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Spitfire fuel vaporization


sulzerman
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Hi all 

Just back from 800 mile trip to North wales.

No problems except, had fuel vaporization twice. first time was after stopping, a mile or so later car stalled. I removed engine side valances, poured cold water onto the fuel pump. All was well and engine ran perfectly. Second time car had been parked in sunshine all day, started up as normal. I left it running for a few minutes and it stopped. Checked float chambers, no fuel. I removed fuel pipe to pump no fuel, removed petrol cap, still no fuel. So sucked pipe got a mouthful of petrol, yuk! fuel ran out of pipe as normal. Reconnected and car ran as normal. Temp was really hot around 30 degrees, but we have been to France with same or hotter temps and no trouble.

Is it the unleaded petrol that is the problem?

Has anyone put heat insulation on fuel pipes? If so where and what manufacturer?

Should there be a heat insulator between fuel pump and block as it felt really hot?

I really want to heat proof the car for future trips!!

Thank you in advance

 

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SM,

You disconnected the fuel line and nothing came out, once you sucked it fuel started coming out. Sounds more like a blockage. I've had debris in the tank drifting around and blocking the outlet. Have a look in the tank.  Also I had sludge in the fuel line which periodically blocked it, then subsided. I used strimmer nylon cord to Dyno-rod the fuel lines. 

Doug

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Yes your not going to get vapour locks between tank and pump,

The heat isolator between pump and block was only used on the 1500 but replacement pumps are not able to use it and the spacer has to be removed.

  If you have a replacement  pump and a spacer then the pump stroke is inadequate

Various views on supply lime and guessing about vaporisation  

Use more rubber 

Use larger diameter supply pipe

Electric pumps

A fuel return system

Keep the filter in the boot  check its not  collapsed under the hose clip spout

Pete

 

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My daughter has had a Mk2 Spit for nearly 20 years here in Aus even in hot summers it didn't have vapor locks issues until around 5 years ago then it was a bugger not even hot days it occurred I eventually tracked it down to the plastic washer locating the float chamber to the carb body & keeping the float chamber vertical on the HS2 carbs. The plastic bush had failed letting the float chamber rotate backwards from vertical towards the exhaust extractors  hence the vaporization. I replaced the float chamber locating bush and also installed a hat shield to ensure the heat transfer was minimized. I have to admit it took me some weeks to realise this I unnecessarily even removed the head to ensure it was all OK, I also renewed and did a basic carb overhaul at the time.

Here's some photos of the home made simple aluminum sheet heat shield you will notice its mounted on the back of the carb inlet flange on the manifold so it can be removed for access without removing the carbs. The original studs were replaced with threaded bar protruding right thro the flange.

Note the front shield is scalloped for the incoming hose and also to give good access to the dip stick.

 

Regards Peter T

Front & Rear shields from top note mounting behind manifold flange..JPG

HS2 Heat Shields from underside.JPG

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Peter (not Pete!)

Your daughter's car had no heat and vapour lock problems until 5 years ago?    When was the four branch exhaust manifold fitted?  Was it around then - it's not OE!

I ask because heat transfer by radiation depends on temperature differential, and surface area.     The four branch has more surface than the OE cast manifold, so will radiate more heat.

In the same way, as Pete says, your solution is an excellent one, as the alloy shield will receive heat from the exhaust side, but radiate less from the carb side, as it will never get as hot as the manifold.   If anyone wants to copy you, alumium is the best material for its high heat conduction, unlike steel.   

John

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Great idea Peter

Will look to see if I can do something like it, for the Strom's, on my Vit (have some stuttering on very hot days, slow moving).

Looks like the're clamped on top and bottom studs?.  If so, could they be clamped on just the bottom ones?.

Dave

 

Edited by daverclasper
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if you get problems you think are heat related why not do a test and hang some cooking foil as a shield.

if its makes a difference  then belt and braces , support shields from any convenient stud etc,  do have a think about engine 

vibrations  as a extended panel held at its end will vibrate and can end up with  a fatigue fracture  given time .

