rough running, about to sputter out

Good question. I've changed a lot of filters over the last couple of weeks. It varies, but it could be anywhere from two minutes to ten or fifteen minutes.

 

There is no pressure in the tanks and there are no check valves on the return lines. I've had the fuel caps off the tanks more than once while I spun off the secondary filter, in order to pour in additives.

I cut a large, rectangular hole in the floor of the cab over the transmission in order to give me easy access to the junction point on the top of the trans. The fuel lines from each tank join at that junction as do the return lines. Also, the air line from the compressor joins with the line to the wet tank at that point. I am as familiar with the back of the cylinder head, the junction, and the return lines as I am with the backs of my own hands. There are no check valves on my return lines.

 

You should have a check valve, regardless, I think the fuel pump also has one, built in. The one you added, shouldn’t be necessary, unless fuel pump check valve is bad. I don’t know enough, myself, but seems getting everything set up as it’s originally designed is a good starting point. For now and future diagnostics. I’ve heard of check valves further down line,toward tank. I know you said you don’t have one, but sounds like you do. Otherwise it would lose prime, and be hard to start.

 

Did you pull the restriction fitting out of the back of head and check there is nothing blocking the tiny hole????

Sorry if you've covered this. Didnt want to read 6 pages.

There should be a check valve in the return somewhere. Other wise you would loose prime . Has to be.

 

I checked for flow where one of the return lines connects to a tank. There was plenty of flow, no restrictions in the return.

There is not and never was a check valve anywhere in the return, (except for one that I placed there temporarily). I've owned this truck for going on 20 years. I've been at the back of that Detroit numerous times over the years for various reasons. I cut a large rectangular hole in the floor of the cab for easy access. Great view of things. No check valve. I was losing prime. I ran it for years that way. More than once I ran the batteries dead from trying to start the truck. I installed a universal check valve from Northern Tool, and that solved the problem, but I was told by a technician that too much back pressure at the back of the head can cause a loss of horsepower and a loss of fuel mileage.

I took his advice seriously. I removed the Northern Tool check valve from the back of the head and placed a check valve at the output of the transfer pump, on the line to the secondary fuel filter. That served to prevent loss of prime as effectively as the check valve on the return.

 

The factory installed restriction fitting on the return line at the back of the head is also a check valve. It has a ball and spring inside it to prevent the fuel from bleeding off when the truck is shut down. If there was no check valve in the return side the engine wouldn't start until you crank it long enough that the fuel pump can pressurize the injectors.

 

I cannot dispute what you say, because I have never removed the restriction fitting. If it has a ball and spring inside it then you know more than me.

There are no check valves of the type shown in Rideandrepair's pictures.

If there are a ball and spring inside the restrictive fitting, they weren't working. I lost prime every time I shut the truck down, until I installed a check valve.

 

The first thing I would do is pull the return fitting on the back of the head to see if it's the factory one with the check valve. If not replace it with the OEM one. It's just under 100 bucks. You don't want to use a cheap after market one because there is no way to know what pressure ir is designed for. To little pressure and the fuel bleeds off. To much leads to fuel injection problems and the truck runs like crap.

 

I put over a million miles on this truck. Never had this problem before. Whatever that fitting is, it's the one that has been there for 20 years that I've owned the truck, and Penske had it for 7 years and 700,000 miles before me.

I'm stumped at this point. I admit that. I don't know what to do next, but I know I have to rule some things out. This truck has always run great. It runs great now, too, until it starts to sputter and chug down. I'm afraid to put freight on it. I never know when it will act up. It might go a thousand miles no problem. It might go ten.

At this point, I only want to get it home and park it. I'm 500 miles from home.

 

I’ve heard of problems with the shut off valve for tanks. I’ve never had a problem, but if you have new style top draw tanks, might want to check that valve. I’ve heard of putting straight T fittings in its place. Of course you can’t switch a tank off once you do that. Hate to mention it again, but are you sure Penske didn’t put a check valve at the tank? It obviously didn’t lose prime when you first bought it. The check valve you installed holds prime for the same reason a straw holds water with your finger on it. And you must lose prime when changing filters, unless it’s done fast bathe check valve you installed may be causing the high pressure in filter. Maybe even the cause of sputtering. I’d get rid of that. The fitting us separate from check valve, the fitting has ,80 mm hole. Some drill it out for faster cooler flow of fuel to gain HP. Check valve screws into fitting. Maybe fuel pump is going bad, from fighting the check valve you put in. I doubt it. They rarely go bad, but you can check it by putting a wire into the weep hole. If you can feel vibration it’s going bad.