Hi Everyone,

I am new to this forum and would like to say how much I appreciate all the great words of wisdom I have found here. I must have spent 6 hours reading without looking up!

My 2000 XK8 coupe will not start. I have not driven it in several months, and it ran fine when I parked it and put the cover on. I use a battery maintainer to keep the battery charged when not in use. Let me say that the car sits outdoors with a cover. Therefore, various mice and squirrels have access the the engine compartment. I had to remove a mouse nest on top of the engine when I popped the hood. Most of the insulation on the hood is chewed away.

This last week, I tried to start. No luck.

Reasoning with the mental tools I learned from my father:

Engines need air, fuel, compression, and spark (at the right time).

The dash lights up. The engine turns over normally. Doesn't even try to start. I pulled a plug and tested for spark (yes) . However, the spark plug was dry and did not smell of fuel.
Next, I checked the fuel rail for pressure at the schrader valve with a gauge... none.

This took me to the trunk for the fuses and relays. All fuses tested with an ohm meter are OK. Checked the relays with an ohm meter by manually supplying the control voltage - OK. Next, pulled the power connector off the fuel pump. No power to the pump.

Back to the relays. I jumpered out of the fuse box and closed the relay manually with a control voltage. This got me power to the fuel pump connector.

From what I understand at this point, the computer sends a signal to the low side (non 12V side) of the fuel pump relay (i.e grounds it) to trigger the relay. Is this correct? I am piecing together information from multiple sources as the wiring diagram I have leaves a lot to be desired.

I put a signal tracer into the fuse box at the relay... and traced it going into the computer with a white/red wire.

It appears to me that the computer is not telling the fuel pump relay to close. I suppose the computer could be bad, but everything else seems to work, so I figure that 1 particular output being bad is not likely.

Some other things I have tried: (I do not have a code reader)
Reset inertia switch
Shorted the battery leads to drain all voltage for reset

Am I on the right track here?

Have I misread the schematics?

What other sensors/inputs might cause the computer to turn off the fuel pump?

Any help is greatly appreciated!

Alan

 

You've done it right so far. The power for the relay comes from fuse #3 in the trunk fuse box.

The ground comes from the ECU. Yes, it is the white/red wire. Check and see which one is missing.

When you "manually" had the relay working, did you try to start the car?

 

Here's the whole circuit.

 

Thank you very much for the reply and the schematic pics. It makes a lot more sense to me what I am seeing now.

To answer your question, no, I did not try to start the car as I had pulled the connector off the fuel pump and had a voltmeter monitoring it. Getting the connector off the fuel pump was challenging, involving an inspection camera on a goose neck and me sitting in the trunk doing a contortionist act involving a tiny screw driver. Needless to say I was hesitant to put the connector back.

However, I can certainly try that tomorrow. I can always check the pressure at the fuel rail from this point on.

The signal tracer tells me that the wire from the computer to the relay is connected, and I get the proper voltages on the relay for the pump... which does get 12V at the pump connector when I trigger the relay (putting jumpers on all the leads from the fuse box to the relay, except the line from the computer, which I ground separately). All the fuses test good with an ohm meter (but I will double check that tomorrow too).

As it sat for several months after running perfectly, I suspect corrosion or rodent tampering somewhere. It does seem the computer is not sending the low signal to start the fuel pump relay.

The trick, I think, is to figure out why!

I'll post the results of trying to start the vehicle with the fuel pump relay tricked into working tomorrow.

Thanks again!

 

I suspect that the engine ECU is not getting the start signal. If it's not cranking it may not run the pump, but I'm not sure.

Look at this schematic and you'll see a wire "GO" designation that goes to the ECU when the starter is engaged.

I'd open up the compartment where your ECU is housed, and look for chewed wires. Look everywhere for that matter. The damned things chewed through my knock sensor harness.

 

Check the inertia sensor in the dash side fusebox. It shuts off the fuel pump in event of impact. It may not be making contact.


Dave

 

It is becoming common to read of fuel pumps failing after extended storage. Since you say the engine turns over okay and you have spark, that would be the most likely culprit. If you jump the ground wire at the ECM with power to the pump that should determine whether the pump and wiring are good. I would first disconnect the neg battery terminal and pull the plug to the ECM to prevent damage.

 

Progress! Night before last I found my old code reader, which had been missing for about 5 years. Read the codes and came up with a whole bunch of seemingly unrelated codes. Along with those was a "System Voltage" code. Well.... hypothesizing that the only thing that related them all together was the voltage supply, I picked up a new Battery.

Installed the battery. Cleared the codes. Just the normal all is well code remained.
Still no start or fuel pressure, so back to the fuel pump relay.

