Help with hollow engine sound after bad injector

[Meatloaf326]

Hello all, This is my first diesel and I’ve been through it and learned a ton but still new and need some help. 7.3 idi

I recently had an injector knock that went away after soaking the injectors in Lucas injector cleaner, so I took the beast on a road trip when the knock came back as well as low power and black smoke under load, so I ordered new injectors and headed home (400miles away). Rookie mistake I know now. About 80 miles from home I began smelling unburnt diesel and then 20 miles from home it gained a low growl noise from the engine that almost sounds hollow, and is much louder under load.

Fast forward to today when I got the new injectors in. She fired up right away and sounds pretty good at idle but that hollow growl is definitely there under load. Especially taking off in second, which normally is no problem.

My theory is a washed out/scored cylinder and I’ve lost compression l but what do I know. Would that cause the hollow sound? Besides sounding bad it drives pretty well. Much better than before the new injectors anyway.

Where do I go from here? Thoughts on what I did to it?

Help me fix the beast! Thanks y’all

 

[IDIBRONCO]

Your description of the noise really doesn't tell me very much. The only thing that I can think of that sounds even remotely like a "hollow growl" would be the sound that comes out of the intake on these engines. That sound is perfectly normal and can be heard fairly easily unless you have a turbo on the engine. I'm not saying that this is what your noise is, but it's my only guess.

 

[Big Bart]

Suggest the following.

1) Pull all the glow plugs and test them while they are out.
2) Do a compression test via the glow plug holes. Then you can determine if you have a cylinder issue. Harbor Freight has a reasonably priced one. Some have suggested they had to cut the end of the glow plug adapter down to make sure it would thread in. (You will understand when you see it.) You are looking for 350-450 psi and no two cylinders more than 20% off from each other.
3) Check your oil level, if over full or your oil smells like unburned diesel you likely did have some wash down. However you may want to change if unsure.

If it idles pretty good likely you do not have a dead cylinder.

The growl -

I would pull the dog house cover over the engine and tranny and drive. Try to determine if it is the engine, tranny, driveshaft, exhaust, etc. Perhaps have a buddy drive so you can better zero in on the noise. Not sure on vans but if the snorkel from the air cleaner to the grill is on a van too. And it is missing or loose, you will hear more noise.

 

[captain720]

Did you do a soup bowl delete? That will make some extra growl

 

[Farmer Rock]

It sounds like you have a manual transmission, are the shifter boots secure/undamaged? Bad shifter boots will allow you to hear growling noise at around 1500 rpms..just a random thought...
Also, could be the condition of your IP matched with new injectors advancing the timing...


Rock

 

[Meatloaf326]

Suggest the following.

1) Pull all the glow plugs and test them while they are out.
2) Do a compression test
3) Check your oil

Bart, I will pick up the harbor freight compression tester today and give it a shot. I did not smell diesel in the oil but changed it anyway.
Also it does not have the snorkel but never has had it since I’ve owned it

 

[Meatloaf326]

It sounds like you have a manual transmission, are the shifter boots secure/undamaged? Bad shifter boots will allow you to hear growling noise at around 1500 rpms..just a random thought...
Also, could be the condition of your IP matched with new injectors advancing the timing...


Rock

The shifter boot is torn where it comes out of the tranny with a little bit of oil leaking out as well (gold color, not atf). I’ll get a new one coming. I really hope this is what’s going on thanks for the advice!

 

[Meatloaf326]

Your description of the noise really doesn't tell me very much. The only thing that I can think of that sounds even remotely like a "hollow growl" would be the sound that comes out of the intake on these engines. That sound is perfectly normal and can be heard fairly easily unless you have a turbo

Definitely going to pull off the intake and see if that’s the source when I’m home. If I can’t figure it after I change the shifter boot and try a compression test I’ll try a video to capture the sound

 

[Selahdoor]

The shifter boot is torn where it comes out of the tranny with a little bit of oil leaking out as well (gold color, not atf). I’ll get a new one coming. I really hope this is what’s going on thanks for the advice!

Wrap and bunch an old bath towel around it, and drive a bit.

 

[Big Bart]

Bart, I will pick up the harbor freight compression tester today and give it a shot. I did not smell diesel in the oil but changed it anyway.
Also it does not have the snorkel but never has had it since I’ve owned it

In case your first compression test on a IDI.

1) Hook up a battery charger if you have one. (Keep the batteries from draining down to far.)
2) Leave the ignition off and use a jumper wire or remote starter switch. Jump from the big post on the fender well starter solenoid (The side the battery connects to.) to the little post on the starter soleniod. Just remove the starter wire so you can access it. Doing it this way your IP will not pump diesel into the cylinders. You also can easily see the compression tester guage. If you use your key unplug the IP on/off solenoid, otherwise you are pumping in diesel or the truck will start if you are pulling one glow plug at a time.
3) Once the glow plug adaptor and compression tester are hooked up. Jump the starter solenoid. Count compression strokes, the test gauge will jump each stroke.
4) I write down the following.
a) Cylinder #
b) First compression stroke reading.
c) Second compression stroke reading.
d) Sixth and final compression stroke and final reading.
5) Test the glow plugs with a ohm meter. No-resistance it is bad. Only use Motorcraft glow plugs. Others balloon or break off.
6) The reason I compare 1st, 2nd, and 6th compression strokes is you can catch worn vs just dead cylinders. Say if #1 only jumps to 50psi on the first stroke, and 100psi on the second. But other cylinders go to 125psi on the first stroke and 250psi on the second it’s worth perhaps retesting to confirm so. Then doing a leak down test to find a valve or ring issue. Cylinder is not dead, but not making as much compression as fast as the other cylinders.

This test will not perhaps find your growl. But will confirm if the engine is compromised. Then your baseline for next time you wish to or need to do the test again.(See any difference.)

Lastly the HF tester is middle of the road quality, works but less accurate than a Snap On or Mac one. So if you do not like the results. No harm in retesting a hole to see if the tester is consistent.

 

[Meatloaf326]

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Video link to hear the sound I’ve got.

I’m not getting any noise specific to the air intake and the exhaust feels/sounds pretty even. No puffs. Have not compression tested yet but will this weekend.

Thanks Bart for the guidance, exactly what I needed

 

[Selahdoor]

Sounds exactly like my truck. There is nothing unusual there.

Maybe yours was unusually quieter before, and something has been cleaned out?

 

[Meatloaf326]

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Startup.

 

[Selahdoor]

Yep. Exactly like mine.

 

[IDIBRONCO]

If anything, it sounds like you may have a hole in the exhaust or a broken exhaust pipe. Other than that, I'm not hearing anything unusual either.