Hi Guys

Nice day grab the Keys go for a drive!

And while we were out 'Tripping' I had a bit of luck, well sort of anyway, as I came across a sort of Auto Jumble where I picked up a few bits and pieces that could come in useful

One of which was a Carb Balancer, which would come in useful to balance the Twin SU's on my MGB, which was only a couple of pounds but probably £30 New and although I don't need it at the 'mo' I just thought why not

But what was of even more interest to me anyway, was a box full of odds and ends, priced at 50p each one of which was a 'Thermal Hot Start Switch' for a Jaguar XJS

OMG! that's just the thing I need! or maybe not!

As completely unbeknown to me that Thermal Hot Start Switch on 'Cherry Blossom' was full of Wax, as it is supposed to be although I didn't know that at the time

But what happened next completely freaked me out, as all day long there was a very Sweet and Sickly sort of smell in the Air

At first I thought it might be some sort of Chemical used by Farmers for Spraying their Fields but that smell was still hanging around when we got home

And so I opened the Bonnet/Hood of 'Cherry B' and had a look at the Engine, where one of the Injectors looked as if it was leaking Fuel into the Vee!

Which meant She could have caught Fire at any moment!

But finding the Source of that leak was proving a Nightmare!

As after days of driving myself crazy trying in trying to find the mystery leak that wouldn't go away, I finally managed to trace it to a Faulty FPR (Fuel Pressure Regulator) on 'B' Bank, where the diaphragm was leaking!

But that wasn't all, because this FPR is also connected to the Thermal Hot Start Switch and the Vacuum from the Inlet Manifold is drawn through the Thermal Hot Start Switch which in turn is then connected to the FPR

So what was actually happening was Raw Petrol from the leaking diaphragm of the FPR was being drawn through the Thermal Hot Start Switch, which was then dissolving the Wax inside and then dripping down all over the Injector underneath it

Which gave the impression that the Injector was leaking out of the rim (which after finally sussing it out it wasn't!)

And so in order to Fix it I replaced the FPR but as the Thermal Hot Start Switch was only good for the dumpster, I decided to by-pass it and go straight from the Inlet Manifold to the FPR

In the UK it Seldom gets Hot enough to need a Hot Start Switch and so I wasn't planning to replace it anytime soon but since I picked one up at this Auto Jumble, I am undecided as to whether to replace it or not

Just in case the same thing happened again in the future and getting Paranoid about that now



My 50p Thermal Hot Start Switch from an Auto Jumble (should I replace the broken one or leave it off altogether?)

You can also read the Full Story of this Mystery Fuel leak complete with all the Pics on Page: 87 of my 'Cherry Blossom' restoration thread and here is a link to that Page: Mystery Fuel Leak on 'Cherry Blossom' and how it was solved

 

OB
No. They are a waste of time. If you ever leave the car parked in hot sun for a few hours, just cycle the ignition on and off a few times to get the pump pushing new fuel into the rail. The simpler the better, say I.
I had a range rover once and it was a sod to start if left on a hot day. I installed a dashboard button to run the fuel pump and after 10 seconds of that, it started perfectly. It is all about vapour in the fuel rail that happens when they are left parked on a hot day after a hot run.

 

Hi Greg

Cheers!

Good idea, at least that's one less 'Gizmo' to restrict the Vacuum to the FPR

 

Does this vapour thing even happen with the 'newer' fuel rail design? I've long since smashed every rich idle or fuel hot start, fuel cannister carbon junk item I could find and never had the car not start after being red hot.

 

Sorry, no idea. But if you have no problem, all good?

 

Hi Vancouver

Since all the Wax mixing with Petrol from my leaking FPR has now run out of my Thermal Hot Start Switch and dumped this mixture all over the Injector underneath it (which is now cleaned off but made me think that the Injector was leaking round the rim)

I wasn't planning to replace it anytime soon but just happened to pick one up at an Auto Jumble for 50p

Not having it connected has not made any difference to the Starting and by-passing this from the Inlet Manifold direct to the FPR in the way that I have done, also helps to ensure good Vacuum to the FPR

Which will help to ensure that my Car doesn't run 'rich'

If anyone wants to see what happened and how I managed to fix it, there is a full description and Photos here but I could not have done this without 'The Wizard of Oz' because I didn't know the Hot Start Switch had any Wax in it but He did!

I would never have 'Sussed' the problem out, without knowing that!

Mystery Injector Leak That Wasn't!