Anti Siphon

My Racor is the turbine which does indeed have the aluminium ball - I have taken it apart and serviced it before. I also had understood the ball is to prevent the fuel flowing back into the tank when the engine is off. I was tempted to think it wasnt the ball as someone had suggested this type of failure was very unlikely, but then again someone else has indicated this was exactly the source of their problem. Conflicting opinions! I suppose the ball could stick but it seems odd to me that it ran for about an hour at 2,500 rpm, then the rpm fell back to 1,500 the vac in the Racor shot up and the rpm wouldnt respond to the throttle - clearly fuel starvation. It didnt recover until I released the vac in the Racor which again rose quickly and after a few minutes with the same result. Strangely the time before it happened by the follwoing w/e the problem had disappeared and it was fine again for about an hour. I suppose this could indicate a sticking ball.

However, I suppose it could also be something on the bottom of the pickup that eventually drops away, although I did have the tank completely cleaned and the fuel polished about three years ago and I get no comtamination in the Racor bowl at all.

Yes, my understanding is the valve is on top of the pickup (if there is one) and is required in the States to prevent the fuel siphoning into the builges in the event of the fuel line splitting - if there is a valve there!

Intermittent faults are very annoying and it will be interesting to see if this weekend the engine runs normally when I switch it on.

I suppose it is going to be clean everything through - but I am still wondering which end to start!
 
Interesting this as I’m having a similar problem following finding the sight bowl full of diesel bug bits. All cleaned out, engine runs at 3000rpm for 15 minutes then won’t rev above 1500. I’ve not noticed any vacuum in the Racor but I suppose it’s possible. The instruction booklet doesn’t mention dismantling the filter unit as part of a service, that little ball bearing would be prime candidate to end up in the bilge under the engine :cautious:
 
Jamie - the first time I dismantled the Racor with an engineer he was very keen on stripping down the Racor and suggested the ball should be cleaned. Perhaps he was right. It is difficult to find clarrity. It is very straightforward once the Racor is on the bench - not a job to do in situ.

I have a vac gauge on the top of the Racor which has proved very useful. It is an instant indication of whether the vac is out of parameters. You probably know the lift pump should be on the engine side, so if the vac. rises it seems to me there are relatively few possible causes. The obvious is the filter has come to the end of its life (which I have had, and is an instant solution) or something along the lines of the problem possibly we both have. I can understand if the ball sticks partinally closed it would result in exactly this issue, I just cant yet see that it is likely it would.

I wish my problem was instantly repeatable for obvious reasons. Strangely I hope when I run the engine next the vac will instantly rise, so when I strip and clean the Racor and it goes away I will know the problem is cured!
 
ip485 said:
Jamie - the first time I dismantled the Racor with an engineer he was very keen on stripping down the Racor and suggested the ball should be cleaned. Perhaps he was right. It is difficult to find clarrity. It is very straightforward once the Racor is on the bench - not a job to do in situ.

I have a vac gauge on the top of the Racor which has proved very useful. It is an instant indication of whether the vac is out of parameters. You probably know the lift pump should be on the engine side, so if the vac. rises it seems to me there are relatively few possible causes. The obvious is the filter has come to the end of its life (which I have had, and is an instant solution) or something along the lines of the problem possibly we both have. I can understand if the ball sticks partinally closed it would result in exactly this issue, I just cant yet see that it is likely it would.

I wish my problem was instantly repeatable for obvious reasons. Strangely I hope when I run the engine next the vac will instantly rise, so when I strip and clean the Racor and it goes away I will know the problem is cured!
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The vac gauge seems like a good idea, my Racor is in a difficult to access place. Removing the unit doesn’t fill me with joy, just hoping my problem is the spin on filter on the engine being gunked up.
 
Jamie - run the engine till you have the problem, shut down and immediately release the lid on the Racor. If there is a hiss as air gets sucked in and / or the fuel isnt at the top, then I sugest the problem is at the Racor or down stream. Swap out the spin on filter. If that doesnt work it is something else. If you are running at less than 30 micron (a 10 or 20) you might try a 30 if there is some contamination in the fuel.
 
ip485 said:
Jamie - the first time I dismantled the Racor with an engineer he was very keen on stripping down the Racor and suggested the ball should be cleaned. Perhaps he was right. It is difficult to find clarrity. It is very straightforward once the Racor is on the bench - not a job to do in situ.

I have a vac gauge on the top of the Racor which has proved very useful. It is an instant indication of whether the vac is out of parameters. You probably know the lift pump should be on the engine side, so if the vac. rises it seems to me there are relatively few possible causes. The obvious is the filter has come to the end of its life (which I have had, and is an instant solution) or something along the lines of the problem possibly we both have. I can understand if the ball sticks partinally closed it would result in exactly this issue, I just cant yet see that it is likely it would.

I wish my problem was instantly repeatable for obvious reasons. Strangely I hope when I run the engine next the vac will instantly rise, so when I strip and clean the Racor and it goes away I will know the problem is cured!
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Having stripped down several Racors, I can't see how the Racor ball could stick in the closed position as it's only gravity that keeps it closed. It could certainly stick in the open position and fail to close and, indeed, many Racors are stuck open because they have been wrongly reassembled but all this means is that fuel tends to drain back to the tank when the engine is stopped. depending upon the relative heights.

Richard
 
RichardS - yes, and thank you, that was the argument I had read before and sounds sensible.

