White stuff in the carburettor mystery

A few weeks ago I moved my E-Type Jag (4.2) (which has had a recent history of baffling starting problems) after it had been laid up for several months to our new house and garage. It just about made it having ground to a halt on the short journey several times. After a further delay of a few weeks I have now investigated the problem. I initially suspected a fuel problem and checked out the fuel pump but that seemed to be working. I then removed the float chamber cover to the first SU carb only to find it full of a strange white slimy gunge/paste which I had never seen before. I subsequently removed the air filter and air intake assembly so I could see the carbs better and found that the first and third carbs had become completely gunked up with this stuff. In the first carb was completely blocked with this white goo.

My initial conclusion was that this was caused by old petrol having deteriorated in the fuel tank and gradually choked up the carbs. But the problem is so severe that I don't think this likely. I am currently removing the inlet manifold and the signs are that the deposits are in there too (certainly in the theromstat housing).

However, my suspicions have now turned to the braking system(!) since I have discovered that the vacuum chamber (an extension in Jaguars to the servo mechanism which provides a back-up supply of vacuum to the braking system) is half full of what looks a lot like very old brake fluid and I suspect that a seal on the servo has deteriorated allowing brake fluid to be drawn into the vacuum chamber and perhaps also the inlet manifold and back to the carbs. Perhaps this would account for the build up of white gunge.

I would be interested to hear of anybody experiencing a similar problem with a Jag or other car who might have some ideas. Would brake fluid getting into the inlet manifold cause this or is this a fuel problem? I certainly have no recollection of the car belching white smoke which I would have expected.

Anyway, what is the white stuff?

Thanks,

GBH

Reply to
GBH
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I don't see any way in which brake fluid could get into the float chambers even it got into the intake manifold. Maybe something got into the petrol tank like a nylon washer and dissolved or it could just be aluminium corrosion which is white mixed with old fuel. Tricky one but I'd be interested to hear any definite outcome if you solve it.

Reply to
Dave Baker

I have often seen this on older cars, AFAIK it is alloy corrosion, probably from condensed water , obviously the vacuum system should not have anything in it, but that would only make white smoke following heavy braking and could not get back into the carbs. If the use is infrequent then you could try some of that special stuff that mixes with the fuel to absorb moisture, car shops sell it.

mrcheerful

Reply to
mrcheerful

This is a bit of a long shot, but I had a similar problem a couple of years ago on my 4.2 E. I use Millers VSP as an additive, and when filling up at my local Shell garage I took the top off the VSP bottle, then watched with horror as the tear-off top fell into the fuel tank. A few hundred miles later the old lady came to a halt and only recovered after a complete clean and flush through of the entire fuel system. Didn't see any "white stuff" though, which is why I say it's a long shot.

But I guess as Dave says it might have dissolved in the petrol and produced something 'orrid.

Good luck!

Geoff MacK

Reply to
Geoff Mackenzie

GBH,

You haven't upset someone recently and they've put sugar in your tank maybe ?

Andrew Mawson

Reply to
Andrew Mawson

Andrew,

Don't think so! But the thought did cross my mind. I couldn't find a single stray grain of any sugar in the filler cap cavity/tray and just to convince myself I (rather bravely I thought) tasted some of the goo. No sweetness at all.

GBH

Reply to
GBH

In article , GBH writes

My son parked his VW Scirocco in my driveway for about a week, and I noticed an odd looking build up of yellow, waxy gunk underneath the car.

On investigation, I found a pinhole in the fuel pipe directly above the deposit. As I watched, a small drop of petrol fell onto the waxy stalagmite, so there was no question about what had caused it. The VW ran on normal unleaded petrol.

God knows what chemicals it contains, but something solidifies when exposed to air.

The received wisdom from the RREC is that pre-war Royces should use unleaded petrol without additives. When I took my 1926 Rolls-Royce for its last MOT, I met an old, retired Rolls-Royce mechanic. He asked whether I had trouble tuning the carburettor. When I told him it was driving me crazy, he said: "You never will get it completely right with modern unleaded petrol. That stuff contains all sorts of shit".

Peter

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Reply to
Peter Adams

The message from Peter Adams contains these words:

Something similar happened to me some time ago (perhaps 10 years) but that was leaded petrol on a Sierra 4*4 estate and the deposit built up round the fuel line rather than on the ground. It had formed a round excrescence much the same size as a cricket ball by the time I noticed it.

