General Re-fuelling

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General Re-fuelling

Cookiebella

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Hi All

I've had the fuel tank out for a couple of weeks to get it powder coated and am about to put it back in.

Will I need to do anything to clear any air from the fuel system or should it sort itself out?

Thanks for your advice.

Ian
 
You might find that the fuel is reluctant to flow initially. I have found that the best way round this problem is to slightly pressurise the fuel tank. If you leave the feed pipe into the fuel pump off, make sure that you have another pair of hands standing by who can quickly fit the 'in' fuel pipe onto the fuel pump when the petrol starts flowing. You can, of course, do this with the fuel pipe left connected onto the fuel pump, but you will not know when the fuel has started flowing into the pump. To pressurise the fuel tank I use an electric air-pump (for tyres). Put the hose from the pump into the filler neck of the fuel-tank, hold it in place with enough rag to seal the filler neck,and then turn the pump on. You won't need a lot of pressure, but be careful when you take the rag and air-pump hose away from the tank, you will get a release of pressure. There are other ways to getting the fuel flowing, but I have found this the easiest.
 
Jack up the front and give a good hard suck on the pipe at the engine end (not too long!!!) to use gravity/siphoning effect?? Just a thought (post boozy lunch so poss not the best suggestion!)
 
The 'slight' fly-in-the-ointment system in the UK is that practically all of the 'Ethanol-resistant' fuel piping sold over here is NOT clear, and due to the amount of ethanol in our fuel, you do really need to use it. I always try to use 98 octane fuel ("super" in the UK) to (a) get round this problem and, (b) my engine is well tuned, but I still use, and fit, 'ethanol-resistant' fuel piping.
 
Hi All

I've had the fuel tank out for a couple of weeks to get it powder coated and am about to put it back in.

Will I need to do anything to clear any air from the fuel system or should it sort itself out?

Thanks for your advice.

Ian
Ian, you shouldn't need to bleed anything. A certain amount of fuel should still be in the pipework and in the pump and chances are that after a maximum of four or five short bursts of the starter your engine will fire. By then the pump should have pulled sufficient fuel through to maintain the engine with a regular supply.
Some people experience a problem in this respect and I suggest that relates either to problems inside the fuel pump (worn valves or seals) or loose pipe clips allowing air to be drawn into the fuel pipework at some point.
 
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Thanks Peter that sounds encouraging. I must admit that I didn't fancy 'sucking on the pipe'!

I think that most of the fuel in the pipe has leaked out or evaporated so won't the air that's now in the pipe get sucked into the filter and carb ahead of the fresh fuel?
 
Thanks Peter that sounds encouraging. I must admit that I didn't fancy 'sucking on the pipe'!

I think that most of the fuel in the pipe has leaked out or evaporated so won't the air that's now in the pipe get sucked into the filter and carb ahead of the fresh fuel?

Yes, but that's how pumps work. The action of the pump reduces the pressure of the air in the pipework to the tank and in the same way as when you suck on a straw (or on the end of the pipe :eek:), atmospheric pressure forces fuel up from the tank and along to the pump-chamber.

The problem that some people have experienced is that the above process doesn't naturally happen in practise. It seems that the innards of the pump need to get wet with fuel before it starts to work properly.

There are some tiny springs inside the pump which act on valves to make the pump work. I can only suggest that these springs or the valve discs possibly get weakened or worn and aren't able to function properly when dry.

I have never heard of this issue on any other type of car with a mechanical fuel-pump and many older cars actually have a hand-lever on the pump to allow you to get the fuel going without using the starter....many of the early cars only had a handle anyway.:bang:

The suggestions previously made by others will work but are a PITA.
Once the tank is re-fitted I would get someone to turn over the engine with the ignition off or disconnected for a few short bursts whilst you check for fuel at the disconnected pipe at the carb inlet; the fuel should flood out if it gets there. If it doesn't then you have at least been told by others how to force it through.(y)
 
Yes, but that's how pumps work. The action of the pump reduces the pressure of the air in the pipework to the tank and in the same way as when you suck on a straw (or on the end of the pipe :eek:), atmospheric pressure forces fuel up from the tank and along to the pump-chamber.

