I am attempting to restart my 3.4 L engine after a long restoration ( I believe engine is from a 57-59 sports saloon).However I get.significant gas flooding of the aux carb as soon as I turn the key and before I push the start button. The fuel pump has been replaced with a rebuilt pump, I have replaced the needle and seat in the float bowl, the floats are fine and I have checked the needles in the main part of the carb, all seem ok. I don’t know what else to check and would appreciate any advice. Thank you, - Brian
Assuming that by aux carb you mean the hisser solenoid enrichment version, and not the complicated AED thermostatic carb, I think the only way it can flood is by having the float valve of the associated carb sticking open. You can check by removing the bell and piston and observe the jet–to see if it too is flooding.
Strange, if it’s flooding the aux carb that much it should also be flooding the main carb, check that, it has to be a fuel level or needle & seat problem.
Yes it sounds like the float bowl feeding the starting carb is flooding. Sometimes it the flooding appears to stop when the engine fires up because the engine is gobbling up the fuel so fast.!
After checking the needle valve, check the serrated fiber washer under the carb vent tube, as the carb needs to breath.
Thanks Robert, will check.
Thanks for the advice Allrand, seems reasonable but I have replaced the needle and seat in the float chamber and there is no leak in the float and flooding of the aux unit is still happening. I see very little gas in the float bowl when I remove the top of the float chamber - maybe a quarter of an inch.
Thanks for your reply. It has flooded volumes out the aux carb when I just turn the key or when I push the start button - not got to the point of it starting yet. There is an aluminium and serrated fibre washer under the cap nut holding down the float chamber lid, I’ll recheck these.
Sounds like the float chamber cannot vent, check for the correct fiber washer with inner cutouts, & check that the overflow pipe isn’t blocked (for both carbs).
I agree with Randall, that would explain all the symptoms, overflowing with only 1/4" of fuel in the bowl.
Welcome to the forums Brian. Just FYI to save multiple postings your can reply to all the suggestions in the one post, saves you multi posting.
Flooding problem solved! Thanks all for the advice, I could not figure this out. It turned out to be a venting problem as suggested. In the restoration, I had painted the overflow or vent pipe and paint had sealed the bottom of the pipe, this prevented proper venting!
Thanks all for your kind and wise advice. - Brian
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I have had a problem with a gas smell at times when starting my MK2. Recently I had the ignition switch turned on to test some interior lighting etc, and gas dripped out of the overflow tubes with the fuel pump pressurizing the fuel line. Not sure why this happened or how to prevent this in the future. Also, I want to be certain that I have the aluminum washer and the serrated fiber washer in the correct position. Looking at the service manual, it appears that the aluminum washer is fitted below the brass overflow banjo and the fiber washer fits on top of the banjo. Is this correct? Or do both washers fit below the banjo? Please let me know. Thanks
The serrated washer goes next to the float bowl cap, the aluminum washer above the banjo, under the bolt head. This probably isn’t causing your leak which may be from a mis-adjusted or sticky needle valve. Lack of a functioning serrated washer in the right place can cause unusual problems, though. I’d fix the washers, if it still leaks, check the needles.
Thanks Ron. I’ll check it out.
In reply to your question… The aluminium washer goes on top of the breather banjo and the fiber washer with the cutouts below it.
If its started without you disturbing the washers, the most likely cause is a small nugget of sludge is causing the needle & seat in one carb to fail to fully close
In general if you remove the float lid, and ensure the float is not sunk, then remove it, you will find some sediment at the bottom of the bowl.
This should be cleaned out
The needle & seat should be inspected and cleaned of any gunk
It doesnt take very much to cause this issue, hence you hear about people tapping the bowl to stop it
Cleaning out the fuel bowl should be done occassionaly
Some cars have little carb filters, sometimes they are missing
You usually need a fuel bowl gasket before doing this job
I had a recent experience, over a long period, with poor engine performance yet no “sunk” floats. Then, I decided to paint the car, and it sat for about six months. When I fired it up last week, I noticed fuel leaking form the hisser as well as the front carb overflow (Mark X triple SUs). I had replaced the float valves, but expected it to be bad. It wasn’t…passed the blow into the intake test fine. Float was floating. Pulled the float and sure enough, it had some petrol in it. I suspect it was leaking for some time, enrichening the mixture, but not enough keep the float valve from closing. From now on I will inspect floats routinely, even if they appear to float.
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Amen to that. I’ve replaced all my cars’ soldered brass floats with the modern nitrophyl versions because of that exact scenario.
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Thanks everyone. I will check the floats and washer position.
I have not driven the car for almost a year as I am redoing the interior….seats, wood trim etc. I have a plastic milk crate for a front seat at the moment. When I rebuilt the engine this car would start immediately with a push of the starter button and the “Hisser” would work warm up the engine and drop to a smooth idle.The car is now much more difficult to start than it used to be. In order to get the motor running I have to press down on the accelerator and rev the motor. After 5-6 starts it will run with the accelerator pressed down and eventually idle. I don’t know if this is due do not being driven and I need to burn off accumulated engine gunk or if this is related to my other problem. Any suggestions will be greatly appreciated. Thanks
Does the ASC work ? Auxilliary starting carb