Petrol fallback

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Sirlisterofsmeg
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Petrol fallback

Post by Sirlisterofsmeg »

I know there are many discussions about starting problems and i have suffered most of them over the years but now my 1.9 DG petrol engine seems to turn over for ages before firing, sometimes flattening the battery. I think the petrol maybe running back to the tank after standing for long periods of time. Would a non return valve in the pipework stop this as it,s driving ne nuts having spent so much time and money on servicing, tuning, hot start relays, starter motor, battery, earth straps etc.etc.etc :(

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Aidan
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Re: Petrol fallback

Post by Aidan »

There is a reservoir in the carb that should hold enough fuel for the start up and there is effectively a vacuum holding fuel in the line from the fuel pump to the fuel filter by the tank and fuel sitting in the line from the tank to the filter; I'd fit a new fuel filter and when disconnecting the fuel lines from it (engine end first) observe if fuel is running out showing that the fuel hasn't drained back to the tank or is otherwise obstructed, obviously be prepared to catch the fuel. It may be that the fuel pump isn't in great shape or that the carb is a bit blocked, if water has got into the fuel it can turn to jelly sat in the carb, I know I have experienced that, it settles in the jet opening and blocks the main jet

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R0B
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Re: Petrol fallback

Post by R0B »

I had a similar problem it turned out to be the petrol had gone off. I put new fuel in and that sorted it. Having said that I have run on LPG for years so that may not solve your problem.
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keynsham1
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Re: Petrol fallback

Post by keynsham1 »

How often do you use your van? I have exactly the same problem with my 1.9DG. But I often don't drive mine for a few weeks and I suspect the petrol in the carburettor evaporates away, bearing in mind it is is a warm engine bay when you stop the engine last. The small mechanical pump then has to pump fuel from the front of the van to the carburettor and fill it up before it will fire!
I thought my problem might have been the automatic choke and I even bought an electric fuel pump to solve the issue, but I never fitted either as I found that if I start my van at least once a week, the problem goes away!

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Mocki
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Re: Petrol fallback

Post by Mocki »

The only way petrol could "run back" to the tank is if your mechanical pump is on its way out . It’s a diaphragm pump, so effectively it’s a one way valve , the petrol cannot run back through it . 
or you have pipe leaking and it’s letting air into the fuel lines , but not necessarily enough to actually leak petrol , or not enough to be noticed 

like Aidan says , there should be enough in the float bowl to start the engine and run for a couple of mins at least .
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chewbacca
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Re: Petrol fallback

Post by chewbacca »

keynsham1 wrote: 09 Feb 2021, 13:59 How often do you use your van? I have exactly the same problem with my 1.9DG. But I often don't drive mine for a few weeks and I suspect the petrol in the carburettor evaporates away, bearing in mind it is is a warm engine bay when you stop the engine last. The small mechanical pump then has to pump fuel from the front of the van to the carburettor and fill it up before it will fire!
I thought my problem might have been the automatic choke and I even bought an electric fuel pump to solve the issue, but I never fitted either as I found that if I start my van at least once a week, the problem goes away!

This is the same as my old 1.9 dg. Start it once a week no issue. Leave it for much longer, you're playing with fire. Leave it a month, air intake off the top of the carb & squirt in lots of easy start until it pulls through petrol through instead of running on easy start!
:run
I always put it down the fuel pump starting to fail, so that's being replaced on the new build.

 
B plate 1.9 petrol bus

Sirlisterofsmeg
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Re: Petrol fallback

Post by Sirlisterofsmeg »

Thanks for the replies everyone. I guess it,s unreasonable of me to expect it to start easy after several weeks or even months. Really isn,t used often at all. It,s a shame as i have replaced all fuel lines, new tank and filter, new pump and had the carb hydrosonically cleaned and rebuilt so can,t do much more👍

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