You have TWO, look on the B bank in the same position. Pressure after the B bank FPR is irrelevant. You need a T off the rail (or at a point BEFORE the b bank FPR) to measure rail pressure. The injectors open electrically, the pressure is just to produce enough of a spray pattern and enough actual fuel to ignite. Here is a snap of the B bank FPR on the UK passenger side.
Greg

 

Hi Tony

The 3 Second Test on the Fuel Pump Wires will let you know if the Fuel Pump Relay is Working or Not.

Its a fairly inexpensive little component to replace, rather than go and buy a new fuel pump for nothing.

The FPR on 'A' Bank doesn't do anything much and can be done away with altogether, which is what I'm planning to do on my own Car.

The FPR on 'A' Bank is the more expensive one of the two, at about £65 so don't go wasting your money on a new one.

Not so with the FPR on 'B' Bank (That's the important one and also the cheapest around £40)

So for the time being reconnect the FPR on 'A' Bank and Concentrate Only on 'B' Bank.

When the Petrol comes in from the Main Feed to the Fuel Rail (which is on the Drivers Side on a UK Car) The 'A' Bank Side.

The Petrol Travels round the Rail until it is Stopped by the FPR on 'B' Bank.

At which point the FPR on 'B' Bank acts like a 'Dam' and as such holds the Petrol Back until it has built up a Predetermined Pressure.

Which I 'Think' is in the region of 40/45lbs at which point the Fuel Rail is Pressurized and sitting there waiting for the Injectors to open to spray

petrol from the Injectors and fire up the Engine.

Any fuel over the Predetermined Pressure, will be let through the 'B' Bank FPR and back into the Fuel Tank via the return pipe.

Inside the FPR on 'B' Bank is a Rubber Diaphragm, which over time can either leak or rupture in some way.

Which means its not holding the Fuel Back to build up much or even any Pressure in the Fuel Rail, which consequently may not be enough to run the Car.

It may not happen all at one but can degrade over time, so its not immediately obvious that it is causing the problem.

Its already starting to sound as if the FBR on 'B' Bank needs replacing.

So now you know that the FPR on 'B' Bank holds back the Fuel like a DAM to build up Pressure in the Fuel Rail.

You need to know if that Fuel Pressure is either there or Not.

So now with all Fuel Pipes and all FPR's Connected.

Turn the Ignition Key until the Dash Lights come on (But don't try and start her)

Do this Key Activation about half a dozen times, to pump up pressure in the Fuel Rail.

Then with the Ignition OFF.

Get back under the Bonnet/Hood and just 'Crack' open the Connection, where Petrol Goes into the Fuel Rail on the 'B' Bank Side (Passenger Side UK Car)

Have a big piece of Rag handy as you do this, because if the Petrol is under Pressure as it should be, then it should come Squirting out of there

like a Fire Hose.

Which of course is why you need the Rag to cover it as you do this to Stop Petrol going everywhere.

If all you get is a few drops or a wimpy little glug.

Then do the Test again with the Pipe undone from the Fuel Rail but this time remove the Dizzy lead (just to be on the safe side)

But have plenty of Rag packed round the Pipe before you turn the Ignition Key ready to catch any Petrol that may come out.

Then turn on the Ignition, to the Point where the Dash lights come on (But don't try and Start her)

You should get some Petrol out, because every time you turn the Key the Pump will only activate for 3 Seconds.

Not so when the Engine is running as that cycle would be continuous.

So while you hold the Rag over the Pipe, ask your assistant to do about 3 Key Activations But (Don't try and start her)

If the Fuel Pump is working you should get Fuel out every time you do a Key Activation.

If you don't get anything out, then it could be:

(1) The Fuel Pump

(2) Blocked Fuel Filter)

(3) Fuel Pump Relay.

Providing you are 100% Sure that the Fuel Pump is Working and Petrol is not Blasting out under pressure when you Crack the Connection on the

Fuel Pipe on the 'B' Bank Side of the Fuel Rail.

Then it does sound like the FPR on 'B' Bank may need replacing.

So then Report back with all the details of what you did and what happened, then we can go from there.

 

ok fuel comes through FRP on A bank around rail and through FRP on B bank. so pressure on rail is over 40psi, on pipe from rail going to B bank FRP i only have 20psi, so is it pump not sending right pressure.

 

As OB explained in his wonderfully clear post, it is far far more likely your B bank FPR has failed during the winter layoff.
Greg

 

Greg, but i have pressure tester on pipe before its going into FPR on b bank, which is 20psi will not go any higher, going to get new pump 2mw see if it works.

 

Hi Tony

If the rubber diaphragm in the FPR on 'B' Bank (Passenger Side on a UK Car) has started to leak or degrade, then it won't hold the required Fuel Pressure of around 40/45 psi.

Instead it will leak Petrol past the rubber diaphragm back into the Fuel Tank and in doing so will reduce the Fuel Pressure in the Fuel Rail.

In just the same way that any Water DAM might leak.

More often than not it just doesn't go 'Ping' and Stop Working, it just doesn't work as good as it did when it was New.

So in a Hypothetical situation:

When New the 'B' Bank FPR holds back 40/45psi (Car Starts and runs great)

A few years later maybe its only holding 35psi (Car 'Maybe' Starts and runs OK ish) 'Sometimes'

After that its downhill from thereon (Sometimes She'll Start and Sometimes She Won't)

Which its why its difficult to always 'Nail it' as the Cause of the problem.

While I don't want to 'Muddy the Waters' it could equally be a 'Lazy Fuel Pump' a Blocked Fuel Filter, or a Blocked Fuel Line.

