No Start: fuel filter & cold weather problems, 89 7.3 IDI - Diesel Forum -
7.3L IDI Diesels (Not Power Strokes) Technical discussion of topics related to vehicles powered by the 7.3 Liter In-Direct Injection Navistar engines.

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post #1 of 4 (permalink) Old 02-20-2008, 02:19 PM Thread Starter
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Unhappy No Start: fuel filter & cold weather problems, 89 7.3 IDI

first of all, this is on a '89 f-250 with a 7.3 idi. also, it is cold here. single digits/below zero...
i was taking the truck for a short spin after fixing something completely unrelated. i started it, idled for like 10 minutes, drove for like 10 minutes, then...
the "fuel filter restriction" dummy light came on, and about 5 minutes later, just as i got it parked, it stalled and wouldn't start again.

i have dieselkleen (white bottle for winter) in the fuel. i have been meaning to change the fuel filters for awhile but i'm pretty sure this sudden stall is related to an unusually cold weather spell.

this morning i plugged the block heater in for 2 or 3 hours and then tried to start again. noticed that with the ignition on, there is a buzzing/humming noise which seems to be coming from driver side frame rail right by the front edge of front fuel tank. the truck has dual fuel tanks, and this noise changes pitch when i flip the tank selector switch (this is all with the engine off but the ignition in start). I was wondering if the noise I described could be the fuel selector switch valve? Or if it's just related to the filter being iced/clogged or something? Should I change the filter then see if the buzz goes away? The noise is not the fan/blower or the block heater. With the ignition on, i can hear blower (on low), glow plugs cycle as usual, dinging, all normal PLUS this louder buzz/hum coming from frame where i described.

I am also stumped as to how there could have been a cold weather related fuel problem like wax/ice/gelling because i have dieselkleen in the fuel. especially after running for 15-20 minutes "just fine". One thing i thought of was checking if the fuel filter heater in the filter header is working. My truck does have one, right? I can't check for heat because the truck won't start. In this picture, which of the 2 electrical connections is the fuel heater? (PICTURE 1) Also, i found a smaller electrical connector (looks like its for a sensor or something) that is just dangling. I think it's the water-in-fuel light connection but i could be wrong. (PIC 2)

Finally, is it stupid to just change the final filter (under the hood), not the frame mounted one as well? Also, does the "fuel filter" light pop on for just the final filter, or for either one, or for any fuel supply problem?

Thanks for reading! maybe i just need to change the filter, or get some of that diesel 911 stuff into the fuel system or something, but i thought i'd get the right info before doing anything.
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post #2 of 4 (permalink) Old 02-20-2008, 07:09 PM
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The black connector on top is the fuel heater........EDIT... the 90* connector should push on the threaded part of the sensor on the base, it's the water in fuel sensor.

Buzzing could be the FSV it is inside on the frame rail at that location...... It should go ZZZIIPPP and stop with a corresponding change of tank level on the guage. If the motor drive gear is fubar the motor may be running.....that could be the buzzing noise.The valve may be stuck between tanks?????? causing the vacuum light to come on........

Do a pressure and flow test of the fuel pump at the Schrader valve on the filter header (FSS- fuel shutoff solenoid disconnected on IP). Remove the tire valve core and hook a hose and pressure guage on it should see 4-6 psi when cranking. Then do a fuel quantity test same place, should see 1/3 pint in 10 seconds of engine cranking, route fuel to a suitable container with a hose.
If there is a problem with the lift pump and you are changing it, ensure the new pump comes with instructions as to correct installation procedure if it is the newer model pump with the almost straight arm.

If you fail the test....... consider hooking a hose directly to the lift pump inlet to a fuel can with diesel. If the pressure/flow parts are now good the valve is most likely the problem. If you PM me your email addy I will forward the FSV test for your truck.

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Last edited by cdnsarguy; 02-20-2008 at 07:34 PM.
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post #3 of 4 (permalink) Old 02-21-2008, 09:34 PM Thread Starter
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i am almost positive my problem is cold weather related, and after doing more research i am also pretty sure the noise is the FSV, especially since the noise changes pitch when i flip the tank selector switch.

i had a very small amount of fuel in the tank at the time of the fuel filter light and stall, too. i added about five more gallons w/ additive & diesel 911, but it seems like something is "frozen" along the way, such as the FSV which is what the noise seems to be coming from.

i took off the old fuel filter and it wasn't icy or anything inside but it definitely needed to be replaced so i put a new one on. trying to bleed the air out of the fuel system i realized that i dont think i'm getting fuel to the filter. i tried having someone cranking while i cracked an injector, no fuel came out but batteries finally died before i could really be sure. they are charging back up now.

is there anything else i can do other than hoping it warms up outside?? hair dryer and extension cord? should i try to bleed air again using the schrader fuel priming valve on the filter header? also i don't want to "burn out" whatever is making that noise (FSV?) by making it keep buzzing.

Last edited by dieseldirt; 02-21-2008 at 09:36 PM.
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post #4 of 4 (permalink) Old 02-23-2008, 04:42 PM
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I used to own an 7.3, reliable truck, i believe the unpluged wire on the bottom was just the water in fuel, i could be wrong though
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