Purging fuel system, would this work?

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Purging fuel system, would this work?

February 18, 2015, 03:06:12 pm

I am aware of the new Racor system with an integrated pump. While it is no doubt an improvement over the Winn, it still seems to have an inherent flaw. I am wondering if there might be a better way.

Either system has to pull fuel through close to 40' of fuel pickup tube, fuel line. My experience with pumps is that if there is any way to have a flooded suction pump, that's always the best solution. Obviously this is not possible except with an in tank pump. The second best way to rig a pump is for the shortest pickup length between pump and tank. This is what I would like to consider.

Let's say you insert two tees into your fuel supply line, tees separated by about 16", close to the fuel tank.
Between these two tees a shutoff valve is installed in the main line.
Between these tees, a piece of line is run, which parallels the fuel line.
In that line, a Facet pump is installed, similar to the pump used on the genset.
Also on that line, on the output side of the Facet pump, another shutoff valve is installed.

So, lets say you need to prime your fuel system due to filter change etc.
Close shutoff valve on main line, open valve on Facet pump line.
Energize pump. Fuel is picked up and pushed down the line to the filters.
Turn pump off. Close facet valve, open main valve. Done.

Lets say you need to transfer some fuel to another vehicle....tractor, truck, fellow motorhomer in a bind.
Insert another tee in Facet pump line, between pump and shutoff. Have a cap that seals off the tee.
Close main shutoff. Close Facet pump shutoff. Remove cap from Facet tee, attach line, insert into tank you wish to transfer to.
Energize pump, transfer fuel, recap tee and open main line valve. The same system could be used for fuel polishing if you so desire.
Though I doubt motorhome theft is much of a problem, these valves could provide some security in that regard.

I like the utility, inexpensiveness, and easy repair of this system. Fuel filtration would just be a couple of plain old filters with no integrated pump, wiring etc. I do have one overriding question I am hoping someone can answer:

Would it be possible for this pump to push fuel through filters, through injection pump, thru banjo bolt relief, down return tube, and back to tank?

If so, this would seem to be an optimal way to purge/prime.

Re: Purging fuel system, would this work?

Reply #1 – February 18, 2015, 03:35:47 pm

What I have on my Peterbilt and am going to put on my 91 GV is a hydraulic test fitting I use a Davco 382 filter myself and am going to change over to one on my GV also. Anyway put the test fitting in the line from the pump to the engine,I have a cheap 1 gal pump sprayer I put tHe hydraulic test fitting quick connect on when I need to prime my engine Like after working on fuel system I can connect the pump sprayer up pump it a few times ,then engine will start and it will pick up and purge in a few seconds. You can buy these at any hydrolic hose supplier.
Test Port Couplings

Re: Purging fuel system, would this work?

Reply #2 – February 18, 2015, 05:26:16 pm

Solenoids like it might work pretty well.

Re: Purging fuel system, would this work?

Reply #3 – February 18, 2015, 10:15:03 pm

Watching Alaska, the Last Frontier, Otto couldn't get his old generator to start after it ran out of fuel so he put in the diesel fuel, then proceeded to create pressure in the tank by blowing into the tank filler neck until the fuel ran out the carb. Kinda wonder if there was a way to put a little pressure on the motorhome fuel tank with the air system and if it would even work.

Amazing what trouble an idle mind can get into, isn't it??

Re: Purging fuel system, would this work?

Reply #4 – February 18, 2015, 11:10:48 pm

When I had a remote filter installed the tech lost prime and he used compressed air at the tank filler neck to push fuel to the lift pump and new filter.
Gary B

Re: Purging fuel system, would this work?

Reply #5 – February 19, 2015, 03:57:56 am

Very simple using a check valve & a ball valve along with most any DC electric pump, works great and the very worst engine to run out of fuel (Dry) is the DDC 2 stroke.

Re: Purging fuel system, would this work?

Reply #6 – February 19, 2015, 07:53:10 am

Late last nite I had another thought (strained the old noggin, didn't I?). Otto had a gravity feed on his generator. Didn't know how the pressurizing a MH tank would work. Looks like others know--see above.

Re: Purging fuel system, would this work?

Reply #7 – February 19, 2015, 01:14:08 pm

Note to those using air to pressurize fuel tank. Be careful with this, I'd guess if you're using an air chuck with a rag to seal the intake it will be OK, but don't rig up a pressurize fitting. 4 psi will probably rupture the tank, depending on how many baffles are in it and how they are welded.

Re: Purging fuel system, would this work?

Reply #8 – February 19, 2015, 01:38:17 pm

Just a FYI,

If you can pressurize your fuel tank you may need to check and see if your vent line has been plugged by a mud dauber. You shouldn't be able to overcome the vent line check valve with air as it is made to float and close on diesel not air.

Pamela & Mike

Re: Purging fuel system, would this work?

Reply #9 – February 19, 2015, 01:55:18 pm

We put a new head on a 60 series Detroit 2 weeks ago and blew air into the tank until I felt sure the dents would pop out... still ended up starting that engine with either which I hate doing... of course head and injectors being removed creates more than usual air... can't get upper cylinder any drier than that.

Re: Purging fuel system, would this work?

Reply #10 – February 19, 2015, 02:30:08 pm

Old 1693 Cats had a hand plunger pump on the injector pump that worked well for pushing fuel... bleeding air.

Re: Purging fuel system, would this work?

Reply #11 – February 19, 2015, 03:02:18 pm

The fuel pump design of the M11 precludes issues (deteriorated fuel line aside.)

5.9L & 8.3L design with their lift pump are another story (not the best from the get-go.. ='s, FASS Fuel System.)

