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TheRide
Senior Member
107 Posts |
 Posted - 09/15/2014 : 1:19:49 PM
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| Im having issues with fuel filter light coming on and the filters are new. the screen below the electric pump was very dirty, I figured the lift pump was weak so installed new one along with new filters and still have the wrench light coming on saying fuel filter needs changed. I have driven the bus with laptop connected and the fdp drops to 63psi then the dash light comes on. My thinking is the fdp sensor is bad. The bus runs and pulls like it always has (just fine). The code was DTC N/A SPN 94 FMI 1 Fuel Delivery Below Critical. |
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Bus Tech II
Senior Member
121 Posts |
Posted - 09/16/2014 : 05:07:49 AM
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| We just had one of these. Try to clamp off the return from the fuel filter canister (Grey/silver line). If the fuel prseesure goes up the you will need to replace the fuel filter canister as a whole. |
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TheRide
Senior Member
107 Posts |
Posted - 09/16/2014 : 09:13:28 AM
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| so it was returning more fuel to tank because of restriction in the filter canister? |
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Bus Tech II
Senior Member
121 Posts |
Posted - 09/16/2014 : 10:40:30 AM
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| No theres a check valve spring and plunger letting fuel return at a lower pressure |
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TheRide
Senior Member
107 Posts |
Posted - 09/16/2014 : 12:28:08 PM
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| this one has a serviceable fuel pressure regulator, and I have changed it already. |
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TheRide
Senior Member
107 Posts |
Posted - 09/16/2014 : 12:35:22 PM
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| next time I have it in the shop I will look at clamping that return line and see what it reads.. Its been reading 70+ while idling. |
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TheRide
Senior Member
107 Posts |
Posted - 09/20/2014 : 6:33:27 PM
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| What should the fdp be at idle and what should be lowest it should drop to under load? I have been looking in the manuals on ISIS but haven't found that spec. |
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Bus Tech II
Senior Member
121 Posts |
Posted - 09/22/2014 : 1:29:08 PM
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| with the electric pump you should never see it below 75. Not sure what the spec is. Depending what year it is servicemaxx will only read up to 75. 2013 emmissions shows above |
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bandit
Active Member
41 Posts |
Posted - 09/22/2014 : 2:12:45 PM
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| We had the same problem with 2 of our dts, changed the filter with a oem one and took care of the problem. we heard from our international saleman that there is a issue with after market filters. |
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Mechan1c
Top Member
USA
853 Posts |
Posted - 09/22/2014 : 3:35:31 PM
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| And it should be steady, not bouncing around... |
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JoeHEB1
Advanced Member
498 Posts |
Posted - 09/24/2014 : 09:00:27 AM
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| Any updates??? I have one doing the same thing, replaced the fuel filter with a Wix and it fixed the problem for about 3 weeks, now the the fuel filter light is back on with the same code. I'm gonna try an OEM fuel filter like @bandit said to see if that fixes it. I'll keep y'all posted. |
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mrschoolbus1
Active Member
15 Posts |
Posted - 09/24/2014 : 4:14:18 PM
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From iKNow article IK1201004
EPA 2010 and later DT, 9 & 10 engines use a fuel module that incorporates many features, including an electric fuel pump, fuel heater and fuel strainer.
-The fuel strainer can be seen when the pump is removed from the filter module. The strainer should be cleaned at the filter replacement interval (30K miles / 43K Km / or 12 months). The strainer P/N is 1899335C91 (see images below)
-Low fuel pressure and Hard Start or No Start conditions can be caused by at least two manufacturers of non OEM fuel filters. See differences in the fuel filter seals here and fuel filter recall G-Letter here.
-Navistar has received complaints that NAPA fuel filter FIL3994 can cause low fuel pressure. CARQUEST and WIX 86994 appear to be made by the same mfg. as the NAPA filter.
-Navistar's OEM fuel filter was developed specifically to work with features that are designed into the fuel filter housing. These features remove air from the fuel system and produce the required fuel pressure, giving the engine optimum performance.