Pete 

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Ref the extractors being a 66 Mk2 I assumed they were OE, definitely look it! The extractors have been there since we brought it in 2001. suppose I could have thought about wrapping them, but it looks so untidy!

As Pete said one bolt mounting would fatigue but you could just mount them on the bottom stud/threaded bar but you would have to have a one piece shield where mine was  two separate shields one for each carb.

It took around 2hrs to make the shields after using a cardboard template to get the mountings right you'll notice the shield has two horizontal folds, that was my error nothing ever goes directly to plan! I reckon they cost around $5Aus to make a bit of scrap Al from the supplier.

The other thing about the heat shields is hopefully it will deflect any fuel leaks from the hoses/jets/floats away from the exhaust,  I've had a bad run on hoses failing cracking in around 2 yrs, only around the pump and carb connections not the in line fuel pipe connections. Hopefully the last lot of Aus McKay hose will fair better with ethanol fuel says it is OK?  just did the Vitesse & Sprint last week.

The 2500TC I had in the late 70's used to have a minor vapor lock on very hot days usually after being stuck at the lights, and a Series 3 XJ6 in the early 80's was a bugger I found changing the fuel filter before summer cured that, gee there was some heat in that cars engine bay, there was no where for it to go, but it never boiled. interestingly Jaguars solution to cool the fuel was to run the fuel pipe in parallel and enclosed with the air conditioner cold supply pipe. 

Somewhere I have the dimensions of the two shields I made.

Peter T

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Aren't all 125 & 150 CD Stroms with the  inlet manifold bolts/studs at 45degrees.

Just looked at my Vitesse Mk2 and I think you could fit a one piece heat shield via the bottom bolt/stud by replacing the stud with threaded bar right thro the flange and bolt the heat shield on the back of the flange it would be held on by only two bolts not 4. If you need a heat shield, but my Vitesse has never suffered from vaporization even here in Aus!.

Peter T

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Hi all 

Think I have discovered the problem. 

Fuel pump failed tonight, had to be trailered home!! Nearly stopped on one of the busiest roundabouts in Exeter😱!!

Any recommends for new pump, or are they all the same?  Or should I go electric?

many thanks

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If you want to go electric, strongly recommend Huco. Probably the best quality you can buy, and they have options of at least 2 pressures (you want the lowest) and whether mounted at front or rear of the car. Rear has the advantage of staying away from excess heat, at the expense of longer wiring runs.

New mechanical pumps seem to be rather too high a pressure, and need external regulators? A rebuild kit may be available if a genuine pump.

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Hello Johny

                      As Clive says fit a HUCO low pressure one I had one on Spitty for 4+ years with no problem and fills the carbs before you try and start the car(not for the Konkers lot?)

But you must fit a safety cut off switch in case of a shunt etc(plenty on Fleabay just make sure you get the plug as well)

Roger

ps never had a problem with heat and we went to Spain twice and Italy in proper heat mounted on the baulkhead

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13 hours ago, johny said:

No need to go electric as that introduces even more complication. How about a rebuild kit for your old pump?

Perhaps if you have an original Triumph pump but I'm going to swap to electric over the coming months as I'm getting through repro pumps at the rate of about 1 per-year (they just start leaking everywhere) - and the repro pump designs seems to change subtly every year so you order a rebuild kit and it isn't quite right for the repro pump you bought from the same supplier last year...

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If you decide against electric for any reason, go for one of the glass-topped Delco pumps - they come up all the time on eBay, both new and used. The internals are all the same so available everywhere and dead easy to recondition simply by removing the glass bowl; plus you can watch the fuel float past when the engine is running...

Make sure you get one with the correct actuating lever for Triumphs, but you can swap them about easily enough just by pressing out a roll pin.

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  • 3 weeks later...
1 hour ago, johny said:

Looks good. Which cut off switch did use and where is it located?

Hello Johny

                     Go with the Huco they are quieter I fitted the cut off switch in the middle of the baulkhead and a small hidden switch in the glove box for anti theft and when working on the car

Roger

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