So my car is having a small problem (1986 XJ6). I got in the car, and the engine cranked but never caught and started. After doing some diagnostic, I believe there is a problem with my fuel pump. Any suggestions on testing to make sure this is in fact the problem? OR any tips to fix this?

 

 

OEM fuel pumps are usually pretty similar in nature.

 

A fuel pressure test is useful at this point.

But it would be helpful to know if the fuel pump even operates. Put the gearshift in "D" and turn the key to "start". You should hear the pump run. If you don't, post back.

Next, remove the air cleaner cannister to access the forward opening of the AFM (Air Flow meter). You'll see a flap...looks sorta like a trap door...inside the AFM. With the key "on", psuh the flap open with your finger. You should hear the pump run. If you don't, post back.

If you DO hear the pump then a fuel pressure test will tell you if the injectors are getting the right pressure.

Have you checked for spark as well?

Do you hear the injectors click while a helper cranks the engine?

Cheers
DD

 

Doug has the right method,.. To add another that I found easy for folks with crap hearing like me, would be to disconnect the hot lead to the pump and attach 12 volts. If you don't hear it, or feel it, the pump is dead. If it's not dead, then you have a power source problem. Like Doug says,.. Post back for further directions.

 

Sounds like the two tiny contacts in the MAF are failing to make contact properly. The whole fuel system relies on these two little contacts. Yes it is crap design, but it ain't going to be changed now ! These contacts close and supply the fuel pump relay.

When cranking, these contacts are bypassed in the ignition switch, and when the switch is relaxed back to "run", the contacts take over to power the fuel pump solenoid. If they fail to close the pump stops.

Read this: -

Fuel injection and the Jaguar XJ6 4.2 Series 3 / AJ6 Engineering

Page 3 has the details of the above fault that affected my car.

 

Doug, I cranked the engine and listened, there is no sound of the fuel pump working at all. Any suggestions?

 

Unplug the fuel pump relay from the plug/connector. Look for the white/green wire(s) at the plug. Using a jumper wire apply 12 volts to the white/green wire(s)....the battery "+" post is a good choice for your 12 volts.

This bypasses the entire pump control circuit.

(If you're realy socket has one green/white wire, that's the one. If it has two white/green wires, apply votage to both of the. One or the other goes to the pump.)

If you don't hear the pump run then you have a dead pump, a poorly grounded pump, or a wiring fault between the relay and the pump.

If you do hear the pump run with the circuit bypassed then you have a problem with the control circuit.

Remove the air filter housing so you can access the front of the air flow meter. With the key 'on', open the air meter flap with your finger. Does the pump run? If it does run for this test, but doesn't run for when the key is turned to "start", then one half the control circuit is working.....the "run" half but not the "start" half.

Here's some reading:

Fuel Pump Circuit Checklist

Cheers
DD

 

Doug, did all the that, still don't hear the buzz of the fuel pump. Are there any tests further to check? If not, how do I go about getting a new pump/poorly grounded pump/or fixing the wiring between relay and pump. According to my car manual, I have a dual fuel pump. Not too sure what that means. When I did the test, there was a clicking from the fuel pump, but not the buzz i'm used to hearing from fuel pump.

 

If you have a Ser III 4.2 engine fuel injected (which I've been assuming) then you have a single fuel pump. If you have a Ser III 3.4 engine on carburettors then you have two fuel pumps...one in each fuel tank

If the pump repsonded to the tests with a clicking then the circuit is probably OK. Sounds to me like your fuel pump has died.

Cheers
DD

 

Sorry for not being more clear. My car has 2 tanks. a Left tank and right tank. So I would have two fuel pumps. Does this mean that both stopped working at the same time?

 

All the Series IIIs have two tanks.

What engine do you have? If you have the fuel injected 4.2 you have one pump, mounted under the spare tire. If you have the carburetted 3.4 you have two pumps, one inside each tank.

If this is a USA-market Ser III then it will be the fuel injected 4.2

Cheers
DD

 

I also have lousy ears. Big flaps, poor inside. One is so bad that aid amplification does nothing. the other one works sorta sans aid, and decent with it in. I have a dummy for the right ear, it collects sound and sends it to the left wifi style!!! Faux sound surround, but helpful. They eat batteries when used for a spell. a set per day. Not on, now. All is quiet.

When I was working on reviving the Jaguar after it's catastrophe, I thought I heard the pump run. I was a tad mystified as wiring was yet in progress??? epiphany, it was the antenae. the radio was on, but the sound muted.

If the pump is running, i supect that putting one's hand on it might detect movement. I do that with a few electrical things around here. The kitchen exhaust fan is actuated by a cord. Just feeling the cord denotes wheter or not it's going.

One of my projects, yesterday was completing a neat jumper cord. Biggish pair of aligator clips on one end, kinda like on big jumper cables. Salvaged from dead jump box. The other ends with smallish aligator clips from my box of patch cords. A garage sale find, decades ago that continues to be a treasure for connectors. Red and black leads. splices soldered and shrink tubed in matching red and black. Longish as well for transfering power from battery to various parts of the car. Mosly in the engine bay and possibly the front portion of the cabin. I have another jump box, better quality than the last pair. Good for 12v away from either car's battery. I have powered start for my WWII era gas generator. it uses a pull cord, the old kind that does not retract. Durnest tendency to whack on where it hurts most on a start effort.

Back to subject. Three major components in the boot well, behnd the spare. Biggish fuel filter, change over valve and the pump itself. Once havong figured those out, diagnostics will make alot more sense.

 

Yes, it is the fuel injected 4.2

 

Ok, 4.2 engine, single fuel pump.

From what you've said I think the pump is on the blink. It appears that the circuit is working (thus the click from the pump) but it should hum, not click.

Try putting your hand on it as Carl says. It should feel like an electric motor is running.

Cheers
DD

 

Doug, do you know how to change a fuel pump? I bought a new one but can't afford to have someone else do it. I feel like with some help and guidance, i can do it myself. Any tips or pointers on it?

 

First make sure you have something to plug off the hoses or you'll have a flood of gas when you remove them from the pump.....especially from the inlet hose! A wooden dowel with one end whittled to a taper (for easy and FAST insertion into the hose) works fine....but you can dream up something on your own as well. The the inlet hose is 1/2" ID as I recall...the outlet hose might be smaller

With your hose-plugging-device ready loosen the inlet hose clamp, wriggle off the hose, and plug it off, quickly.

Do the same for the outlet hose.

Remove the voltage wire (just a slide-on connector as I recall). Remove the ground wire.....can't remember if there's a slide-on connector or if it screws directly to the body. Should be self evident once you look.

The pump is held in place by a clamping bracket that encircles the pump body. Undo the two small bolts to release the clamp tension, open the clamp, and remove pump.

There is a foam or rubber cushion that you'll probably have to remove from the old pump and intall on the new one....or dream up a suitable substitute.

Best to disconnect battery first just to be safe.

Even using the hose plugging devices be ready from some spilled fuel. Have rags ready to wipe it up and then toss them into the driveway (or wherever) to dry.

Cheers
DD

 

I've never tried it. But, clamping a line with fuel seems possible. Small "C"clamps or a couple of vice grip pliers.

If not done before and the tanks are on the lowish side as to fuel, it be a good time to drain them and get rid of any sediment. Have gaskets available.

My thinking is that dirt is a major cause of changeover valve and fuel pump failures.

Also, it might be the time to install small low pressure filters before the pump to catch any debris.

And, a garden hose or better yet a fire extinguisher on the ready.

Done in the open is a good idea as well.

Carl