Any ideas? 94 Metro 1.1S, Carb, drinking fuel

Silenced

Silenced

Silenced

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Hey OcUK,

I know this forum is amazing for any tech help needed, never tried out anything motor related.

I have a 94 Rover Metro 1.1S with a SU KIF38 Carb in it. Since around October I've been struggling to get 150 miles on a tank (~£30, especially with prices as they are), before this I would be hitting 250 miles with no problems.

Taken to 3 garages and this is what has happened:
  1. Changed fuel mixtures
  2. Changed fuel mixtures AND re-plugged in an idle temp sensor
  3. Changed fuel mixtures AND replace a choke valve (On inspecting my engine today I couldn't see any such thing as the choke is just a cable)

So around £200 later I'm still no better off for fuel. I was going to have to drive 60 miles to the garage for them to possibly service my carb, of which this is the only other issue I think it could be.

Today I opened up my carb and checked what I've read to be called a power valve (The replacement part is called a FLE Diaphagrm), it seemed as if on this valve it possibly could be broken but didn't look too bad (Not an expert mind you).

Any ideas if this is the issue or something else?
 
In which case, I best check if the hole spotted on my exhaust during the MOT has been fixed as it was requested to be. Will check that out tomorrow. Thanks for the idea.
 
When did you last change the plugs?
has the oil in the float chamber been checked for a level recently?

Certainly a damaged diaphragm can cause an issue, SU's are fairly simple carbs though.
 
taske said:
When did you last change the plugs?
has the oil in the float chamber been checked for a level recently?

Certainly a damaged diaphragm can cause an issue, SU's are fairly simple carbs though.
Click to expand...

On 10-2-11 there were new spark plugs and oil and air filters.

When you say oil in the float chamber, I know there must be oil in the dashpot which I filled, although it went down during the course of the day, I assume it was overfilled and it then removed any overfilled oil.

I believe there is a float chamber for allowing fuel into the carb? If this is what you're talking about then it was probably done a long long time ago, we have had the car for a good 2 years, I've only been driving it since June, before then for a long while it has just been sitting.

The diaphragm only looked damaged on one section, where it has a spring to move a piece of metal

Lashout_UK said:
Does it run OK?
Click to expand...

Prior to any fiddling I did find that it would bog out when accelerating from rest, it would do a go stop go sort of movement to it.
 
I've never taken a KIF SU apart, but if it's anything like the HIF the choke mechanism has an o-ring seal that is prone to cracking. This allows fuel to leak past, effectively keeping the choke on all the time.
 
As far as I've seen on my carb the choke cable pulls a wire which in turn twists the throttle bar, this bar is just kept in place according to where the choke is adjusted. Unsure if this is the same on a HIF or not.

I've purchased a service kit which has all the gaskets and seals I may need, so after replacing all of that I'll have to go get the mixtures done, again.
 
Check the fuel tank isn't leaking. The filler necks have a habit of rotting away due to the build up of mud that sits on them, and when you go round a corner, the fuel spills out.
 
Silenced said:
As far as I've seen on my carb the choke cable pulls a wire which in turn twists the throttle bar, this bar is just kept in place according to where the choke is adjusted. Unsure if this is the same on a HIF or not.
Click to expand...

The choke does raise the idle speed by opening the throttle, but this is only a secondary function. It's main function is to richen the mixture, which it does by opening a small valve within the carb. This valve is sealed with small o-rings, and these are the ones that can fail.

In this picture the O-rings you need to check are the two green ones on the left hand side of the picture underneath the throttle spindle and throttle butterfly.
 
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Silenced said:
What would be the best way of checking that? I supposed that is possible, as I always drive the same route
Click to expand...

Fill the tank & see if its leaking in situ, failing that, empty car park, a few very sharp turns, stop jump out & have a good sniff, if you can't see the fuel, you'd certainly smell it.

A match would be the next logical step....;)
 
You've already spent £200 trying to nail the problem down, haven't you?

I'd baulk at spending any more trying to fix a '94 metro.
 
Dogbreath said:
The choke does raise the idle speed by opening the throttle, but this is only a secondary function. It's main function is to richen the mixture, which it does by opening a small valve within the carb. This valve is sealed with small o-rings, and these are the ones that can fail.

In this picture the O-rings you need to check are the two green ones on the left hand side of the picture underneath the throttle spindle and throttle butterfly.
Click to expand...

Ah right, hopefully tomorrow I can change everything I need to and will see if that made a difference.

R420LA6X2/4MNA said:
Fill the tank & see if its leaking in situ, failing that, empty car park, a few very sharp turns, stop jump out & have a good sniff, if you can't see the fuel, you'd certainly smell it.

A match would be the next logical step....;)
Click to expand...

If this were the case I'm sure I'd have noticed by now, or so I'd think
 
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