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Rodney Collins
United Kingdom
424 Posts |
 Posted - 19/06/2008 : 09:59:40
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Re the recient flooding of my SU resulting in my Volumex be filled with neat petrol (seemed like 5 gallons when I had to empty it). I am a bit perplexed, it is about the third time this has happened. The only conclusion I can come to is dirt in the petrol from the tank. When I removed the float chamber there was sediment in the bottom which I washed out. I then used my airline and blew everything dry reassembled the carb put it all back together and all was fine. I can only think that the dirt is blocking ball bearing valve into the float chamber. Any other suggestions. I am thing of trying an inline petrol filter.
Regards Rodney |
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David Allison
United Kingdom
665 Posts |
Posted - 19/06/2008 : 10:51:29
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Rodney
I would fit an in line tap on the fuel line as a first line defense.
The problem is that the fuel lines are inclined to syphon the tank.
The NA has always had in-line taps on the ful lines and unless I remmember to turn them off the carb fills up and although it has never flooded, because my garage is in unit with my house there is always a d9istict whiff of petrol in the house.
I also tend to turn the fuel pumps off a few seconds before I cut the engine, this empties the float chamber and prevents the syphoning between cutting the engine and shutting the fuel tap.
I have never had much success with in line filters - they tend to limit fuel flow too much and also dont have large enough capacity for a blown engine.
The problem that you have with sediment is almost certainly caused by the tanker driver strikes - the garages have lower stocks than normal and ps the pumps are stirring up the sediment in the base of the tanks and distributing it in your fuel (at no extra charge).
Try the fule tap idea - it works.
Regards David
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George Eagle
United Kingdom
3244 Posts |
Posted - 19/06/2008 : 11:55:55
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I have an in line filter on my NB, it is in the fuel line between the pump and carb. I do not agree with David's comments about fuel flow, I have experienced no problems at all with fuel flow.
I also have a modern Facet fuel pump which has a filter built into it.
It is far better to have a filter than risk having the dirt sucked into the blower and scoring the rotors!
Have you checked your fuel tank? When I have rebuilt cars I have always found it necessary to have the tank cleaned out, this involved cutting out a square in the rear of the tank, having it all shot blasted and then having a new plate fitted over the cut out hole. To finish the job I usually use a slosh tank sealant, but be careful about the reserve feed!!
George |
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David Allison
United Kingdom
665 Posts |
Posted - 19/06/2008 : 13:33:16
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George
I agree if you are using a Facet hi delivery pump and are using the car for road use there are normally no problems.
However the problems with filter I had in the past were some years ago and my attitude is therefore clouded agin them!
I probably drive my NA harder than many others for road use too which has some bearing on this.
My personal experience supplying fuel during the time my parents ran a fuel filling station is that dirty fuel is very rare and I only came across it once in 15 years (that too during a tanker driver strike and another local garage ran dry causing problems for local inhabitants).
Dirty fuel is as I said earlier a case of bad housekeeping but not entirely the garage managers fault.
I do have concerns with the patent "slosh sealers" a number of scare stories here and on other forums - have cases of blocked fuel outlets and even chemical reactions between the sealers and the fuel.
My personal point of view is - clean the tank carefully and as long as the tank itself is in good condition leave it be.
I dont personally like shot blasting tanks - because of the difficulty of cleaning the grit out of the tank afterwards - is this not what we are trying to clean in the first place?
Only buy fuel from the larger forecourt chains - they have larger tanks - are less likely to run their tanks low and because they are renovated on a regular basis have newer tanks.
Smaller fuel retailers are normally more expensive and therefore the fuel hangs around unsold for longer and the tanks are potentially dirtier - although in fairness this is not always the case.
I think we are getting away from Rodney's problem.
He has inadvertently picked up some bad fuel - the chances of it happening again are small - why introduce a modern contraption into a proven system which does not normally give trouble?
My NA has the standard (albeit modified in 1935 to larger fuel lines and twin pumps) fuel system with no filter.
In over 50 years of ownership by my family the car has never experienced this problem!
I had the tank to pieces last year when the fuel feed pipes came adrift of the fitting in the top of the tank - the tank is an original and there was nothing other than petrol in there.
My dad is not renowned for his lavishing of loving care on the car - indeed he is more famous for the poor cars abuse.
We dont have a fuel filter - an air filter on the carb or anything else that Abingdon would not recognise, although if it was thought necessary it probably would have been fitted.
Rodney I think you have been unlucky - clean it all out and it will be fine I am sure.
I think I have been ranting - sorry chaps!
Regards David
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Peter Scott
United Kingdom
1240 Posts |
Posted - 19/06/2008 : 15:34:08
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Rodney
I experienced float bowl flooding. The problem, which was sorted by advice from this forum, was that the float lever was dropping too far and resulted in a jammed needle valve. So I would check that your lever cannot fall to far.
I do not have a blower, but if I did I would definitely fit a fuel tap in a prominent place. That would be guaranteed to solve your problem - as long as you remember to use it. (I like simple solutions.)
Good luck, Peter
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George Eagle
United Kingdom
3244 Posts |
Posted - 19/06/2008 : 20:43:04
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To clarify the position on cleaning petrol tanks - in my case they were original, had not been used for aeons and were full of gunge including petrol residue that had turned to tar!
Cleaning out after shot blasting was thorough including a high pressure airline. Using a sealant immediately ensured the cleaned surface had no chance to rust. I have not experienced any problems/reactions to petrol with the sealant.
George |
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David Allison
United Kingdom
665 Posts |
Posted - 20/06/2008 : 10:33:14
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George
You make a very good point - however if a tank is in a really bad condition I prefer to re-make it using leaded steel sheet (we need all the lead we can get).
