Bogging and misfiring

[Charles H]

I had a similar problem years ago and found that the answer was very simple. The symptoms were similar, but the car only ran on 3 cylinders when the nose pointed up, so a hill or when towing. Eventually I discovered water in the float chamber (SU) in the debris trap at the bottom on the front carb. When the car was pointed upwards, the water 'rolled' over the bar to the entrance of the pipe to the jet. The water was more viscous and could not be drawn through. Pointing the car downhill moved this droplet back and no problem! It took 'AGES' to find this, so try cleaning out everything from both float chambers..... you never know!

[Mike Stevens]

Hi Daryl,

It certainly sounds like a fuel delivery problem to me. I had something similar which was (eventually) tracked down to one needle valve sticking shut after a bit of 'active' driving. However, you have new needle valves so that is ruled out.

On the basis of single faults, things you have changed are unlikely to be the cause, so maybe concentrate on those you haven't changed yet.

I would try disconnecting the fuel pipe from pump to carbs, and put it into a can or something similar. Hand operate the pump to see what flow you can get. It should be a fair old squirt each hand pump. You can also try feeding the pump from another can and compare the flow rates.

You may also be able to blow back into the tank and see if that dislodges anything in there. Due to the non-return valves in the pump, you'll have to do that at the pipe before the pump.

I assume you got suitable oil in the dash-pots? Silly question I know!

Keep us informed of progress! Good luck.

Cheers,
Mike.

[Crockett]

I assume you got suitable oil in the dash-pots? Silly question I know!

In this case I have but it's not such a silly question. I do remember that keeping the oil levels up in some Stromberg carbs I had on a previous car, was a nightmare as it kept sucking it out. These are SUs so that's not so much of a problem but it was one of the first things I checked (through habit) , nonetheless.

[stag estate man]

hi i had a problem similar to this a few years ago it turned out that a previous owner had replaced the rubber fuel line and had used a braided water hose instead of proper braided fuel pipe. the pipe looked ok as the braid was intact but the internal rubber pipe had collapsed and was causing fuel starvation as you describe worth a look! hope this may help

[owen1183]

Had this on a peugeot 205, turned out to be an air leak in the carb..... I got rid of the car and the problem went away

[Crockett]

Had this on a peugeot 205, turned out to be an air leak in the carb..... I got rid of the car and the problem went away

That's not an option

[Crockett]

Hi,

I figured I'd take advantage of the better weather to strip down the float chambers etc.. I was on the look out for any water at the bottom.which might slosh about from time to time, causing the intermittent problems I'd been having.

I didn't notice any water but I did find a ton of dirt in float chamber no. 1. I'd used a syringe to extract all the petrol from
the float chambers and as I drew it up I thought "Hang on a sec. Petrol shouldn't be dark brown!"

There was thick dark brown sludge coating the entire inside of float chamber no. 1. No. 2 wasn't as bad but still had light brown petrol in the bottom (tea colour).

Anyway, I thoroughly cleaned these out and reassebled them. The car does now seem to be running very much better (time will tell).

As some of this dirt was quite loose, I figure any increased petrol flow at wider throttle openings may have been dislodging some of the debris and washing it into the jet, presumably occasionally blocking it.

I'll see how it now behaves now it's clean, for a while. but hopefully this is what's been causing the problem. It certainly won't have helped!

Daryl.

[Greeks]

Have you got an in-line filter in the fuel line? If not, then it's time to fit one! You've probably got sludge in your tank or lines.

[Crockett]

Hi,

I have yes although I moved it very recently from the input of the carbs to the input of the fuel pump (when I replaced the fuel pump).

It's probably been a few years since the float chambers had a good clear-out (4-5?), when I last replaced the needle valves. I certainly don't recall them being that full of sludge at that time.

I think I'll keep a closer eye on them in future. It's not hard to pop the top of the float chamber on SUs, just to keep watch. Always assuming this has genuinely (finally) solved the problem, of course.

Regards
Daryl.