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International 4700 Fuel Gauge Dual Tanks

Discussion in 'Trucks' started by redneckracin, Jun 13, 2016.

  1. redneckracin

    redneckracin Senior Member

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    Ok fellas I have been trying to figure this out for awhile now. I have a 2001 int 4700 with dual saddle tanks. My fuel gauge only reads the one tank. The gauge is accurate for the one tank (its escaping me which tank at the moment) aside from the sloshing, but how does the fuel from the opposing tank get handled? Does the pump pull from the tank with the gauge and the 2nd tank gravity feeds or is there some balancing by the fuel pump? The reason I'm asking is that my gauge reads almost empty and I have significantly more fuel in the 2nd tank. Any ideas?
     
  2. walkerv

    walkerv Senior Member

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    yes a common problem with these , the tank that is lower is the one the guage reads off of and the engine feeds from , the other tank sender goes to a module and then goes a eletric transfer pump , the module compares both tank readings to run the pump . best bet is to replace both sending units in the tanks first , If that doesnt fix it I have some more advanced trouble shooting I can dig up . one question though has the alternator been changed recently ? It doesnt seem like it should have anything to do with it but it can .
     
  3. Old Doug

    Old Doug Senior Member

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    I was called to look at a truck the other day that was doing this and it had a pluged vent on one tank. I thought maybe it was returning fuel to tank while useing it from the other?
     
  4. redneckracin

    redneckracin Senior Member

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    No alternator replacement. I have only done PM to this truck since I got it aside from replacing the radiator and the electrical nightmare the previous idiot owner concocted. Where would the sending units be? I'm assuming right in the top of the tank which means I gotta drain the tanks and unbolt them to get them off the truck..... I checked it again last night and it only appears to be about an inch out of being equal. I was thinking that they were farther out than that.


    Any idea where the breather hose may be? Or where it pulls air from?
     
  5. walkerv

    walkerv Senior Member

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    yes you have to pull the tanks on these trucks to change the sending units the vent s are also on top of the tanks , If its only an inch difference I personally wouldnt mess with them yet, there is a small wire on the alternator make sure it is not hooked up to the 12 volt post it should be hooked to the post that read something like 7 volts when its running. The senders in these trucks have had alot of problems not sure if the latest ones are an updated version its been awhile since I worked at the IH dealer. So if you want to prevent a problem in the future or are not happy with your slight fuel imbalance go ahead and change both senders out and see if they balance out better. the good part is that your transfer pump seems to be working . incase you are wondering about the small wire on the alternator , it goes directly to the transfer pump if it is hooked up to the small 12 volt post it will not work or wont work correctly .

    International went to this set up to stop truck that were just filled up and left idling on lets say a uneven ramp to a highway while driver is sleeping , sometimes one tank would overfill with a dual draw and return set-up or more specifically the tanks with a transfer hose between tanks that gravity fed other tank , so this system although a real pain to diagnose sometimes was created to prevent fuel spillage and to create headaches for owner ops as well as mechanics :Banghead
     
  6. Shimmy1

    Shimmy1 Senior Member

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    Even with top draw/return they still end up filling up the downhill tank. The reason crossovers went away is due to them being torn off due to accident or road debris. If your truck is like the bigger Internationals, it will only have a sender in one tank, usually the left. It draws from both, and has a divider valve in the return. Plugged vent would be a good place to start, after that replace all fuel lines and check pickup tubes. Sometimes a little tinfoil bottle sealer gets pulled up into the pickup tube and restricts the fuel from one tank.
     
  7. The Peej

    The Peej Well-Known Member

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    I was told there was a line connecting both tanks so that they would seek the same level, problem is if the truck is not parked on level ground the fuel will run to the lower side.
     
  8. redneckracin

    redneckracin Senior Member

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    Ok a little update, I finally got a chance to pull both breathers off and they were both clear. The passenger side tank has the fuel level sender in it. I went to the fuel station and put in around 12 gallons in one tank and 32 in the other. I took a look at the alternator and it appears to have two main posts and two auxiliary posts in between. The main posts have several hot wires and one ground. The auxiliary posts each have a wire running to them.

    One thing to note is that the tanks seem to be getti ng more out of balance over the past year or so. I guess it's time to check the price of the units in the tanks. How do they work exactly? I tried looking around them and there appears to be a send and return line to each tank and that's it besides the breathers and the level guage on the passenger side.
     
  9. bighorn06

    bighorn06 Active Member

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    Thanks for posting this info. I also have 2001 4700 with two saddle tanks, I never asked but always wondered how it worked.
     
  10. redneckracin

    redneckracin Senior Member

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    Well, I call zacheral's in clarion and they gave me the "wtf?" over the phone. The saddle tanks don't use a pump in the tank to level them, there is a diverter valve I believe that controls the flow. I'm not sure how it works so I'm off to do some research!
     
  11. walkerv

    walkerv Senior Member

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    Yep my bad I blame the heat . Hope my pm helps. I got confused on years and model Numbers
     
  12. Shimmy1

    Shimmy1 Senior Member

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    You're going to need to do some diagnosing. These systems are simple. Pulls equally from both tanks, return flow goes through a flow divider. First thing is to measure return flow. Get two identical fuel cans, pull the return hoses off the tanks, put them into the cans. Make sure the cans are in as close to identical position in relation to the truck. Start it and let run, should take between 5-10 minutes to fill one of the cans to at least half. If one can is ahead of the other, change the return hose for the other tank. If that doesn't fix it, change the diverter. If the can test checks out, deeper you need to go. Pull the elbows out of the tank fittings, run a wire down all four tubes. If all tubes and fittings are clear, change the suction lines up to the tee fitting. Take the tee out and make sure it doesn't have any debris in it. These systems are extremely simple, and they work. One final note: since the basic principle behind the function is gravity, both suction lines have to be identical size and length, same for return lines. Good luck.
     
  13. redneckracin

    redneckracin Senior Member

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    No problem walkerv, you have been a big help so far!


    Shimmy, I'm going to try clearing the lines first then try your diagnosis. Any idea how much the divider valve would be? $100?
     
  14. Shimmy1

    Shimmy1 Senior Member

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    It's been a few years, but I think it's a bit more than that, if it's the same one on the big trucks. I'd be willing to bet though that you have a bit of foil or plastic caught up in an elbow or pickup tube, or a hose with some sort of restriction.