Hello!

Ok – so my engine has a whistle for about 5 minutes after starting and I was able to locate where it was coming from - see pics.


So this hose is coming from the fuel injection rail. Should the whistle be scaring me in that I should not drive this until it is fixed? I pull the hose and it seems to be in pretty good shape – it is plyable with no cracks or anything; however the nozzle it fits over is completely smooth so I can’t imagine it carries any kind of real pressure.

If the hose seems to be ok is there some sort of compound I should use to tighten the seal? Should I just replace the hose – and if so can someone tell me what I am looking for (material, diameter, etc)?

Thank you!

-martin

 

It's a vacuum hose. There are one of 2 possibilities - split hose that is leaking vacuum, or the sensor is broken and leaking vacuum. The hose with the white stripe looks a bit short, I'd try replacing that.

Also, I notice that heat shield on your cruise control bellows is upside down. It's the piece that is sitting in between the fuel rails, and in the photo immediately toward the top of of the photo from your circled sensor. The shield should be under the rubber bellows to shield them from the heat of the engine, not trapping the heat around the bellows and cooking them.

 

Hi Bortbox

That Plastic 'thingy' is the Thermal Valve that is supposed to assist with hot starting and those pipes are Vacuum pipes

Hence the reason that those spigots are smooth

The reason for the 'Whistling' 'could' be down to a blockage in a narrow hole under its lid

Don't break it, as they are NLA although the one for the XJ6 is the same

Check out this link to see how it all works

EAC 5086 EAC5086 Jaguar Vacuum Thermal Valve

 

It's definitely where the hose meets the nozzle. I can crimp the end by hand and the whistle stops. If I just manipulate the sensor it makes no change.

Do you have any idea what the spec is on that hose?

Thank you!

-martin

 

I don't think there is a rigid spec on the hose, if you measure the OD of the nipple on the sensor an autoparts store should be able to match it up. Or just take in the old hose as a sample.

I've used tubing for the windshield washer and it works fine as long as you get the right size.

 

The one I took off a 92 was a blind hole in the fuel rail, there is no direct contact with the fuel and sensor.

 

Agree, its a pad sensor, NO direct connection to ANY fluid at all.

Most are removed with no ill affects, but others want them as made.

The hose is nothing special at all, just a standard automotive vac hose of the size related to the spigot (as mentioned).

 

I'll edit that last bit out to avoid confusion but what about the one on the other side, is that blanked off from the fuel as well?



Is this Sensor in contact with the Fuel or is it blanked off like the one on the other side?

 

If that Thermal Sensor (The one with all the Vacuum Pipes) isn't really needed, could you remove it from the Fuel Rail altogether

And then replace it with something a bit more useful, by drilling a hole through its blanking plate in the Fuel Rail

Then screwing in either a Fuel Pressure Gauge or a Schrader Valve into the now empty stub, which may or may not need an adapter

Good idea or Not?

 

Terrifically good idea. Even better, fit an electronic pressure sensor and have the gauge in the cabin!
Greg

 

Oh Wow, Greg Cheers!

Would I just pull all the Vacuum pipes off, or would I have to block them off in some way and

Where would I get an electronic pressure Sensor, with the right thread to fit in the Stub

As for drilling the hole would a small hole be ok or would it need to be full size?

 

I had a Range Rover once and was interested in the fuel pressure and did this, worked fine. You would be surprised how much fuel pressure can vary as the FPR or fuel changes temp. At least I was on the RR.

 

Hi Greg

Too Cold for the 'Deckchairs' at the moment but what I will do is take the Fuel Rail off my Parts Car and experiment with that

And then if I take it into my local Hydraulic shop, they might be able to sort me out some adapters, to take a Gauge

 

This is the sort of thing, OB. Look at the sensor pic, this needs a boss welded to the rail, that's all. Then just wire it up.
https://www.glowshiftdirect.com/tint...ressure-gauge/


Greg

 

Hi Greg

Cheers! got the idea

But I was thinking more along the lines of fitting a Schrader Valve, which I could put on all my Cars

To use only as a diagnostic check, for the Fuel Pump/Fuel Filter and Leaking Diaphragm on an FPR

Which took a long while to track down, the last time it went bad on 'Cherry Blossom' which I would add I could never have done

Without the Fault Finding Skills of Yourself and 'The Wizard'

So I'm thinking of a Schrader Valve and a Fuel Pressure Gauge which I can get off Amazon for about £20 + The cost of the Valve

 

OK, understood. I am not 100% sure on the reliability of schrader valves in this application though. Maybe someone else will be able to advise? Greg

 

REALLY.

Where is the FAITH guys, fair dinkum.

OK, later cars, and USA cars have a schrader in the fuel rail, we dont. Never looked the S Types, care factor quite low, the car does what a JAG does, why mess with it.

The a/c charge ports are sealed with a schrader valve, and that pressure is WAY higher than any fuel system we will encounter.

Once you have sorted the V12, and verified pressure properly, drive it, worry not, and repeat in 15 - 20 years time, works for me.

I see all this stuff as something else to go wrong, and worry about, too old for that, fact.

 

Hi Bortbox

I took the Thermal Switch off (my parts cars) to see how it works and what it does



When Cold this Valve is open allowing Vacuum to pass through and closes when it reaches a certain Temperature



The Thermal Switch allows Vacuum to pass through it, from the Inlet Manifold to the FPR (Fuel Pressure Regulator)

In Normal Operation: The Thermal Switch/Valve is Open by default and allows Vacuum from the Inlet Manifold to pass to the FPR Fuel Pressure Regulator

The Default Position for the FPR is Closed (within its set parameters) and needs Vacuum to make it open and operate correctly

At Idle the Vacuum is Higher which gives you a maximum return flow to the Petrol Tank and because of this the Fuel Pressure will be lower

Which also gives you Minimum Injector Pulse Length at Idle

If/When, the Thermal Switch Sensor reaches a Certain Temperature, it can either reduce or cut that Vacuum off (not sure which)

If/When this happens, this loss of Vacuum causes the FPR to Close, which then increases Fuel Pressure and also Injector Pulse Length

Enriching the Engine (ie giving more fuel to the Injectors) to make Starting easier if the Fuel in the Rail gets too hot and starts to Vaporize

Then once the Engine Starts and the Fuel starts Flowing normally again, then the Valve/Switch re-opens allowing normal operation

So what this could mean in your case is, if you've got a leak in your Vacuum Hose from the Inlet Manifold, through the Thermal Switch/Valve to the FPR

The FPR will not operate properly and start to close off or 'Maybe' even close completely depending on how bad the Vacuum leak is

Which could then increase Fuel Pressure and make your Car run Rich, as the Flow Back to the Fuel Tank would be more restricted

So to prevent your Car from Running Rich, make sure that the Vacuum Hoses from the Inlet Manifold, through the Thermal Switch/Valve to the FPR are not leaking

That's the basics of how it works, without getting too technical