FWIW.. I have both currently.

The OE fuel system for the M11 equipped MH's works well IMO when maintained. pc

Re: Purging fuel system, would this work?

Reply #12 – February 19, 2015, 03:22:10 pm

Anytime you pressurize the tank, you defeat the purpose as the return line is also pressurized so the fuel goes nowhere. A simple OEM hand pump like CATs and Detroits have works very well. I just loosen the filters a little, pump until the bubbles are gone, tighten the filters and then continue to pump to force all the air out of the system. I installed a pressure gauge on both the intake of the primary as well as another gauge on the discharge of the secondary. The Detroit pump is OEM on the frame so could be installed on any coach.

Pierce

Re: Purging fuel system, would this work?

Reply #13 – February 19, 2015, 04:12:13 pm

You know now that I read you guys posts on pressurizing the fuel tank I think maybe that the tech that did it was maybe not as smart as he thought he was. What he was doing was installing a PRIME LOC remote filter on an 8.3 along with a lift pump so there was plenty of air in the system. It took forever to get it primed and started and it was several years ago and at the time I did not have the benefit of the knowledge of this group.
Gary B

Re: Purging fuel system, would this work?

Reply #14 – February 19, 2015, 05:34:09 pm

Quote from: Pierce & Gaylie Stewart – February 19, 2015, 03:22:10 pm

Anytime you pressurize the tank, you defeat the purpose as the return line is also pressurized so the fuel goes nowhere.

Pierce

Pierce. Most diesels I have worked on have a check valve at the engine in the return line to maintain fuel pressure for the next start-up. So at the under 5 PSI one would use to pressurize the fuel tank, the return line should not be an issue. Agree a large vent line could be an issue if the pump's volume was inadequate.

This was a standard way to remove air from fuel systems on Caterpillar engines when the chassis maker cheaped out and deleted the manual primer pump. And, with the high location of the filter housing, when the filter is removed, the fuel drained all the way back to the tank. That is lot of air to purge with no primer pump. But, crack the outlet vent of the primary fuel filter, pressurize the tank to a few PSI and fuel will flow through the system and fill the filter. Close the vent and a couple of cranks gets them going.

Re: Purging fuel system, would this work?

Reply #15 – February 19, 2015, 07:18:36 pm

Brett,

Quite correct if you crack the secondary or primary (depending on setup) filter a little and then pressurize the tank with 2 to 5 psi. But it then becomes a two person job with one to pressurize and the other to yell "stop" before the diesel has flooded the ground. I was trying to keep the owners from simply pressurizing the tank and figuring it was going to bleed all the air out of the system.

Not all filter assemblies have a easily opened vent so the easiest way is to unscrew a filter a turn or so.

Pierce

Re: Purging fuel system, would this work?

Reply #16 – February 19, 2015, 11:17:33 pm

How about a ball valve on the primary fuel filter input hose fitting? Closing ball valve whenever any fuel filters are opened will prevent fuel from flowing back to tank.

Re: Purging fuel system, would this work?

Reply #17 – February 19, 2015, 11:44:41 pm

Barry,

Yours may already have a spring loaded check valve designed to do exactly the same thing. Here are a couple of photos from an old post of mine. The U300 chassis mounted pump is also pictured in one of the photos as mounted on the chassis. My check valve had a crack so I replace it with the gold colored one. Lets the diesel flow in one direction but not the other. They are under $40 if you search a bit, otherwise $65 or so.

Pierce

Re: Purging fuel system, would this work?

Reply #18 – February 20, 2015, 09:04:14 am

Man, that Detroit prime system looks good. Simple and straightforward. Will it pull fuel from tank even when the line is full of air?

Re: Purging fuel system, would this work?

Reply #19 – February 20, 2015, 09:56:39 am

Quote from: Barry & Cindy – February 19, 2015, 11:17:33 pm

How about a ball valve on the primary fuel filter input hose fitting? Closing ball valve whenever any fuel filters are opened will prevent fuel from flowing back to tank.

An excellent idea. I show this as part of my "ideal fuel system" when I do the seminars. Prevents fuel spillage, prevents fuel from draining back to the tank (depending on relative level of fuel in tank to location of filter head). It is also a great anti-theft device-- left off, no one is going anywhere.

Re: Purging fuel system, would this work?

Reply #20 – February 20, 2015, 10:01:19 am

Chuck,

I replaced the old valve with a new one as someone had overtightened it during installation and put a crack in it. It kept leaking air back to the tank. Since it is about a foot from the bottom of the tank elevation wise, it does and did not during replacement, have any trouble bringing fuel to the primary filter.

So, after changing filters, you unlock the little chassis pump, pump it really fast until you feel resistance a few seconds later. Once both the primary and secondary filters have been purged of air, I tighten them and then pump until the pressure builds and then it's ready to go. I could just tighten the filters but it's easier to purge them of air first as it takes less time. I just replaced the gauge on top of the primary filter (pictured) with a nice weather proof model with a vertical face. During pumping, it indicates about 15 psi max. The gauge on the discharge side of the secondary filter reads about 35 psi when the engine is running. Gives a fair indication of filter condition but not under maximum flow (full throttle on a long grade) as I would need a video camera mounted to view it (or wire a remote sensor).

Testing the injectors with the Pro-Link, I can see they are working well but I suspect a couple may be leaking down during the night and take several seconds to start firing on a cold morning. This is what gives the white smoke for a few seconds as the temp gets near freezing. Also due to the lower compression ratio on the turbo engines. If the engine has not been started in a couple of weeks, I like to pressurize the system with the hand pump as it will start a little faster.

Pierce

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