Minor fueling problem

Post by **rusty** » Mon Sep 18, 2006 12:59 pm

Hi there,

Having trouble with a standard SU carbed Morris 1000.
It seems to be running out of fuel or have a fuel blockage.

So far I've cleaned out the fuel bowl and fitted an in line fuel filter, but after the car has been driven for about 5-10 min it starts spluttering and chugging.... eventaully getting worse and worse until it will barely move.

When cold the filter seemed to fill up very nicely, but duning the chugging problems the clear plastic filter only had a trickle running through it.

(The car also has a new standard electric fuel pump fitted).
I'm not familiar with SU carbs so I'm not sure where to clean apart from the obvious fuel bowl. Also underneath the sliver bottle on the carb there seems top be a lot of runny yellow luquid, (which I'm asuming is oil!) is this correct?

Any ideas or advice would be much appreciated!

Ratbag · Post by **Ratbag** » Mon Sep 18, 2006 1:08 pm

If the (clear plastic) fuel filter isn't full then you have fuel supply problems upstream of that .. blockage/dirt in tank/kinked fuel line/wrong fuel filler cap/blocked vent or fuel pump (if this is fitted upstream of the filter).

Phil.

Post by **bmcecosse** » Mon Sep 18, 2006 1:11 pm

Hmm - another Glasgow Minor!! Welcome aboard. You need to test the fuel pump - take the pipe which is leading to the carb and put it into a container - and switch on the ignition. There should be a steady clicking from the pump and strong steady spurts of fuel into the container. It should be able to pump 1 pint in 2 minutes - beware it's petrol - no sparks and no smoking!! If this is ok then you are looking for a blockage in the carb - which is very very unusual on the SU. It has a large jet area and rarely blocks up. Remove the air filter - try lifting the piston inside the carb with your finger - it should rise with some resistance - and then fall back with a clunk. The top of the carb unscrews - (black knob) - and there should be some thin oil in there - I use 3 in 1 - others will say it's too thin. Use a little engine oil if think 3 in 1 is too thin. Come back and report how you get on !

Post by **rusty** » Mon Sep 18, 2006 1:12 pm

Ratbag wrote:If the (clear plastic) fuel filter isn't full then you have fuel supply problems upstream of that .. blockage/dirt in tank/kinked fuel line/wrong fuel filler cap/blocked vent or fuel pump (if this is fitted upstream of the filter).

Phil.

Cheers, I was thinking it might be a problem at the back of the car myself

Any advice on what's usually best to try first (and how to go about it)?

Thanks!

Post by **rusty** » Mon Sep 18, 2006 1:21 pm

bmcecosse wrote: There should be a steady clicking from the pump and strong steady spurts of fuel into the container. It should be able to pump 1 pint in 2 minutes

It seemed to click away fine and fill up the filter well when cold but when it was having trouble driving the pump was still clicking but not filling up the filter nearly as well.

bmcecosse wrote: try lifting the piston inside the carb with your finger - it should rise with some resistance - and then fall back with a clunk.

Is this the rod that is attached to the black srew top? It had resistance before we cleaned bits of the carb, but after there was little to no resistance.....

Post by **alex_holden** » Mon Sep 18, 2006 1:57 pm

As BMCEcosse says, start by taking the pipe off the carb and pumping into a container - that will tell you for sure if there is a problem before the carb. There won't be much fuel going into the filter if the carb isn't taking much fuel in, so the flow rate through the filter doesn't tell you whether the problem is before or after the filter.

If there's no resistance when you pull the damper rod out and there's oil leaking out of the bottom of the lid that means you've lost the oil from the damper somehow (maybe by turning it upside down?). Top it up with engine oil or 3 in 1 - it's up to you. I bought a little bottle of the official SU damper oil and its viscosity seems to be part way between 3 in 1 and engine oil.

Post by **rusty** » Mon Sep 18, 2006 2:30 pm

Hmmm... any other car I've had before would have the plastic in line filter completely filled up, this one only before it's been driven for a bit.

Could the plunger not having enough oil on it cause these symptoms?
(Some was definately lost during cleaning)

Ratbag · Post by **Ratbag** » Mon Sep 18, 2006 3:00 pm

No - not having enough oil in the dashpot will only cause a problem on acceleration (assuming you still have a spring in there). Still going to be a fuel supply problem. Try rigging up a temporary tank from a jerrycan to the inlet of the fuel pump, if the fuel pump tests out OK (see above).

