Carb problems, I think!

[philmerson]

I am looking for some advice please.
I have a 1965 S1 4.2 DHC which has been faultless till a couple of weeks ago when after stopping briefly and restarted there seemed to be a fuel starvation problem as every time I accelerated she stutterd badly and I limped home.

To remedy I have changed the fuel filter
Cleaned the fuel lines
Cleaned the Float Chamber filters
Reset the Float Levers to 11.1mm from the top, only needed tiny adjustment
Cleaned the Dampers, Pistons and added more oil to the dampers as they were a little low
Cleaned the air filter

Fuel is pumping through to the filter well and there seems to be good pressure in the system, fuel is comming up the jets easily, the pistons are moving up and down freely.

However, no change, quick acceleration and she stutters.

I there anything else I can try?

[christopher storey]

I should have a look next at the distributor. Points closing up (common) can produce this effect , as can stuck mechanical advance weights ( uncommon). The old adage is that 90% of carburation problems are infact caused by ignition faults!

[Heuer]

Did you check the fuel tank sump filter? Could be sharp acceleration stirs up the debris and blocks the gauze. You need to run the tank to almost empty to check it though which is why most owners rarely bother.

Christopher is correct though - suspect the electrics including leads (how old are they), coil (try a spare), plug caps (the 'Champion' ones are prone to failure), plugs (gaps) and the points. Also heard of a bad earth and faulty ignition switch causing misfires.

[christopher storey]

Ah yes, David makes a good point about the fuel tank filter, but also one which I overlooked , which is to check that the earthing strap from engine to the frame is intact. This should be a braided one usually from bellhousing, but some people ( including me) use other locations . An ohmmeter is invaluable in checking for this type of fault to see that the distributor itself has a good earth to the engine as well as checking the generic engine to frame earth . It is also very useful for checking the other items which David lists

[philmerson]

Yes I have checked the fuel tank sump filter and it is absolutely fine.

The leads are only a year old and in excellent condition, or look it and I have electronic ignition, so I have ordered and new Lucas Gold Sports Coil to see if this is the problem and will let you all know the outcome, thank you for your comments. I will aslo check the earthing and have an ohmmeter to use. Just a matter of deduction at the end of the day.

[philmerson]

Just to let you all know that I think I have solved the problem! There was some water sitting in the distributor, not sure how it got there, but every time Iwent for a run, it obviously splashed up into the cap creating the fault, the dist cap would then dry out and the problem disapeared until I went for a run again.

In the process of dismantling the distributor, I found that one of the HT Leads was also corroded. I am going to replace the Rotor arm, HT leads and spark plugs, is it worth doing the distributor cap as well?

The good thing about this is that the fuel system is now immaculate, the ignition will all be brand spanking new, what else could go wrong!!!

[Heuer]

Phil

For the relatively small cost it is worth replacing the leads, cap and coil. The Moroso leads Rob Beere sells are excellent. Maybe worth investing in a new rotor arm as well, even if you only keep it in the toolkit. Make sure you buy the latest Lucas style one (SNG Barratt) with the arm riveted to the bakelite as the earlier replicas quickly fall to bits.

[HarryW]

Phil,
I too had misfiring and did most of the usuals. What I eventually found was that there was a tiny water leak from the thermostat housing gasket - only under pressure and detectable only by feeling the bottom of the housing. The drips from this fell onto one of the leads and dribbled down into the bottom of the lead socket where gunge formed , causing a misfire on that cylinder. Did no harm to change the coil, condenser, plugs and points anyway

[philmerson]

Thanks for the comments, I have made up some new HT leads and the new cap, rotor arm and spark plugs are on their way from SNG.

Interesting point about the leak from the housing, I checked and it seems there is a small leak there, so have tightened the hosing to see if this makes a difference, otherwise, what is the best solution for a leaking housing, new gasket?

[GSR 54D]

Hi Phil

Yes renewing the gasket is your best bet, I have had to do this job twice so be aware of a few points. Obviously undo the 3 nuts holding the thermostat housing to the carburetor manifold but also undo the hose attached to the thermostat housing as well, this enables you to hold the thermostat exactly in place while you tighten the 3 nuts back up. I didn't on the first occasion and had a major leak after-wards because the thermostat dislodged out of position and cut the new gasket. Secondly it's worth making sure the surface areas that the gasket fits on are clean and perfectly flat, I have recently used a gasket sealing paste to help secure the fitment which to date has been completely leak proof.

John H

[attwood]

I also had a small but persistent leak from the thermostat housing which did not respond to extra tightening or liquid gasket. It turned out to be a crack in the housing close to the nut you can't get to very easily.

A secondhand housing from the Spares Day at Stoneleigh was the solution.

[Moeregaard]

My experiences with non-Lucas distributor caps and rotors have been mixed. They always seemed prone to tracking and premature failure. My recommendation? Use only genuine Lucas components with the original dizzy.

You can salvage a questionable cap by putting it in the dishwasher along with the dinner plates. Do this when She Who Must Be Obeyed has momentarily left the room. Dishwashing detergent is extremely aggressive and the cap will come out squeaky clean. I've also cleaned other components this way and it's amazing what will fit in there. I should also mention that I'm currently unattached...

[philmerson]

The electrical spare should turn up tomorrow, Saturday, and hopefully fitted before I wing my way up to Twickenham to watch the England v Wales match, not with the old girl I hasten to add, or the Jag come to that......

I will let you all know of progress, and the dreaded leak, what this space!

[MarkE]

Should be a good match, Phil. But with an English father, American mother, Australian passport and bought up in Wales my loyalty can be divided. However, as I worked for Brains Brewery in the late 70s, the boys in red get my support!!

[philmerson]

So sorry MarkE, a good match though, could be our (England) year for the 6 Nations!?

Seems that the change of all the electric parts has sorted the problem, also the leak has stopped since tightening up the jubilee clips, all well again, satisfaction!

[MarkE]

It was a superb match, by far the best of the three this weekend. The French look pretty scary though!

Something that is coming up quite frequently now is the issue of reliability of the electronic ignition systems. I know of several cases of unusual misfires, complete breakdown, or even symptoms very similar to running out of fuel, all attributed to the 'fit and forget' systems. It seems that cars that are laid up for a significant part of the year get more affected than those used more frequently, which seems to point to damp / poor earth affecting the electronics.

The problem is that they are quite difficult to diagnose. With the old system, replacing the coil, condenser and points for less than ?20 usually sorts any ignition problem out.

Something to keep an eye on. Having said that, my S3 still has its original Opus system after 38 years, and I've never had a problem with it....and that was meant to be quite a weak system!

There?s never an easy or foolproof answer to ?upgrading?, eh?