fuel return banjo bolt question, Yanmar

[Canibul]

I'm slowly working my way through systems on old boat we bought. One of the 3HM35F's has started running rough since the delivery trip. I had the three injectors tested yesterday, all okay, and reinstalled today. Examined all the hardware as I put it back on the engine, and one of the three banjo bolts holding the return fuel harness to the top of the injectors was really bad. Half way cracked through, with the other half just about to let go.

I can see that fuel would be going down the crack in the bolt, and getting around the lower copper washer. I can't see that this would hurt anything, other than being a small fuel leak onto the top of the injector. However, I thought I better ask some of you more knowledgeable diesel mechanics.

Would a slight leak in the fuel return line cause any issues on one of these engines? I can imagine that this is low pressure fuel, so I'm thinking it wouldn't affect anything going on in the engine.

[sailorchic34]

I think, your going to want to replace that bolt. Plus verify that the return piping is not obstructed at all..

[dabbler]

Replace the banjo bolt and both copper washers. Diesel engines are very sensitive to air leaks in the both the supply and return fuel lines. Learned the heard way on a BMW turbo diesel in my RV.

[gjordan]

Why would a bubble in the return line affect engine running????______Grant.

[sww914]

That banjo bolt is the victim of overtightening.

[Canibul]

Yeah yeah, I KNOW the banjo bolt is damaged. Duh. That's kinda why I went to the trouble of taking the photo and posting it. Question is if this could possibly have any effect on engine performance. Of course I am hoping that it would, because this would be a very easy fix. I'm still new to working on diesels. I'm thinking that a leak in the fuel return line isn't going to do anything other than dribble fuel.

By the way, you don't have to replace those expensive copper washers. Just heat them cherry red and let them cool. That anneals the copper. Presto change, all soft again. Good as new.

[casual]

1Stink of diesel fuel. 2 already weakened bolt if you break it retightening WOW you will never forgive yourself. Probably a hard place to get parts. If you can't find them e me we have a local Yanmar dealer. Perhaps I can help.

[a64pilot]

Bet you could go to the local auto parts store and match it up with a bolt used on automotive brake systems if needed.
Fuel return shouldn't matter running wise

[FlyingCloud1937]

If the return line is plumbed back into the supply side. It would introduce air into the system and cause problems. If it returns to the tank by separate piping, no on most diesels. But could be a fire hazard.

Lloyd

Originally Posted by Canibul

Yeah yeah, I KNOW the banjo bolt is damaged. Duh. That's kinda why I went to the trouble of taking the photo and posting it. Question is if this could possibly have any effect on engine performance. Of course I am hoping that it would, because this would be a very easy fix. I'm still new to working on diesels. I'm thinking that a leak in the fuel return line isn't going to do anything other than dribble fuel.

By the way, you don't have to replace those expensive copper washers. Just heat them cherry red and let them cool. That anneals the copper. Presto change, all soft again. Good as new.

[O32]

Originally Posted by a64pilot

Bet you could go to the local auto parts store and match it up with a bolt used on automotive brake systems if needed.
Fuel return shouldn't matter running wise

I wish that was true.

Today, as the last step in my engine head gasket repair, I went to install the injector return line. The injector company had provided me with two copper crush washers (I think they should be nylon). Anyway, with hardly any force on a small spanner, the banjo sheared off.

I think the bolt bottomed out because the copper washers were too thin.

I spent 1/2 my day driving around to motorcycle shops, injector shop, NAPA, Canadian Tire etc. Some had some banjo bolts, but none an 8mm one, never mind the correct length.

So faced with making one. Or waiting 3 weeks for one from Yanmar

If anyone knows of a part number for a similar part, I would be grateful Engine is otherwise ready to run!

My fallback position, is to use the one on the filter and put a plug in there. My return line already has a tee that returns fuel (and air) to the tank.

[O32]

Found an almost identical M8 bolt off my old car. Drilled a few holes and it is hard to tell it is not a Yanmar part

[capt jgw]

Even easier than that: get the proper size regular bolt from the hardware store, probably about fifty cents. Then grind the threads off one side so it looks like a "D" from the end. Don't have to take much off, just enough to let the air pass through. Leave a little space under the head untouched. On one engine I had all the banjos were done that way, my guess is the PO got tired of breaking the hollow ones off. These will not break and work just like the original hollow ones.

[O32]

Originally Posted by capt jgw

Even easier than that: get the proper size regular bolt from the hardware store, probably about fifty cents. Then grind the threads off one side so it looks like a "D" from the end. Don't have to take much off, just enough to let the air pass through. Leave a little space under the head untouched. On one engine I had all the banjos were done that way, my guess is the PO got tired of breaking the hollow ones off. These will not break and work just like the original hollow ones.

Our injector guy suggested that too. Problem is, that all the M8 bolts I could find in stores were either full thread or the unthreaded shank was too long.

After filing/grinding off part of the threads, the threads need cleaning up. Need an M8x1.0 die which I did not have. Only way to get one locally, was to buy a whole set for $XXX.XX!

I found an M8 bolt that I scavenged off some old parts off my old 300D car. It had exactly same shank length. It was easy 10min job to drill the holes in drill press. Probably 3 weeks to get the Yanmar bolt!

[capt jgw]

Originally Posted by O32

Our injector guy suggested that too. Problem is, that all the M8 bolts I could find in stores were either full thread or the unthreaded shank was too long.

After filing/grinding off part of the threads, the threads need cleaning up. Need an M8x1.0 die which I did not have. Only way to get one locally, was to buy a whole set for $XXX.XX!

I found an M8 bolt that I scavenged off some old parts off my old 300D car. It had exactly same shank length. It was easy 10min job to drill the holes in drill press. Probably 3 weeks to get the Yanmar bolt!

Good point about the threads. I've made a couple banjo bolts this way, and I just used a correct size nut to chase the threads. Worked pretty well.
Drilling the long hole up the shaft of the bolt would be pretty easy with a drill press, but not everyone has access to one. It would be next to impossible with a hand drill. I could file the side of the bolt off with my Leatherman if I had to.