Engine/Transmission (1994 - 1998) Lift Pump ticking quesiton

[JGheen]

So, I have read a bunch of threads on the lift pump ticking and have come up with some questions.

I have heard the ticking that ya'll claim is the lift pump, but on my engine(155K) I hear the ticking every now and then. Sometimes I won't hear it for a couple of days, then some mornings on the way to work I hear it. I was going to first try and replace the overflow valve and see how that cures the intermediate ticking, but what causes this ticking every now and then and not all the time? Is my lift pump getting ready to go or would you say it is more a overflow valve issue? I have not checked my fuel pressure, but the engine runs fine all the time, no sputtering or hesitation what-so-ever. I will eventually be installing a fuel pressure gauge, probably when I replace my overflow.

Also, I have been reading a bunch of threads on lift pump replacement and some mention not droping the lift pump push rod into the engine and some don't. Is this something that I should be worried about when the time comes for me to replace my first lift pump? Is the push rod similar to a basic Chevy mechanical fuel pump push rod that rides the camshaft? If it does take a chance in falling into the engine, what steps can I take to prevent that?



Thanks guys, Joe

 

[RBratby]

my truck was doing the same as you discribed yours as doing. i was also going to change the lift pump but i figured i would do the overflow valve first(its easier). i call piers and ordered a overflow valve and installed it the tick is not there anymore. when i was talking to pdr they told me that it was more than likely the overflow valve. im still going to do the lift pump but that will be another day soon. i did the overflow valve first for 2 reasons. 1st being it is easier and 2nd it was less money.

 

[SMorneau]

I posted on this subject with similar questions and I didn't get much feedback either. My lift pump is still doing fine and it has produced a tick sound from underneath the cab for years... it is seems to be most evident if you put a stethoscope on the fuel lines inside the frame rail. I quieted it down by isolating the mounts.

 

[bmoeller]

Could be the ov. My pump was ticking, but it was the pump. Seemed to work fine (didn't put a gauge on it) when it was replaced. What was, was that one of the springs was tired. It was about a half inch short (about the length of the pumps stroke).



The rod could come out. Two o-rings are really the only things keeping it in. Just pull the pump straight out, so it won't catch the block, it is shaped kinda like a golf tee on the end that follows the cam lobe.



#ad

 

[Vaughn MacKenzie]

I've been having a problem with my truck which I hope a new lift pump with fix. I've had an irritating miss under part load that's been driving me nuts which I've spent quite a bit of time on to no avail.



My lift pump ticks as well and I'm wondering if it's related. I need to chase down the parts to set up a fuel pressure gauge to check it out.



So far I have replaced the overflow valve, fuel filter twice, injectors, removed and inspected delivery valves, and tonight I moved the timing from 13. 3 degrees to 15. 75 and that didn't help much either.



Vaughn

 

[JGK]

JGheen, SMorneau,



I think the reason that there's been little response to this question is that there is only a few things to try to resolve it, and if that doesn't do it, there's not much else to suggest. I think half the 12-valve members here have experienced and dealt with this issue, and some have resolved it and some haven't, including me. I replaced the lift pump. No change. I replaced the OF valve, little, if any, change. I had the pump bench tuned (twice) maybe a little change. Eventually you learn to live with it, and, as you said, it comes and goes.



I swore a few years ago mine had developed a serious knock or lope. Tried everything (second bench tune of pump), compression test (bought a gauge and adapter for the injector hole), swapped injectors around, used a remote infrared thermometer to measure exhaust manifold temperatures. Nothing solved it. Eventually, it just sort of went away. It still comes back a little now and then. I think now it has something to do with cold temperatures and winter fuel.



The point is, sometimes you can go nuts trying to chase down a noise on these engines. They are a diesel. They tend (at least in the past) to be noisy, clanky, rattley, etc. 'Tis their nature. Sometimes you just have to drive them until something breaks and learn to appreciate the nuances in the mean time. Most of the time, they go like hell for a long time - the CTDs anyway!



Keep checking things as you think of them. But at some point, after you've tried everything, just drive it and go on. Don't loose too much sleep over it.



Just my late night, humble, tired opinion!

-Jay

 

[McCRam]

I haven't read about the fuel pump making noise before. Does It sound like a lifter, or an exhaust leak? I'm hoping so, then I won't have to keep worrying about it. It has gotten a little louder lately though.

 

[JGK]

Well, a sound, as described by someone here in writing, is difficult to relate to by those of us reading the description. We all have our own notions about what is being heard. It's pretty subjective. What may be an unusual noise to you may sound perfectly normal to me!



But as to the injection pump, I do know from being in the room and watching the Bosch tech run mine on the test machine both times, these pumps are loud clackety machines! Especially at higher speeds. The tech wore hearing protectors and I plugged my ears. I was amazed at the noise they make.