Or Maybe a combination of all Three.

On my Car I replaced the Fuel Pump and The Fuel Filter and the FPR on 'B' Bank.

In Total I Spent £100 because I didn't want to break down in the middle of nowhere.

Its more likely to be the FPR on 'B' Bank but as no one on this Forum can be there to fault find it for you.

There is no way that any of us are going to give you a cast iron guarantee.

 

I may have missed something so apologies in advance if this is redundant or not helpful.

First things first. Verify, once and for all, that the pump is operational and strong. I would do this:

There is a supply hose from the tank to the engine. Item #1 in this illustration:

Fuel Pressure Regulator-5.3 Litre - Parts For XJS from (V)139052 to (V)179736 | Jaguar Classic Parts UK


Disconnect this hose from the underbody supply pipe....which juts upwards into the engine bay....you'll see it. Now attach your fuel pressure gauge directly to the now-vacant nipple of the pipe. Run the fuel pump and note the reading. This is your 'deadhead' pressure reading....what the pump itself is actually capable of producing. You should see 50-60 psi at least, maybe even 75 psi, virtually instantly. I don't know the exact deadhead spec but of you only see 20-30-40 psi deadhead pressure then your pump is weak and needs to be replaced. And, if the pressure...whatever reading you get...take more than a couple seconds to build up you have a pump problem or a flow problem somewhere along the line

Cheers
DD

 

'Lefts' and 'rights' are always from the perspective of sitting in the car looking forward.

Sitting in the car looking forward the "A" bank is on the right, the "B" bank is on the left.

Cheers
DD

 

100% correct, brilliantly explained. Ring up Manners and buy one! Low fuel pressure is far more likely to be the B bank FPR NOT "damming up" the fuel properly than an tired pump.
Doug, when he tested the pump he said he got loads of fuel out using the feed to the A bank FPR.
Greg

 

Greg

You're forgetting one Big Thing!

It was You and Grant who explained that to me in the first place.

As I don't mind admitting that without the help I got from You and 'Grant' (aka: 'The Wizard of OZ')

I would have probably 'topped myself' by now.

 

OB
We all started out knowing nothing. It is just knowledge slowly accumulated (in my case) and being retired I now have the time to spend on my lifelong hobby. And soon, within a decade or so at the most, there will be so few people who know about these cars, that the forum is the best way to ensure something is available to people who want to learn. The big thing is you have learned, and got stuck in, AND done things on the ABS that I would never be brave enough to do!
Greg

 

It can be worse than a "know nothing" beginning. And that is false knowledge.


Starting with a clean slate as opposed to one with old chalkings, even if partly erased.


Things need a rethink as we go don the road.


Philosophical post ended.


I think I am coming down with a "doozy" of a head cold. Hope it isn't flu!!! I did get my flu shot... No guarantees though!!




Carl

 

EDIT: Oops. Replying to the last post on page 1 of 2. Feel free to disregard.

I do wish everyone would settle on maritime norms. Drivers side varies. Left right changes depending on your orientation.

Port is always Port. Starboard is Starboard.

A bank is on the Starboard.

The significant FPR on an XJS is on the Port. This is on the fuels way out of the rail. Limiting its flow here creates pressure in the rail. If the pressure exceeds the rating of the FPR then it pushes through the FPRs spring loaded valve and returns to the tank.

If you only have one FPR and its on the Starboard side of the car then that's your problem right there. But I doubt that's the case as you said that it was previously running well.

 

Up Date, new pump bosch fitted yesterday 40psi now on rail test still no start, first try 2day loud bang from exhaust pipes sounds if fuel got in2 eng, im thinking got 2 be timing or dis leads.

 

if the FPR is leaking, all you have is a higher rail pressure readout from a better pump, but not necessarily a decent spray.
Pull the injector again and look at the pattern.
How can it be timing if you have not changed anything over the winter?

 

Greg, ok will try it again,

 

Greg, removed no 1 inj, fuel spit out but not a lot, so removed all leads from dis cap removed dis cap and plastic cover under roter arm messed about with wires from trigger arm, now im getting a spray from inj each time i crank car, so im going to fix it all back together and see what happens , fingers crossed,

 

still no start ???????

 

Tonyboy
It is next to impossible to diagnose if you do not work through the possibilities methodically.
The wires you have disturbed in the dizzy might have wiggled something that is connected to the amplifier (if you have Lucas ignition, your signature does not give car info) and that might have started the ECU signal working better. Equally, you might have wiggles the injector loom while you fiddled about and that might have done something. Equally it might be something coincidental. Equally you might have stopped the spark, wrongly connected the HT leads, or knackered the dizzy cap carbon brush.
In your position I would:

• Check the HT leads are correctly connected
• Check there is a fat blue spark at the plugs (check at least the easy to get at ones
• Check the dizzy cap carbon brush is there
• Check the rotor arm is clean
• Ensure all the connections from the amplifier are all good (if a Lucas car)
• Having done all this check the injector spray pattern again

I still believe your B bank FPR is the problem.
Greg

 

greg, just been out to car with my mechanic mate for past 2 hours removed dizzy cap and rotor arm, replaced with new dizzy cap and rotor arm, tested spark on no3 plug on a bank and no3 plug on b bank good spark, tested compression over 200psi, removed inj to no1 b bank working o/k, refixed leads in right order to dizzy, car still popping, firing once and continuing to crank, if psi on rail is right and inj are working dont see how it can be FPR, if it was not working would it not hold pressure on rail, we think ECU it firing fuel on the exhaust stroke, only thing i can try now it have ECU tested. Tony