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Hot Starts

JonathanT

JonathanT

Not normal for Norfolk
Messages
1,332
Location
Wymondham Norfolk
I can get problems with hot starts. Cold starts are great and running all good. So I’m going to experiment with a stainless heat shield between the manifold and the carb (will be sandwiched through carb attachment) . It’s tray like so in the event of petrol leak it cannot drip onto the hot manifold. Third attempt coming up . First attempt rather better than the second. Tried welding corners but kept blowing through. Will Araldite the corners instead
 
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Interesting project. Might it help to shield the carb from the exhaust manifold as well? (Petrol seems to evaporate from the carb when not used for a while, perhaps because of heat from exhuast?)
 
Nice concept, I'm curious for this solution in the long term.
The hot restart problems are a common issue for the GTL models with the Zenith 28IF carb.
It's documented in the Haynes manual (the Dutch version) as well as the "solution" and (or) the modification to make.

Afbeelding.jpg

My own solution for my GTL is to apply a professional thermal ceramic coating on the complete manifold and a modification on the fuel supply system with a different fuelpump
brandstofpomp 3 aansluitingen.jpg
 
JdeW said:
Nice concept, I'm curious for this solution in the long term.
The hot restart problems are a common issue for the GTL models with the Zenith 28IF carb.
It's documented in the Haynes manual (the Dutch version) as well as the "solution" and (or) the modification to make.

View attachment 25250

My own solution for my GTL is to apply a professional thermal ceramic coating on the complete manifold and a modification on the fuel supply system with a different fuelpump
View attachment 25251
Click to expand...
Thats very interesting JdeW . I have an expensive coating applied to the manifold but I actually think I was duped. It was nothing special and is showing signs of rust. I suspect it was a spray can! Yes I have a GTL . I have a spare pump like the one in the picture above but how does that help?
 
JdeW said:
Nice concept, I'm curious for this solution in the long term.
The hot restart problems are a common issue for the GTL models with the Zenith 28IF carb.
It's documented in the Haynes manual (the Dutch version) as well as the "solution" and (or) the modification to make.

View attachment 25250

My own solution for my GTL is to apply a professional thermal ceramic coating on the complete manifold and a modification on the fuel supply system with a different fuelpump
View attachment 25251
Click to expand...
 
The hot starting problem has come about because modern petrol has a lower boiling point and on the 1100 Renault 4 there is no air flow no under the bonnet you will be better off-putting longer studs between the carburettor and manifold fitting and using two factory spacers spaces which are hard plastic or get something made to keep the carburettor away from the manifold the heat shield you are suggesting would work only if if it sits between the spacers all modern cars are fuel injection where the fuel all is in constant flow back to the tank to stop it vaporising
 
It might also be the case that the engine is flooded and has dumped fuel after a long drive rather than the fuel vaporising, you could try starting the car with the throttle held fully open until it fires, don't pump the pedal.

I would also be wary of that heat shield as it might turn into a frying pan of hot petrol, collecting it might be worse than just letting it drip.
 
There's an article attached to this modification, it's in Dutch and a bit of an effort to translate :whistle:.
The hot start problems where always an issue with the 1108 GTL's as I encountered in the 80's and 90's with my first GTL even with the normal higher octane petrols in those days, and keep in mind I drove a lot with my first GTL and with a lot I mean really a lot of miles.

The main problem is indeed that the carb is mounted directly on the in and outlet manifold. When the engine is shut off the excess heat from the manifold causes the hot start trouble. The temperature under the bonnet rises excesivly and can cause a pressure rise in the fuel line between the fuel pump and carb. This rise in presure is a cause that the float needle won't close correctly so extra fuel flows thrue the float chamber into the manifold and causes the trouble.

I'm curious about this modification described in my Haynes manual, and will apply it when I can continue working on my GTL so a 3 line fuel pump with the calibrated returnline and applying a ceramic coating on the complete manifold just for my curiosity, maybe in combination with a fan that runs for 10 minutes after the engine is shut off, just to rapidly cool the manifold.
 
JonathanT said:
JdeW

I see I only need two 'T' junctions and a fuel pump with two outlets ?

Can you send me link for correct fuel pump? 84 GTL:artist:

Perhaps this one?? https://www.melun-retro-passion.com...ec-retour-renault-r4-4l-r12-r15-r18-a110.html
Click to expand...
Hello Jonathan,

It's a 3 line fuelpump so 1 inlet, 1 outlet (to the carb, and 1 return with a calibrated (very small) opening, so 1 T-junction will be obsolete (the one with the calibrated opening
I'm just curious and will do my own modification when I can continue working on my GTL again.
Here's my link in The Netherlands for the fuelpump https://www.renault4onderdelen.nl/W...etour-(3-aansluitingen)-prod-aftermarket.html
And keep in mind the remark Paul @mr-reno-139 wrote.

Best regards, Joop
 
mr-reno-139 said:
The hot starting problem has come about because modern petrol has a lower boiling point and on the 1100 Renault 4 there is no air flow no under the bonnet you will be better off-putting longer studs between the carburettor and manifold fitting and using two factory spacers spaces which are hard plastic or get something made to keep the carburettor away from the manifold the heat shield you are suggesting would work only if if it sits between the spacers all modern cars are fuel injection where the fuel all is in constant flow back to the tank to stop it vaporising
Click to expand...
The R5 with 840 engine might be the solution it didn't have the hot start problem, only the cilinder 4 hot spot problem ;)

840motor.jpg
 
Years ago go there was problems on the Renault 21 with carburettors distorting due to excess heat solution was an electric fan under the bonnet with a timer relay to blow cold air over the carburettor after you switch the engine off no doubt somebody could improvise something similar for a Renault 4 the 850 with mechanical fan don't suffer so much as the air is circulated right up until the point the engine is switched off
 
In the piping modification drawing above, note that the one T-joint has a small constriction (effectively in the return from the carb), to keep fuel pressure up a bit so the carb actually receives fuel. This can be a restriction in the pipe rather than the T-joint, but it is necessary.
 
Jnr-Renospeed said:
It might also be the case that the engine is flooded and has dumped fuel after a long drive rather than the fuel vaporising, you could try starting the car with the throttle held fully open until it fires, don't pump the pedal.

I would also be wary of that heat shield as it might turn into a frying pan of hot petrol, collecting it might be worse than just letting it drip.
Click to expand...
This sounds very plausible for the symptoms I’ve been getting. The frying pan however has an open edge so any petrol would drip but be conducted away from the manifold
 
JdeW said:
Hello Jonathan,

It's a 3 line fuelpump so 1 inlet, 1 outlet (to the carb, and 1 return with a calibrated (very small) opening, so 1 T-junction will be obsolete (the one with the calibrated opening
I'm just curious and will do my own modification when I can continue working on my GTL again.
Here's my link in The Netherlands for the fuelpump https://www.renault4onderdelen.nl/W...etour-(3-aansluitingen)-prod-aftermarket.html
And keep in mind the remark Paul @mr-reno-139 wrote.

Best regards, Joop
Click to expand...
Thank you Joop
 
An electric fuel pump might also help with fuel vaporisation where the float chamber level drops with the heak soak from the now stopped, hot engine. The electric fuel pump will ensure a full float chamber when trying to restart a hot motor.

The owner's manual tells you to use full throttle when starting hot -: maybe they had issues back in the day.
 
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