Curiously I have just had 2 (probably long term) leaks fixed on my current car (Audi, unleaded) and there was no buildup at either site. Only difference I can think of is that while the Audi only leaked when the fuel system was pressurised the Ford leaked less but continuously.

Reply to
Roger

----snip----

Oh, you've met my ex-lodgers..... Entirely possible.

Geoff MacK

Reply to
Geoff Mackenzie

_snip-

Is it the original RR carb, or a later mod?

Geoff MacK (ex RR20. 1927, RH change not that horrible ball centre thing)

Reply to
Geoff Mackenzie

In article , Geoff Mackenzie writes

It is the original Rolls-Royce brass 3-in-1 carburettor - all 17 lbs of it. I weighed it when I foolishly sent it to a RR 'expert' for overhaul, and got it back not much improved, but with a bill that took my breath away.

I had to learn to do it myself, and four strip-downs later, I know that carburettor quite well. The great revelation came when I realised that just one sixteenth of an inch adjustment on the high speed jet is the difference between fully rich and fully lean. This knowledge enabled me to improve the petrol consumption from 5 to 20 mpg.

My car also has the original Autovac to supply petrol - and a remarkably efficient and reliable mechanism it is, too.

There are people who have fitted electric fuel pumps and SU carburettors, and claim great improvements, but I consider that vandalism - if not sacrilege. I am not the owner of my 1926 car - merely the custodian pro tempore. I know she will still be running long after I have been called in to the pits.

I'm sure I'm not the only member of this group who remembers the 1950s, when old cars were not worth much, and there was a vogue for fitting Perkins diesel engines to Rolls-Royces, particularly the 7.688cc Phantoms. These hybrids failed to appreciate in value like original cars, so they have all now been re-converted or scrapped.

As for the gear lever, mine is the original right-hand, 'hot knife through butter' gate change. I'm pretty sure the 'horrible ball centre thing' was fitted only to the cars assembled at the American plant in Springfield, Massachusetts. That always struck me as odd, when they retained the right-hand steering.

To revert to the original topic of waxy, yellow gunge, I forgot to mention that after removing my son's car, I left the stalagmite on the drive to see whether it would become petrified. It didn't. When it was no longer sustained by new drips, it evaporated and disappeared within hours.

Peter

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Reply to
Peter Adams

-snip-

The one I drove had a fuel pump and SU, but the chap we bought it from, David Scott-Moncrieff (wonderful character!) let us wander around his estate and pick up any bits we wanted. These included a proper RR carb and Autovac, and once fitted the old girl went much better.

I'm by no means an RR expert, but I think the earliest 20's all had the centre ball change and went over to RH change around 1925. I didn't know Springfield assembled 20s - I thought it was only the larger ones, but again I'm not an expert.

Isn't that right hand change lovely, though?

Geoff MacK

Reply to
Geoff Mackenzie

In article , Geoff Mackenzie writes

"Purveyor of horseless carriages to the Nobility and Gentry"

He is dead now, unfortunately.

Ah - now I'm with you. You were talking about the original 20hp 3-speed gearbox with central change. Your date is spot on - it was changed to

4-speed RH in November 1925.

When under development before its launch in 1922, the 20hp was known as the Goshawk. I have often wondered why the name was not retained. Perhaps Riley had a monopoly on all the birds of prey.

Yes it is - and you can always spot an experienced 20hp driver. He's the one who can enter the car without getting the gear lever up his trouser leg.

Peter

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Reply to
Peter Adams

It was. They used for an aero engine which didn't work. Probably put them off it for good.

Ron Robinson

Reply to
R.N. Robinson

A feat which is also remarkably easy on a Bentley R-Type.....

Alex

Reply to
Alex

Thought the Goshawk was a sort of half a V12. Don'think it put off really, they weren't bad about sticking engines into quite a few rather good aeroplanes.

Geoff MacK

Reply to
Geoff Mackenzie

I meant put them off using the name, not making aero engines. The Goshawk was a derivative of the Kestrel and is described as having 'evaporative water' or steam cooling. It was used in Supermarine's Type 224, designed in answer to Air Ministry specification F.7/30 (according to 'The Rolls-Royce Story", Book 1). Luckily R. J. Mitchell and Rolls-Royce went back to their drawing boards and came up with the Spitfire and the Merlin respectively.

Ron Robinson

Reply to
R.N. Robinson

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