[FIXED] Listen to this Injector Buzz Test, please!

vimeo.com/232573539

The question is: Am I listening to one bad injector and seven good ones? Or seven bad injectors and one good one? Sorry about the camera angle. :blush: Had to stuff my phone in next to the filter to get it out of the wind.

For reference, I found this video with one bad injector:

$5 to anyone who has a known good 7.3 and will video their Buzz Test. :lol:

Took another video after we got this truck to start and run:

vimeo.com/232751127?ref=em-share

What do we think? I still think there's too much variance between injectors.

no idea. have no experience with the injector buzz test

cheryl hartkorn wrote: no idea. have no experience with the injector buzz test

No worries. :lol: I never used it much until this truck showed up. :silly:

what is the point in the test? either you have 1 bad injector or 7 bad injectors? better put an order in for 7!!

I can definitely hear the variance better in the second video. I'm not really a diesel tech, but can you hook up a fuel pressure gauge and watch the pressure drop like automotive? Or is the fuel pressure to high?

I found an article about the 7.3 and the buzz test. Here is a snippet, will attach.

Cylinder contribution tests (CCT) & rotational velocity tests are not "injector" specific tests. A
buzz test is as close to an injector specific test...but...an injector buzz test, merely checks the
electrical continuity to/from each inj to the IDM.
basically...if all 8 injs 'buzz'...then that merely means that they are plugged in. No determination
can be made about whether the injectors are good or bad..or somewhere in-between.
The consistency (in tone) of the buzz test (audibly) should be considered and paid attention to
when a buzz test is performed ...since any difference in sound can indicate problems (or just
normal wear issues) related to the movement of the poppet valve, when it is pulled up by the
(energized) solenoid.
While any injector can immediately and permanently be damaged by lack of fuel pressure, fuel
contamination, gas, water, etc.... the poppet valve in the injs is really the only part of the injector
that 'wears'


I would take the mileage into consideration and possibly sell all 8 Injectors due to the variance related to mechanical wear. But can I ask what the issue with the truck is? Start/stall, no start? Or why the injectors are in question?

cheryl hartkorn wrote: what is the point in the test? either you have 1 bad injector or 7 bad injectors? better put an order in for 7!!

Gjauto wrote: I would take the mileage into consideration and possibly sell all 8 Injectors due to the variance related to mechanical wear. But can I ask what the issue with the truck is? Start/stall, no start? Or why the injectors are in question?

We ended up at the same place - replace all injectors. Lotsa $$$, but hey, we didn't break it/build it. :lol:

The history is that a local bought this recently, and the owner struggled to get it started after it'd been sitting for two days or more. Cranks all day, won't start without external fuel. We let it sit over Labor Day weekend, and got it to not start in our lot. That first video was taken when the truck still wouldn't start.

IPC is there, fuel pressure is there, cranking speed is good, glow plugs are working. Going by the 'one of these things is not like the other', you'd tend to think that one injector is bad in the first video, right? Seven 'lighter' buzzes, and one sharper buzz on #7. However, after doing some reading online, I'm thinking that the lighter buzz actually represents the problem, and it's the sharper buzz on #7 that signals a good injector. This is reaffirmed when cranking, as you can hear one cylinder 'hitting' every two crank revolutions.

I performed the Buzz Test early on in the diag, but missed the significance of the results until later on, when I'd checked everything else and hit a wall. :blush: :lol:

After we got it to start, I redid the Buzz Test, and noticed the difference between it and the first video. To me, it shows that the injectors are somehow failing to flow fuel when they've been sitting long enough, but come around once the vehicle has been driven. I suspect oil quality and (lack of) maintenance may have a lot to do with this condition.

Tyler wrote: Going by the 'one of these things is not like the other', you'd tend to think that one injector is bad in the first video, right? Seven 'lighter' buzzes, and one sharper buzz on #7. However, after doing some reading online, I'm thinking that the lighter buzz actually represents the problem, and it's the sharper buzz on #7 that signals a good injector.

I heard that in the first video and didn't know what to make of it. What's actually making the noise when buzzed? I guess it doesn't matter I would just picture it better. Whether its an electrical or mechanical noise, to me louder would be better. If the valve is louder it's moving faster and more freely I would think.

Gjauto wrote: I heard that in the first video and didn't know what to make of it. What's actually making the noise when buzzed?

From what I understand, only the electrical portion of the injector is getting operated by this test. Since its performed KOEO, there's no oil pressure to actually do anything beyond that. I freely admit I'm not as familiar with this engine, or this style of injector, as I'd like to be. :blush: :lol: But I learned a ton during this process. The next one will go much faster!

I guess it doesn't matter I would just picture it better. Whether its an electrical or mechanical noise, to me louder would be better. If the valve is louder it's moving faster and more freely I would think.

In retrospect, this philosophy makes all kinds of sense. :lol: New gas fuel injectors always sound better than old ones when heard with a stethoscope, why would this one be any different? Oh well, I've got a much better ear for it next time.

So this one got all injectors. It has a much easier time starting now. Plus, check out this Buzz Test:



They all sound nice and sharp now.

I'll slap a [FIXED] on this once I can check how it starts after sitting for a day or two.

This one is [FIXED] and down the road.

For any future readers looking for help on their 7.3, there's another way to go about finding this issue. Because these injectors use oil pressure to make the magic happen, there's a little spout built into the top of each injector to allow oil to flow out after the injector fires. The relative amount of oil flowing out of each injector can be indicative of injector health.

In this example, while cranking the engine with both valve covers off, we saw one injector spitting oil out of it's spout. The same one that sounded OK during the Buzz Test. The others didn't spit out a drop. :lol: I take this to mean that no oil is actually flowing through the injector, so no fuel is getting injected.

I've read about injectors at the other extreme, flowing TOO much oil, which acts like a leak in the high pressure oil system. Again, a visual on the injectors can show one flowing more oil than the others.