Diesel gurus question

[Twist]

I think that flinch is asking... if they say that it's because of a collapsed fuel line, then how do they explain a fuel filter swap making the situation better for another 5,000 miles?

There's probably enough fuel pressure for the truck to perform somewhat normal until the filter starts to get dirty. Once there's restriction in the filter, it lowers the pressure even more and doesn't allow for enough fuel in order for the engine to run properly.

It's kind of what I was alluding to in my initial post.

edit- Obviously the lines aren't completely collapsed or there wouldn't be fuel at all. It could be partially collapsed though, I suppose.

[Etxbuckman]

I think that flinch is asking... if they say that it's because of a collapsed fuel line, then how do they explain a fuel filter swap making the situation better for another 5,000 miles?

Gotcha. So assuming there is a restriction, and assuming the fuel lines are collapsed, should I be looking for a different cause of the line collapse?

Perhaps opening the vacuum when the fuel filter is replaced releases the suction in the lines causing the collapse? And then over time the suction collapses the lines, rinse and repeat. If that were the case the lines may very well be collapsed, but maybe there’s a different underlying issue somewhere.

[Radar]

Its the fuel line from the tank, mine was a rubber hose that would collapse and is routed next to the transmission. When you change the fuel filter it relieves the pressure, you can also loosen the bleeder screw and it will run again. I replaced the hose and drilled a small hole in the fuel tank cap valve, never had anymore issues.

[Etxbuckman]

Its the fuel line from the tank, mine was a rubber hose that would collapse and is routed next to the transmission. When you change the fuel filter it relieves the pressure, you can also loosen the bleeder screw and it will run again. I replaced the hose and drilled a small hole in the fuel tank cap valve, never had anymore issues.

Drilled a hole in the actual fuel cap where you pump diesel into?

[Radar]

Drilled a hole in the actual fuel cap where you pump diesel into?

In the pressure valve in the cap, I replaced the cap with a new one but every time I would fill up the filler neck hose would be collapsed. There is a small white valve inside the cap and I drilled a tiny hole just in the valve not the cap itself. I believe the vacuum pressure is only like 5psi - 10psi from the tank to the pump.

[MacDaddy67]

CP3 getting weak...get a FASS system or some sort of lift pump...the CP3 has to pull from the tank......

FASS will get it done...

[ramrod]

How do you know it's starving for fuel? Is it loosing prime or spuddering under load?

[Etxbuckman]

CP3 getting weak...get a FASS system or some sort of lift pump...the CP3 has to pull from the tank......

FASS will get it done...

Would a failing CP3 cause the lines to collapse? The dealership told me the lines are definitely collapsed and need to be replaced, but it sounds like that may just be a symptom of an underlying cause. The CP3 has never been replaced, and with nearly 206k miles it sounds like it's past time for it to crap out anyway.

Perhaps it's sucking so hard to try and get fuel that suction is causing this collapse?

[Etxbuckman]

How do you know it's starving for fuel? Is it loosing prime or spuddering under load?

Sputtering under load, and it's especially noticeable going up a hill even if you're not pulling anything. You can feel the truck trying, but it’s sluggish and/or sputtering as you say. And if you press harder on the accelerator you can feel it sputtering slightly, but it doesn't increase the speed at all.

The weird thing is that when you crest and begin to come down the hill it sounds like the RPM's are up, but the tachometer doesn't reflect that.

[freestylest22]

I didn't read thru all the comments but I'd bet money its the fuel filter housing. They are prone to small cracks, bleeder screw and the prime pump leaking. If you can swing it put a FASS pump on it and remove the factory filter housing.

[Etxbuckman]

I didn't read thru all the comments but I'd bet money its the fuel filter housing. They are prone to small cracks, bleeder screw and the prime pump leaking. If you can swing it put a FASS pump on it and remove the factory filter housing.

Is a Fass and lift-pump the same thing? That's been mentioned here several times, and it's been mentioned to me a few times in the past as well.

[Swampa]

Ya pretty much, Air Dog makes a lift pump also


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[freestylest22]

Is a Fass and lift-pump the same thing? That's been mentioned here several times, and it's been mentioned to me a few times in the past as well.

Yes same thing. But for sure remove the factory filter housing if you do that route. Or replace it with an OEM one to maybe resolve your problem.

[Kingfisher789]

Let’s start all over. What’s the complaint?

[BLACKFINTURKEY]

Lift pump…

Install a fuel pressure gauge, critical for diagnosis in diesels.

Fass/air dog are just brands of aftermarket lift pumps. Both my Cummins have them. High flow pump provides tons of fuel to motor. When/if you do install one save the trouble of dropping the tank and install a sump on your tank. It’s so much easier and it ensures you get all the fuel from the tank.