Engine/Transmission (1994 - 1998) Need help with strange sound.....

[JGheen]

So after my current lift pump change I thought this noise would go away. Well it hasen't ,and I am getting really annoyed by it and want to figure out what it is. The sound does come and go and to be specific it sounds like a "T, T, T, T, T, T" or even sounds like the lift pump pumping fuel.

In search of this sound I have done the following... ... ... changed overflow valve, sound went away for a while but came back... ... changed lift pump, sound went away for the first five minutes of engine running with new pump, then came back... ... almost sounds like an exhaust leak, so checked the torque on the 3 piece manifold some were a bit loose but sound didn't go away after start up. Quick question while I mentioned an exhaust leak, wouldn't the pulsating sound of an exahust leak come from the manifold area before the turbo and if there was a leak after the turbo it would be a steady flow leak, not pulsating due to the turbo dampening the exhaust pulses???

So what does anyone think this sound could be? I swear it sounds like the lift pump ticking but I just put a brand new one in and the overflow valve is brand new as well. When you really listen to it, it becomes more like an exhaust leak sound but when you get under the truck it sounds like it is coming from both sides of the engine and I can't pin point where it is making the noise. It is quiet on top of the engine with the hood up but when you get under the truck or are standing on either side of the truck you can really hear it.



Sorry for the long post guys, but I have been putting this thread off for a while now thinking I could find this strange noise, but now that I can't figure it out, I need your help.



Thanks, Joe

 

[DPinkston]

Sorry to hear the lift pump didn't fix your ticking. I have a new lift pump on order hoping it will solve my ticking. Maybe I'll have better luck than you did.

In order to eliminate vacuum in the tank as a cause you could just drive around with the diesel cap loose for a while.

Danny

 

[Johnstra]

Joe - With the engine running, put a finger on your fuel input and return lines. Try different places (back near the tank, under the cab, up closer to the engine. I don't know if it means there's air entering the lines or not, but on my lines I can feel a strong pulse and I can hear the fuel moving through the lines. Try getting a bucket of diesel and run a flexible line from the bucket to your pump and see if the sound goes away. Try the same thing with the return side too. I suspect the fuel moving through the metal lines can make a pretty good tick under the right conditions.

-john

 

[HEMI®Dart]

What Johnstra said



Are you sure you are not hearing the fuel returning to the tank? It's more or a sh,sh,sh,sh sound. It's more noticable in cooler weather and a full tank.

 

[JGheen]

What Johnstra said



Are you sure you are not hearing the fuel returning to the tank? It's more or a sh,sh,sh,sh sound. It's more noticable in cooler weather and a full tank.

That is definatley the sound it makes, kind of a t, t, t, t, t, or sh, sh, sh, sh. I haven't really noticed it either in hot or cold weather neither full or getting low fuel tank. I'll have to make note of what the weather and fuel tank level is when I hear it but as far as I know I hear it just about all the time.



I agree with Johnstra, I have been reading a few threads on fuel tank vacuum and maybe the breather valve on top of the tank is clogged up. I bet it is with all the undercarriage truck washing I do after a good mud run. I will try leaving the fuel cap a little loose and see if the sound goes away.

I will also try Johstras "touch" method and see what I come up with.



Thanks for all the help guys and any other suggestions you can think of let me know and we'll see if this noise can go away and let me hear the sound of the engine again.



Joe

 

[Woodenhead]

So after my current lift pump change I thought this noise would go away. Well it hasen't ,and I am getting really annoyed by it and want to figure out what it is. The sound does come and go and to be specific it sounds like a "T, T, T, T, T, T" or even sounds like the lift pump pumping fuel.

In search of this sound I have done the following... ... ... changed overflow valve, sound went away for a while but came back... ... changed lift pump, sound went away for the first five minutes of engine running with new pump, then came back... ... almost sounds like an exhaust leak, so checked the torque on the 3 piece manifold some were a bit loose but sound didn't go away after start up. Quick question while I mentioned an exhaust leak, wouldn't the pulsating sound of an exahust leak come from the manifold area before the turbo and if there was a leak after the turbo it would be a steady flow leak, not pulsating due to the turbo dampening the exhaust pulses???

So what does anyone think this sound could be? I swear it sounds like the lift pump ticking but I just put a brand new one in and the overflow valve is brand new as well. When you really listen to it, it becomes more like an exhaust leak sound but when you get under the truck it sounds like it is coming from both sides of the engine and I can't pin point where it is making the noise. It is quiet on top of the engine with the hood up but when you get under the truck or are standing on either side of the truck you can really hear it.



Sorry for the long post guys, but I have been putting this thread off for a while now thinking I could find this strange noise, but now that I can't figure it out, I need your help.



Thanks, Joe

I've got the same deal going, and like you was putting off posting for a while. I also changed the lift pump and overflow valve, partly to try and fix the tick but also since I had enough miles to figure it couldn't hurt. I hear it loudest standing on the drivers side and when I've been cruising for a while so everythings hot, like when you stop at a rest area but leave it running. After reading some other posts I was thinking maybe it was tank vacuum but then noticed it still did it immediatly after having the tank open for re-fueling so I would think the vacuum would be gone from the tank. Keep us posted with what you find.



Mike

 

[JGheen]

Thanks for the post Mike, good to hear someone else is having similar symptoms. Maybe we can both figure out what the heck that noise is.



