Weird fuel issue after changing filters... - Diesel Forum - TheDieselStop.com
'99 & up 7.3L Power Stroke Engine and Drivetrain Discussion of the '99 & up 7.3L Power Stroke diesel engine and drivetrain in the 1999-Up Super Duty trucks and Excursions. No gas engine discussion allowed except on transmissions and drivetrain that pertain to all models. Please confine discussion of topics in this forum to those items that are specific to the 7.3L Power Stroke engine.

 
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post #1 of 10 (permalink) Old 05-24-2019, 03:35 PM Thread Starter
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Weird fuel issue after changing filters...

Ya know, I've come to the realization that the more you know about our trucks, the more complicated and obscure our problems become. Anyway, here's the latest...
I replaced the filters in my truck... the 2 piece (cap/filter) on the fuel bowl, and a new Dahl 100 element (30 micron) underneath. I've run this pre-pump filter for years without issue. So when I fire her back up, it starts sputtering, duh, as it starts to purge all the air out. No concern, as it does take a while. Well it has taken forever to purge that air out, and it still runs rough, even though the fuel gauge says 50ish psi fuel pressure. When I get on it, the pressure slowly starts dropping to 35, then will eventually climb back up. Also, when I first turn the key on, the pressure gauge takes it's sweet time building pressure... which it never did before... it was always within seconds. What the heck?!!!


My theory is that an injector is stuck open, and is bleeding the residual fuel pressure when I turn it off. And is also the reason the fuel pressure slowly declines when I get on the throttle.


Anyone care to share their thoughts and ideas?

2001 F250 Lariat, crewcab, 2wd, 3.73ls, auto, 4" exhaust, BTS transmission and torque converter, V10 tranny cooler, Isspro fuel pressure and tranny temp gauges, billet t-stat housing w/ 203 deg t-stat, Dahl 100 pre-pump filter, Ford severe duty AIS, Hutch mod, intake heater delete
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post #2 of 10 (permalink) Old 05-24-2019, 08:15 PM
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I think it more likely the fuel pressure regulator is at fault. Might have caught a piece of debris when the air was being forced through it after the filter change. If a fuel injector was stuck open (?) to a point where it affected fuel pressure, you'd hydrolock in about 60 milliseconds.

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post #3 of 10 (permalink) Old 05-24-2019, 11:00 PM Thread Starter
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Ah, that makes sense. I'll check it out.

2001 F250 Lariat, crewcab, 2wd, 3.73ls, auto, 4" exhaust, BTS transmission and torque converter, V10 tranny cooler, Isspro fuel pressure and tranny temp gauges, billet t-stat housing w/ 203 deg t-stat, Dahl 100 pre-pump filter, Ford severe duty AIS, Hutch mod, intake heater delete
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post #4 of 10 (permalink) Old 05-25-2019, 10:31 PM Thread Starter
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I drained the bowl, removed the filter, and disassembled the FPR. Everything was clean as a whistle and nothing looked out of place. I had replaced the spring with a 60 pound version during my 300K service, and usually see 56 psi at idle. Cycled thru the ignition a couple times to refill the bowl and get the fuel up to pressure. Once I had full pressure, I fired her up. Ran the slightest bit rough, but almost smoothed completely out and the pressure remained steady at 56. Turned it off, then back... fuel pressure went up to full very quickly this time, and then fired right up. I'll take 'er for a spin tomorrow and see if the fuel pressure builds quickly and see how she runs.

2001 F250 Lariat, crewcab, 2wd, 3.73ls, auto, 4" exhaust, BTS transmission and torque converter, V10 tranny cooler, Isspro fuel pressure and tranny temp gauges, billet t-stat housing w/ 203 deg t-stat, Dahl 100 pre-pump filter, Ford severe duty AIS, Hutch mod, intake heater delete
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post #5 of 10 (permalink) Old 05-28-2019, 09:39 PM Thread Starter
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Nope, still runs like doo doo. The fuel pressure gauge shows 56 psi and it's running like it has air in the lines. When I get on it to try and "clear" the lines, it drops to about 45, which is pretty normal, but still runs rough. Must be something between the fuel gauge port and the injectors. ***?

2001 F250 Lariat, crewcab, 2wd, 3.73ls, auto, 4" exhaust, BTS transmission and torque converter, V10 tranny cooler, Isspro fuel pressure and tranny temp gauges, billet t-stat housing w/ 203 deg t-stat, Dahl 100 pre-pump filter, Ford severe duty AIS, Hutch mod, intake heater delete
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post #6 of 10 (permalink) Old 06-01-2019, 11:45 AM Thread Starter
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The only thing that I changed was a new 2 piece fuel filter and cap, which replaced the old 1 piece variety. I noticed the new filter has an additional o-ring/seal in the middle of the filter... the old filter did not have that.

2001 F250 Lariat, crewcab, 2wd, 3.73ls, auto, 4" exhaust, BTS transmission and torque converter, V10 tranny cooler, Isspro fuel pressure and tranny temp gauges, billet t-stat housing w/ 203 deg t-stat, Dahl 100 pre-pump filter, Ford severe duty AIS, Hutch mod, intake heater delete
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post #7 of 10 (permalink) Old 06-01-2019, 12:35 PM
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Quote:
Originally Posted by LEMKE View Post
The only thing that I changed was a new 2 piece fuel filter and cap, which replaced the old 1 piece variety. I noticed the new filter has an additional o-ring/seal in the middle of the filter... the old filter did not have that.
I remember when all I could get was 2 piece fuel filters. But anyway, if you can I’d try pulling that o-ring out that you didn’t see on the old style and run it. Also is the new cap sealing tight on top of the filter bowl, is that seal still triangular shaped?
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post #8 of 10 (permalink) Old 06-02-2019, 09:07 PM
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You shouldn't remove that o-ring on the filter skirt. It's there for a purpose (water separation).


Recheck things on the suction side of the fuel pump. Maybe you have a leak on the Dahl filter (which I'm assuming is between the tank and pump.) If it's leaking there, it will likely suck in air, which is not good, and could cause what you're seeing.

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post #9 of 10 (permalink) Old 06-04-2019, 12:06 PM Thread Starter
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I will definitely check the pre-pump filter. As far as the additional seal on the fuel bowl filter, I thought that element separates water by way of filter media, not specific gravity like the Dahl. Anyway, thanks for the replies and I'll check all suggestions.

2001 F250 Lariat, crewcab, 2wd, 3.73ls, auto, 4" exhaust, BTS transmission and torque converter, V10 tranny cooler, Isspro fuel pressure and tranny temp gauges, billet t-stat housing w/ 203 deg t-stat, Dahl 100 pre-pump filter, Ford severe duty AIS, Hutch mod, intake heater delete
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post #10 of 10 (permalink) Old 06-09-2019, 11:37 AM Thread Starter
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Update: Removed the internal o-ring seal on the fuel bowl filter... no change. Great, scratch that idea. Just bypassed the pre-pump Dahl filter, and everything is back to normal... fuel pressure builds immediately when the key is switched on, and idles at 56-58 psi. Under hard acceleration, pressure drops to 50... just like it use to be. Something is causing a restriction in the Dahl unit. I'm using a 30 micron filter, and it wasn't a prob in the past. I'll R&R the filter and report back.

2001 F250 Lariat, crewcab, 2wd, 3.73ls, auto, 4" exhaust, BTS transmission and torque converter, V10 tranny cooler, Isspro fuel pressure and tranny temp gauges, billet t-stat housing w/ 203 deg t-stat, Dahl 100 pre-pump filter, Ford severe duty AIS, Hutch mod, intake heater delete
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