What I was thinking when I had mine retested as part of chasing down the lope is that one barrel may have gone bad and pushing a weak fuel charge. However the pump was fine. These pumps, unless abused severely, are pretty darn tough and reliable. So I would leave that as a source of a click because of a malfunction as the last item to check. It's an expensive service to have them bench tuned. The main advantage of the bench tuning is to get them all pushing the same quanity of fuel and to adjust them up to push as much as they can.



Pursue things like OF valve, lift pump pressure, compression testing, swap injectors around, check valve lash, use an engine stethoscope to isolate the location of the click, etc. . These are all fairly cheap to do.



-Jay

 

[JGheen]

Cool! Thanks a lot for the replys guys. I ordered a overflow valve from Piers yesterday, so we'll try that first. I haven't checked my valve lash in a while but last time I did they were all within about . 002"-. 005" of what they should be. Will probably be doing that this weekend as well.

Good to know that others experience the same issue with it coming and going. At the very first sign of this ticking I swear I thought it was an exhaust leak some where cuz it was kind of going to the rythm of the engine, until you get under the truck and hear it coming from the driver side rather than the passenger side.

Well, haven't heard it for a couple days now, it should be back tomorrow, but I will follow up on this thread after this weekend to let you guys know if the OF valve fixed the issue. Valve lash will be on the list as well but one before the other to see if there is any change.

 

[Sasquatch]

My truck has 120,000 miles on it, and I've noticed a subtle change in it recently. It's producing a greyish smoke under light throttle (especially when cold) that it never used to. Also, the truck sounds "raspy" and there is a ticking noise that I haven't been aware of before, which seems to quiet a lot as the engine warms up.



I did the valves last weekend, and that didn't seem to quiet things, but I did them again, yesterday, because I couldn't convince myself that I wasn't hearing rocker-arm, tappet noise...



The last time I cleaned the fuel pre-filter, there was a small amount of light, silvery metal in the bottom of the filter. It looked like pot metal, more so than steel. I'm not looking forward to changing out the lift pump if it entails removing and replacing the starter motor. I did that last year, and it's a job I don't relish again, as it's a bee-atch working around my 4x4's front drive shaft, cross-member, etc. , to get the starter in and out.



I'm 6'6" tall, with long arms, so I'm wondering if it'd be easier to do this job from the top. What's the overflow valve; where's it located, and could it be causing the same symptoms I'm seeing and hearing?

 

[Sasquatch]

Another, maybe related, follow-up: I read a thread on this site recently that talked about "vacuum" in the fuel tank putting pressure on the system and making the lift pump work harder. My fuel tank has had this vacuum since the day it was delivered, and I've always assumed it was normal.



When I crack the tank's cap, there's a noticeable sound of air rushing in, but I've always noticed a slight vaccum in fuel tanks, and thought nothing of it. Is the vent-cock on the top of the fuel tank exposed/accessible? Can it be cleaned out without dropping the tank? Can the vacuum be relieved (I don't want to drop the tank) by a replacement, venting, fuel cap instead?



Thanks for any replies.

 

[JJW_ND]

Changing Lift pump....

I changed my lift pump a couple years ago chasing a ticking sound even though I had checked the fuel pressure at about 210K miles.



I have a 4x4 with 4-wheel anti-lock vaccumn brakes, and had no problem changing the pump from the top. It is not to hard a job. The only think I did was remove the fuel filter. Having changed the starter, it is a much harder job (awkward attack angle) and those extremely tight 10mm bolts. Plus you are above any fuel leaks. It helps if this area is pretty clean.



I too would like to hear about the vent system in the tank. Mine used to not have much pressure but it has developed much more presssure these days. Too use my gravity feed axillary tank I now have to leave the fuel cap cracked. I would not think this pressure would negatively affect the fuel pump as it is the same as pressureing up the tank (mine has positive pressure . . not negative). I can see were there is more backpressure on the return line.



jjw

ND

 

[bmoeller]

The tank does have a vent. It is a small hose that comes off the top of the tank. It is part of the same piece that the sending unit is attached to. Just disconnect the tank end, and blow air throught it if it is plugged like mine was. Some trucks have a cap that was supposed to be removed, but some weren't.



The lift pump can be replaced from the top. I'm 6'6" also, wasn't that big of a deal. Bought my pump from the local C-IH dealer. Was les than $100 for me. You do need to swap a fitting on the pump, if you go that route.

 

[Sasquatch]

bmoeler:



Do you have to drop the tank to get at the vent?

 

[Vaughn MacKenzie]

Hmm, the vent problem makes sense. Whenever I go to fill up my tank is under quite a bit of vacuum.



Vaughn

 

[Cooker]

I mentioned the vaccume in the tank in another thread. Eliminating the vaccume in the tank solved the ticking noise on both mine and my fathers trucks.



I have found the vaccume on both trucks to be the a plugged up rollover valve. I tried cleaning it but replacement was the only option. Some trucks had a capped rollover valve from the factory but I think this was more common on the early 24v trucks. The vaccume on m truck was so severe it deformed the tank.



You do not need to drop the tank, it can be accessed while in place but it is a tight fit.



For more information and part number for the rollover valve can be found in a recent thread about lift pump replacement.