I have a 1968 S-Type 3.4. All the time it is going along on the flat or downhill it is fine. But going uphill it falters & on occasion I have ended up in 1st gear struggling up the hill. When I get eventually to the top it is okay and I can again go along the flat or down hill. All the ignition components have been replaced, Shell petrol is in the tanks. Someone thinks that the fuel might be icing up. Please can any one help? I am really concerned that as I lose power another car on the motor way could come careering into the back of me! Thank you Glynis
Does it happen on both tanks, regardless of if the tanks are full, half, or nearly empty? If it is just one tank, then there might be a problem with the pickup or pump on that tank.
You might have what I call “Wobbly float lever” syndrome.
The float in the chamber presses on a metal stamping which in turn presses the needle valve up to close off the feed, or allows it to fall down so that fuel can enter the chamber. The levers are a thin metal stamping, and they pivot on a pin pressed into two ears on the lid.
Sometimes the lever binds against the ears when the car is on a hill, which can result in the needle not closing and that carb then runs richer.
It’s no big deal to take the bowl tops off and check that they operate freely. (and check that the floats are ok, and set correctly etc).
It happens regardless of having a full or half full tanks on either side. It has been suggested that the fuel might freeze?
Well, having lived in Canada and Switzerland, I can claim passing familiarity with frozen fuel lines. In my experience, when a fuel line does freeze then it does so regardless of the angle of the road. How would going level or downhill warm the frozen fuel up?
A bottle of fuel line antifreeze in each tank would eliminate the problem if it were freezing.
How steep does the hill have to be?
My bet is that you have a fuel delivery issue:
That it does the same thing on both tanks, regardless of fill level indicates that the fuel delivery issue is forward of the firewall.
That it gradually loses power, but doesn’t buck or die completely speaks against a 12v electrical issue.
It might be a Plug wire grounding out, but it would be unusual for that to only happen going uphill.
I take it that the engine pulls well on the level.
What happens if you stop going uphill and try to drive off again? Will it idle normally with the nose up?
After going down the gears to 1, and gradually getting up the hill, I am able to go along the flat and down hill properly again. It is weird because it runs really well until I get almost to the top of a hill.
It sounds like fuel starvation to me.
If you stop on a hill, does the car idle normally?
Can you pull away normally if you stop on a hill?
Hi, yes the car idles well. It pulls away normally whilst going up the hill in 1st gear?
When was the last time the fuel filter was changed?
It was changed two weeks ago, are there two filters or just the one?
If original, just one.
Does this happen on a steep incline, or also on a long gentle incline?
It is usually a steep long incline
Can you check the pressure and flow of the pump?
Pressure should be 2.5 - 3.5 psi
Flow should be about a Pint in 20 seconds.
If you measure those two figures after the filter then you probably have a problem at the carbs.
Hopefully I will be able to do this tomorrow. I will email once I have checked it.
Dear Andrew,
We have managed to sort out the problem.
The wire from the fuel pump was loose but not noticed until it moved and showed a wire not connected, just a really minor thing and it stop the car!
It has just passed the MOT so we are very pleased.
We washed and polished it but have come across some very strange dark marks on the paintwork, we thought it was dirt, but it will not come off.
Thaks for your help.
Glynis & Graham