12 replies to this topic

[EasterBern]

I've recently put the Mini (1987 998cc) back together, and somehow it even passed an MOT!

 

I say somehow because it barely runs!

 

I've recently had the fuel tank out and also put a new fuel line in.

 

It has a few times dumped lots of fuel through the overflow pipe. So I suspected dirt in the line somewhere. I've drained out all the petrol and put fresh in, along with an inline fuel filter between the metal pipe from the pump and the carb.

 

Because it's transparent I can see that sometimes hardly any fuel is coming through!

 

I'm thinking that it could be:

 

1. Some dirt in the fuel line.

2. My new fuel line (copper) has a slightly larger inside diameter than the original steel one, could that cause any problems?

3. Weak fuel pump

 

Or maybe it's something else!

 

I've got a classic car run tomorrow afternoon, and have got the Mini booked in, so ideally want it running ASAP!!

 

Any ideas?

 

Thanks in advance,

 

Bern.

[Spider]

It could be that the float level in the carb is too high or the needle & seat in the float bowl isn't sealing off. Or the fuel pressure is too high.

[cal844]

I've had it where we've had to prime the line from the pump to the tank and pump to the carb, then use brake clean to get the car to fire up

[Jamdog]

An overflowing carb won’t cause the car to run badly, and it also won’t cause a fire so long as the overflow pipe is routed down past the exhaust manifold.

If you’ve got a run tomorrow, the first thing to do is check points and ignition timing. In 90% of cases this will make the car run perfectly fine again. If not, adjust the carb mixture. Neither of these things will stop fuel pouring out, but they’ll make it run well enough.

Solving the fuel overflow can be much harder. You are absolutely right in thinking that dirt could be the issue, if you’ve got one of the plastic mesh type fuel filters like this one then replace it with a paper one because the mesh types just don’t work. https://www.minispar...|Back to search

What fuel pump and what carb have you got?

[EasterBern]

It could be that the float level in the carb is too high or the needle & seat in the float bowl isn't sealing off. Or the fuel pressure is too high.

I thought that too! There was no washer under the needle valve seat so I added one. The overflowing has stopped, but it doesn't run any better. How could the pressure be too high, and what can I do about it?

 

I've had it where we've had to prime the line from the pump to the tank and pump to the carb, then use brake clean to get the car to fire up

That's interesting, I remember having to do something similar with a Citroen Dyane. 

 

An overflowing carb won’t cause the car to run badly, and it also won’t cause a fire so long as the overflow pipe is routed down past the exhaust manifold.

If you’ve got a run tomorrow, the first thing to do is check points and ignition timing. In 90% of cases this will make the car run perfectly fine again. If not, adjust the carb mixture. Neither of these things will stop fuel pouring out, but they’ll make it run well enough.

Solving the fuel overflow can be much harder. You are absolutely right in thinking that dirt could be the issue, if you’ve got one of the plastic mesh type fuel filters like this one then replace it with a paper one because the mesh types just don’t work. https://www.minispar...|Back to search

What fuel pump and what carb have you got?

The overflowing has stopped, and the overflow pipe is routed correctly.

 

I have checked the points, ignition timing and mixture. It runs fine at idle, it's just when I try and drive it that it doesn't work. It will drive fine for a bit, then it will start hesitating, I live at the top of a steep hill and it only just makes it up to the top.

 

I've got a paper filter from Halfords. And it's an HS4 with the standard engine driven pump.

 

At times there is no fuel running into the filter, at best it's a dribble. I may try blowing air back through the line to the pump. Though if there is dirt in there and I just blow it back into the tank it could be an issue again I guess!

 

Thanks for the replies though, much appreciated.

[EasterBern]

Thinking about it, at idle there wouldn't be much fuel coming through (as the pump is running slowly) and when the float chamber is full it shuts off so no fuel would be coming through.

 

But it feels fuel related.

 

It's firing on all 4. But maybe its the condensor breaking down?

 

One thing I forgot to mention is that it seems to be running quite hot. Well, the temp gauge is nearly on "H", but it doesn't feel excessively hot under the bonnet.

 

I've swapped the carb over too.

Edited by EasterBern, 02 June 2018 - 04:44 AM.

[Spider]

If the float level is too high, and especially to the point where it's coming out the overflow on a HS type SU, it will cause it to run pretty bad as it will be very rich, basically with fuel literally pouring in to the cylinders, almost uncontrolled. The top of the float chamber is higher than the top of the Jet in these Carbs, so when the fuel level is lapping around the lid, you can be sure it's also going straight in to the engine.

 

I'd suggest for starters measure the fuel pressure at the Carb.

 

Also, what type of fuel pump are you running ?

[EasterBern]

I think there are 2 problems here, but looking like 1!

 

The first is the overflow problem, and it's not doing that now that I've put new clean fuel in the tank and the paper filter in line. So far today the filter has been full of fuel.

 

The second is that it's running too lean. I can start it up, drive through the village which has a gentle downhill followed by a steep downhill. When I get to the bottom of the hill and accelerate it starts to hesitate. If I pull the choke out fully it starts to run properly. So it looks like it's running too lean.

 

I've got stage 1 exhaust and inlet manifold, but the needle looks to be an "AC". 

 

Looking at the Minispares site they have an "AAU" for the stage 1.

 

I've set up the fuel mixture using a colourtune, but of course that's at idle so not an indication of the engine at higher revs under load.

[EasterBern]

The AAU is a swinging needle, but mine is fixed :-(

[EasterBern]

I went to Moss and got an AAA needle, fitted it with an hour to spare, and then did 70 problem free miles! Phew.

 

Thanks for the replies

[cal844]

I went to Moss and got an AAA needle, fitted it with an hour to spare, and then did 70 problem free miles! Phew.

Thanks for the replies

An AAA is probably way too rich, best to do a plug chop to check the colour of them.

[EasterBern]

Yes, will do. It was a lot thinner than the AAU!

[cal844]

The AAU is the recommended needle for a 998 with stage one kit, ideally you'd then get the engine emissions checked by an MOT station