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Old 09-22-2020, 05:25 AM   #1
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Fuel starvation problems going uphill?

I'm having a problem recently with my bus. When I start to climb a steep hill, the transmission will downshift and the RPMs will go up, but the engine will pretty much lose most of its power. Or else it kind of chugs where the power will cut in and out. I ease off the pedal and then it downshifts and I can get up the hill, just slower than usual. This seems to happen at about 1800 RPM or higher, if it's lower than that the engine seems to be fine. And this only happens on an uphill, on flats or downhill I can rev higher and the engine has power like normal.

It was suggested that it sounds like a fuel filter problem, so I researched changing them and then took my bus to the shop last week. The mechanic sort of dismissed this power problem as possibly just air bubbles in the fuel line, but it's been happening consistently for the last five or six trips. My fuel filters were changed in May 2019 and I've only driven 700 or 800 miles since then, so he didn't think it was likely to be a fuel filter problem.

Any ideas on what might be happening? There's no check engine light coming on, no unusual smoke out the back end or anything. I have to take the bus back this week to have other things done (new front brake drums and a new exhaust, gulp) and I'm going to re-emphasize this problem to him.
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Old 09-22-2020, 06:19 AM   #2
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lack of power....

hmm, air in your pump. those air bubbles get stuck in the pump, crack each line open and see if you can find the bubble. fuel pumps are great with liquid, not with air.

check out your turbo. the charge air lines, the manifold. do you know the boost pressure? a cracked manifold or torn charge air boot will cause low power.

good luck tracking down the problem
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Old 09-22-2020, 06:30 AM   #3
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check out your turbo. the charge air lines, the manifold. do you know the boost pressure? a cracked manifold or torn charge air boot will cause low power.
Would these be problems only when going uphill, or would they be happening all the time?

I don't know the boost pressure, although I did get my new Bluefire gadget in the mail yesterday. I'm not sure if that displays stuff related to the turbo?

I am ignorant of all things mechanical in my bus, so I'm at the mercy of the mechanic here.
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Old 09-22-2020, 07:39 AM   #4
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Hmm, maybe the problem is clearing itself? I drove an alternate route this morning, without the two hill climbs right at the beginning. Did 50 mph at 2000 RPM on a slight downhill stretch and had no power problems. Only had a slight hiccup towards the end.

The problem first appeared after I had let the fuel tank get as low as it's ever been, and it was possibly almost empty. It was at 1/4 but when I fill it up the needle goes way past F, so I dunno where E really is.
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Old 09-22-2020, 08:25 AM   #5
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Check the sediment filter just behind the fuel filter. It is ribbed and normally black. Unscrew the ribbed base and check the filter inside.

Sed1.png
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Old 09-22-2020, 09:01 AM   #6
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Air in the lines will def cause the issue, is this truly a tilt angle thing or if you start from a dead stop and floor it on flat ground, keeping it nailed till you reach either a top road speed like 65 or the governor kicks in will it falter at all? If it’s an angle thing is d begin to think of either a pinhole in the fuel pickup tube, or it’s bent, sucking air, etc.. I’m assuming you drive it enough that your fuel is fresh. Any change if you make sure your tank is topped fully before doing a hill climb ?
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Old 09-22-2020, 09:02 AM   #7
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I seem to recall your bus as having higher than usual rust content. This may extend to your fuel tank. Changing your fuel filter and examining the filters to see what is there may be of use. I you have a fuel/water separator with a clear bowl, examine it for debris.
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Old 09-22-2020, 11:34 AM   #8
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Navistar dealer tells me the DT466E is HEUI, which can develop fuel pressure / injection problems with neglected oil. How long / many miles since the oil was last changed, and what is the maintenance history?
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Old 09-22-2020, 12:09 PM   #9
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Navistar dealer tells me the DT466E is HEUI, which can develop fuel pressure / injection problems with neglected oil. How long / many miles since the oil was last changed, and what is the maintenance history?
I have no idea about the maintenance history pre-me, but I had the oil and filters changed in May 2019, about 600 or 700 miles ago. Oil looks good on the dipstick (although I don't pretend to know what a diesel engine's oil should look like).
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Old 09-22-2020, 12:22 PM   #10
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Have you ever opened the drain plug on the bottom of the fuel tank to flush any debris & water contamination?

Need to let the bus sit level and undisturbed for 24hrs or so for the suspended water and grit to settle at the bottom of the tank -- then remove the plug and let a couple gallons of fuel rush out into a bucket.

Sounds messier than it really is...

If you had a lot of crud in your tank from sitting it's possible to have mucked up your new filters already...

Going uphill obviously puts more load on the system -- demands more fuel flow...

Do as Cadilackid suggests and create the same demand on level ground and see if you get the same results as when hill climbing.
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Old 09-25-2020, 08:32 AM   #11
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Welp, I think I may have blown or damaged my engine because of this. I picked it up this morning and was driving it home, but on the first (relatively small) hill the power cut out and then stayed cut out. I was barely able to limp to the top and then turn around, and while trying to limp up a hill going back the engine warning light came on. I stopped and shut the engine off and then turned it back on (the engine warning light did not come back on, at least) and then limped back to my lot.

I popped the hood and pushed the primer pump a few times. It was easy to press in and a frothy foam came out. After maybe 10 pumps it stiffened up and then pure fuel (no air bubbles) started coming out. I tried the engine again and it has a strange sound in idle now.

