Stuttering at 50+

[Bornfree]

I’ve restarted my post as it got hijacked by a couple of other issues

We got a 1967 traveller a couple of months ago. It’d not been doing much for around 3 years. Once it’s warmed up with choke off at around 45-50+ it starts to stutter and lose power. Once we’ve pulled over we can then start up again. It’s a 1098cc with a recent unleaded head, electronic ignition, alternator conversion. This is what we’ve done to date;

Filled up with fresh fuel, second tank with super.
Loosened fuel cap
Replaced coil
Cleaned rotor
Cleaned carb float chamber and checking jet clear
Cleaned fuel pump filter
Tightened up fuel pipe feed to carb
Blown down supply pipe and heard reassuring bubbling.

After all this it went really well on a couple of runs. But the latest one was not good, lots of stuttering! So,
Checked the float chamber again, and a very very small amount of muck at the bottom. Cleaned that out.
Checked the fuel filter in the fuel pump again, and struggled to see any muck.

Tried another run out, but again get to 50-55Mph then same behaviour recurs. Again needed to slow and stop and then off I went again.

So now I’m wondering if I should drain the fuel tank and clean it. My thinking is that as I pick up speed maybe muck is being sucked up in the tank, and the faster the pumping the more muck. This then reduces the flow of fuel. When I slow down the muck is still stuck on the inlet. Then when I stop after it’s started stuttering all the muck falls away and off we can go again smoothly. Does that sound logical?

So is draining the tank by using the nut underneath sufficient to drain, and see what comes out? And then wash it through with some clean petrol. Or do I need to remove the tank and put some tank cleaner in and shake it around? (Yes I’d rather not have to take the tank out!)

What are your thoughts, please?

[Murrayminor]

To properly clean the tank and to ensure any loose flakes of rust are removed it will have to come out.

The tank on my minor was in a horrendous state, the car was running but occasionally it stuttered, on removal of the tank the amount of rust that came out had to be seen to be believed.

I then cleaned it using fresh fuel and a few nuts and bolts rattled it round for a while.

My tank was then put into storage but before I use it again I will do the same.

Some people say have the tank lined, I think unless its done professionally you cannot be guaranteed success with lining it at home.

My old 1275GT mini had twin tanks and both of those were gummed up and rusty but the above nut and bolt system worked fine and cleaned the tanks out without issue.

Regards

Dermot.

[simmitc]

Replace the air filter. That's not a flippant comment, see viewtopic.php?f=4&t=49906&hilit=not+the+average+misfire

[liammonty]

I would go through all the easy stuff first before looking at the fuel tank, as cleaning it won't be a trivial task. People often suspect fuel issues when (in my experience) most trouble is normally ignition-related. When you say the car begins to misbehave at 50+ mph, if you slow down to, say 30 mph once it's started stuttering, does it begin to run normally again, or continue stuttering? If it's the latter, it sounds to me as though you've got an ignition fault somewhere that is causing you trouble when it gets hot. Rotor arms and coils are classics for giving those kinds of symptoms. Don't think that because you have replaced your old coil, dissy cap, rotor arm, points etc. with new, that it means they aren't at fault. Pretty much all the components I've had trouble with in recent times have been new.

[Bornfree]

Thanks for the suggestions.

Before I do the tank I will try some of the simpler things! That’s much my preferred route.
I have already changed the air filter (forgot to list that).

I’ve ordered a new rotor arm and will try that, and a new fuel pipe from the pump to carb.

I did wonder about the electronic ignition unit, which was a recent (before the 3 year’s rest the car had) but was trying to avoid replacing it with the original one!

Thanks again

[Nickol]

If a lot of crud is coming from the fuel tank as surmised, would not the filter in the fuel pump become continually blocked? If it is not then there must be another root cause soemwhere.

[kevin s]

Ours had the same issue, there is a completely innaccesable plastic gauze filter on the fuel pick up line in the tank, which had blocked and partialy collapsed. (I think it might havd been affected by something in the fuel)

Blowing it backwards would sort it for a few days but even though there was very little dirt in the tank it would eventually block again.

In the end I turned up a brass fitting to go in the sender unit and fitted a pick up in there with a modern plastc mesh filter on the end instead. I did this so it could easily be removed and cleaned but have never needed too.

rps20190202_224925.jpg (69.79 KiB) Viewed 1841 times

The original pick up pipe was blanked with a plug I turned up.

[myoldjalopy]

I did wonder about the electronic ignition unit, which was a recent (before the 3 year’s rest the car had) but was trying to avoid replacing it with the original one!

Surely worth a try to swap it out for the original. They can - and do - go wrong, as occasionally reported on here..

[Tea]

We had the same issue a few years back. The stuttering disappeared after blowing the jet with the use of an air compressor. A couple of weeks later, the same thing happened and so again we used the air compressor and we’ve not had the stuttering since.

[Biggles1957]

Did you change the condenser yet? Sometimes when they get warm they start to break down...

[Bornfree]

Did you change the condenser yet? Sometimes when they get warm they start to break down...

It’s electronic ignition, so no condenser. ( Whether the whole unit is overheating is another possibility!!)