Hello all.
I recently purchased a 1979 XJ6 series 2, 4.2. I drove it 60 miles and all was well. The same night I moved it to a different parking space and the car cut out twice whilst on the move. The following day it was not starting at all. I did not have time to work on it so it was sat for 5 months. I have been trying to diagnose the issue this week. I discovered both fuel pumps were not functioning. Looking through some threads on this forum, I saw Grant Francis advise others that a faulty oil switch could be the culprit, so I replaced it. After this, both pumps were running, i can hear them whizzing with the ignition on, and the fuel filter bowl gets fuel. Thank you, Grant.

However, the car is still not starting.

I don't have any previous experience on working on cars let alone anything of this age, so maybe I'm missing something. Any suggestions would be highly appreciated.

Kind regards,
Syed

 

I should add, I did charge the battery.

I bought the the car from auction. When I went to pick it up, it didn't start in the first couple of attempts, but when it did, I drove it 60 miles back to my house.

Kind regards,
Syed

 

Syed,
does it have standard ignitions system as in points etc, with a basic test light check you have power to ballast resistor ignition on (white ceramic block near coil) power in and out, power at coil + from resistor, remove distributor cap and with ignition on open the points if closed & should be a spark, so if there's no power to all that then there is an ignition protection relay usually located top of fire wall center, not unusual for the brown wire to come lose, check other wiring white/pink and earth are fitted correctly as well.......check all that & let us know what you find

 

OK, glad that helped.

Now, I am confused, so I will scribe on and see what returns.

S2 Carby cars, had a "Reverse" oil switch for the Fuel Pump Relay Earth circuit.
Meaning, when the oil pressure in the engine was less than 6PSI, it "broke" the earth circuit for the relay, and the Pump stopped, the Carbies ran out of fuel (eventually), and the engine stopped.
Soooo, with the Ign ON, the pumps should not be running. The only way that can happen is:
1) The oil switch fitted is a "standard" spec switch, which has Earth at Zero oil pressure, thus the Idiot light glowing, and NO Earth path when pressure is applied above approx 6PSI.
2) The wire to the Pump Oil Switch is earthed permanently (Aussie fix), as the Reverse Switches were HARD to get a few years ago.

The correct Reverse switch looks the same as a Normal Oil Switch, but the innards are different, lots of confusion back in the day.

The PROBLEM with that Reverse switch and that Earth Path is when the car has sat for a while and the Carbies are empty, so cranking to get oil pressure to activate that switch, then the relay, to get the pumps running, to fill the Carbies, and run the engine, NOT good for the starter motor.
BUT
The cars were never designed to be Garage Queens, so, daily, weekly usage was fine, as the Carbies were still full of fuel, the engine started, the pressure arrived, the switch completed Earth path, the relay clicked, the pumps ran, and all was happy in Jag Land, SIMPLE. NOT

That Switch was a Lucas Item, it leaked, was erratic at times, and did not age well. Hence the Aussie fix ( #2 above) of earthing that wire for the Pump Relay, so the relay ran the pump/s whenever the Ign was ON. The safety Switch still killed the system on impact, so all was good.

I need a drink.

 

One would have to wonder at the warped design mentality to introduce a "reverse' switch into the system as Grant described.
I had a S2 XJ6 for many years and I disposed of these systems and the bloody SU pumps which I detest.
I still kept the impact switch in the system.

 

Hello all,

I managed to get it started but it cuts off as soon as get my foot off of the accelerator.

I recharged the battery again overnight as it was a bit low after cranking yesterday.

​​​​​​I followed Tom's advice and i found there was power to both wires on the ballast resistor while off and only power to the top wire with ignition on (picture below). There was also continuity through the resistor. I also cleaned all the contacts on the relay and wires. The points ignition system and distributor cap was replaced by the previous owner last year. so before messing around with the distributor, I thought i would try cranking it once. I sprayed a bit of easy start into the air intake to the carbs. With the accelerator down, it started and there was some backfire initially. I tried 5 times and each time it started but I had to hold the revs at around 1500-2000, and as soon as I let off the pedal, it cut off. In the last attempt, I held up the revs for around 45 seconds and when I stopped pressing down, the car idled for about 5 seconds which was an improvement. The engine sounded as it should.

What could be causing it to cut off? The results were the same when using left or right tank.

Also, when I put ignition on, the fuel filter bowl fills up with a little bit of fuel initially, then stops filling up eventhough the pumps are constantly running. When revving, the bowl becomes empty. I'm not sure if this is normal or if there is an issue with the fuel pressure. But then again, the engine runs for as long as I rev, so it must be getting enough fuel somehow, right?

Another thing which I noticed is, there is a small hose coming off of the AED, but it is not connected to anything, not sure if this is relavant to the engine cutting off. I have attached a picture for reference.

Thank you all, for the advice so far.

