Solex problems / starting from hot

[ianj]

Hi all, last year I started having problems with the car cutting out whilst on a drive and then not starting again until it had cooled down. I have installed a new tank and completely flushed the carbs as when I inspected them it turned out that there was all kinds of stuff floating around in there from the original tank. I was surprised it ran at all to be honest and was sure that this would solve the problem.
I haven't had it back on the road since as I am trying to get it set up and running right in the garage before I brave it on the road.
The issue is still, that it will sit there ticking away beautifully for 15 minutes but then it appears to me to choke itself up and cut out and then there is no way it will start again.

Has anyone had similar problems or have any ideas what could be causing it?

Any advice welcome.

Thanks,

Ian

[Nick Moss]

Replace all the old fuel lines with a type that will withstand modern fuels. It's a problem that has been discussed many, many times on here.

[100702mark]

I had a similar issue admittedly I was on webbers. In my case it was caused the fact that the standard mechanical fuel pump sits pretty much right above the exhaust outlet on number 4 cylinder separated by only some thin tinwear. Whilst its fine on the move if left ticking over for any length of time in the garage the fuel pump gets hot and causes the petrol to boil and vapourise. If I leave it to stand or pour cold water on the fuel pump it works again. It was made worse by a slightly blowing manifold gasket on number 4 cylinder. When replaced it was much better but I'm still careful about leaving ticking over in the garage with little airflow.

Mark

[ianj]

Thanks, Nick all of the flexi fuel hoses have been replaced recently. Would you recommend replacing the metal fuel pipe running front to back also?

Mark, so was your car running itself out of fuel then when it started vapouriising
as I am still getting petrol up to the carbs?

Ian

[100702mark]

I have a glass in line filter between pump and carbs and you could see lots of air bubbles going up which presumably prevented flow and pump priming, once anything in bowl had been used.I guess you should be able to check if my option is a possibility by just touching to feel how hot the fuel pump is, mine was too hot to touch and similarly if you gently douse it with cold water (being careful not to damage anything else) you'll soon know if you have a similar problem.

Mark

[912uk]

have you the tool to check the float bowl levels?

It does sound the classic lack of fuel issue.

Replacing the fuel lines ( including the one between the tank and the start of the metal fuel line is commonly missed )
is a very good start anyway. I need to do mine again. They don't last like they used to as Nick says it's the modern fuels mixed with cheaper fuel lines.

The metal tube will be fine unless you know of any damage or kink in it? that would restrict fuel delivery? just jet an air line down it your soon know.

also worth checking the fuel pump is doing it;s job.. 99.9% it is but open it up to check the rubber diaphragm.

Then up to the metal fuel lines to each carb again inspect and run an air line up them to check.

It;s normally the float bowls running out of fuel starving the carbs of fuel. The tool I forget the name now ( I know I broke the glass tube first time I used mine ! doh! moment the replacement plastic one is crap ) I have the tool on my desk right now but it doesn't say any number on there or anything else it;s from Stoddard.

check your jets are all the same? as I have come across this before even check they are the correct length seen ones filed down! ( I kid you NOT! )

I would start with that lot first I am more than confident it's float bowl level

come back on that after that your looking at jet sizes. But then I would ask have you ever had them run ok before? is this a new problem? or an existing old problem?

[ianj]

Thanks 912uk. It is a new problem. I haven't done many miles in the car since it went back on the road but it ran ok until last year and I left it until a couple of months ago when I finally got the time and desire to investigate. That is when I realised that the tank needed to be pulled out to get a clean supply of fuel.
The carbs have off and cleaned out including all original jets and I have also had the pump apart to confirm it was clean inside and operating correctly.
The main centre fuel pipe does have a slight kink in it at the front but it seams to be pulling fuel up ok. I am going to replace the pipe from the pump outlet with a see though one for a trial period a just to confirm that is flowing up to the carbs as it should.
I suppose the best way to test the fuel starvation theory would be to run the car until it cuts out and then whip the tops of the carbs off to check the bowls. I do not have the tool you show and have always set the float levels by removing the screw as it describes in the workshop manual and adjusting until fuel comes out.

I'm going to have another look over the weekend with a bit of luck so will update if I get anywhere.

Thank you for your suggestions.

Ian

[neilbardsley]

Ian may I ask where where you got your soft fuel lines from and what size? I haven't replaced mine on my 356 and it would be a worthwhile exercise.

[912uk]

Ok a new problem. Well to start with a small kink in the main fuel line isn't really going to make too much of a difference as the fuel only comes though to fill the bowls. On a correct set up you would have to be racing the car at speed for long periods to notice a kink in the line might not be keeping up with the fuel demad. But still it's not really good to have it but I doubt it's an issue here. On a daily car.

I'm not a fan of Glass Filters BTW too easy to break and the exhaust is just below where it would leak.

Are you getting nice flow of fuel when you take the top off ( air filters ) when it's hot and not starting.. the elbow tube ( brass ) that delivers the fuel in to the carb. 1 on each pot if you put your finger under each one and then operate the accelerator rod down once you should have a wet finger on all 4 ( one per pot ) .. if not! there's your problem..

either blocked or not enough fuel ( back to the bowl level ) I really can't see it being anything else..





Item Number 47


anyway what do I know Not driven my car in a very long time..... may be I should get it out at the weekend, got a weeks MOT left

[ianj]

Neil, I got my fuel pipes from a local auto parts place. I am running 5/16'' internal diameter.

[ianj]

912uk, these were working fine when I took the carbs off and cleaned everything out. I don't think fuel delivery is the issue, well certainly not initially as the car starts ok and revs nicely.
I'm going to have another look at it tomorrow.

Cheers,

Ian

[ianj]

Another observation made today. I have removed the plugs to check whether or not they look ok and there is a definite difference between the temperature that cylinder 3 & 4 are at compared to the much cooler 1 & 2 side. Is this normal? Or would it suggest that 3 & 4 are running lean?

[neilbardsley]

3 and 4 have the oil cooler above them. Doesn't that mean they can run hotter