Hi gccch

This sound symptomatic of a failing diaphragm which is inside the FPR 'Fuel Pressure Regulator' on 'B' Bank, which is the FPR on the same side of the Car as the Oil Filler Cap

Don't worry about the FPR on 'A' Bank, as it isn't needed and was eliminated on the later Cars

If the Diaphragm inside the FPR on 'B' Bank Starts to fail, then by default this can result in lowering the Fuel Pressure, then guess what? She could be a nightmare to start

A new one is about £45 (uk) and is very easy to replace but don't do it on a hot engine and disconnect the battery, just to be on the Safe Side

The Other thing that it could be is a Blocked Fuel Filter £10 or a Fuel Pump that could be on the way out £35 so best to start at the Cheap end and then work your way up from there

You can See the FPR on 'B' Bank about halfway down on Page:87 of my 'Cherry Blossom' restoration thread including Pics

Click: on the Link Below to see all the Photos

The FPR on 'B' Bank had a Leaking Diaphragm and had to be replaced

 

If the car is a 92, then it only has one fuel pressure regulator and it looks totally different from earlier cars. Check it anyway

Were the fuel lines replaced/rebuilt lately? If so, maybe the non return valve was omitted. It will be spliced into the rubber fuel line that runs from the metal fuel line on the inner fender/wing to the fuel rail. If these hoses are old, then perhaps you have a bad non return valve.

But... to be certain either way, t-in a fuel pressure gauge on the high side. Don’t make the fuel pressure gauge a dead end, it has to T off. You can get a cheap Chinese one that will work at least once.

 

 

Hi gccch

It sound like a failing diaphragm on the FPR on 'B' Bank, in view of what you've just described above

 

 

Hi gccch

All you need is a New FPR for 'B' Bank which is very easy to put on but don't forget to put the pipe back on the other end of it, as that is the return Pipe to the Fuel Tank

Make sure you do that properly, as if that Pipe comes off, then you could have a Fireball on your hands!

FPR diaphragm failure is a lot more common than you at first may think and can play havoc with getting the Car Started and on my own Car, I've replaced that twice in just 3 years

As for the one on 'A' Bank don't bother to buy a New one, as it isn't needed and if you know what you're doing can be taken out of the Circuit altogether and then just bridged with Top Quality high pressure fuel pipe, or else you can just leave it as it is

 

 

Hi gccch

You could well have hit upon the cause of the problem, as a loss of Vacuum anywhere is a great big No! No!

Where any loss of Vacuum on the FPR could make your Car run rich

So get the Vacuum Pipes sorted out first to make sure that there are no leaks and then see if you find there is any improvement

 

So I have had some work done and this problem has gone away. New ignition coils were needed to solve intermittent loss of power. Also got my AC fixed and the cats cleaned out.

Car is running and idling very nicely and keeping me comfortable. The FPR had a small leak but the mechanic confirmed it is working properly.

Still cranks for a long time before starting. That really bugs me.

 

How long is "long"?

5 seconds? 15 seconds?

Under any and all conditions?

I've owned some cars that would start on the first spin of the starter. My V12 Jags have always needed a few spins....although not to the point where I'd consider it to be excessive or 'extended cranking'.

Cheers
DD

 

Always longer when warm and up to ten seconds. He checked the FPR and said it was fine. He thinks maybe the check valve which I am unsure where that resides in the 92 model. But I think I gathered form the conversation it would be in the tank.

 

Ten seconds is certainly excessive.

Don't take mine as the final word but I'm not so sure about the check valve being a culprit. A healthy fuel pump will re-pressurize the fuel rail almost instantly. Maybe 2-3 seconds at the most......which, coincidentally, is the duration of the "prime" function of the fuel pump circuit on the V12s.

A quick experiment would be to turn the key 'on' and listen for the pump. It should run 2-3 seconds. Turn key 'off'. Repeat this 'priming' exercise 2 or 3 times....which should be more than enough to pressurize the system. Now try starting the engine. If the engine starts quickly, you're on the right track.

Cheers
DD

 

 

Then you may indeed have a drainback/pressurization problem.

I dunno where the check valve resides. But, if the location remains a mystery, a universal check valve could probably be plumbed-in without too much fuss.

Cheers
DD

 

Hi gccch

'The FPR had a small leak but the mechanic confirmed it is working properly'

The FPR shouldn't have any leaks

One of the reasons why I would never take my Car to a 'Shop'

A New FPR on 'B' Bank may certainly help to fix your slow start problem

 

The FPR leaked where the fuel line enters into it. Not the FPR itself.

 

Hi gccch

A fuel leaks even worse!

As a little drop of Petrol weeping out around a Pipe, could easily turn your Car into a Fireball