My XJ6 - series II 1978 suddenly stops. Problem is a fuel delivery. A fuel pump (left and right) does not run anymore - no electric power in a wire. I already change switch inside the cabin - same problem. I check relay - also good. Is fuse for fuel pump somewhere ?What now? Please advice.

 

Is this a fuel injected or carbureted engine? 4.2 or 3.4 ?

Cheers
DD

 

78 Would be carburetor with a small electric fuel pump in each tank. Selector switch provides voltage to the selected tank's pump.

I think the early cars also had a safety inertia switch on the front door jam area. perhaps the car was bumped and the inertia switch triggered. Simply press the top to reset it.

If thats not it... check for voltage in at the switch. Since its ignition switched the wire will be white, then check for voltage at the pump..

To solve this... get a simple test light. https://www.amazon.com/Professional-.../dp/B003UHNMMS

 

USA market (and perhaps others?) Series II XJ6s got fuel injection in 1978....like this one:

https://classiccars.com/listings/vie...lifornia-92101

It's the same system used in the Series III cars.

Cheers
DD

 

sorry , it's 4.2 (English market RHD) , with carburetor and small electric fuel pump in each tank. Today I will check this safety inertia switch...

 

Also I *think* there might a tie-in between the oil pressure switch and the fuel pump circuit. That is, if the pressure drops low enough to turn on the oil warning light, the pumps wont work.

Cheers
DD

 

Doug is right.

There are 2 smaller oil switches, one is the light, the other works in reverse, and is the earth control for the fuel pump relay.

By reverse I mean, NO oil pressure at that switch = NO earth for that relay, so NO fuel pump. Then add the fact that the switch is a LUCAS product, and reliablity just went AWOL. Memory has that switch at 4psi. It is usually, not always, screwed direct into the oil gallery, either just forward of the oil filter block, or just aft.

Mine had that switch wire firmly attached under a close by PK screw.

The larger oil switch, usually on top of the oil filter alloy block, is the gauge sender, and has nothing to do with fuel pump operation.

 

Yes, relying on a trouble prone OP idiot light sensor for anything is risky.


Guage definitely, light ,????


Carl

 

Hi, car is running now. I checked all connectors + WD40 and now is OK...i made 300km without stop - new record

 

I have a similar issue to what you had, what did you find out was the problem with the circuit? And where is the inertia cut off switch located, thanks.

 

I just messed with my inertia switch last night. It is a white cylindrical looking thing on the passenger front door jam, just inside of the cabin near the bottom of the dash. It is pressed onto a clip with 2 wires coming in the bottom of it.

 

I'll check it later today to see if there's current flowing through it

 

Do you think there could be some other problem with the system? the fuel switch on the dash does work considering the fuel gauge changes when the switch is changed but voltage not supplied to the pumps themselves puzzles me. the pumps are the submersible ones located in the rear wheel wells, thanks.

 

As we deal with left hand drive cars as well as right hand drive cars, I refer to locations as left and right, and try to avoid driver and passenger.. Our "common language is confusing enough.

Decades ago, I was driving my real nice 88 Tbird on a freeway. Wham,. a truck made a dumb lane change and whacked the left rear of my car!! The engine quit!! I coasted to the shoulder. Luckily, there was a shoulder. The offending driver pulled in ahead of me. Decent guy. Admitted error. apologized and interested in my well being. We agreed to call the CHP's. 911 operator very helpful. As was the responding cop!

After the interview, we looked in to firing up the bird. I looked in the manual and it identified the location of the inertia switch. In that car, in the trunk, behind a trim piece. We found it . Reset it and I cranked it up!!! Cop pleased. he told me he ahd a Mustang of the same vintage. Both cars built on the Fox plat form. He commented. "I'm putting my manual in my car as soon as I go home!!!

Brings back another old business adage, "look in the book".

Carl,

 

According to my wiring diagram, the switch has separate contacts/wires for switching power of the gauges/sender and the pump power. So in theory the contact of the switch could be changing the senders but not changing power to the pumps. This is based on a 1977 Service Manual Diagram.

 

So I checked the inertia switch and it's fine, I see two relays though I figured one is the starter relay, can't figure the second, I need help figuring out which wires to check for the relay(s), thanks.

 

 

Sorry to bring up an old thread.

Grant, do you happen to have a wiring diagram/ photo showing the connections to the fuel cut off relay? Only issue is, mine has the later plastic Lucas diode relay...

Reason being, the car has just 40,000 miles and I want to keep it original. Also, cant work out what is what from the Haynes manual diagram. (Old age I guess).

 

No snaps. never bothered way back then.

MAYBE????? a mud map drawing in one of the boxes in the shed, I will look later.

I am unsure if the S3 Carby cars ran the same system as the S2 cars??, never had the pleasure of seeing one of them, not in our market.

 

Cheers Grant,

Have spent today messing with relays. To follow the Haynes manual, I replaced my red fuel safety relay with a Lucas starter R22. Followed Mr. Haynes wiring diagram and didn't even have fuel flowing. Then moved a couple of wires, had fuel whilst cranking but then stopped on key release. Time to ground the oil pressure switch maybe.

I have no idea how these relays are wired as two differing wiring diagrams do not provide the answer. Anyone have a photo of their relay wiring?