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Serious fuel system issues, NEED HELP NOW

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  #16  
Old 10-11-2017, 01:50 PM
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anyone have input on the new sending unit sitting flush on bottom of the tank?
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  #17  
Old 10-11-2017, 02:00 PM
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if it is a venting issue, wouldn't removing the fuel fill cap be an accurate test?
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Old 10-11-2017, 02:19 PM
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The rubber foot aka umbrella like in the pic is ok on the bottom of the tank. It is designed to do that. The little nubs on the bottom to prevent sealing on the bottom of the tank.

Possibly the fuel return line is clogged? Remove fuel fill cap and pass some air back from where the return line attaches to the fuel bowl. Be gentle with the nut on the fuel pressure regulator there. The FPR is just pot metal and breaks easy.
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  #19  
Old 10-11-2017, 02:42 PM
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Quote:
Originally Posted by retiredsparky View Post
Could the tank be building a vacuum due to no venting? A couple of miles would be just about right for this to happen.

If your return line is working ok, I would run a hose off that tee you installed to your vacuum gauge and tie wrap the gauge to the windshield wiper so you can read the gauge. If the vacuum builds gradually as you drive it, your tank is not venting properly.

Rich and the others make a good point about the hutch mod, in my opinion
Larry

Nope...not a venting issue
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  #20  
Old 10-11-2017, 03:00 PM
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Originally Posted by aawlberninf350 View Post
The rubber foot aka umbrella like in the pic is ok on the bottom of the tank. It is designed to do that. The little nubs on the bottom to prevent sealing on the bottom of the tank.

Possibly the fuel return line is clogged? Remove fuel fill cap and pass some air back from where the return line attaches to the fuel bowl. Be gentle with the nut on the fuel pressure regulator there. The FPR is just pot metal and breaks easy.

I took fuel bowl back off to bench test for leaks and found that fuel drain was not leaking under pressure BUT FPR was leaking small amount even when I blocked off injector lines and blew through fuel inlet line with my mouth. Shouldn't that stay sealed totally until it reaches 60 psi and then return fuel to tank? I don't get it because it can sit awhile and still have pressure in fuel bowl.
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Old 10-11-2017, 04:27 PM
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So what is your fuel pressure when running and when it quits? Even if there is some air getting into the system, 60 psi fuel will still keep the engine running, just with less power.

Until you check fuel pressure and then do a flow test using the fuel filter drain with a 3/8" rubber hose into a measured bucket, you don't really know whether fuel is the problem.

If the IPR on the HPOP has a failing solenoid or the sensor is giving varying inputs, you could have very similar results-engine shutting down after a short run. The oil system on the 7.3 functions much like the ignition on a gas rig-without good HPOP, no power.
Larry
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Old 10-11-2017, 06:02 PM
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I think one or more of the quick disconnect fittings are leaking air into the fuel line. It did not reseal properly when you serviced the tank. That is why some guys replace the steel fuel lines. Here is a test you might be able to do. First you will have to add a fuel filter right at the inlet of the pump. Then mount an action cam to record a view for the filter. Go for a drive, if there is an air leak in your system you will see show up in the filter. I put a WIX filter screen there. It just takes a foot of fuel line, a couple of perfect circle type hose clamps and about 20 min to install.
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Old 10-11-2017, 08:07 PM
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Quote:
Originally Posted by Karlow View Post
I think one or more of the quick disconnect fittings are leaking air into the fuel line. It did not reseal properly when you serviced the tank. That is why some guys replace the steel fuel lines. Here is a test you might be able to do. First you will have to add a fuel filter right at the inlet of the pump. Then mount an action cam to record a view for the filter. Go for a drive, if there is an air leak in your system you will see show up in the filter. I put a WIX filter screen there. It just takes a foot of fuel line, a couple of perfect circle type hose clamps and about 20 min to install.
Karlow , did you cut the steel fuel line up by the pump and run your foot of hose over the steel with clamps? if so were you able to pull the metal fuel line off the frame rail enough to get tubing cutters on it?
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Old 10-11-2017, 08:58 PM
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Quote:
Originally Posted by shestrokesat7.3 View Post
I took fuel bowl back off to bench test for leaks and found that fuel drain was not leaking under pressure BUT FPR was leaking small amount even when I blocked off injector lines and blew through fuel inlet line with my mouth. Shouldn't that stay sealed totally until it reaches 60 psi and then return fuel to tank? I don't get it because it can sit awhile and still have pressure in fuel bowl.
The brass piston in the FPR has a little hole in it, so even if the fuel pressure cannot overcome the spring it will still leak a bit. It is odd that your seeing pressure in the bowl after sitting, fuel pressure should bleed off right away. That's what leads me to think the return line is clogged or bent or something.