-Calibration updates have been made due to low fuel pressure DTC's 94-1, 94-17 being set erroneously. Do not perform diagnostics for these faults unless there is a starting or performance complaints.
-Update the engine calibration (see calibration scorecard)
-If the vehicle has this code(s) and has a performance complaint then update the engine calibration AND follow step-based diagnostics (at the beginning of this article)
-Some low fuel pressure complaints are caused by a worn fuel pressure regulator valve & spring. Kit 1893801C94 is available to remedy this.
-Low fuel pressure complaints can be caused by the wrong O-ring being installed on the fuel pump
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mrschoolbus1
Active Member
15 Posts |
Posted - 09/24/2014 : 4:19:24 PM
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Here is the rest of the details from the article:
-Fuel pressures above 60 psi will not cause low power or performance complaints on this engine
-Fuel inlet restriction should not exceed 8.14" Hg. / -4 psi. High inlet restriction can cause the pump to draw too much current and shut off or behave erratically (this could be caused by an intermittent fuel restriction in the fuel tank or anywhere in the line). Use ZTSE6009 adapter to attach a vacuum gauge to the fuel inlet.
ELECTRIC FUEL PUMP OVERVIEW
At key ON, the ECM closes the fuel pump relay (provides ground via pin C-76) and battery voltage is supplied to the pump. The pump will run for ten seconds (time varies with coolant temperature) and then shuts off. During the run time if the ECM does not detect crankshaft rotation it switches the fuel pump relay off. The key must be OFF for at least 10 seconds and then cycled ON before the ECM will restart the fuel pump.
DIAGNOSTIC TIPS:
The pump has internal overload protection that turns the pump off under overload (high current draw situations). High current draw can be caused by high inlet restriction or restriction in return line to tank. When current limiting protection is triggered, the pump will cycle on and off causing the system pressure to fluctuate until the overload condition is resolved. The pump may eventually turn itself off. This situation can occur without a fault code being set. When the ignition key is cycled OFF for 10+ seconds and ON the pump will restart
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RidgeLine
Active Member
29 Posts |
Posted - 09/25/2014 : 09:21:15 AM
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| FYI, Last time I researched which was about a year and half ago, WIX is the manufacture of NAPA filters. |
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mhernandez73
Senior Member
124 Posts |
Posted - 09/29/2014 : 05:33:08 AM
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| we had several buses with the same problem. we were using aftermarket filters. we went back to OE filters and fixed the problem. |
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TheRide
Senior Member
107 Posts |
Posted - 10/01/2014 : 05:49:56 AM
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| I plan on working on it today. I have a new filter housing to put on it...all we use is Napa because we get such a good deal..We may have to go to OEM filters...I will update after the filter housing had been Removed and replaced..Thanks for the feedback. |
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TheRide
Senior Member
107 Posts |
Posted - 10/01/2014 : 09:00:27 AM
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| Replaced the filter housing and now the fuel filter dtc is constant with 52 psi at idle, I blew back though the fuel lines with shop air and the return line seems plugged...it should be free from restriction right??? I mean no check valve? Im gonna look and the top side of the fuel tank next and remove the return line there and see if there is air from one end to the next when I use shop air.. wow I thought the filter housing would have sovled it. |
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TheRide
Senior Member
107 Posts |
Posted - 10/01/2014 : 12:45:52 PM
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| Ok found that the fdp sensor on the new filter housing was yellow and the original one and new one I replaced old one with is blue, switched the yellow one out with the new blue one and it started reading 75psi. Road tested with the laptop hooked up and it maintained 75psi throughout the trip with no fuel filter dtc. So the housing was plugged and new one had wrong fdp sensor. I pulled the elect lift pump out of the old one and the screen that had been on only a week had crap that looked like pieces of sponge, thinking bus was vandalized at an away ball game maybe so will get it in here when fuel level is lower and remove and steam it out. what a day!! |
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Maxxforce DT fuel delivery pressure