I popped the top off the relay (really easy by the way) and just engaged it with my finger while watching the voltage across it. There was some drop, indicating some sort of load. Next, I used the key, and now, with the higher battery voltage, the computer does tell the fuel pump relay to close. It did not do so with the lower battery voltage (and we are only talking half a volt here). The car cranks a whole lot better too.

I pulled the power connector off the fuel pump, again with a small screwdriver and a contortionist routine. There is now power to the pump when the key is turned. Some current is being drawn as there is a small voltage drop, but no sound of a running pump at all.

Tomorrow, I will find a new fuel pump and try it out.

Thanks for all the suggestions!

 

When my Pump(s) Failed, one of them acted the same, Current draw but did not turn. Eventually they both went open circuit.

 

See if this information helps

Link.http://jagrepair.com/FuelPumpVoltageChecks.htm

Gus
www.jagrepair.com

 

More progress... and a let down. The fuel pump is changed. Put in a NAPA DFP FE0479. Cost about $100 including tax. Saved 10% by reserving it online. Could have found it cheaper, but we live far from civilization, and this was the closest place that had one. About 20miles away.

NAPA AUTO PARTS

We put in the pump using the bracket from the old pump. It comes with a wiring adapter. Pretty easy to change.

By the way. I have a 2000 XK8 Coupe. It has a large subwoofer on the back deck right above (and offset a bit) the access to the fuel pump. Removed the subwoofer. Loosened the straps, pulled the tank back a little till it stopped... and managed to get the unit out, change the pump, and put it back without pulling the tank. Did a lot of the work through the hole left by the subwoofer.

Now, I can hear the pump running. We have good pressure at the schrader valve.... still cranks, but no attempt at starting.

I am guessing we messed something up.... misplaced or disturbed a fuse or relay when troubleshooting the computer.

In any case, tomorrow I will pull a plug to check spark again and will check the compression at the same time.

Almost there!

Thanks again everyone for the info and suggestions.

 

In case it's a 4.0 look for excess fuel which can cause bore wash.

 

+1 bore wash. If your compression check shows under 100 lbs. put a little oil (1/4 tsp.) in each cylinder, pull the fuel injection fuse, place rags over the plug holes and turn the engine over a few times. Then put it all back together and it should start with clouds of oil smoke.

 

See if this link helps

Link. http://jagrepair.com/JaguarXKXJSTypeNoStart.htm.

Link. http://jagrepair.com/NikasilNoStartCylinderWashing.htm.

Gus
www.jagrepair.com.

 

Success!

Checked the spark. Good. Compression good.

It appears when I checked the fuses in the engine management box, I put one back in the wrong place. Serves me right for working on it while tired in the wee hours of the morning. (by halogen light in the yard)

The fuse was for the Injectors.

Moved the fuse, turned the key, and it started right up. Nice and smooth.

Next, a few other things.
Dash lights.
Oil leak that hits the manifold and smokes, only after heavy throttle.
A seat switch that is coming apart.
Re-dye part of the drivers seat black where it is worn.
Then off to the detailer to get it looking good.

I want to thank everyone again for their ideas, diagrams, and comments. It really made this go a lot smoother. What a great site!

Alan

 

Good job! Sometimes you need to go back and start double checking things.

 

Well done Alan, with your procedures and in what order, this will give the next guy a direction. Thanks for the documentation. I can do real well with mechanical bits and have no trouble with electrics of the MG and Triumph range, but the Jag is somewhat of a challenge. I look forward to learning and you just helped.


Wayne

 

I am working on a 2001 Xk8 with 153k miles.

Check engine light came on P01743 lean on bank 2.

Engine whicha had been very strong suddenly felt sluggish.
Cleared the code. Eventually it came back.

Next day no start.
Engine light p0301/0306 and p1316.

Suspected fuel issues.
No pressure at schraeder valve confirmed it.

Figuring fuel filter might not have been changed, Jaguar original, released lines at fittings. With a mirror in hand turned swith on and a strong jet of fuel came out. So pump was working. Replaced filter and car started inmediately.

Went for a test drive 20 miles. Engine responsive and pulling strong. I was very happy and smiling at how smart I had suddenly become.

Next day No Start. Rats!

So dove into the tank. Up on stands she went. Removed ebreak yoke for better access.
Releasing the fuel lines turned out to be harder than expected. This is probably the filthiest spoton the car. Really disgusting.

In retrospect making the PVC pipe tool is a great idea. To make matter worse the tool got stuck on the line and all the fuel came down on me. My wife kindly suggested I go sleep with the Jag!

When i pulled the pump, found an after market unit. Tested on bench it works fine. Still I replaced with a Jaguar one.
The wiring on the other hand was fried.

How many good pumps have been replaced unneceserally?
Here are some pictures of the burns.

 

Here is another burnspot.
Sorry Allan I did not mean to hijack your thread.
I was trying to start new one on Iphone.