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Hot STARTS CURE ?

JonathanT

JonathanT

Not normal for Norfolk
Messages
1,332
Location
Wymondham Norfolk
Hello all it’s been some time since I was on here .
My R4 has suffered problems with hot starts . However, when I change to the new hire octane E5 fuel. The problem seem to go away. However, it’s back with avengeance!

I made up a generous heat shield to experiment with and placed it between the manifold and the carburettor. I took the car for a spin round the block and then left the car with the bonnet shut to see what would happen. Turns out the problem is still manifest. The carburettor body was quite cool but the fuel in the pot was still boiling vapour was escaping and fuel was being pushed over the overflow clearly this is a dangerous state and I can’t allow this to continue. On my car, the fuel filter is on top of the engine. And I think this is where the majority of the heat is being collected so my plan is to fit an electric fuel pump and place it away from the engine itself then run the fuel pipe away from the engine up to the carburettor via a fuel filter
I have seen various in the past which involve a loop allowing the boiling petrol to be transferred back to the supply. However, I still see this as a dangerous situation as it’s not curing the problem it simply making the symptoms go away. I would be pleased to hear if anyone else is having problems and if they have any solutions to offer.
Jonathan

327D78AE-31B2-46BE-A125-2F6228068663.jpeg 1F8A1011-D82A-467E-A24C-EE68AD231531.jpeg
 
Hi Jonathan

I noticed the carburettor has not got the brass dome on the top half of the carburettor which houses a gauze filter as per an original Zenith 281F. Might this have something to do with the issue you are having?
 
Yes the air filter is not fitted in this photo so you can see what I meant by heat shield
. Air filter was re-fitted all exactly as normal but still big problem
 
Hi again Jonathan

Note the brass/silver dome riveted in place at the top of this original Zenith 281F which I believe acts as a breather for the float chamber.

image.jpg
 
JonathanT said:
Hello all it’s been some time since I was on here .
My R4 has suffered problems with hot starts . However, when I change to the new hire octane E5 fuel. The problem seem to go away. However, it’s back with avengeance!
Click to expand...
This answer might seem a little "left field", but may I ask which brand of E5 you've been using? I mention this because Esso "99" was, until recently (and may possibly be still) ethanol-free. For various legal reasons Esso were obliged to sell it as "E5", but in fact it was "E0". I use this in my car as its octane rating is higher than most other "premium" fuels, having a rating of 99, as opposed to the more normal 97. This, coupled with a lower (or zero) ethanol percentage makes it a better buy in my opinion. As I say, it's possible Esso now do add 5% ethanol into their fuel, and this change might (if you're using it) coincide with the problem reoccurring.
 
jcarruthers2 said:
Hi again Jonathan

Note the brass/silver dome riveted in place at the top of this original Zenith 281F which I believe acts as a breather for the float chamber.

View attachment 32976
Click to expand...
Yes I see ! I do have original carb and I’m curious as ti why I had not noticed it’s not on the current one - however that’s a breather and is not itself a cure as such
I think my carb must have a breather but maybe looks different
 
André4Renaults said:
This answer might seem a little "left field", but may I ask which brand of E5 you've been using? I mention this because Esso "99" was, until recently (and may possibly be still) ethanol-free. For various legal reasons Esso were obliged to sell it as "E5", but in fact it was "E0". I use this in my car as its octane rating is higher than most other "premium" fuels, having a rating of 99, as opposed to the more normal 97. This, coupled with a lower (or zero) ethanol percentage makes it a better buy in my opinion. As I say, it's possible Esso now do add 5% ethanol into their fuel, and this change might (if you're using it) coincide with the problem reoccurring.
Click to expand...
That is VERY interesting and YES it’s esso I buy - that could well be the problem thank you for the suggestion - I’m going to try a number of solutions but mainly get the fuel line away from the hot engine
 
I would be wondering about the carb too. Normally when you have fuel vaporisation the fuel boils off through a breather. The boiling should never force fuel out of any overflow.

Hot restarting is typical for the R4. Good to see another heatshield there. I did some work on fuel vaporisation on the MG a few years back. Might help with some ideas - https://www.vord.net/cars/helga/mga-fuel-vaporisation.html
 
André4Renaults said:
This answer might seem a little "left field", but may I ask which brand of E5 you've been using? I mention this because Esso "99" was, until recently (and may possibly be still) ethanol-free. For various legal reasons Esso were obliged to sell it as "E5", but in fact it was "E0". I use this in my car as its octane rating is higher than most other "premium" fuels, having a rating of 99, as opposed to the more normal 97. This, coupled with a lower (or zero) ethanol percentage makes it a better buy in my opinion. As I say, it's possible Esso now do add 5% ethanol into their fuel, and this change might (if you're using it) coincide with the problem reoccurring.
Click to expand...
That is VERY interesting and YES it’s esso I buy - that could well be the problem thank you for the suggestion - I’m going to try a number of solutions but mainly get the fuel line away from the hot engine
malcolm said:
I would be wondering about the carb too. Normally when you have fuel vaporisation the fuel boils off through a breather. The boiling should never force fuel out of any overflow.

