Hi Guys,

Ok, from the other thread (Preventative Maintenance on Series III).

I have not yet been able to work on the car to find the leak. At the moment (only when engine cold) I get a fast drip of fuel in the rear-center. More toward the right wheel though (looking at back of car).

I thought I fixed this leak, because there was a fuel leak on the pipe on the fuel pump. I replaced this pipe, tested and there was no more leak. What happened was that the car must have warmed up. I tested the next day.. Leak was back and is always present on first start in the morning.

Symptom No.2: I put around 10 liters (2 gallons) of fuel in the left tank. This appeared to have moved itself somehow to the right tank... (right tank went from half full to 3/4 full almost by itself, left tank went to 0). Have not put fuel in left tank since. Running right only.

Symptom No.3: Intermittent difficult start. Engine cranks but no start (or start and die). Put gear in R, crank - hear the pump running. Put back in P, fires right up.

Symptom No.4: Slight loss of power / hesitation on wide open throttle... SOMETIMES...

Ok.. Any ideas guys? I need to do this job on Saturday. From the end of this month this Jag becomes my daily driver for a couple months so need it to be as close to 100% reliable as possible.

My thoughts: The fuel system is losing pressure somewhere (due most likely to this leak) causing the intermittent hard start and power loss. This does not explain the fuel moving from one tank to the other though. Also, not sure where this could be leaking from.. Doesn't seem to be from the maze of fuel pipes in the boot/trunk...

 

A changeover valve in the trunk determines which tank fuel is drawn *from*. Two return valves (located in the left and right rear wheel wells) control the flow of returning fuel so that unused fuel get returned to the same tank it was drawn from. If there's a problem with the return valves fuel can be drawn drawn from one tank but returned to the opposite tank. Over a period of time this can actually cause the receiver tank to overflow.

Sometimes the return valves mechanically fail or stick. Often they can be brought back to life with a good cleaning.

Other times there's an electrical fault. In that case, this might help:

http://www.jag-lovers.org/xjlovers/x...changeover.htm

 

Thanks again Doug. Do you think the leak could be from the return? That wouldn't cause the lack of fuel pressure I seem to be experiencing? Or could it?

 

This damn problem is going to be the end of me. Today, she started right up, absolutely no sign of a fuel leak, no loss of power, no matter how hard I tried I couldn't find a fuel leak.

 

Update: Still asolutely no fuel leak in the original place. I have however discovered that the fuel pump is wet at the bottom and 'weeping' near the wire connections. Could be Doug's theory that its dripping here but collecting and dripping on the floor further to the front of the car.

I am going to check the pipes to the pump, failing which I'm going to replace the pump. Can a generic in line pump work here or do we need a specific part?

Thanks guys.

 

Yes, you can use a generic pump, so long as it's capable of making about 75+ psi.

Cheers
DD

 

Thanks Doug. Will check it out today and let you know.

 

This problem is resolved!

The problem in the end was the fuel pump. Doug was correct, the fuel was leaking from the fuel pump, going through the spare wheel area and pooling elsewhere causing the drip further forward on the car.

I've never seen anything like this, the fuel pump was leaking out the side! Not out of the pipe connections. Shown below in red:


The new fuel pump:


Work in progress:


New pump in place:

 

This is why forums work so well.
I just discovered a major leak from my fuel pump.
My mechanic hadn't seen the failure previously, so I googled and found your thread.
Although I was hoping the pump was repairable, the replacement from the wrecker cost $20.