Ideas to stop fuel vaporising please

[RobSun]

I have been having problems with what I suspect to be fuel vaporisation since last summer on my Dolomite 1300 (1982) and its getting worse.

The first time it happened was last summer on a very hot day and then nothing until later around September but nothing severe and pop the bonnet for ten minutes and then all ok. I was also getting hunting when cruising at 50/55 ok at any lower speed and this was put down to the waxstat jet being worn. It was also impossible to set the mixture. This was changed and a red jet fitted and the mixture could be set and the engine ran much smoother. However the hunting continued. I had also noticed that the radiator was not getting hot at the bottom but the temp did not overheat. The last owner had fitted it with an 88 degree stat.

I needed a new exhaust and one was fabricated for me by a restorer and he noticed the rad also and suggested fitting an 82 degree stat. I laid the car up for winter and started on it a few weeks ago.

I fitted a new stat the car ran at a lower temp but the bottom of the rad still did not get hot. When I tried to restart it wouldn't until it had cooled down. Next day I got the colour tune out ran it up to temp. and set the mixture as it was still a bit rich. Same again couldn't restart it until it had cooled down. I suspected that the rad not cooling properly may be causing the vaporising so drained it out and gave it a good flush etc. still the same rad cold at the bottom so I got a new water pump and a fuel pump just in case. Fitted the water pump and new top and bottom hoses, warmth at the bottom of the rad.

Today I took it for its first run and did 12 miles in it, to check all is working for the MOT later this week. She ran as sweet as a nut, got home stopped the engine whilst I opened the gates and it wouldn't re start. Left it to cool, no go, checked the plugs, dry and chocolate coloured. Still no joy, poured cold water over carb and manifold in desperation no joy. By the way the rad was hot top to bottom. Eventually it started and I was able to get it on the drive but when I came to put it in the garage again it wouldn't start. Checked the float chamber this was full of fuel and clean, the jet was clear, and there was pressure from the still old fuel pump when I pulled off the line. Put it back together and it started on the button. Put it in the garage and left it and went back after 1/2 hour started straight away.

I can only assume this is fuel vaporisation. Where does it happen if the float chamber is full and the plugs are dry. In the Carb? has it got anything to do with the red jet? How can I stop it? This hasn't been a problem until now.

I have thought may be a heat shield, is one available for the single hs4? Wrapping the exhaust down pipe?

Any help or suggestions will be gratefully received.

Thanks Bob

[grifterkid]

When I had my V8 P6 it was a right g!t for fuel vapourisation to say the least...!!!

Ideas...?! Well first of all I would suggest a thorough flush of the cooling system, a REALLY thorough flush that is! Although it's not related to fueling it helps things to run cooler and it's the temperature under the bonnet that you want to reduce as that's what make the fuel vanish...!

Secondly I think wrapping the manifold could well be a good idea in that the heat coming off of that item will indeed add to the heat in the engine bay...

Next up a heat-shield could be fashioned so as to protect the carb's from direct heat but the ambient temperature in the engine bay would change that much with that mod' but it is still worth doing if you want to be thorough...

I don't know how this didn't cause problems when our cars were new (I posed the same question on the Classic Rover Forum when I had my P6B) but maybe the fuel we use nowadays just isn't as good as it once was...?! Whatever, I know that this problem is a ruddy frustrating one so I hope you can cure it in some way...

A final suggestion it maybe getting a 'summer bonnet' made...! It is something I have often thought of doing (although I've yet to get round to it!) whereby you get another bonnet and get some vents/louvres added to help with the escape of warm air from the engine bay. Just another though of course!!!

Good luck...

[RobSun]

Thanks for that you seem to be on the same page as me. When I flushed the rad the whole engine was done also, hot and cold several times until just clean water came out.

I was surprised the new pump sorted out the circulation because other than rust on the vanes the old one looked ok, no play in the bearing etc. I didn't expect it to have had the effect it did. And with the engine now running at a lower temp I hoped that the vaporising would have been cured.