Quick update on this... ... after work today, before I started the truck I loosened the fuel fill cap a bit and went ahead and started it. I thought I was on to something, until after a little driving the noise appeared again. Interesting how it went away for a little while, but that has happened before. On the way to the fuel station, getting off the freeway, it seemed to be much quieter. Got to the fuel pump and could still hear it but as I was filling the tank, I could have sworn it got a little louder as the tank got fuller. I walked around the truck many times trying to pin point the noise again. Everytime I went to either side of the truck it sounded like it was coming from the opposite side. Underneath the driver side, it sounds like and exhaust leak from up by the manifold. Underneath the passenger side, it sounds like it is coming from the lift pump or fuel lines and has that more sh, sh, sh, ch, ch, ch, ch sound.

I tried Johnstras advice and felt a good pulse on both lines, so I guess it is flowing fuel good enough. I need to get a fuel pressure gauge very soon, have everything I need but the darn gauge.

I'll keep searching, maybe something will come up.....



Joe

 

[MLee]

Joe;

Have you tried a listening tube [rubber hose] or a automotive stethoscope? [got mine at Harbor frieght] This will help you determine the source of the sound better than guessing. The hose you will be able to hear the exhaust sound better than the stethoscope. I assume you adjusted your valves. One of these being out of adjustment will drive me nuts.

 

[JGheen]

Joe;

I assume you adjusted your valves. One of these being out of adjustment will drive me nuts.

Haven't tried the mechanics stethescope but I did adjust the valves not too long ago and to tell you the truth, this sound got a little more noticeable after that. All the valves were very tight, each one was probably . 001-. 004" under the spec. I loosened each one up to the proper spec, but the noise comes from the bottom of the engine somewhere, if it were the valve lash causing this noise wouldn't I hear it from the top somewhere with the hood open?? I guess I could re-check the valves... ... never had any make any noise before with all the previous adjustments... ..... another thing is, everytime on a cold start up in the mornings, I don't hear this noise. It is only after it is warm and I arrive at work then I can hear it with the door open or window down. Since the lash tightens up as the engine warms up, I don't think it could be that, but who knows, this is driving me nuts.



Joe

 

[Berrigan]

Mine does this too. Comes and goes mostly when warmed up and worst at about 1500 rpm. Mine is coming from the fuel return line. A stethascope on the metal return line under the truck confirmed this. Dealer says its normal. Bill

 

[JGheen]

Mine does this too. Comes and goes mostly when warmed up and worst at about 1500 rpm. Mine is coming from the fuel return line. A stethascope on the metal return line under the truck confirmed this. Dealer says its normal. Bill

That is just what mine does as well, waits till it's warm and usually hearing it idling or anything below 1500rpms.

I don't trust anything that the dealer says whether they say it is normal or not. If it is normal, then why does it make this noise? I never heard it till I went over around 150K, so something is wearing out, but power and overall engine performance is still good which doesn't help in the search for this noise.



Joe

 

[Berrigan]

Mine has done it since new. Question, Is the overflow valve the source of the fuel that goes through the fuel return line? If so that would seem to be the noise maker. Bill

 

[JGheen]

The overflow valve is brand new, I guess I could start there and see if that is exactly where the noise starts. But if it is where the noise is coming from how come it never made that noise until over 150K on the stocker and then I decide to install a new one for poops and giggles and it still makes the same noise?



Joe

 

[Berrigan]

I dont Know Ive never worked on one. Ive heard of guys stretching the spring and such to tweek them. Bill

 

[JGheen]

Well, thats the thing, the OF valve is brand new. I wouldn't think a brand new OF valve would need to be messed with.



Joe

 

[Rams-n-Hogs]

Joe,



My truck has made that noise since it was new. 130000 miles later, it still does it. A louder exhaust helped , but I just don't notice it any more because I got so used to it.



Jim

 

[PKemp]

Something to consider. I also have had the nefarious "ticking" sound that drove me nuts for several years. I changed out OF valves and Lift Pumps galore and sometimes the noise would go away for awhile but the sound eventually always came back. From the "history" of this irritation posted in the archives you'll note that this is nothing new. I spent a lot of time and money trying to cure mine. I believe you'll find that it isn't really a problem of great significance barring the fact that it could mask other problems. After a lot of research into the P7100 pump and its connecting hardware, lines, pumps, valves etc I did find a solution. It is however not a cheap one. I personally converted my fuel system over to a F. A. S. S. Continuous flow pump to feed the P7100. It did completely cure the "Tick", but most would consider this an expensive and outrageous fix. Thats true, I must admit that it is. I believe you will find that the standard mechanical lift pump as (I think) JoeG would say is: "practically bulletproof". You really only need to watch the fuel heater connections/gaskets, rubber fuel lines, and the OF valve as they wear out more often than other parts. Many have learned to just ignore the sound. Like an irritating child always complaining, we tend to tune out the noise. Just my 2cents... ... .

 

[JGheen]

Thanks for the post PKemp, you definatley explained this noise well. I guess I will be living with this noise now since it doesn't seem fixable without eliminating the lift pump and going to a FASS system. That was what I was thinking could cure the problem once and for all but like you mentioned it is a expensive fix but pretty much unnecessary.



Maybe someone has a used system out there for sale on E-bay or something.



Joe