When I got my truck it came with one of those intergral fuel cap and filter things instead of the OE cap and filter. I peeked in the bowl to see how dirty it was, and putting the lid/filter back on was kinda stiff. Turns out a tiny sliver of the cap was sliced off by the threads of the bowl, and that curly cue poked it's tiny head into the hole on the brass FPR piston. Again be gentle with the FPR, make sure the spring seats fully not hung up on a land, and if it breaks nifty billet FPRs are available.
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  #25  
Old 10-12-2017, 01:48 PM
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UPDATE!

Quote:
Originally Posted by retiredsparky View Post
So what is your fuel pressure when running and when it quits? Even if there is some air getting into the system, 60 psi fuel will still keep the engine running, just with less power.

Until you check fuel pressure and then do a flow test using the fuel filter drain with a 3/8" rubber hose into a measured bucket, you don't really know whether fuel is the problem.

If the IPR on the HPOP has a failing solenoid or the sensor is giving varying inputs, you could have very similar results-engine shutting down after a short run. The oil system on the 7.3 functions much like the ignition on a gas rig-without good HPOP, no power.
Larry
Installed a tee and fuel pressure gauge on pressure side of the pump, cranked and bled air out of gauge line. Drove until he acted like he was running out of fuel and he held pressure at exactly 60 psi from start to finish...maybe this info will help. going to do flow test now
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  #26  
Old 10-12-2017, 01:59 PM
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UPDATE!

Quote:
Originally Posted by retiredsparky View Post
So what is your fuel pressure when running and when it quits? Even if there is some air getting into the system, 60 psi fuel will still keep the engine running, just with less power.

Until you check fuel pressure and then do a flow test using the fuel filter drain with a 3/8" rubber hose into a measured bucket, you don't really know whether fuel is the problem.

If the IPR on the HPOP has a failing solenoid or the sensor is giving varying inputs, you could have very similar results-engine shutting down after a short run. The oil system on the 7.3 functions much like the ignition on a gas rig-without good HPOP, no power.
Larry

put hose on fuel drain and into 5gal bucket cycling key off and on for pump took 8 min to fill the bucket... something I did notice however was when I ran the pressure test as soon as you kill the engine fuel pressure dropped immediately BUT the fuel bowl held the pressure
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  #27  
Old 10-13-2017, 12:23 AM
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So you could still have enough air getting sucked in through the poorly designed quick release fittings. A rubber hose from the tank to the pump eliminates that possibility.

If you still have running problems, check your HPOP pressure.
Larry
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  #28  
Old 10-13-2017, 12:56 PM
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There is no cutting required. Just some clamps a filter and some hose.
Its maybe a 20 min job. No cutting or bending required. You simply pull the incoming fuel line off the pump and install it on the filter.
Add a length of fuel line between filter and the pump. I think its 5/16" tubing. Through in a few zip ties and you are good to go.
As for pressure in the fuel bowl, my truck has been setting for a week, It has a fuel pressure gauge on it.
When I turn on the ignition today it will be pressurized at about 50-60 psig.
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  #29  
Old 10-13-2017, 03:09 PM
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ok even though i have already pull vacum on suction side of pump and it held 2in for 30min of testing. i replaced suction line anyway. still no change in condition. one mile down rd. acts like its running out of fuel. so whats next. how do i chk hpop pressure. i dont have a scan tool. and trk is stock no programmer.
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  #30  
Old 10-13-2017, 06:09 PM
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I'm thinking you may have got something into the return path when you ran it with out the filter prior to cleaning the tank. I'm not sure how to check that. There is a back pressure regulator in there somewhere. It might have caught a bit of something and you might be sucking a bit of air. If the fuel/ air is not able to get returned to the tank it could be a problem. But first, what does the fuel pressure look like when all this is happening? With a new pump, and a failed return, I would expect high fuel pressure, something over 70 psig maybe.
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