I suppose it is just conceivable that if it was very sticky and coated maybe it could hang on partially closed, but I keep thinking this seems very unlikely.

I know what you mean by gravity, and I guess it is even a bit more than that, with the engine off and the fuel wanting to drain back to the tank the pressure of the fuel also contributes to forcing it to close.

It is even more unlikely it would stick partially open it seems to be - I can understand even jammed closed, but not the partial bit, as I get enough fuel through mine to run at 1,500 rpm.
 
ip485 said:
It is even more unlikely it would stick partially open it seems to be - I can understand even jammed closed, but not the partial bit, as I get enough fuel through mine to run at 1,500 rpm.
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Sticking partially open is very common with the Racors. Both mine were sticking open because the valve seat was installed upside down. However, sticking open will not affect the running of the engine at all so that cannot be your problem.

Richard
 
Richard - no I meant sticking partly closed, in other words the ball in some way stuck to its hole - but, I agree this seems so unlikely because as soon as the pressure builds up in the Racor I would imagine it would have to almost be stuck with super glue for it not to release, especially if only partially stuck.

BTW you have pretty much convinced me that it is very unlikely the Racor is the source of the problem and I am leaning to a blockage in the fuel pipe or in the pickup or the elbow at the tank exit.
 
For those who might be interested, I disconnected the fuel pipe from the tank which proved easier than I thought. I sucked out the pipe with an oil remover and blew through some air. There was no obvious blockage. it was correct there was no anti siphon valve on the tank, just a right angle connector and on / off tap. Blew through the tap and no issue. The pickup was interesting. I expected a removable pickup but it was a wide aluminium tube welded in place and of original manufacture. I blew through this as well. No signs of blockage either. Engine ran perfectly on two one hour runs at high revs with no sign of excess vac. in the Racor. Inevitbaly a complete mystery but fingers crossed. I have a diagram of the 300 gallon diesel tank somewhere so will look out how the pickup works. Someone else suggests that the "washer" the ball in the Racor sits on if installed upside down can cause exactly this problem, but I didnt take the Racor apart, and dont entirely follow the suggestion as a cause.
 
ip485 said:
For those who might be interested, I disconnected the fuel pipe from the tank which proved easier than I thought. I sucked out the pipe with an oil remover and blew through some air. There was no obvious blockage. it was correct there was no anti siphon valve on the tank, just a right angle connector and on / off tap. Blew through the tap and no issue. The pickup was interesting. I expected a removable pickup but it was a wide aluminium tube welded in place and of original manufacture. I blew through this as well. No signs of blockage either. Engine ran perfectly on two one hour runs at high revs with no sign of excess vac. in the Racor. Inevitbaly a complete mystery but fingers crossed. I have a diagram of the 300 gallon diesel tank somewhere so will look out how the pickup works. Someone else suggests that the "washer" the ball in the Racor sits on if installed upside down can cause exactly this problem, but I didnt take the Racor apart, and dont entirely follow the suggestion as a cause.
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As I said above, an incorrectly installed valve seat in the Racor allows fuel to drain back to the tank when the engine is stopped but that is all.

Richard
 
Good to hear it seems to be ok, unsatisfactory though not to have a cause. Took mine out for a run today having changed the engine filter, all seems ok though I’ll be doing some pumping out of the bottom of the tank when the new hand pump arrives. Get most of the muck out, dose it up again then fill it with clean fuel. Fingers crossed sorted.
 
Just mulling over this vacuum thing. Presumably, unless the Racor is gravity fed from the tank which mine isn’t, a vacuum in the Racor is necessary to draw fuel through from the tank and into the system. Similar to a raw water strainer. Or am I missing something? Obviously the vacuum should be within acceptable limits.

edited, just had a closer look at the gauge which shows that a certain amount of vacuum is ok.
 
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Jamie Dundee said:
Just mulling over this vacuum thing. Presumably, unless the Racor is gravity fed from the tank which mine isn’t, a vacuum in the Racor is necessary to draw fuel through from the tank and into the system. Similar to a raw water strainer. Or am I missing something? Obviously the vacuum should be within acceptable limits.
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There would only ever be a partial vacuum, and a small one at that, in the filter. Once the lift pump starts to draw fuel, atmospheric pressure in the fuel tank will immediately start to push the fuel through to the Racor. The light ball will lift immediately and the fuel will flow through the filter and on to the pump. Of course, if there is a blockage somewhere, such as the filter itself, then the vacuum on the pump side will start to rise.

Richard
 
RichardS said:
There would only ever be a partial vacuum, and a small one at that, in the filter. Once the lift pump starts to draw fuel, atmospheric pressure in the fuel tank will immediately start to push the fuel through to the Racor. The light ball will lift immediately and the fuel will flow through the filter and on to the pump. Of course, if there is a blockage somewhere, such as the filter itself, then the vacuum on the pump side will start to rise.

Richard
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Was editing my post as you replied (y)
 
I 'm aware that the thread is not recent, but it might be of interest: I took my new and 'perfect copy' (all metal and with a mounting strap) Racor FG 500 apart yesterday before starting to install it. There was quite a bit of resistance in the inlet pipe, and applying pressure with a bulb produduced a 'popping' sound. There was no ball inside, but at the bottom of the vertical pipe is a simple rubber non-return valve with a spring. I can very well imagine this flow restriction offering resistance to greater demand from the engine.
 
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