 

That AED is killin' ya, hate the things with a passion, try staring without the AED functioning, block the fuel to it if need be, hand check that the throttle moves both carbs at the same time, then back off the throttle idle screws & reset them to an extra 1/2 turn in to make it idle a bit faster, you can reset them later.

 

MMMMM, 5 coffees and 1 Canadian Club down, so here is some more tjoughts.

Fuel starvation sounds like a possibility. That bowl should fill and STAY full at all times.

1) Look under the RH side of the car, look carefully, and you will wee the fuel supply metal pipe from the rear to the engine bay. Follow this pipe and see if its crushed. Tyre fitters, and other idiots, jack these cars without using the supplied jacking points, and that pipe suffers. I have lost count of how many I have repaired over the years. Now I take the wheels for tyres, the car stays home, simple.

Electrical, I will stay out of, as I trashed the Opus nonsense day 1 of ownership, and went to contact points, or S3 electronic, never looked back.

That AED, I agree, more strife than ever thought about. All my Carby beasts were manual choke on 1 carby only, and only few 10 seconds max.

At least it runs, its just the fun part now to get rid of "Freddy Fiddler" and his handiwork, and that is TIME only.

 

Grant think you got that the wrong way round>>> 5 CC's and 1 coffee, i have wire rims i definitely take them off myself and refit, AED wa a major problem when i bought the car, completely removed and evidence of it existing and made my own choke system the same as down draft carbs, choke flap at the intake face with a fast idle solenoid, electrical i'm happy to do, fitted a hot spark ignition 2012 & haven't touched it since..........i'm guessing Syed wish he had some of those CC's by now

 

HAHAHA that was the old days, before all the metal appeared inside the skeleton, and I was told to stop the alcohol, or pay the top price. Airports are fun, NOT.

BUT

Some of the goings on in here, just tip the scales sometimes.

Electrickery I love, if I am hands on. Sorting other peoples messing by remote control never works. Rewired the engine bays of most of my Series and XJS cars myself, that way I know what is happening at any time, never looked back.

Syed,

Another thought.

The pumps may be running, BUT if there is NO fuel on the supply side FROM the tanks, there is nothing to pump. That would be well worth sorting before the CC is consumed. That gravity feed is a mongrel at best, especially on little used cars. The debris that gathers at the tank bottom, is SCARY.

 

Thank you both. It's 7am now, here in the UK, I shall act on your suggestions this evening.

Tom, when you say I should try starting without the AED functioning, what do you mean? How would I go about doing that? Sorry, I'm still learning as I go along. Also, which part of the carbs should I be looking at when pumping the throttle?

Grant, I was thinking the same thing, because the day before yesterday when I got the fuel pumps working, the fuel bowl filled up to about 3/4 and yesterday it only filled to about 1/8 in a short burst after ignition on, Then there is fuel dripping down drop by drop very slowly, into the bowl. I will check the hose as you said. Could this be pressure related, or perhaps a pressure regulator?

I do wonder though, if there is fuel starvation, why does it continue running smoothly at higher revs but not at idle or anything below 1400 even though revving would require more fuel, right?

Also, does anyone know where the hose from the AED (pictured above) is supposed to be connected to
Kind regards?

Thank you, both

Syed

 

I filled up both tanks to about 25 litres each. I was scared about the potential debris too, but so far the fuel bowl and filter look ok.
The odd thing is, when I put the ignition on, and the fuel bowl fills up about 1/8 of the way in a short burst immediately, this does not happen again if i switch tank before starting. It only fills up to 1/8 in a short burst again, after the engine cuts off and I put ignition on again. Even if I switch on the ignition and off and on again, without starting, I still only have the one short burst from the first turn of the key. Very confusing.

 

5PM here, and my thoughts

I would make sure that the fuel pump relay is actually getting a GOOD Earth path, sounds like NO. Find that switch, the pump earth oil switch, and remove the wire, attach it to any earth point near by, there are many on a S2. That way the pump/s should run whenever the Ign is ON. That just simplifies the trouble shooting. You can return it as factory if you wish once sorted.

Fuel bowl not filling, strange, and not as designed. More thoughts needed.

Running fine at higher revs, and not so lower down. That could simply be the carbies need a GOOD clean, Bell Chambers off, clean the chamber inner face, and piston circumference. This cleanliness is critical to SU's operating correctly.

The AED I will not discuss, as I removed them from all mine, there simply were a PITA. Others that still run them and understand the operation will speak up soon.

 

Grant,
i share the metal, got a bit in the body as well, gotta carry a mini pic of my xrays going though metal detectors.........Syed, to disconnect the AED just cut the fuel supply to it as in block it, it will run at higher revs with AED flooding it but won't 'cause a good chance the AED is flooding the motor, do as i described previously about idle setting etc, i'm on the same page with Grant with electrical, it's what i do + carbs, where does that tube go to?.........Syed - follow a few points from Grant as well.......
Grant, you might be interested in some of my free library inf>>> www.jaguar-wiring-schematics.info