The problem that some people have experienced is that the above process doesn't naturally happen in practise. It seems that the innards of the pump need to get wet with fuel before it starts to work properly.

There are some tiny springs inside the pump which act on valves to make the pump work. I can only suggest that these springs or the valve discs possibly get weakened or worn and aren't able to function properly when dry.

I have never heard of this issue on any other type of car with a mechanical fuel-pump and many older cars actually have a hand-lever on the pump to allow you to get the fuel going without using the starter....many of the early cars only had a handle anyway.:bang:

The suggestions previously made by others will work but are a PITA.
Once the tank is re-fitted I would get someone to turn over the engine with the ignition off or disconnected for a few short bursts whilst you check for fuel at the disconnected pipe at the carb inlet; the fuel should flood out if it gets there. If it doesn't then you have at least been told by others how to force it through.(y)

I agree I always suck on the end of the pipe!!!!! If you get a bit of petrol in the mouth it won’t kill you, well it hasn’t killed me yet, literally takes less than a minute to do. Just make sure the car is parked on a flat surface.
Tony
 
.......If you get a bit of petrol in the mouth it won’t kill you, well it hasn’t killed me yet.....

Nahh the renal failure does though....

(see Beirne and Brennan 1972)

Diesel has the same effect....
 
Nahh the renal failure does though....

(see Beirne and Brennan 1972)

Diesel has the same effect....
You can avoid that by taking the other suggested approach. Then there's the possibility that as you pressurise the fuel-tank, a spark from your electric compressor will ignite the petroleum vapour, thus blowing the whole problem to Kingdom Come. [emoji3]
Give me a low-tech suck any day. (Should I re-phrase that?) [emoji28]
 
I'm not sorry to labour this point [emoji28], but a few weeks ago I decided it was time for my original 499 engine and box, which sit on a pallet at the back of the garage, to have their bi-annual run. So I rigged up a battery to the starter etc. and a short length of pipe between a can of petrol and the pump and turned the engine over for less than half a minute and it coughed a little. I got the "choke" just right, tried again and it fired up....no drama. In this scenario the petrol was below the level of the pump so there was no siphoning advantage and the pump was able to draw fuel... mysterious......
 
To suck or not to suck that is the question!! Whether tis nobler in the mind to suffer a mouth full of petrol or take against a sea of troubles and rely upon the pump to do its thing! :eek::eek:

With apologies to William Shakespeare!

The fuel tank should hopefully go back in tomorrow and I'll follow Peter's advice and try firing her up just relying on the fuel pump to do its thing. If that fails I'll revert to plan B.

Wish me luck!
 
To suck or not to suck that is the question!! Whether tis nobler in the mind to suffer a mouth full of petrol or take against a sea of troubles and rely upon the pump to do its thing! :eek::eek:

With apologies to William Shakespeare!

The fuel tank should hopefully go back in tomorrow and I'll follow Peter's advice and try firing her up just relying on the fuel pump to do its thing. If that fails I'll revert to plan B.

Wish me luck!

I think Shakespeare must have owned a Fiat because apparently he said in Henry IV, Part 2;

"I were better to be eaten to death with a rust than to be scoured to nothing with perpetual motion".

For once he was wrong though...far better to wear your 500 down through use than let it sit there and deteriorate. :D
As with most subjects by now, those of us who have been learning from and contributing to this Forum for a year or two have seen these issues discussed on previous occasions and on other Forums. I think that the thread linked to below refers back to another discussion where it was pointed out that the 126 pump might be different from the 500 in more than just the obvious physical way. The tank on the 126 is lower than the engine so has more work to do in supplying fuel. This possibly explains the problems some people experience:

https://www.fiatforum.com/500-classic/444867-fuel-pump-types-500-v-126-a.html
 
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So, having got the fuel tank back in I had a go at firing her up.

I followed Peter's advice and initially turned the engine over a few times with the ignition turned off. I then turned the ignition on, pulled the starter again and she fired up straight away!

Thank you all for your advice and especially to Peter who saved me from attempting the pipe sucking!

Ian
 
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