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Old 12-31-2018, 04:13 AM   #1 (permalink)
tehbald
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05 6500 fuel tank issues need help!

Truck is an 05 C6500 7.2 Cat. Born a box truck but shortened and converted to a dump truck. My company recently purchased it with no problems. Now a couple weeks later it seems to only be drawing fuel from the passenger side 25 gallon tank. The level is reading ďcorrectlyĒ I guess since the passenger side is dry and the driver side big tank is basically full and the gauge reads half. Best I can tell on the setup it comes to a T between the tanks and goes to the engine. I donít see any diverting valve or any way to switch between the tanks. My next thought is to remove the big tank and check for a blockage but was hoping for a better idea before I start. Any suggestions would be appreciated!

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06 Chevy 2500HD, 4x4, Crew Cab, Short Box, LLY (LBZ), 265/75 r16,- K&N Drop In, FlowPro 4" duals, PPE Standard tuner, PPE High Flow fuel inlet, FASS 150 Lift Pump.

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05 Chevy C6500 Dump Truck- 7.2 CAT, Allison, Agricultural Diesel Solutions "TRUCK EDITION" box
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Old 12-31-2018, 04:39 AM   #2 (permalink)
ronjhall
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Lots of fuel tank/gauge threads for MDT's.
Here is one I ran for Fuel Gauge. Hope this helps.

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2004 C5500 Kodiak LLY. Gulf Stream Endura 25,000lbs with car, EGR Blocker & stick. PVC reroute. No programmer, Bilstien shocks, Ride Rite air Bags, Train horns, Filter minder, ISSPRO trans temp gauge, VDO EGT gauge, TST tire pressure monitor, Scangauge II, MBRP muffler, Modified turbo MP.
Avg mileage over 76k miles 10.3 mpg. Sold it 5/17.
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Old 12-31-2018, 06:48 PM   #3 (permalink)
tehbald
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The link didn’t work and like I said above as far as I can tell the gauge works. Unless the sending units have a valve of some kind in them that’s level based.
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03 GMC 2500HD, 4x4, Crew Cab, Short Box, Pickup w/Duramax LB7, 265/75 R16 - 8 fresh injectors (thank you warranty), curse of pump rub found and fixed with the kennedy adapter, banks ram air, monster duals, waste gate actuator, and economind tuner, SPORT'N TRUCK NUTZ

06 Chevy 2500HD, 4x4, Crew Cab, Short Box, LLY (LBZ), 265/75 r16,- K&N Drop In, FlowPro 4" duals, PPE Standard tuner, PPE High Flow fuel inlet, FASS 150 Lift Pump.

Work Truck:
13 Ram 3500 Cummins, stock

05 Chevy C6500 Dump Truck- 7.2 CAT, Allison, Agricultural Diesel Solutions "TRUCK EDITION" box
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Old 01-01-2019, 04:50 AM   #4 (permalink)
ronjhall
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Quote:
Originally Posted by tehbald View Post
The link didnít work and like I said above as far as I can tell the gauge works. Unless the sending units have a valve of some kind in them thatís level based.
I did not work for me either. Not sure why.
Since my truck only had one tank I never needed to troubleshoot this problem. But I read enough of the post that do understand that the whole system needs to work to get fuel to move from one tank to the other.
Do a search using the DP search option. Make sure you select only MDT.
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2004 C5500 Kodiak LLY. Gulf Stream Endura 25,000lbs with car, EGR Blocker & stick. PVC reroute. No programmer, Bilstien shocks, Ride Rite air Bags, Train horns, Filter minder, ISSPRO trans temp gauge, VDO EGT gauge, TST tire pressure monitor, Scangauge II, MBRP muffler, Modified turbo MP.
Avg mileage over 76k miles 10.3 mpg. Sold it 5/17.
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Old 01-01-2019, 12:44 PM   #5 (permalink)
rdminter
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I have the 25gal and 15 gal standard tanks system. The ecm monitors both tanks and draws fuel from the front tank to the engine, while transferring fuel from the rear tank to the front. If either sending unit is faulty the truck will think it is out of fuel and shut down. Also, check the transfer pump to make sure it is working as well. Located on the frame rail on the passenger side.
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Old 01-02-2019, 04:25 PM   #6 (permalink)
07yellowkodiak
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I recently replaced my transfer pump. Fuel gauge read 1/4 but was a bad reading. The transfer pump only sent a small trickle of fuel to front/main tank. It ran dry leaving fuel in rear tank not going to front. Don't know if this helps. Good luck
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Old 01-02-2019, 09:50 PM   #7 (permalink)
tehbald
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So this is a pic of the T fittings between the tanks. This is not a front and back style system with a transfer pump. This has side tanks with steps and it seems to draw from both together. There is no pump in the tank itself only the lift pump on the CAT motor itself. There is no switching valve either. While at the dealer today getting other parts for the truck I had the guy look up the fuel sending unit. It is basically just a rod with a level sender on it. No sock or anything else visible in the image or component list. I have not been able to check the driver side tank yet but the passenger side only has a 2wire connector and I assume thatís the 2wires for the level sender (but yes I do know what happens when you assume).
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03 GMC 2500HD, 4x4, Crew Cab, Short Box, Pickup w/Duramax LB7, 265/75 R16 - 8 fresh injectors (thank you warranty), curse of pump rub found and fixed with the kennedy adapter, banks ram air, monster duals, waste gate actuator, and economind tuner, SPORT'N TRUCK NUTZ

