Carb Problem...HELP!!!!!!!!

Well my KVA passed its MOT yesterday and I had my first proper drive, now the problems start!. I have a weber 500 carb on my rover 4.5L engine and it keeps flooding then stalling when the car has warmed up and stops at idle. I have set the carb screws as per the manual but to no avail.

Much more alarming is that on the way to work this morning it did it and after some investigation I notice that the fuel is boiling in the carb!!. This was noticed after the air filter was taken off and I can see a well of fuel bubbling away. This fuel only left the chamber when I opened the fuel filler cap, then it dissapeared. Would this be down to my breather system on the fuel tank not working right and allowing air into the carb? Is that possible?.

One other alarming thing is that I checked the oil and found some white slime and condensation in the top of the filler cap. This I am sure is not normal but this engine has been sat around not being used for a few years. There is no slime on the dipstick when I checked the level. Is this a head gasket for sure?
Could the intake below the carb be getting too hot and boiling the fuel?

I really don't know where to start looking first. A great shame with the bank holiday coming as I wanted to have a good drive in my car. That being said I am more than pleased at how the car drives. It is superb with no bump steer like before. However when it comes to fuel problems I am a complete coward!. I would be very worried if I could not findwhat is causing this!

If any one can advise I would be most grateful.

Regards

Simon

Simon

Join up with
http://www.v-8.org.uk/forum/
And re ask the question there

they are gurus with Rover V8's (helped solve my problems!)

One thing that springs to mind is that you may have some air in the cooling sustem (real bugger to blead all the air out) this will cause hot spots and could be then radiating the heat to the carb.

I also know there are some heat shield bits that fit between some manifolds and carb systems to reduce heat soak.

I would think with your engine being sat for a while there would be condensation build up inside and this would / could be shown as sludge. Again easy to see if you use coolant. Also sheck coolant header tank to see if oil has managed to migrate there.

Perhaps easy try is to remove your rear clip window to release excess heat and see if that helps with the fuel boiling. (Carb would be open to atmosphere and not inside greenhouse)

Cheers
Ian

Cheers Ian

I will join up to that forum and post my problem. I have just had a look in my carb manual and it states that boing fuel can be down to the fuel line being too close to a heat source, missing gaskets or spacers. Also if an exhaust heat riser is stuck (whatever that is!). I will try going back to RPI where I bought it from to see if they can help. I hope you are right regarding the condensation in the engine. I can not see any oil migrating into the water system. I will also have a go at bleeding the radiator etc. again.

I am more than gutted as if it were not for this problem the car would be perfect!. I really enjoyed my drive home last night and to see other peoples reaction was great.

Simon

Simon, I am no carb expert but I had a similar problem with that carb on my TR7V8, the boiling, not the flooding. It would lose power after idling, or being switched off for a time and would be difficult to launch at the start of a rallly stage. This was caused by not running an insulator block under the carb and was totally cured by using an aftermarket 1" plastic spacer.

What makes you think it is flooding? Have you checked your fuel pressure and needle valves and float level?

As far as setting the idle mixture goes my experience is these carbs are very tolerant to a wide variation in idle mixture settings. What jets and rods are you running?



"This fuel only left the chamber when I opened the fuel filler cap, then it dissapeared."

Sorry you've lost me here Simon. What chamber?

"Would this be down to my breather system on the fuel tank not working right and allowing air into the carb? Is that possible?." You've lost me here too. Describe your breather system.

Cheers,

Russ

Hi Russ

Sorry for my very bad description of my setup. I am a complete duffer when it comes to explaining parts!. The jets and rods were set up by RPI when I bought the carb, specificaly for my engine. They specialise in rover v8's and I have not yet found out what they put in. Flooding may have been an incorrect description. Becuase it is having this boiling and vapourisation taking place it will not start and gives the same impression as when flooded. I think I still need to make it run leaner so I will have to adjust this. I have just ordered the 1 inch thermal spacer you have described from RPI who also said this will help. Particularly where under bonnet temperatures are high like in a GT40.

The breathers on my tank has one going from the front to the cap and one going from the sender at the rear (it has two outlets, one for the fuel feed and a breather) to the cap. Sounds a bit of a bodge but this is how it was when I bought it. I just did not know if an air lock could cause such a problem. On refection I think it must be down to issues with the carb itself.

I will keep you posted on what else I foind this morning.

Regards

Simon

After some internet surfing I found quite a helpful site regarding carb problems. One quite interesting part covers fuel boiling and the cause:

Quote: "" Edelbrock highly recommends you *always* use a heat insulating gasket if your intake manifold is heated... which they are on most V8 engines. Some IH intake manifolds use coolant and some use exhaust gases to heat the area under the intake manifold plenum, but they all get heated. The intake manifold doesn't just get warm; it gets damn hot! Plenty hot to quickly bring the gasoline in the carburetor to a boil. Boiling or percolating fuel inside the carburetor will wreak havoc on the carburetor's proper metering of the fuel mixture. It will cause problems with trying to achieve a consistent idle as well as idle mixture adjustments. When you shut off your engine, it will result in losses of fuel through excessive evaporation. ""


I hope that when I install this new thermal barrier the problem will be cured and I can adjust the idle correctly. If it does I may get to use the car over the bank holiday after all !!!!.

Yeah I'm pretty familiar with RPI. I think they'll have the carb setup pretty close. What manifold are you running?

I think the spacer will cure the problems, if it doesn't completely, you may find heat sink before the carb is the problem. In which case you may want to look at insulating the fuel lines and maybe installing a bypass pressure regulator close to the carb to keep cooler fuel circulating through the lines and bypassing the excess back to the tank.

If there's still a problem and you think it's the breather try temporarily venting the cap or leaving it off but be careful of fuel spillage from the filler.

Good luck.

Hi Russ

I hope that it will be the solution. I get the part tomorrow and will see how it goes. Before I started to use the car I anticipated that the fuel pipe may need some extra protection and had it insulated. I have tried as (well as I can) keeping it away for the main heat sources (exhaust etc.). My regulator has the pressure set at 5.5psi as advised. All I can do is check these thing one at a time and see what happens.

Many thanks for the advice.

Regards

Simon

Take the window out - it will let a LOT of heat escape

Ian

On my site http://www.hemipanter.se/ klick The engine ans scroll down a little, ther is a image of a can filled with moisture from my crankcase ventilation catch can. From about 200 miles of driving, and some numbers of starts and stops. The can contains a large quantities of water from condesations. More than imaginable. This show the importance of running the engine to a fully warmed up oiltemperature everytime the engine fires up.
Or else, this quantities of water should have stayed at the bottom of the oilpan. This only applies to hobby cars or cars that might not be fired up again in a few weeks or so. A car driven everyday does allways reach full oiltempeerature now and then to condesate out all water collected in the oilpan.
Regards
Goran Malmberg