I couldn't put vents in the bonnet the car is to original and has won best in show on a few occasions.

I cant help wandering if the red jet is the cause and I should have put a new waxstat jet in instead. Everybody I spoke to said the red jet will be more reliable.

[grifterkid]

I couldn't put vents in the bonnet the car is to original and has won best in show on a few occasions...

I wouldn't advise cutting into your original bonnet but I was thinking of having a spare that could be stashed away and used during the hotter times of the year...?! If you do show the car though this may not be the best idea...!!!

[mantney]

I had similar symptoms with my Opel Manta. Fuel vaporisation was suggested. Turned out to be the condenser. This 1500 was hunting and conking out when warm. Condenser again.

[RobSun]

Its got electronic ignition fitted so it won't be that.

[cliftyhanger]

Fuel pump?

[RobSun]

I have a new one to fit waiting for a filter to come and then I will do it.

[Edin Dundee]

Electronic ignition or coil?
I've had both break down when hot...

[GlenM]

Hunting at 50-55 mph doesn't sound like fuel vaporisation to me. I have a 1500cc Midget that suffers from this in the Summer, it runs like a pig in traffic and at low speed but by the time you get upwards of 30 mph, it has usually cleared. The causes in this case are wax-stat jets and a completely missing heat shield. It is going to have a tubular exhaust manifold and a carb re-build soon, so I will probably wrap the manifold, too.

I had a Dolomite 1300 in 1988, that suffered from fuel vaporisation and I found a heat-shield for the single HS4 at a scrapyard, probably from another 1300 Dolomite or a Toledo, so they do exist for this model.

[Jon Tilson]

If you have a float chamber full of fuel and it wont start it is NOT fuel vaporisation that you are suffering from.

You have a dodgy coil or electronic ignition unit.

I would say its an over expanded waxstat pellet leaning it off too much, but you've gone non waxtstat.

There is no comparison between a 1300 dolly and a Rover V8. These are known for hot start issues because of the location of the fuel pump and pipes. Mine has no issues as I have an electric fuel pump.

When a 1300 or any dolly suffers from fuel starvation you get emty or low level float chambers and it MAY restart by pulling the choke. This is often caused by persihed sections of fuel pipe allowing the pump to suck air. You can also get some blocked breathers at the filler cap, but thats again pretty obscure and tends to happen to cars left standing a while.

I think you have ignition issues as I've said already...

Jonners

[RobSun]

Thanks Jonners

I am going to change the pump today regardless and to be honest after having a bit of a think last night was wandering if it could be the coil or ignition. I recalled vague memories from my youth and my dads A30 having similar problems and a new coil sorted that out.

[mantney]

Does the coil get hot, like really hot?

[Jon Tilson]

The way to diagnose the pump is this...

Remove coil + lead - no unwanted sparks...

Disconnect fuel inlet to carb an vent to suitable container.

Spin engine on starter. If the pump is good you should get a healthy squirt of fuel each crank rotation.

If you get a trickle its the pump....or an air leak so its sucking air.

Best of luck with it. If you do swap the pump be careful the lever goes in on top of the cam.

Jonners

[Toledo Man]

This was discussed at last night's West Yorkshire meeting.

Modern unleaded burns hotter than 4 star so there's going to be more heat. An efficient cooling system will help. Bob has flushed the block and the radiator (I forgot to mention the heater matrix. What is it like?) and replaced the water pump so the cooling system should be fine now. I wonder if the waterless coolant would help. Has anybody tried it in the 1300 or 1500 engine? As Glen has found out, a heat shield is available for single SU carb OHV engines. I'm sure the 1500FWD had them. It might even be possible to get a Spitfire one and cut it in half to fit the single carb car. Using exhaust wrap is another option. I've also mentioned getting the exhaust manifold coated (Zircotec or a ceramic coating).