06 Chevy 2500HD, 4x4, Crew Cab, Short Box, LLY (LBZ), 265/75 r16,- K&N Drop In, FlowPro 4" duals, PPE Standard tuner, PPE High Flow fuel inlet, FASS 150 Lift Pump.

Work Truck:
13 Ram 3500 Cummins, stock

05 Chevy C6500 Dump Truck- 7.2 CAT, Allison, Agricultural Diesel Solutions "TRUCK EDITION" box
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Old 01-03-2019, 04:55 AM   #8 (permalink)
ronjhall
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My son has a Semi truck. One of his trucks had a similar problem. Someone had dropped a additive bottle cap into one of the tanks. It was blocking the flow from one tank to the other.
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2004 C5500 Kodiak LLY. Gulf Stream Endura 25,000lbs with car, EGR Blocker & stick. PVC reroute. No programmer, Bilstien shocks, Ride Rite air Bags, Train horns, Filter minder, ISSPRO trans temp gauge, VDO EGT gauge, TST tire pressure monitor, Scangauge II, MBRP muffler, Modified turbo MP.
Avg mileage over 76k miles 10.3 mpg. Sold it 5/17.
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Old 01-13-2019, 01:03 PM   #9 (permalink)
jsteele05
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my guess is there could be a check valve or anti siphon valve in the line that has either gotten gelled or just a lot of dirt in there. Not completely related but Ive experienced transmission lines on vehicles that had anti drain back valves degrade to the point of causing low or no pressure. They can be integrated in one of the fittings and hard to locate.
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Old 07-19-2019, 12:53 AM   #10 (permalink)
tehbald
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FOLLOW UP!!! So I found the issue. Turns out it was simple siphon properties. So it pulls and returns from both tanks keeping them both level, however, when the tank vent is completely blocked then it will pull and push very little to and from that tank. So for me, the little hose running from the sending unit to atmosphere had been invaded by a bug of some kind that built a nest and blocked the line. Some times it’s the simplest things.

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03 GMC 2500HD, 4x4, Crew Cab, Short Box, Pickup w/Duramax LB7, 265/75 R16 - 8 fresh injectors (thank you warranty), curse of pump rub found and fixed with the kennedy adapter, banks ram air, monster duals, waste gate actuator, and economind tuner, SPORT'N TRUCK NUTZ

06 Chevy 2500HD, 4x4, Crew Cab, Short Box, LLY (LBZ), 265/75 r16,- K&N Drop In, FlowPro 4" duals, PPE Standard tuner, PPE High Flow fuel inlet, FASS 150 Lift Pump.

Work Truck:
13 Ram 3500 Cummins, stock

05 Chevy C6500 Dump Truck- 7.2 CAT, Allison, Agricultural Diesel Solutions "TRUCK EDITION" box
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