This car likes to be the Drama Queen whenever it can. You just can’t take it anywhere without it putting on a show.

We were out on Halloween for our anniversary andwhile coming home late from dinner. All of a sudden the tires started making noise. We pull off the highway as soon as we could and found one rear tire lowand the other one flat. I aired them up but when I went to leave the service station the car would only miss at idle and then die.

The computer said P0506 (RPM Lower Than Expected).I’m thinking fuel pumps. My car has two.

If what I have read is true, the secondary primes the fuel rail when you turn the key on, then the primary kicks in while cranking and to run the car. If the primary dies the secondary will run the car.


If the secondary dies it would show signs as mine has over the past six years, long cranking to start and lean fuel warning when driven hard.
Also, the same as mine, turning the key on and off many times before cranking would not solve the long cranking before starting, because unlike most cars it's not running the primary/only fuel pump at that time.

Any ideas?

Those you had written in with P0506and replaces the fuel pump never stated if this fixed the problem.

I will report back with solution.

 

That would have been the smart way to design it. But no, only if the Primary RELAY goes open circuit, then the secondary pump kicks in after 5 or 6 starts. You can therefore remove the primary relay as a test to force the car to run on the secondary pump.

 

So if I would have pulled the primary relay and tried to start it 5 or 6 times (which I did w/o pulling the relay) it would have started? I'll have to put that info in the glove box with the AAA tow number.
So they would rather leave you sitting on the side of the rode than give you a check engine light. How does it decide to run the secondary if it doesn't use fuel pressure?

 

It will work provided that your secondary pump and relay are good.

It decides by sensing an open circuit in the primary fuel pump relay circuit (and that will set a fault code). It is a rather absurd 'failsafe feature' because there are probably 1000 fuel pump failures for every relay coil failure. Its main value is it can get you home if your primary fuel pump fails and you know this trick.

 

So does the secondary prime the fuel line by running a few seconds when the key is turned on?
My has had to crank a few seconds before starting after is has sat awhile for years. I always thought it was the fuel pump check valve but this may explain why even after turning the key on and off a few times before starting it still needed to crank if the secondary was not working also.


The shop call and said it had no fuel pressure but the injectors were firing, they still need to check relays in the trunk.

 

Yes, the secondary does prime the system. From your description, it could be that your secondary has failed for some time and your primary is in the process of failing. More info here: https://www.jaguarforums.com/forum/x...el-pump-85882/

 

Well I told them if it's the fuel pump, replace them both. Not an easy place to get to.

 

Definitely the right move.

 

2 fuel pumps at $273 ea, Seal $25, Filter $34, 2 screens at $22 ea, Labor $651
Total $1,300
Runs great, hopefully it will start right up now w/o cranking. I'll know tomorrow on that.

 

In Spring 2009, my car would not start after winter storage (first year that ethanol-only fuel was available here). Both fuel pumps failed. Had a indy replace them, $1374.

I have added two pushbuttons that bypass Fuel Pump Relays to "Exercise" Pumps during winter storage:

 

Fixed the cranking before firing, Really goes now when you hit the gas, traction control light blinks at me when on hard acceleration!
We're back in love again!