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Discussion Starter · #1 ·
I have a problem with a Ford F750 SD that will not draw from the driver side fuel tank. I see no switch valve , nor is there a selector switch on the dash. The two tanks are plumbed together under the cab. No fuel level sender on driver side. Wires broken off on pass side. It's an 04 or5. Any suggestions?:bathroom. It has a 3126 Cat eng. if that makes any diff.
 

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I have a problem with a Ford F750 SD that will not draw from the driver side fuel tank. I see no switch valve , nor is there a selector switch on the dash. The two tanks are plumbed together under the cab. No fuel level sender on driver side. Wires broken off on pass side. It's an 04 or5. Any suggestions?:bathroom. It has a 3126 Cat eng. if that makes any diff.
You probably have a clogged equalization line running between the two tanks. I had a couple of 3126 series engines and fuel was only drawn from the right side tank. If the tanks have hand valves on them shut them off and remove the equalize tube. Blow compressed air through the valve, and through the line and valve to the other tank. If this breaks the blockage, drain the fuel and clean the tanks. Most of the medium duty trucks had steel tanks and rust was problematic as they aged and could present the problem you are experiencing.
 

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Discussion Starter · #3 ·
Backslap, There lies the problem. The suction lines run from each tankacross the top of the frame just under the cab floor. The return lines are right beside them . Each one joins in a T and goes to the engine. No equalization line or valves. That's old school, I guess. Thanks.---Bob
:bang
 

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Backslap, There lies the problem. The suction lines run from each tankacross the top of the frame just under the cab floor. The return lines are right beside them . Each one joins in a T and goes to the engine. No equalization line or valves. That's old school, I guess. Thanks.---Bob
:bang
I'd bet you either have a rotted pick up tube, or corrosion has been sucked up and plugged the tube on that side. I'd take the suction line loose from the tank and blow air down it listening for bubbling in the tank. If you get the bubbling, try to get fuel to pull from the tank via some type of suction pump. Diesel fuel really doesn't taste all that good so I'd probably look for some other type of vacuum source if it were me......

There has to be either a solenoid valve, a manual fuel selection valve, or an equalization tube in the plumbing between the tanks. If there was none and the left side tank in this instance were filled and the fuel draw is only from the right side tank, a call to the world famous transportation company "Shoe Leather Express" is in short order.

Also, something else Ford and nobody else was good for was mounting a combination external lift pump/tank selector valve on the inside of the frame rail that required just a whole lot of proper "vocabulary" to get at. It had a filter in the bottom, (usually) that was seldom if ever touched.
 

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If you have a proper line on the suction or return, side going from the tanks to a common junction with no air leakage, when you shut it off the fuel will level out. We had a customer that had a constant complaint that the fuel was higher in one tank than the other, ended up he was parking on an angle. You have to check the every connection, for blockages, and or restrictions. I did one, the driver threw the foam ear plugs in the tank and one got into the suction line. That took, a while to find.
 
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Discussion Starter · #6 ·
Thanks John. Both suction & return lines from each tank "t" off under the cab with no provision for drawing on one & then the other or drawing from both & returning to both. I just cannot wrap my head around the concept. I can understand a switch valve, either manual or electric, or draw from one tank & have an equalizer line from tank to tank. Do you see my delima.Not only do I want to solve the problem, but I would like to understand the system. :confused::confused::gaah---Bob
 

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Discussion Starter · #7 ·
Thanks for the input, Backslap. I told the foreman at the construction site I have never worked on this type set up, but would consult some of the sharpest minds in the business. Now I have done that. I usually over anilize every thing I do. Sometimes it is a simple fix & I make it a major thing in my mind.:swear:imok. Can't help it. But I digress. I will have to go to the site where the truck is & do what has been suggested. Tear it apart & work my way from the tanks up to where ever the problem is.:gaah:gaah.---Bob
 

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If you have a restriction on the suction side then it will draw fuel from the other tank. If you have a restriction in the return hose it will return to the other tank. You have to find out what it is.
The fuel will draw from the easiest restriction, and return to the easyest path.
Just a thought!
 

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Discussion Starter · #9 ·
Thanks John. I've decided to pull hoses and start checking. I suppose I thought There might be something simple, like maybe the fuel guage determined which tank to use. I'm probably over thinking things again!:thumbsup---Bob
 

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Park the unit on a level area and put a tape measure into the tank all the way to the bottom, measure the wet area then dry it off and do the other tank.
I made up a set of plug off fittings, but I did a lot of trucks. Just a piece of fuel line will block off enough for you to remove the hose and preferably look threw it. Use a clean drain tray, and you can dump the fuel back into the tank, if it does not flow properly from the fitting out of the tank then you will have to remove the fitting and look at that. I have seen units were the problem was plumbers tape over the fitting end, I use paste.
Just a thought!
 
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Discussion Starter · #11 ·
Monday, when I looked at it, The driver side step tank was full. the driver said he could run all day back & forth to the landfill, but would have to fill it the next day. The driver side never changed.I am still puzzled what switches the tanks. :madpoke---Bob
 

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Just a dumb question so don't laugh but would the sending units in the tanks have a float shutoff so as one tank empties the fuel is drawn from the other? I have zero experience with big trucks but if their are no shutoff's externally there must be something in the tank.

No :wedgie please or :kick thanks
 

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I have never seen a float system shut off, the only thing that causes the fuel to draw from both tanks is Gravity, which ever tank is higher the fuel will draw from that tank. It will return to both equally.
 

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Discussion Starter · #14 ·
Next week I will put all speculation to bed. I will open it up and when I find the problem, I'll fix it & post (probably) how simple it was. How's that for dreaming?:woohoo:woohoo.---Bob
 

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Discussion Starter · #15 ·
Next week has not got here yet. They are working the truck & don't want to shut it down right now. My reprieve.---Bob
 

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Next week has not got here yet. They are working the truck & don't want to shut it down right now. My reprieve.---Bob
Bob, I'm dying to know the answer to this puzzle. Been on the edge of my seat for weeks

Any news?

:kick:popcorn
 

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Discussion Starter · #17 ·
I'm supposed to get the truch the first of the week. They got a write up by the illustrious dot(notice the "small"letters) for no annual inspection, so I'll get my hands dirty,kind of.:bang---Bob:wiggle
 

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Discussion Starter · #18 ·
Still don't know, Wes. I pulled the lines @ the tank & blew out both suction & return plus into the tank on both. Haven't been back to the truck since I've been (and still am) out of town. Will find out when I get back. I'll let you know.:whip:sleep---Bob
 

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Still don't know, Wes. I pulled the lines @ the tank & blew out both suction & return plus into the tank on both. Haven't been back to the truck since I've been (and still am) out of town. Will find out when I get back. I'll let you know.:whip:sleep---Bob
Did you ever find the answer? My man and I are working on an 06 Kenworth that was overflowing driver side tank and emptying passenger side
 
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