Help narrowing down cause of the tapping noise..

[Fredrickson]

just a dime.. not a quarter or half dollars..

 

[Nero]

Fuel knock could be a timing issue, but if it just recently started and you did not make any changes to your engine, I'll still bank om worn parts. There's my $1.00

 

[Lumberjackchuck]

Ill check, but with the combination of new injectors with an original IP..
wouldn't it be more likely the injectors are opening late?

Yeah it would make more sense that way.

But, is the knocking worse when the cold advance is on or no ? Jumper 12V to the cold advance terminal on the IP and if it doesn’t make a difference I wouldn’t expect it timing related.

My truck recently started tapping/knocking a little when the cold advance is on, goes away when it kicks off. I should re-time but that dumb tech-time thing doesn’t work for me. DIMES WIDTH it is lol.

When it gets cold like this, my fuel inlet pressure to the IP gets much higher (I’m running an E pump) and I’ve heard that can mess with your timing as well.

 

[Jesus Freak]

just a dime.. not a quarter or half dollars..

Start cheap, senor.....lol

 

[HammerDown]

Interesting that I don't hear the 'tapping' increase with engine speed... it sounds consistent as you're rising in MPH.

 

[Fredrickson]

It's as if the noise tracks with what gear the transmission (E4OD) is in.. at 35 mph it drops a bit when it shifts.

 

[BrianX128]

Could be something smacking ever so slightly into inspection plate area on trans. When I put my new clutch and flywheel on my 7.3, the new stuff ever so slightly kissed the inspection plate. Yet only under torque. Coasting didn't hit it, but when the engine was under load it must have pushed components back 1mm to touch it enough to make the noise.

 

[Fredrickson]

Thanks! I will crawl under the truck this weekend and do some investigating

 

[BrianX128]

xc_hide_links_from_guests_guests_error_hide_media

This is what mine sounded like laying under it for reference.

 

[Big Z]

I am apologizing in advance for this being one of those.. "It could be one of any number of things" issues.
I have seen threads on this before, but I would really appreciate some insight from the group to narrow down possibilities.

There is an engine noise (clicking/tapping) that can be heard when the truck is moving.
It's always there when the truck is moving and gets faster with rpms.

The truck idles and revs fine (in PARK).
No noise, no smoke (white or black), and no strange noises at the tail pipe

The tapping starts only when there is load on the engine. (it's a 10k lb 1994 7.3 NA Ambulance)

To my uneducated ear, it sounds like the tap/clack is once per revolution.
So I am thinking it is happening at one cylinder.

Something that probably matters is:
I put in rebuilt injectors, but have not changed the IP or re-timed the engine, yet.

I have read through many threads and watched videos for similar symptoms.
Which left me more confused..than when I started.

So according to the internet
The noise could be:
injector knock, or compression coming back up into the injector, or a leak at the exhaust manifold, or a stuck lifter, or a rod, or the rocker arm or a wrist pin, etc..etc.

I recently drove it a few hundred miles all in one go.
The (idiot) gauges showed good and didn't move once the engine got up to temperature, and there were no smells..or smoke.

HERE IS THE VIDEO LINK
Here is the link in plain format:

xc_hide_links_from_guests_guests_error_hide_media

You can hear the noise best in the beginning.. and it disappears when I take my foot off the gas just past 40 MPH

I will be picking up a mechanics stethoscope this week to poke around more.

Thoughts? Things to look for? Things to try?

I was in the same situation. First i thought a bent pushrod. Then i thought a lifter bleeding off. All same symptoms as yours. Turns out to be an exhaust leak. If you retard the timing it quits ticking or quiets down quite a bit. If you advance the timing it becomes more noticable. After checking and testing, turns out its an exhaust leak. Trust me it drove me nuts. It does not sound like your typical gas powered exhaust leak.