DT466 Fuel Issues - Any Advice?

[OJ_Bus]

Hi Everybody,

I'm not new to the forum, I had a different username but I can't get it to work for some reason. Always get locked out. Anyways, I created this one and I'm not sure if I'll be able to post pictures yet but I'll try...

Anyways, I have a 2008 ICCO RE300 with 160K miles. It has a 7.6L L6 Engine with a 466 CID Transmission. I'm having issues which I believe are fuel related but am not sure how to fix.

A month or so ago my bus would start but then die after about 1 minute of idling. It sounded like it just wasn't getting enough fuel. I changed out the fuel filter and got it to start and run for 30 minutes. The next week I couldn't start it again. I changed out the fuel strainer and charged the batteries. After quite a few tries it fired up. I was able to move it and let it run for about an hour with no issues. It started right up the next day as well.

The following week, however, it did the same thing where it starts then dies after 1 minute. I don't think it can be air in the fuel system since I'm able to let it run for quite some time with no issues when I get it started. Any ideas on what this could be? Maybe a clog?

 

[OJ_Bus]

Here are some pictures. The housing is from another bus. It sits right above what I believe to be the pump (which I have a picture of as well as an online breakdown of). I also attached a drawing of what I could see. Its hard to get to all this in my bus but I tracked the fuel lines to the tank. I'm not sure which way the fuel flows.

I was able to drain all water out of the filter. The filter and screen were pretty crudy when I changed it. I'm not sure what tool I need to check the fuel pressure or how to go about trying to get rid of any clogs there may be in the fuel lines.

Not sure how it can be a clog or air in the line if I was able to get the bus to run well for an hour or so straight a couple of times. Any help is much appreciated!

 

[rensch26]

So the bus is really only having a hard time getting started after it has set for a while? And once it is started it is having no trouble continuing to run?

If that is the case I don't think you have too big of a problem on your hands. I'm not as familiar with the newer buses but there is probably a check valve built in to the fuel delivery circuit to prevent fuel from draining backwards toward the fuel tank. After you leave the bus sit for so long it is inevitable that some fuel is going to drain back into the fuel tank but ideally your check valve keeps enough fuel in the circuit in order for the engine to initially start and stay running as your fuel pump sucks fuel all the way back up from the tank. On the older buses this check valve is actually a small ball built into the fuel primer pump assembly. Does your bus have a primer pump?

 

[OJ_Bus]

I haven't found a primer pump. I followed all the fuel lines as best I could and only found what I drew up in one of the pictures I attached. However, it's very difficult to get to all this on my bus as there are many things in the way, and I'm also not mechanically inclined, so I may have missed it.

So you think it may be the fuel check valve not holding fuel in place while the bus sits?

 

[rensch26]

As long as you're not having any issues once you actually get the bus started, yes. In some of the older buses with the DT466E in them the primer pump housing has a small plastic ball that acts as the check valve. Fuel can flow past it when you're using the primer pump but the plastic ball is supposed to prevent fuel from flowing back to the fuel tank. Over time this little plastic ball can develop small dents or flat spots on it and it doesn't do a great job of sealing anymore. Do some more snooping around and see if you can locate a primer pump. If your bus has sat for a long period of time you can always use that to help suck some fuel back up to the engine before you try starting it up. That should help ease your starting woes.

 

[rensch26]

Actually, now that I look at it. I think your primer pump is that big round button on your pre filter (or your "fuel screen"). If that is what I think it is, you can press that and suck fuel up out of your tank, through the pre filter, and through the fuel filter. When it starts to stiffen up on you that means your fuel system is primed. Go ahead and start the engine at that point.

 

[jazty]

A quick Google search: Google Search

Do you have a primer pump that looks anything like this?

or this?

 

[jazty]

Also, as rensch26 was mentioning, check if this is a primer pump:

 

[jazty]

One more video:

 

[siloguy]

My 1999 466 has that one and I had to replace it at a cost of about $9. It was leaking air and a bit of fuel so that you would start the engine and it would die less than a minute later. The fuel was running back into the tank, but if you ran it at least once in a week, it would retain enough fuel in the lines to stay running.

 

[capnron-SKO]

My 1999 466 has that one and I had to replace it at a cost of about $9. It was leaking air and a bit of fuel so that you would start the engine and it would die less than a minute later. The fuel was running back into the tank, but if you ran it at least once in a week, it would retain enough fuel in the lines to stay running.

That sounds about right. I had a 5 ton straight truck with a similar problem and it was air getting into the fuel line. It would run about a minute and die. You then had to prime it to start. Diesels don't like air in the fuel. Check fuels line for possible leaks.

 

[o1marc]

That sounds about right. I had a 5 ton straight truck with a similar problem and it was air getting into the fuel line. It would run about a minute and die. You then had to prime it to start. Diesels don't like air in the fuel. Check fuels line for possible leaks.

I have the same issue right now, how did you prime it, using the engine prime pump? That does nothing on mine right now.

 

[capnron-SKO]

I have the same issue right now, how did you prime it, using the engine prime pump? That does nothing on mine right now.

I had to remove the fuel filter (just a twist off) and top up the holder. That gave the engine enough fuel to run long enough to pull up fuel from the line and expel any air in the line.

 

[o1marc]

I had to remove the fuel filter (just a twist off) and top up the holder. That gave the engine enough fuel to run long enough to pull up fuel from the line and expel any air in the line.

That's my job for tomorrow, get it running. "Top up the holder"?
My filter is mounted in such a position that you just can't get a good grip and have room to turn the wrench. I may get one of those sockets the push onto the bottom of the filter get it out. Waiting for my water separator that should be here tomorrow. I hope what you did cures mine, because I am past frustrated.

 

[capnron-SKO]

That's my job for tomorrow, get it running. "Top up the holder"?
My filter is mounted in such a position that you just can't get a good grip and have room to turn the wrench. I may get one of those sockets the push onto the bottom of the filter get it out. Waiting for my water separator that should be here tomorrow. I hope what you did cures mine, because I am past frustrated.

Good luck with it Marc I hope it works for you.

 

[OJ_Bus]

Any good tips on how to check fuel lines for leaks?

 

[OJ_Bus]

Also, as rensch26 was mentioning, check if this is a primer pump:

Turns out that is the primer pump, good call.

The bus has been sitting for two weeks. I'm going to check the fuel filter and see if there is fuel. If not, I imagine something is letting fuel back into the tank and that's the issue.

If there is fuel, I think it may either be air getting in the fuel lines, in the primer pump, or the filter I put in may not be good enough. Apparently there are issues with this model where they recommend the OEM fuel filter that is designed to remove air from the fuel system. I some of this info from the link below as well as the youtube video below.

Hope this helps if someone else has the same issue. I'll let you guys know what I figure out. Thanks for all the info.

Maxxforce DT fuel delivery pressure - School Bus Fleet Magazine Forums

 

[rensch26]

Any good tips on how to check fuel lines for leaks?

Pressurizing your fuel tank with air is the best way to test the suction side of the system. Leaks on the pressurized side of the system should be pretty evident.

 

[o1marc]

Pressurizing your fuel tank with air is the best way to test the suction side of the system. Leaks on the pressurized side of the system should be pretty evident.

Show me how to pressurize the fuel tank?:Thanx:

 

[Brad_SwiftFur]

Show me how to pressurize the fuel tank?:Thanx:

I have seen fuel caps with Schrader valves added specifically for this purpose. A word of warning, though. Do *NOT* pressurize more than just a few PSI.