11 replies to this topic

[Jamdog]

Started my  1977 clubman estate 998 up the other day and found fuel pouring out of the bottom from where the jet connects to the bottom of the fuel bowl (the rubber bits had disintegrated).

I picked up one of the genuine SU service kits and took apart the carb, giving it a proper going over with a can of carb cleaner and replacing the gaskets, float needle valve and jet.

 

She ran perfectly straight afterwards and ran so smoothly and quietly you could mistake the sound for a modern car! I gave it some revs in neutral to test it, and when i took my foot off of the throttle it cut out and ran incredibly lean afterwards, struggling to keep the engine going at about 2000RPM and hunting, etc. This was strange but I didn't have time to sort it out that day.

 

The next day i started it up and it ran fine again, but with loads fuel overflowing from the fuel float overflow pipe. The needle valve is brand new and the float itself seems fine, the whole thing having just been cleaned out. If i blow in the fuel inlet and close the needle valve by pushing the float up, I can feel it close and cant keep blowing. The fuel pump is mechanical and works normally, so i doubt fuel pressure is to blame.

 

I really have no idea why such a simple system which is clean and seemingly in good order is overfilling the fuel bowl.

 

 

[cal844]

Which pump did you fit? A 998/1275 or a 1380 one?

[Jamdog]

Which pump did you fit? A 998/1275 or a 1380 one?

It's presumably the standard one that came with the car, I had a quick look at it and it was mechanical and unserviceable.

[Ethel]

Did you set the float gap? New needle valve and seat? Sometimes a worn float pivot pin can be to blame.

[Jamdog]

Did you set the float gap? New needle valve and seat? Sometimes a worn float pivot pin can be to blame.

The float gap isn't adjustable, but I did try putting a washer between the valve seat and lid, but it didn't fix it.

Maybe the pivot pin is worn, I'll get a new one and see if it helps

[carbon]

Do you have a fuel filter fitted?

 

Only takes a small bit of dirt or rust to cause float chamber flooding, worth putting an in-line filter just before the carb.

[Spider]

Fit a gauge and check the actual pressure being delivered from the Pump.

 

I went through a similar exercise on the wife's Moke about a year back to find that the pressure from the Mechanical Pump was quite high. It wasn't too old either (about 8 years old at that time). I haven't dismantled the Pump, so I have no explanation as to why.

[cal844]

Did you set the float gap? New needle valve and seat? Sometimes a worn float pivot pin can be to blame.

The float gap isn't adjustable, but I did try putting a washer between the valve seat and lid, but it didn't fix it.

Maybe the pivot pin is worn, I'll get a new one and see if it helps

The float is adjustable, the tab which sits against the valve can be bent to set the gap

[cal844]

Did you set the float gap? New needle valve and seat? Sometimes a worn float pivot pin can be to blame.

The float gap isn't adjustable, but I did try putting a washer between the valve seat and lid, but it didn't fix it.

Maybe the pivot pin is worn, I'll get a new one and see if it helps

The float is adjustable, the tab which sits against the valve can be bent to set the gap

[Jamdog]

Did you set the float gap? New needle valve and seat? Sometimes a worn float pivot pin can be to blame.

The float gap isn't adjustable, but I did try putting a washer between the valve seat and lid, but it didn't fix it.

Maybe the pivot pin is worn, I'll get a new one and see if it helps

The float is adjustable, the tab which sits against the valve can be bent to set the gap

Cheers, never realised that! I'll give that a go too, and get a filter too when I get a chance

[Ethel]

 

The bigger the gap the more pressure they'll be holding the valve shut

[cal844]

 
The bigger the gap the more pressure they'll be holding the valve shut

Good video that 😁