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Discussion Starter #1
what’s going on fellas. Got a 2001 3500 HO 6speed dually 4wd. As mentioned on previous post, i bought it and have slowly been rebuilding from ground up. Truck is pretty much new everything as of this time. Last mod I did, I added a air dog system to replace the factory lift pump. The new air dog works great and I have bad fuel pressure when driving now. One thing I am having an issue with is hard starts on inclines. If I park with the front facing upwards on a slight incline, the truck turns over for quite a while before it will start. This is after it sits over night of course. If I park in the same spot with the front facing down the incline, it fires right up with a key bump. Now when I say incline, this isn’t a mountain, it’s part of my rock driveway so not too crazy. It’s like the fuel is running back towards the tank and the pump wont get it to the injection pump?

I have been over all the fuel lines and everything. My buddy assumes it’s getting air, but I would not know where from because nothing is leaking. The fittings are all press on fittings that don’t use clamps, but could that be an issue? Could it be pulling air in from there? I’m stumped and didn’t have this issue until I put the air dog on. The air dog runs for about 5 seconds and then stops but everything I read said that is normal. Let me know what you think...
 

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Check the return line at the back of the head.
 

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Check the return line at the back of the head.

Fern, are you saying check the return back there for a leak? I’ve already checked all that. Or are you saying the air dog runs into that and could be leaking there? Mind you, it starts all day with no issues, only when it’s parked on incline with front up for more than 8 hours or so
 

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The airdog or any lift pump all use the whole fuel line system. If there is a loose fitting, cracked line or bad sealing washers on any fitting air will siphon back into the lines causing your hard/non start issue. It is a common problem and 95% likely the problem. Back of the head fitting is most common but not only place. The T fitting joint below it is the next most common followed by any other fitting that has been apart like on the pump, filter or VP44, with near the tank being last unless it to has been apart. You commonly DON'T get much of a fuel leak because the return line is not pressurised. So check them all again and replace any washers and T fitting seals that have been apart.
 

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I have the same exact issue with my 2001 2500 HO 6-speed, also with an AirDog 150. I've been reading about a banjo bolt on the back of the head, near the firewall that can work loose, letting in a little bit of air. Is that the same bolt/line you're talking about? Is it as simple as snugging it up or do I need to pull it out and replace a seal or o-ring? Can I over-tighten it to where it's restricting fuel, other than over-tightening it to where it strips/breaks?
 

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I have the same exact issue with my 2001 2500 HO 6-speed, also with an AirDog 150. I've been reading about a banjo bolt on the back of the head, near the firewall that can work loose, letting in a little bit of air. Is that the same bolt/line you're talking about? Is it as simple as snugging it up or do I need to pull it out and replace a seal or o-ring? Can I over-tighten it to where it's restricting fuel, other than over-tightening it to where it strips/breaks?

That's the one. It has sealing washers. Rubber coated washers basically. If you climb under the truck with a light and shine it up to the back of the head you can see it. You can't over tighten it in regards to restriction but like any fastener it can be damaged.
 

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Discussion Starter #7
Glad someone else is having the same issues. I’m going to check out the return and see what happens. That one is a PITA to work on too
 

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Fern, are you saying check the return back there for a leak? I’ve already checked all that. Or are you saying the air dog runs into that and could be leaking there? Mind you, it starts all day with no issues, only when it’s parked on incline with front up for more than 8 hours or so
Yes, mine does the same thing. Haven't got around to it, but it is the most likely culprit based on my reading.
 

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That's the one. It has sealing washers. Rubber coated washers basically. If you climb under the truck with a light and shine it up to the back of the head you can see it. You can't over tighten it in regards to restriction but like any fastener it can be damaged.
Thank you. When I get a minute, I'll check and see if it's noticeably loose and snug it up if so. If that doesn't fix it, I'll pull it and replace that washer.
 

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Discussion Starter #10
I’m assuming those washers are something we need to buy from dealer or online? I’m hoping to get to it this weekend.
 

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Don't give up locally so easily. Things like that are available from any local truck or cummins shop or diesel injection repair/rebuild shop. Brand does not matter much as many use
Bosch parts and many are interchangeable. Some good parts stores even have somethings.
 

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Discussion Starter #13
Just wanted to give everyone an update. I checked every single possible area that this thing could leak and cause the hard start. Nothing. I even had my buddy who is the master diesel tech at a dealer check it out. He didn’t find anything. One of my battery’s was weak, replaced it and for some reason, it starts every time with a pause now lol! The pump isn’t tied into this battery so who knows. I’ll post more if it does it again...
 

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The uphill/down hill part may have been you imagination or just checking things fixed it. NO fuel leak is usually visible, as it takes a bigger hole for fuel to come out and be visible then it does for air to seep back in and cause hard or no start due to air getting into the VP.
Slightly slow crank from a bad battery will feel similar but cannot imagine up or down hill making a difference.
You do need to replace the other battery as they need to be matched pairs to run all systems correctly and the other one will likely be bad shortly.
If you had a leak you probably sealed it just checking it.
 

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Discussion Starter #15
The uphill/down hill part may have been you imagination or just checking things fixed it. NO fuel leak is usually visible, as it takes a bigger hole for fuel to come out and be visible then it does for air to seep back in and cause hard or no start due to air getting into the VP.
Slightly slow crank from a bad battery will feel similar but cannot imagine up or down hill making a difference.
You do need to replace the other battery as they need to be matched pairs to run all systems correctly and the other one will likely be bad shortly.
If you had a leak you probably sealed it just checking it.
It definitely was a hard start issue. I got a video of it doing it. I was stumped, I’m assuming your right on the “we fixed it” by re checking everything and all that. That’s the only logical explanation I can think of.

As for the battery, I’ve replaced only one and replaced both at the same time on several occasions and trucks. I’ve never noticed a difference in starting but do admit the older battery tends to go quickly afterwards. I will get around to changing it here soon, it’s been hooked to a trailer and running to rigs for weeks now so haven’t had time to really slow down.
 

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PS, for those above. Just tightening the banjo on back of the head usually solves the problem. The washers are available at some parts stores and all diesel truck shops and fuel injection shops. They are actually a universal part like any other nut, bolt or washer used on many fuel systems. There are TWO on each banjo, one on each side of fitting.
 
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