Post by **rusty** » Mon Sep 18, 2006 3:06 pm

Ratbag wrote:No - not having enough oil in the dashpot will only cause a problem on acceleration (assuming you still have a spring in there). Still going to be a fuel supply problem. Try rigging up a temporary tank from a jerrycan to the inlet of the fuel pump, if the fuel pump tests out OK (see above).

On the stalk with the black screw thread top there's no spring..... only a cylindrical device near the base (which is quite loose).

Post by **alex_holden** » Mon Sep 18, 2006 3:26 pm

The spring isn't on the damper stalk, it's underneath the big cylindrical cover - you can check it's working properly by taking the air filter off and lifting the big piston with your finger. It should be fairly hard to lift but fall quickly with a "thunk" when you let go.
The little piston on the bottom of the damper rod is meant to be loose.
I have one of the transparent inline filters and it doesn't completely fill with fuel either.

Post by **rusty** » Mon Sep 18, 2006 3:48 pm

Right..... it's all coming together slowly (I'm far more used to the likes of Weber carbs!).

Under the damper stalk theres a brass jet like circular part with a hole in the middle, I'm assuming I should be trying to lift whatever part this is fitted to to check the spring?

Also where else in the carb should I be cleaning?
I have a nagging feeling that there's dirt trapped in the carb somewhere... and so far I've only cleaned out the fuel bowl (which was pretty dirty!).

Cheers!

Post by **bmcecosse** » Mon Sep 18, 2006 11:45 pm

Don't like the sound of this 'cleaning'. If you damage the inside of the piston 'bell' the carb is scrap. With air cleaner removed - put finger in mouth of carb - nd lift the piston - hich has a thin needle attached on the base. Don't bend the needle. Release the piston - it should fall with clunk - does it ? Other possibility is vacuum in the petrol tank - remove filler cap to test. Have you actually tried the pint in 2 minutes test yet - or are you just fascinated by the 'filter' thing ? This is a non-standard part and completely unnecessary with an SU carb - in any case the SU fuel pump has a filter gauze built in. Maybe the 'filter' is blocked - bypass it and see if all is then well.

Post by **rusty** » Tue Sep 19, 2006 10:19 am

Some replies and questions............

Cleaning is only with carb spray and a cloth to wipe away any residue.

I will try the pump test, going to be working on the car this afternoon.

The in line filter can't do any harm, it's just a method of catching dirt before it enters the carb.

Is it worthwhile dismantling and cleaning out the pipe below the fuel bowl?

If the tank is full of crap what's the best way to go about curing this?

Post by **alex_holden** » Tue Sep 19, 2006 11:10 am

There should be a drain plug on the bottom of the tank that you can use to drain it if the problem turns out to be that the fuel is dirty.

I can't say for sure the inline filter is what cured the fuelling problem on my car as I rebuilt the carb at the same time, but it is visibly collecting a lot of fine dirt and rust particles that would otherwise have got trapped in the float bowl or sucked through the jet.

Have you tried cleaning the filter on the bottom of your fuel pump?

Post by **bmcecosse** » Tue Sep 19, 2006 1:13 pm

Do the fuel flow test after the filter - then you will see what's what. Only problem with filter would be if it's restricting the flow - the SU can deal with all sorts of rubbish in the fuel!

Post by **rusty** » Tue Sep 19, 2006 3:16 pm

alex_holden wrote:
Have you tried cleaning the filter on the bottom of your fuel pump?

Hmm, I'm not sure if it has one!
It's a brand new one but it seems to be a sealed unit.

The filter would be at the far end away from the inlet outlet pipes wouldn't it?
(that's covered in blue plastic/tape stuff on this unit)

Post by **alex_holden** » Tue Sep 19, 2006 3:48 pm

The filter on my pump is under a plug on the bottom, at the end with the pipes. What happened when you did the flow test?

Post by **rusty** » Tue Sep 19, 2006 4:09 pm

Hmm, will look at that end!

Going over to do it in a min'!

Post by **rusty** » Tue Sep 19, 2006 10:08 pm

Ok, done the pint in 2 min test and it managed it easy!

No dirt in the pump either.

Today it was idling for a while and eventually conked out, a first for that!

Thinking it might be a stuck thermostat now? As there's no dirt in the fuel and the pump is fine, and the car only dies when it's heated up.
No steam or real extreme heat but an idea?

Post by **alex_holden** » Tue Sep 19, 2006 10:13 pm

I don't think it will be the thermostat. Conking out when it gets hot sounds suspiciously like it could be the coil breaking down.