3B dies after sitting at idle (1 Viewer)

[Crazjtk]

The long and short: bought a BJ42 a couple years ago, it ran great when I parked it. I replaced the hand pump with the Bosch one as recommended. The fuel lines from the tank to the hand pump are new rubber. I have a return line from the engine back to the tank. Nothing seems to be visibly leaking, although the injectors weep a tiny bit on occasion. EDIC appears to be in full working order. When I prime it, it starts up and runs great. After a few minutes at idle, it starts running a little rough, then deteriorates to shaking, chugging, and eventually a stall out. We haven’t driven the truck on the road for any significant time yet.

Our two theories are either SOMETHING (dunno what) letting in air, or perhaps the fuel pump not supplying enough fuel at idle.

Thoughts?

 

[BreckenridgeCruiser]

The injectors weeping would start my search there. Have the injectors been serviced at all? Also, how old is your fuel filter? A leaking or clogged fuel filter can result in your symptoms...

 

[Crazjtk]

Oh, right, forgot to mention that the filter is new too.

We haven’t touched the injectors.

 

[too tall]

I would take a piece of fuel line and run directly from the pump inlet fitting into a jerry can of some sort. See if the problem continues. If it does not stall I would assume there is a hole in the line from the tank. You could also put a clear glass filter inline just before the pump and see if you are getting bubbles in it.

 

[mmcinnis]

Is your fuel filter dry?
Mike

 

[gerg]

I would add to the Jerry can test .. if symptoms persist replace the small rubber hose on the back of the engine that returns fuel from the injectors to the pump. It can be loose and be another source for Aur the enter the system. Another good thing to check is crack the bleeder Nipple on the fuel filter while it's running. Fuel should shoot out under pressure .if it doesn't your lift pump is probably frozen or the internals aren't sealing and need to be replaced. Very easy fix but without positive pressure between the lift pump and the injection pump body every connection in between can be a source for air to enter the system.

 

[Crazjtk]

I don’t believe the air is entering in the initial line from tank to primer pump, as it is all brand new rubber hose, though I suppose I could check the connection at the tank.

When we pulled out the old fuel filter to replace it, it was only filled about 1/3 of the way with diesel. We haven’t rechecked the new filter, but have used the bleeder screw. It squirts a bit of fuel, but not a steady stream.

The fuel return line we have running back to the tank is actually run from that small hose on the back of the engine. Now that you mention it though, that old hose is still partially there, and could be letting air in.

 

[RufusTheDufus]

That return line at the back of the engine shouldn't be routed to the tank if you have an inline injection pump. The inline injection pump doesn't send much fuel back to the tank. The rotary injection pump on the later model 3B needs a return to the tank.

That little hose is one of the most common places for air to enter the injection system. Lots of posts here talking about it. I think Lost Marbles even has some great photos to go along with the diagnostics somewhere here.

 

[gerg]

Dont take it for granted cus it's new hose. I can almost guarantee you your probably stating at the leak sight but won't know till you run clear hose or eliminate it from the system .air leaks only need to be small to make your life suck. Simple things like not tightening a clamp enough is all it taken to entrain air for me in the past.

 

[roscoFJ73]

I have a return line from the engine back to the tank.

Is that how they are supposed to be? I know the newer types with rotary pumps do that but I thought the inline pump engines sent excess fuel back to the fuel pump.

 

[tornio]

like Rufus said there is no fuel return to tank on b - 3b engine , (maybe on 3bII i don't know never see one)
and i would say it doesn't have to be....

 

[roscoFJ73]

like Rufus said there is no fuel return to tank on b - 3b engine , (maybe on 3bII i don't know never see one)
and i would say it doesn't have to be....

The 3B with a rotary pump have a fuel return like the other rotary pumps. They also have the built in vacuum pump and power steering pump like a 1HZ etc.

But I think this was only for Dyna trucks and Coaster buses

 

[tornio]

well , now the first thing to do Crazjtk is run the return hose to the pump like stock setup
.....assuming yuo have inline pump off course.... but never see a stock 42 with 3bII...

 

[Crazjtk]

Well, that seems to have sorted it. Pulled the tank return line, used a chunk of it to replace the return line to the pump which was 1, capped with a screw, 2, cracked, and 3, not held on with any clamps. Then I started it and it sat at a nice idle without a single chug for about 15 minutes. Thank you guys so much for the help!

 

[gerg]

Wahoo. The the return line strikes again!

 

[tornio]

Wahoo. The the return line strikes again!

he he , yes , happy you solved Crazjtk !!

 

[gerg]

It's not me. It's just one of many potential entry points. Methodical elemination is really the only way to approach the problem when you get air in the system. The problem comes from identifying all the suspects.