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Old 03-06-2013, 09:58 AM   #21
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.............. Wouldn't it be enough to simply fill the filter and let the lift pump do its job?............
I have a different engine, but that is what I do and it seems to work just fine.
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Old 03-06-2013, 11:40 AM   #22
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The inlet check valve will open from either a vacuum applied downstream by the diaphragm or by pressure applied upstream by an external pump.

Bob
That makes sense to me. Unfortunately the FL120 service manual only describes how the mechanical lift pump works. It does not go into details like how much pressure is required to open the spring-loaded inlet and outflow valves.

But the accurate answer to the original question is easy enough to get by simply calling Bob or Brian Smith at American Diesel.
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Old 03-07-2013, 04:56 PM   #23
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I just read the section on the FL120s fuel lift pump in the Ford service manual for this engine which is on the Grand Banks forum. It would appear that it is NOT a flow-through pump. There are spring-loaded valves on both the intake AND the outlet side of the pump. The inlet valve is opened under vacuum from the movement of the pump's diaphragm.

When the chamber is full the pressure from the diaphragm against the fuel opens the spring-loaded outlet valve while at the same time the spring-loaded inlet valve closes.

When the pump is not developing alternatiing vacuum and pressure from the action of the diaphragm-- in other words when the engine is not turning over--- BOTH the inlet and outlet valves are closed under spring pressure.

This is obviously why the people I know who have installed an electric auxiliary pump on their FL120s plumbed around the mechanical lift pump. Priming the fuel system using the electrical pump without the engine turning over means the inlet and outlet valves on the mechanical pump will be closed.

If the diaphragm fails with the engine running, the inlet and outlet valves will not open since there is no pressure available from the diaphragm to open them. So the auxiiary electric pump must be able to send fuel to the injection pump around the mechanical pump, not through it.
Thanks Marin. Now that you explained it i can understand that when the engine is not running the presure on the check vbalve wont open it because the outlet side check valve is closed. If the pumpos valves are worn it may leak through but it would likely have to be really old. These thread are a cornicopia of information
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Old 03-07-2013, 06:54 PM   #24
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Thanks Marin. Now that you explained it i can understand that when the engine is not running the presure on the check vbalve wont open it because the outlet side check valve is closed. If the pumpos valves are worn it may leak through but it would likely have to be really old. These thread are a cornicopia of information
Just read the service manual and my guess is....

I don't think thats the way the check valves work...any pressure greater than a few psi on the inlet side should be enough to let fuel pass freely through this kind of pump. The diaphram would create a slight vacuum, inside the pump , then a slight pressure to open and close the valves...I think these diaphram pumps operate on very low pessures so any electric fuel pump would pump freely through it.
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Old 03-07-2013, 07:23 PM   #25
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One of the reasons I'm doing this is to help flush my Racors. By having a shut-off valve after the filter, I can run the pump and open the Racor drain, flushing out the crud without having to open the filter or worry about air getting in the system.
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Old 03-07-2013, 08:30 PM   #26
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Greetings,
Mr. meridian. Ahh....something I hadn't considered. GOOD idea although at one point in the recent past I had to mechanically agitate the crud at the bottom of my Racors, with a long plastic cable tie to unpack it in order to drain the crud. So you're planning to put this electric pump before the Racor? In series or parallel? If in series, the question arises is the mechanical pump strong enough to draw fuel through the, not used all the time, electrical pump?
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Old 03-07-2013, 08:37 PM   #27
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probably in parallel. If I keep up with maintenance, the crud shouldn't solidify if I'm lucky. We will be on the Loop for the next year or two so I will be in the ER almost daily.
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Old 03-07-2013, 08:59 PM   #28
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Greetings,
So, 3 way valve, electric pump, 3 way valve in parallel before the Racor then? I concur, more frequent maintenance/draining would have eliminated or at least minimized my hardened crud.
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Old 03-07-2013, 11:58 PM   #29
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FWIW I posed the question to the GB owners forum. This has been discussed there in the past and all the responses I recall had the electric pump plumbed around the mechanical pump, not through it.

However one fellow just responded to my recent question saying that he had installed an electric pump in series (before) the mechanical pump as part of his fuel polishing system and this setup pushed fuel through the mechanical pump with no problem. So it can be done.

