather than "Doug"

I'm of no help on the Series II fuel pump circuits and such. Never worked on one or even sat in one!

If Grant replies to a post it's a rare, rare event that I can add anything of value

Cheers
DD

 

yes you are right, my apologies Grant it is.
geneo