Technical Fuel system (filters, etc)

F30Msport

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So yesterday the 500 seemed to be struggling to get fuel on a ride around the block. Seems fine at idle, but not going down the road where it bucked and sputtered. I stopped and gave it a second, then made it back to the house with little drama.

I've searched and had trouble finding clarity on the fuel system and what should, and what should not, be there. I am wondering about the multiple filters and how to service them. I also think I have a fuel filter added in, that some on here say is not needed. See the picture attached.

Any guidance on servicing the fuel system, or diagrams pointing things out, is appreciated.
 

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Mike1alike

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By the low quantity of fuel in that filter, I'd say the fuel pump is underperforming (I think is the one below the filter). You'll need to either replace the gaskets inside the pump (if possible), either replace entire pump.
 

the hobbler

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So yesterday the 500 seemed to be struggling to get fuel on a ride around the block. Seems fine at idle, but not going down the road where it bucked and sputtered. I stopped and gave it a second, then made it back to the house with little drama.

I've searched and had trouble finding clarity on the fuel system and what should, and what should not, be there. I am wondering about the multiple filters and how to service them. I also think I have a fuel filter added in, that some on here say is not needed. See the picture attached.

Any guidance on servicing the fuel system, or diagrams pointing things out, is appreciated.
For a start, that filter between the pump and the carb is (a) totally surperfluous and, (b) in a dangerous position. If that filter was to leak, it would be leaking fuel over the dynamo/alternator---not a good scenario! Before you go the fuel-pump 'route', I would suggest that you replace the filter with a piece of E10 resistant fuel line between the pump and the carb. The E10 fuel line should be available at any GOOD car accessory shop. I am notsure whether it is 8mm or 6mm fuel line---take one of the removed pieces with you when you go to buy the new fuel line. Try that, and if that doesn't improve things, come back to us and we will tell you how to 'adjust' the fuel pump
 
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F30Msport

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Thanks Hobbler. I figured that was the advice. So I did get a ride in it and the fuel filter goes empty when I shut it off, but filling up about half way when it start it back up. Stupid question, but which way is the fuel flowing?
 

the hobbler

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Thanks Hobbler. I figured that was the advice. So I did get a ride in it and the fuel filter goes empty when I shut it off, but filling up about half way when it start it back up. Stupid question, but which way is the fuel flowing?
The fuel flows FROM the pump up TOWARDS the carb. Despite the fact that the filter probably has the direction of flow marked on it, there is always the chance that the filter has been fitted the wrong way round----but as I said earlier---take it OFF!
 
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I too have read & seen photos of many classsic 500s fitted with fuel filters over the dynamo or alternator where they have leaked or failed then BANG! ⛽🚭🧯 your pride & joy is gone into a cloud of ash. There should be a warning at the top of the classic 500 page DO NOT IT A FUEL ⛽FILTER IN THE ENGINE COMPARTMENT or even at the tank end it serves no purpose! apart from a major fire problem.
 
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F30Msport

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Took the top portion of the hose off to go to the auto parts store, but the fuel keeps seeping out the top of the filter that's still on. Any ideas how to stop it until I get back from the store with the new hose?
 
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F30Msport

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Fixed. Seems to have resolved the issue too! Now, should I consider adjusting the full pump?
 

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the hobbler

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Fixed. Seems to have resolved the issue too! Now, should I consider adjusting the full pump?
If you have sorted the running problem of the engine, leave wellalone----in the words of that well known German air-cooled sports-car engine maker---"if it ain't broke, don't repair it". If you still DO have a running problem, I will go through how to 'adjust' the fuel pump
 
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F30Msport

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If you have sorted the running problem of the engine, leave wellalone----in the words of that well known German air-cooled sports-car engine maker---"if it ain't broke, don't repair it". If you still DO have a running problem, I will go through how to 'adjust' the fuel pump
So...the car has been sitting for about a week. It started right up, and warmed up fine. I made it two house down the street before it started bucking and sputtering again. Any guidance on identifying and fixing this issue is appreciated.

On a side note, if I am looking for professional help, should I start with a shop that knows air cooled cars?

@the hobbler
 

the hobbler

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So...the car has been sitting for about a week. It started right up, and warmed up fine. I made it two house down the street before it started bucking and sputtering again. Any guidance on identifying and fixing this issue is appreciated.

On a side note, if I am looking for professional help, should I start with a shop that knows air cooled cars?

@the hobbler
Where do you live?
 

the hobbler

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Where do you live?
Where do you live?
A thought--does the engine run OK when you have the 'choke' in operation and then start playing silly b---ers when you stop using the choke? If this is what happens, have you checked that there is no warping of the carb flange and the bakelite spacer? Both these parts are known to suffer from this (due mainly through people over-tightening the carb retaining nuts). If these parts are warped, they will draw in air, making the engine run very weak, which might be the cause of your problem
 
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F30Msport

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Took it out yesterday and once again it did its bucking Bronco impression, but only for a few seconds, then back to running fine. Should I look at the fuel pump now?
 
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Sounds potentially electrical to me, for it to go from fine to Bronco and back again doesn’t figure for it to be mechanical. Naturally you did have fuel filter issues to which you have sorted but in my experience a pump either works or doesn’t. There is the potential it is a sticking float valve in the carb but if it was a blatant good bad good scenario I’m not sure it would be that either.
 

the hobbler

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Is there another filter beside the one in the tank I missed?
There is a small filter in the top of the fuel pump and usually, another small filter in the top of the carb. Have you still got the original condenser fitted, or are you using electronic ignition?
 
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F30Msport

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original condenser. I cleaned and oiled the distributer this morning, but it happened again...
 

the hobbler

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Any thoughts on what to check/fix next?
Have you tried a new condenser?--they are affected by heat. The distributor and condenser (in its original position on the distributor) are directly in the path of the 'cooling' air from the engine. As you are still on points, it might be worthwhile (anyway) to invest in one of the Swiftune condensers which, due to the fact they have long leads for both the feed AND the earth, can be positioned up by the distributor, out of heats way.
 
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