XJ6 & XJ12 Series I, II & III 1968-1992

fuel pump relay

 
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Old 05-20-2014, 02:44 AM
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Default fuel pump relay

Hello
I have a xjc that will run fine then cut out occasionally or idle rough from time to time I'm told that it may be a faulty relay is this located in the engine bay and will a replacement be easy to find
Thanks for your help
Aaron
 
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Old 05-20-2014, 05:13 AM
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Ummmm, Aaron, 6 or 12, Carby or Infected??

I'm guessing 12 and Infected.
 
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Old 05-20-2014, 06:10 AM
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6 and carb :-)
 
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Old 05-20-2014, 06:27 AM
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Faulty relay, nah, I seriously doubt it.

The carbies have fuel in the bowls, so even if the pump stops, the engine will run normal for a few minutes before getting wobbly as that fuel runs out.

Some of them had the Opus electronic ignition, which had major issues from NEW. If it has, I would look for a S3 distributor and "black box", and swap it out.

If its still got "points" system, then the condensor inside the distributor is high on my list.

Then come the carby state of service.

If they are SU carbs, then a good clean of the bell chamber and piston is mandatory.

If they are Strombergs, the diaphragm under the top lid is prone to pin holes, and all sorts of running issues from that.

The myriad of vac hoses related to emissions in your market will/do cause issues.

One earlier thread in the XJ6 section had odd idle issues, and the vac hoses were the issue.
 
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Old 05-20-2014, 09:26 AM
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Thanks for the reply, I have had the plugs and points replaced. when it's running poorly I get very bad throttle response and rough idle. I have had the carbs cleaned and balanced but as it's intermittent I having real trouble getting the fault diagnosed by a mechanic.
 
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Old 05-21-2014, 05:44 AM
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Plugs and points, GOOD, we are narrowing this beast down.

I seriously doubt the condensor, SHOULD have been replaced with the points, but sooooooo many do not do this.

The coil also sits pretty high on my list.

IF, and that is IF, it has a "ballast resistor" for the coil, that is also suspect.

Then comes the good OLD Lucas wiring, AND the connectors, as serious resistance can develop in that area.
 
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Old 05-22-2014, 05:52 AM
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IF you have a fuel pump relay it's red and on the bulkhead. It came around 1976-77-ish, before there were no relay, they were connected directly to the inertia switch (located in front of right front door). Clean all connections and check fuel pumps, tankfilter and fuel filter as well. Does it get better when you switch tanks?
 
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Old 05-22-2014, 10:28 AM
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I dont know if this helps but i had issues with my red fuel relay not clicking in until i cranked over my 3.4 for a good minute or so after she was left for a couple of weeks or more. The fuel bowls were empty after lying up and relay was not switching on pump until i cranked her over and over. The only way i could resolve issue was to bridge the positive connections with a switch on the dash, essentially bypassing the relay and switching pump on direct to run for a few seconds and deliver fuel. The car then starts immediately, i switch off the bypass and pump relay takes over the job from there on. I have no idea why relay doesn't click on itself with ignition as it should but thats how i solved my problem. Car is 100% reliable and starts 1st time every time now. (And yes i have changed relay twice with new ones and still doesnt come on with key after lying up) jj.
 
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Old 05-24-2014, 03:37 AM
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I bought a new coil and I have a auto electrician coming to look at the car today will keep you updated thanks for the replies.
 
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Old 05-25-2014, 09:19 AM
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So had a auto electrician come out look at the car it was running very rough poor throttle response changed the coil and instant improvement ran perfectly. Went to start the car this morning and problem has returned so back to square one. However now I know the points plugs and coil can be ruled out. I'm thinking I will clean up the connectors tomorrow only question is where do I start. Any other ideas much appreciated people
 
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Old 05-26-2014, 04:01 AM
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If it's only when cold start it must be the AED (automatic choke between the carbs) it gets clogged inside with soot and the rubber needle diaphragm under it gets stiff by time and must be replaced or the intake won't get that extra rich mixture for cold start. I restore AEDs and you know it fully works when engine starts cold at 1000 rpm idle and then settles down at 750 after 5 minutes (...ish).
 
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Old 05-26-2014, 04:04 AM
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If the AED don't close after those 5 mins it will make the engine run too rich and poorly.
 
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Old 05-26-2014, 06:33 AM
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Actually just re reading that mine has a manual choke not auto so im not sure if that's the issue.
 

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Old 05-27-2014, 05:14 AM
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Originally Posted by Anfield Dreaming View Post
Actually just re reading that mine has a manual choke not auto so im not sure if that's the issue.
Ok sorry, but if it's the usual manual conversion you still got the needle and (probably stiff) rubber diaphragm that won't pump any fuel in.

I once got a hole in that diaphragm which makes the fuel spray uncontrolled right into the intake and fill the neighbourhood with white smoke, luckily no one came and lighted a cigarette lol
 
 
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