I found the data plug on my bus so I'm going to try plugging in my new Bluefire and seeing what I can see.
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Old 09-25-2020, 08:45 AM   #12
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You picked up from the shop? If so what did you have them do?
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Old 09-25-2020, 09:03 AM   #13
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You picked up from the shop? If so what did you have them do?
Well, ironically I took it in for this exact problem but the mechanic sort of poo-pooed it. They scheduled me to have a new exhaust system put in and the front brake drums replaced, but since they had to wait a week for some parts to come in, I went and got the bus so I could work on it in the meantime.
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Old 09-25-2020, 10:23 AM   #14
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I would wonder if you have any stored codes which you may be able to get from your Bluefire. Do you have a small button just beside the data port you found? If so you can pull codes from that but I'm not sure if that process has been changed in this year model.

But it really seems to be a fuel supply issue. You can check the lines from the fuel tank to the filter for any dampness that would indicate a source of sucking air. Otherwise consider replacing the fuel filter(s) again since your ran the fuel level low thereby causing a sediment issue. Check with the shop to find out what filter they used and get another regardless of what you do now. You could still have an issue with low mileage you have driven. Check the sediment filter. These are things you can do.
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Old 09-25-2020, 10:34 AM   #15
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Quote:
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I popped the hood and pushed the primer pump a few times. It was easy to press in and a frothy foam came out. After maybe 10 pumps it stiffened up and then pure fuel (no air bubbles) started coming out. I tried the engine again and it has a strange sound in idle now.
Sounds like something in the fuel system has a weak seal that is allowing air into the system. I had something weird like that with a Davco water separator that was triggering the "water in fuel" light driving through a rainstorm and a high exhaust temp code running against the governor. The truck never failed to start or showed any fuel issues like this. But if you're getting frothy, foaming fuel from priming, that's air between the primer pump and the tank. Possibly an in-tank fuel pump could have a bad check valve bleeding pressure back into the tank.
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Old 09-25-2020, 12:11 PM   #16
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what type of sound is your strange idle sound? if the injectors have air in them which your fuel lines definitely did from the primer pump being easy to push then they will make a pretty loud clackety clacking and the engine may idle pretty rough.


just google what happens when people swap injectors how getting the air out of the injection system is a royal pain... if you are sucking air which it sure acts like you are then the results would be the same.
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Old 09-25-2020, 12:13 PM   #17
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Quote:
Originally Posted by turf View Post
lack of power....

hmm, air in your pump. those air bubbles get stuck in the pump, crack each line open and see if you can find the bubble. fuel pumps are great with liquid, not with air.

check out your turbo. the charge air lines, the manifold. do you know the boost pressure? a cracked manifold or torn charge air boot will cause low power.

good luck tracking down the problem

he has an electronic HEUI engine, the injectors dont have individual lines going to them.. im betting that the fuel pickup is cracked and sucking air much like if you get a crack in a drinking straw.. you still can suck some drink but also get air
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Old 09-25-2020, 12:28 PM   #18
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Originally Posted by cadillackid View Post
what type of sound is your strange idle sound? if the injectors have air in them which your fuel lines definitely did from the primer pump being easy to push then they will make a pretty loud clackety clacking and the engine may idle pretty rough.


just google what happens when people swap injectors how getting the air out of the injection system is a royal pain... if you are sucking air which it sure acts like you are then the results would be the same.
"a pretty loud clackety clacking and the engine may idle pretty rough" sounds like exactly what is happening. Initially when I was just having the uphill problem, I wasn't getting this sound.

Quote:
im betting that the fuel pickup is cracked and sucking air much like if you get a crack in a drinking straw.. you still can suck some drink but also get air
I'm kind of hopeful that this isn't the result of anything breaking and it was just that I let the fuel tank get low enough to suck some air in. There have been long stretches (including a bunch yesterday) where everything seemed to be running fine. Would a cracked fuel pickup cause a constant problem or just occasional?
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Old 09-25-2020, 12:41 PM   #19
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if its split near the bottom ands the tank is low..



my DEV bus hada wierd issue where it would suck air but only when it sat.. id start it up it would run for 30 seconds then want to die.. id go prime it up and drive it for all day no issues.. in my case ai had a tiny leak in a fuel line up by the injection pump (its mechanical engine)..



the fuel system can overcome some amount of air.. the incline could be taking the fuel level at the pickup low enough any crack is exposed.. or the fact you floor it going up a hill, the engine requires more fuel therefore making any air in the lines become a problem because it starved for fuel, where it otherwise wouldnt starve because enough fuel is still provided .. at some point you may need to pressureize the system and see if any leaks happen...

-Christopher
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Old 09-25-2020, 12:43 PM   #20
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Quote:
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"a pretty loud clackety clacking and the engine may idle pretty rough" sounds like exactly what is happening. Initially when I was just having the uphill problem, I wasn't getting this sound.
Noisy injectors will have a loud tapping or clicking sound to them. This can happen when they're extremely dirty, but it should have a rhythm to it in time with the cylinders, unless you've got an injector going bad or coming apart internally perhaps.

Quote:
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I'm kind of hopeful that this isn't the result of anything breaking and it was just that I let the fuel tank get low enough to suck some air in. There have been long stretches (including a bunch yesterday) where everything seemed to be running fine. Would a cracked fuel pickup cause a constant problem or just occasional?
I'd say that would depend on where it was cracked. Dead bottom of the pickup tube, it would come and go based on fuel level. If it was fairly high on the pickup tube, it would be there pretty consistently.
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