Hot restarting is typical for the R4. Good to see another heatshield there. I did some work on fuel vaporisation on the MG a few years back. Might help with some ideas - https://www.vord.net/cars/helga/mga-fuel-vaporisation.html
Click to expand...
malcolm said:
I would be wondering about the carb too. Normally when you have fuel vaporisation the fuel boils off through a breather. The boiling should never force fuel out of any overflow.

Hot restarting is typical for the R4. Good to see another heatshield there. I did some work on fuel vaporisation on the MG a few years back. Might help with some ideas - https://www.vord.net/cars/helga/mga-fuel-vaporisation.html
Click to expand...
Malcolm good to hear from you again and thank you for keeping this brilliant resource running .

Yes fuel is boiling and yes it is a breather as you say - I have just checked and it does have a breather cap

The carb I have been using is good quality repro - very very similar to the original 28if
Honestly no problems with it

The fuel is clearly hot as it comes into the chamber - so I’m pretty convinced there are several things happening but the worst contributor beyond the moder fuel itself is the filter on top of the rocker box

IMG_1910.jpeg IMG_1908.jpeg
 
I was wondering about that strange huge metal fuel filter as well ? Metal retains the heat, so I would change it for the smaller plastic see through original type. So you can see the fuel flowing. We use Shell 98 (Ethanol free) in Classic cars over here.20240416_081952.jpg
 
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Cyprusnoddycar said:
I was wondering about that strange huge metal fuel filter as well ? Metal retains the heat, so I would change it for the smaller plastic see through original type. So you can see the fuel flowing. We use Shell 98 (Ethanol free) in Classic cars over here.View attachment 32979
Click to expand...
Jjad Nice to be in contact again yes I agree with your point re plastic. I think however if you had ethanol in your fuel you might suffer too

I have a small plastic filter on order
 
The R4 GTL with Zenith carb has indeed a history with hot (re)starts, even the Hayes mentioned a modification regarding fuelpump and fuel lines.
Also I came once accross an article regarding a combination of heatshield and real ceramic coated manifold.
A single sheet of metal is not really a heatshield, it must consist of several layers to radiate the heat.
I don't have experience with the Chinese :vsad: remake Zenith but on several forums (Netherlands as well as this forum) people are not really convinced.

Heatshield_01.jpg Heatshield_02.jpg

Heatshield_03.jpgHeatshield_04.jpg
 
malcolm said:
I would be wondering about the carb too. Normally when you have fuel vaporisation the fuel boils off through a breather. The boiling should never force fuel out of any overflow.

Hot restarting is typical for the R4. Good to see another heatshield there. I did some work on fuel vaporisation on the MG a few years back. Might help with some ideas - https://www.vord.net/cars/helga/mga-fuel-vaporisation.html
Click to expand...
Malcolm I have just read your MG thread
You had exactly the same idea as me a small computer fan etc .
I’m going to route the fuel away from the engine and straight to the carb

Note your comment at bottom of MG post that petrol must boil close to 100deg
I strongly suspect it’s substantially lower than that but anyway thank you kindly for your thoughts - I will press on with my experiments
 
JdeW said:
The R4 GTL with Zenith carb has indeed a history with hot (re)starts, even the Hayes mentioned a modification regarding fuelpump and fuel lines.
Also I came once accross an article regarding a combination of heatshield and real ceramic coated manifold.
A single sheet of metal is not really a heatshield, it must consist of several layers to radiate the heat.
I don't have experience with the Chinese :vsad: remake Zenith but on several forums (Netherlands as well as this forum) people are not really convinced.

View attachment 32982 View attachment 32983

View attachment 32984View attachment 32985
Click to expand...
I really like your design and agree a layered approach would be best

My attempt was a first experiment and it is currently fouling the accelerator cam on flat out .

I will remodel incorporating a layered approach

I have seen modern exhausts wrapped with a crinkly aluminium sheet - the extra surface area must help
Might try and find a piece of that lying on a road somewhere

Good to be in touch and thank you for your suggestions

Jonathan
 
Would a soldering mat placed on top work cut around the carb and held on somehow? thinking the type that plumbers use when heating pipes with a blow torch to avoid damage to surrounding areas? similar material they use on exhaust headers to retain heat?
 
After reading this thread, I have decided to fit an additional extra thick asbestos gasket on my carb. All I had to do was fit some longer studs on the manifold. An easy job.
20240417_105334.jpg
 
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