fuel return line noise

[treeguy]

I've searched around and couldn't find anything on this. With the LDT running the fuel return line makes a pulsating vibrating noise that you can hear if you stand near the tank. Everything runs fine, does this noise seem normal, does anyone else have this?

 

[glcaines]

When I first start my Deuce, the engine RPM is not steady until the engine warms up unless I set the idle higher. I have noticed that my in-tank fuel pump will pulse in rhythm with the engine RPM and I suspect this is caused by alternate increases and decreases of electrical output from the generator as the engine RPM varies up and down. At higher engine RPM at idle, I don't hear this pulsing.

 

[WillWagner]

You sure that the noise you hear isn't the in tank pump working?

 

[treeguy]

Mine is a steady noise all the time. If you put your hand on the return line you can feel it and if you crawl under the truck you can hear the noise all along the return line but not on the supply line from the in tank pump. Its probably nothing, just wanted to ask.

 

[WillWagner]

Well, the only thing that has any return fuel is the pump. Injectors have only drops of return.

 

[treeguy]

Does anyone else have this noise on their trucks?

 

[flyxpl]

I have that on my A3 , very noticeable . I do not believe I have heard it near as pronounced as on my A3 though .

 

[doghead]

The check valve between air tanks, will make a rattling sound.

 

[treeguy]

I have been giving this issue some thought and wonder if it is a chain of events. I think that this may all be related.

I had a fuel leak at the #1 injector where the steel line threads into the injector. I replaced the line and noticed a pronounced tapping from within the line. Thinking that the injector may be dirty, I dissassembled it and found that it was fine. Reassembled everything (count the dissassembly turns to get the spring press. correct.) still #1 tapping. Cracked all lines at all injectors and all normal. Felt all lines, #1 taps anoyingly loud, the rest have slight taps you can just feel, I also used a stethescope (this will make you really worry with all the noise you hear!). And the fuel retrun line to the tank still has the pulsating/vibrating sound and feel.

I think my truck has the power she should, but I have nothing to compare to. I was going to send out all 6 injectors to have them cleaned and pop tested, getting them all opening at the proper range. But now I'm wondering if the IP is the problem. Is it possible for the compression of the engine to back feed thru the injector, thru the line, into the IP and down into the fuel return line and dump into the tank. Could this be causing all the racket? If there is something like this going on, I would think that its all bad news in regard to the Pandora's Box within the IP.

The shop that can test the injectors can also test the IP. Before I go disabling my truck I wanted to feel out the thoughts of this chain of events. ??????????

 

[doghead]

Sounds like your # 1 injector may be stuck open or have a problem. I think you should get them all cleaned/tested/adjusted, and go from there.

Personally, I would pull a used injector out of a spare motor and swap the #1 injector and see if that solved it.

 

[WillWagner]

It is possble for the injector to hang open and allow compression past the pintle, but when that happens, the engine stops running. The compression is pushed all the way back into the pump and pushes the fuel out of the delivery area of the pump. If you had any broken/weak springs you'd see it in the performance of the engine, either by not starting from the above issue, or unusual smoke, white/grey, and possibly a fuel knock, that will sound like marbles in the cylinder, and there would be black smoke involved. Pulsing/ticking in the return line is pretty common in Bosch type fuel systems. There is a check valve at the outlet of the pump where the return line starts back to the tank that pops off at a given pressure. That valve is there to keep the correct galley pressure in the pump so the pump can make the proper injection pressure. If the engine runs good, has no unusual smoke and starts/stops fine, I would honestly leave it be. These things, as well as other compression fired engines all make different noises and if you listen too carefully, you'll think you hear something "abnormal". If you want, take a video of the engine runing and put it up on YouTube, then post a link to it here and we can have a listen.

 

[WillWagner]

Sounds like your # 1 injector may be stuck open or have a problem. I think you should get them all cleaned/tested/adjusted, and go from there.

Personally, I would pull a used injector out of a spare motor and swap the #1 injector and see if that solved it.

Or you could swap #1 with say 6 and see if the noise follows the injector.

 

[treeguy]

"if you listen too carefully, you'll think you hear something "abnormal" - Yea, thats where its tough to settle with yourself what is normal.

The engine seems to run smooth. There may be a knock, but after listening to other members videos the consensus is thats normal. I have cracked the injector line to the suspect area and when the fuel starts to come out the engine starts to stutter, so it would seem that the injector is functioning. In referance to smoke - on idle there is a steady stream of normal darkness (can't remember the exact color but its good) but there is an intermitant puff of white-ish. One puff, random - only noticible if you concentrate on the flow and colors. I called a mech. at Memphis (figured their familiar with tuning up) he said it may be water some where in the fuel system. I don't really agree - checked. Anyway, I think that this is an indicator to the status of a cylinder. Acceleration hard provides dark smoke so overall I think things are near OK.

I am leary about videoing, I don't think it will capture the fine detail that I'm concerned with. (what do guys use to video with now-a-days anyway?)

Swapping the injector #1 with another sounds like a good idea. I'll try that when I get a chance. Any ideas if I'm about to really kill something, I do need to use it, and like I said she seems ok? Thanks

Gotta go start it right now, I'll check the colors of the exhaust.

 

[treeguy]

Its hard to tell, on idle maybe a light greyish with a touch of blue?

 

[WillWagner]

I use a Flip video recorder.

[media]http://www.youtube.com/watch?v=YMidg_WYyMU&feature=mfu_in_order&list=UL[/media]

White smoke is normal for cold start especially ion low ambient conditions.

 

[misupratwin]

My return line does the same thing.

 

[big hoss]

My truck has the same sound i always thought it was the fuel pump. I dont have any problems with it though.

 

[treeguy]

My number one injector line is also tapping (esp. when listened to with a stethescope). I swapped it with the number two injector. The number one spot is still tapping, also increases speed with engine rpm. I am beginning to believe that there may be a stuck check valve some where in the injector pump. Any thoughts?

 

[Chevyman_15237]

Treeguy- I'm also in the same boat as you. Just picked this thread up... my number #5 injection line is really tapping. Almost sounds like something metal on metal. That's the only one that does it, might try and take the truck to a diesel shop and see what they say. I don't want an injector to scatter and have all that drama to deal with. Other than that, truck runs great, smokes a little black when running (turned up the go-go juice)

 

[treeguy]

Mine has been tapping for quite some time (possibly a year). Mine hasn't blown up yet. I only get black smoke if you stomp on the throttle or are trying to accelerate up a hill. If you listen to all the high pressure lines with a stethescope (with just rubber tubing on the end) you will hear all sorts of different pitch tapping from them all. Kinda scary! I think this all has to do with the IP or the IP head. Do you also have a noise in the fuel return line that is most noticable at the fuel tank?