Regards the MMM fuel system (the point of the post):
The standard pipe-work for the P Type encourages the fuel to syphon naturally to the float chambers from the fuel pump.
On blown cars this is definately a boon - blown cars need all the fuel they can get.
However it can also be a problem.
Under bonnet blowers are not so bad because the carb is installed high up and the fuel tends to drain back.
Dumb iron installed units however are very prone to flooding and that is why the factory used to fit taps to the fuel lines.
As I said in the earlier posting - I always switch the fuel pumps off and run the engine for a few seconds to empty the float chambers prior to cutting the engine.
Mostly to prevent my getting moaned at for stinking out the ground floor of the house with a petrol odour (which is unpleasant) because our garage is part of the ground floor of the house.
I also shut off the fuel lines after switch off to prevent the fuel syphoning through.
I agree with Peter Scott about the fuel level inside the float chamber - it never ceases to amaze me how high some people set this level - often the carb is flooding without the owners knowlege.
You can often have a flooding float chamber caused by things other than the float level itself.
If the levers are damaged - the pin is worn in the fucrums - or even a sticking primer pin.
The levers - are the little fork which acts on the float needle.
Often the curve on these levers is unequal and not set at the right height for the float level. This can cause the float to run higher or lower than the desired position.
The fulcrum pin - is usually a brass pin pressed through two hole drilled in the float chamber lid.
Over time these holes become enlarged and the pin also wears.
This leads to sticking floats and often an inconsistent float level.
The primer pin - this is a little brass pin sticking through the top od the float chamber lid which acts direct on the float to "flood the carb".
Very common on cars and motor cycles before and just after WWII - if this pin is sticking it can cause flooding by accident.
These little "tickling pins" as they are sometimes known were often removed from carbs because of their unreliability.
Float Level (engine off - remove the carb dash pot):
The fuel level inside the float chamber should be just below the level of the top of the jet with the fuel taps open and the fuel pump switched on.
Too high and the engine will hunt at idle and you end up doing "Trev The Rev" to stop oiling plugs - too low and the engine runs dry at high revs and gives all the symptoms of weak mixture, however richer needles make no diference.
This is a "by eye" proceedure.
I was taught to set the levers acting on the float using a large drill (7/16 or 1/2 inch) - this makes sure both levers are at the same starting point.
Then gradually increase or decrease the float level height to suit.
Only alter one thing at a time!
Always make sure that everything else is ok before you start messing about.
Always make sure if you fit a fuel tap - it is switched to the on position before you drive off - there is nothing worse than spluttering to a halt afte a few hundred yards.
Hope all of this is useful
Regards David
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Richard Hardy
United Kingdom
2165 Posts |
Posted - 21/06/2008 : 14:38:21
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Responding to David's comment that he has never had much luck with in-line filters ie limiting throughput capacity, the simple solution, which I did years ago, was to purchase an in-line glass tube Flexilite style filter and simply machine new ends up incorporating larger unions. Works great.
Rich H |
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Rodney Collins
United Kingdom
424 Posts |
Posted - 21/06/2008 : 17:10:33
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I have decided to fit a fuel tap, I guess between the fuel pump and the carb, the problem is where, i don't want to have to lift up the bonet each time I stop to turn off the fuel so where is the best place to fit the tap?
Rodney |
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McEvoy
United Kingdom
252 Posts |
Posted - 22/06/2008 : 17:45:53
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| I have always found the by-eye method advised by David using a drill has always proved to be a very good starting point for setting float levels. One of the first things I was taught by my Dad in the 50s. Good practice never changes. |
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Rodney Collins
United Kingdom
424 Posts |
Posted - 22/06/2008 : 18:25:32
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Thanks for that Paul I also have the B/W O ring switch over valve so I guess I have the fuel on /off tap built in I will do some experimenting.
Rodney |
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Peter Green
United Kingdom
1682 Posts |
Posted - 23/06/2008 : 00:45:13
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I would like to elaborate on what David has said about setting the fuel level in the float bowls. He is correct in saying that a 7/16ö bar (drill) should just pass under the fork but this only applies to 1 7/8ö and 2 1/4ö diameter float bowls the larger 3ö diameter float bowls require a 5/8ö bar (drill).
Peter.
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David Allison
United Kingdom
665 Posts |
Posted - 23/06/2008 : 08:57:56
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Peter
Many thanks - you saved me a post this morning (rats I have now posted and therefore saved nothing)!
Indeed the different float chambers all have a different set up point - although these are only a guide.
Regards David |
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John K
New Zealand
5 Posts |
Posted - 23/06/2008 : 10:41:10
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Hi Rodney
As well as all the excellent advice you have recd on this topic have you thought of putting an electric solenoid fuel valve in the line between the pump and carb. I know the purists will scream but they do work and are small enough to hide within the chassis rails. You can wire it into the ignition circuit. They take less than an amp to hold open so current draw is minimal. Some of them have a manual override if the valve should fail in the closed position.
Food for thought as a blower full of petrol could be an expensive exercise.
Will await the reaction of the members with interest.
Good luck. John |
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David Allison
United Kingdom
665 Posts |
Posted - 23/06/2008 : 11:26:49
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John
I think the idea is a good one - if rather over complicating the issue.
A simple tap is much easier to install and less troublesome in my opinion.
Regards David |
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KevinH
United Kingdom
156 Posts |
Posted - 23/06/2008 : 14:22:11
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John,
Exactly what I've been thinking of doing as the needle valve in the SU on my front mounted blower leaks slightly and slowly floods the carb, and siphons petrol from the tank when the car is left standing.
Does anyone know of a suitable solenoid valve, preferably with a manual override? I think I prefer this to a manually operated one that one day I'll forget to turn on!
Kevin |
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