CLICK-CLICK-CLICK goes the injector

Ahh yes… injector clicking… So, after cleaning all the injectors, new fuel lines, injector seals, injector connectors, etc. I have a single injector, #2 A-bank to be precise, that is much louder than the others. All the others sound exactly as they should, just a nice little tick-tick-tick, barely even there. In addition to the loud CLICK on this one injector, there’s a noticeable knock/clack that can be felt on the intake manifold in time to the injector clicks. When I pull power to that injector, it goes away, replaced with the expected soft miss.

I’ll start the standard troubleshooting steps - injector cleaner, spark plug, spark wire, injector power, pulling the injector and checking on bench again, etc - but the intake knock has me a bit worried as this was not there before the project overall.

Any input, of course, is greatly appreciated :slight_smile:


Find someone with 2-channel USB oscilloscope, or buy one. Fantastic and quite forgotten tool that will tell you everything. This way you will see any deviation in your engine on your laptop*
It will also allow you to save some money of the cleaner and consumables…

Alternatively - start frok replacing injector with 2nd hand one, these are $10ish…

(*- don’t try this if you’re over 60y.o.)

Ahemm, they are the ones that developed the computer!

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As I was running the car to purge the fuel lines (via my nice new fuel cut-off which does a very nice job of preventing a ton of fuel spilling everywhere after de-pressurizing), I noticed that just before the engine cut-off, for about 30 seconds, the knocking stopped. As I increased the throttle a touch, the knocking came back, and then all the gas was gone and the engine stopped.

The only thing I could think of was that I removed the FPR from the A-bank side. I’m wondering if the pulsing of the fuel straight into the rail could be causing the knocking I’m hearing from the A2 injector.

When I listen using a mechanics stethoscopic, I the injectors all sound about the same. Again, I unplug the A2 injector wire and it stops. Another weird thing is the pulsing of the fuel rail is on the same cadence as the knock I’m hearing. I listen further back on a fuel line and it doesn’t have the pulsing, just on the rail. I bet it has to do with the FPR-A not being that makes that injector louder - it is the injector closest to where the fuel comes in on the rail…

I removed the A bank regulator on my 87. I dont get the sound you are describing at all.

Same same here, no ill effects what so ever.


  1. New injector - same tick-tick
  2. New spark plug - same tick-tick
  3. New spark plug wire - same tick-tick
  4. Ran without the spark plug wire attached - NO tick-tick… Engine runs rough, but definitely no tick-tick

Next steps?


Compression test on cylinder A2. If low, do a leak-down test. SD Faircloth

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Yep - that’s what I was thinking. Thanks @SD_Faircloth !

A bit more diagnostics…

  • I can feel a thud-thud in time with the tick-ticks when I put my hand on the A/C compressor
  • The ticks and thuds speed up in time with RPMs
  • I put seafoam in a while ago, but I can’t remember if it was before or after the symptoms started; oil change coming anyway

So if you remove fuel (disconnect injector) or remove spark (disconnect plug wire) noise goes away?

What would cylinder firing do to make a tick sound? Loose valve?

Loose or dropped valve seat…a loose seat ticks…a dropped seat is very loud, either of which is in time with rpms. Usually will be the exhaust valve seat. Check the exhaust on the A bank side for popping pressure although the gold test would be a leakdown test. I would hold off on the oil change until you confirm. SD Faircloth

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Yup - gonna do the compression and leak down tomorrow. I do smell exhaust - I was thinking it might just be an exhaust manifold leak, but would that also explain the thud-thud on the A/C compressor that is in time with the tick-tick?

I did muck with the downpipes… I can’t imagine that would cause the thud thud I feel, but if I’ve got bad exhaust and bad back pressure on the exhaust valves on 2A, then maybe?

Well, gonna check anyway…

  1. Compression and leak down
  2. Check for exhaust manifold issues
  3. Check downpipes to manifold

Could also be exhaust leak for that cylinder at the exhaust manifold? Exhaust leaks can make a ticking sound.

Dry compression cold engine reads right about 180 on 2A. Haven’t done the others for comparison yet.

That is good, right about what mine is. (180 cold, 220 warm)

I would get one of those mechanic stethoscopes and see if you can pinpoint noise. I still wonder if its as simple as an exhaust leak at manifold.

Yep @gregma actually saw your numbers from a post a while back.

Dry compression cold engine 2B the same, right at 180…

Gonna check the exhaust manifold and downpipe now.

If the gasket is still ok, maybe it is as simple as checking/tightening the manifold bolts ? Could you not hear the exhaust blowing at that point if the gasket was bad or the bolts were loose ? If it’s not that (and my not knowing the engine history) …it may be mechanical…like a valve that needs adjustment, or worse, a slapping piston, worn wrist pin, ?? SD

Jacked the front end up to check the exhaust connections. Everything seems to be torqued down nicely.

When I started the car with it still jacked in the front, it started and then died after about 5 seconds - as if it was starved for gas. Started about 5 more times with the exact same result. Starts briefly, then dies…

Also, ran it without the A bank exhaust manifold shield. And you can still hear the loud tick.

Sounds like a bad fuel pump, right? I’m thinking this might be the source of the click to if the fuel pressure is low.

Photos of the 2 holes used to secure the heat shield that cause a nice loud rumble and no loud click… and a bunch of exhaust to pour out into the engine bay😁

You removed the heat shield and still have the clicking. If, as you now suspect, it’s the fuel pump…why does the clicking stop on A2 cylinder, when the electrical connector to A2 injector is removed, but the fuel pump is still running. If it’s the fuel pump, the clicking should be continuous…as long as the pump runs. Where is the pump on your vehicle…in the boot, or in the tank ? Remember…the clicking is in time with engine rpm. I don’t think the pump rpm changes in time with engine rpm. During your ownership of this vehicle…has it ever overheated ? I think you now need to do a leakdown test on A2. I’m back to thinking again…possibly a loose or ill-fitting (not dropped) valve seat on the A2 exhaust cylinder. It may be that you will also need to pull the A bank valve cover and check the clearances on both valves on A2 cylinder. SD

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