However this same fellow said he had not considered the notion of the electric pump pushing fuel into the crankcase in the event of a pump diaphragm rupture and that it was a possibility worth taking into account if one was planning an auxiliary electric pump installation. To that end, he said routing around the mechanical pump was a better plan.
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Old 03-08-2013, 07:14 AM   #30
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One of the reasons I'm doing this is to help flush my Racors. By having a shut-off valve after the filter, I can run the pump and open the Racor drain, flushing out the crud without having to open the filter or worry about air getting in the system.
Your filters must be different from mine. Mine (Racor) have a filter element and a plastic bowl on the bottom with a drain. I can open the drain and remove any water or sediment in the bowl, bit to remove "crud", I have to replace the filter.

I installed a Racor indicator that monitors the vacuum and indicates if the filters are clogged enough to need replacement.
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Old 03-08-2013, 07:42 AM   #31
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Greetings,
Mr. meridian. Ahh....something I hadn't considered. GOOD idea although at one point in the recent past I had to mechanically agitate the crud at the bottom of my Racors, with a long plastic cable tie to unpack it in order to drain the crud. So you're planning to put this electric pump before the Racor? In series or parallel? If in series, the question arises is the mechanical pump strong enough to draw fuel through the, not used all the time, electrical pump?

Agreed....crud does often form and I don't think forcing fuel through it is going to help as the whole idea of the turbine is to spin the flow of fuel so stuff settles out into the bowl.

The easiest way I have found to clean the bowl without disassembly is to unscrew the whole drain assembly and use a bottle brush up in there.
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Old 03-08-2013, 09:02 AM   #32
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A pump will not get that crud out. It didn't get it out on my series installed pump.
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Old 03-10-2013, 08:01 PM   #33
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Smile My experience

After converting to an electric pump (Wahlbro FRB-9) to transfer fuel between tanks, and do a "poor mans polishing system" the pump on the engine started leaking diesel fuel after about five hours of operation due, in my opinion, to the increased feed pressure created by the pump.

I removed it, and ran the pump output directly to the first filter on the engine.

No problem at all since. I fabricated a simple cover for the hole where the pump was.

Electric fuel pumps have been powering cars and trucks for twenty years...
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Old 03-10-2013, 09:02 PM   #34
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Agreed....crud does often form and I don't think forcing fuel through it is going to help as the whole idea of the turbine is to spin the flow of fuel so stuff settles out into the bowl.

The easiest way I have found to clean the bowl without disassembly is to unscrew the whole drain assembly and use a bottle brush up in there.

That reminds me, where do you get a bottle brush these days?
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Old 03-10-2013, 11:07 PM   #35
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That reminds me, where do you get a bottle brush these days?
No friends with stills in their back yards?

Here's but a few...

bottle brush at Target
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Old 03-11-2013, 07:26 AM   #36
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That reminds me, where do you get a bottle brush these days?
Bed Bath and Beyond or any kitchen store.
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Old 03-11-2013, 08:53 AM   #37
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Baby bottle brush at any decent grocery store.
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Old 03-12-2013, 02:42 PM   #38
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Just read the service manual and my guess is....

I don't think thats the way the check valves work...any pressure greater than a few psi on the inlet side should be enough to let fuel pass freely through this kind of pump. The diaphram would create a slight vacuum, inside the pump , then a slight pressure to open and close the valves...I think these diaphram pumps operate on very low pessures so any electric fuel pump would pump freely through it.
I think i said that wrong....thanks. What i meant was the fuel already on the outlet side of the pump should stay there if there is a check valve in good working order at the lift pump.
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Old 03-12-2013, 02:57 PM   #39
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I think i said that wrong....thanks. What i meant was the fuel already on the outlet side of the pump should stay there if there is a check valve in good working order at the lift pump.
Still don't know what you mean...if you put a pump in line with it at even a few psi...it should flow through...
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Old 03-12-2013, 03:10 PM   #40
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Still don't know what you mean...if you put a pump in line with it at even a few psi...it should flow through...
you are right it will. All i was saying if there is a check valve then when there is no presure the fuel in the line above the check valve should stay there and not drain back into the tank because the valve only allows flow in one direction..
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