pokegama

My engine is makes a lot of tapping noises when it idles. I was poking around with a stethascope to see if I could find the source of the noise. The only things that were clicking were the injectors. I listened to each one and #6 wasn't clicking. What's that mean? Can I just replace one injector? Will running the car like it is do any damage? It seems to run OK just a little rough at idle.
The car is a 1981 US model.

danglerb

Take a look at a couple of plugs including the one for the silent injector.

Also sometimes tapping will loosen up a frozen injector.

Pretty sure you should be able to hear each one clicking if its working.

If you do decide that its bad, I would suggest pulling all of them and sending them out for cleaning and matching.

123quattro

Quite often if you have an injector not firing, you can hit it with 12v across the contacts. Several times of bumping it with 12v will get them going again. If you do get it firing, I would certainly run a can of Chevron Techron through the engine at a mininum. You'd be better off to send all the injectors out for a cleaning, but maybe not completely necessary depending on how much of a beater it is.

zoltan944

You can idle the car and pull the connector off of the #6 injector. If there is no change in anything it is not working. If it changes your idle then obviously thats not it

danglerb

Make sure you remove the retaining clip on the injector connector. Its a wire in a groove that runs around the connector near the bottom.

Lizard928

if one injector isnt clicking, I would strongly recommend removing them ALL and rebuilding or replacing them all.

VehiGAZ

Where are the injector connectors?

123quattro

On the side of the injectors just below where the fuel comes in.

pokegama

Thanks for all the suggestions so far.
Am I doing any damage to the cylinder by driving it if the injector is bad? What's an easy method of checking the circuit to it to make sure it's getting voltage?

123quattro

I believe the injector should always have 12 volts, and then it grounds the other side of the coil to fire it. You won't be able to find continuity unless you have an O-scope, but you should be able to measure 12v on the other side.

dr bob

There's a risk of lean operation if that cylinder is getting enough fuel to support misfiring. It's a wash really, becuase really lean mixture doesn't really have enough energy to get hot, but there's still the risk of detonation from the lean mixture if it actually explodes in the chamber. Simple way to check is to look for signs of detonation on the plugs. That will also give you an idea which cylinder is the problem if it is in fact just one. Run the engine under high load, shut it off while still under load, coast to the side and check the plugs. If one or two are causing problems they will be obvious.

A too-lean-to-fire cylinder also means that raw fuel is passing to the catalyst. There's a risk of overheating but not that severe.

danglerb

$5 to $10 at most auto stores, its called a Noid light and you plug it into the harness instead of the injector and the electric pulses make it blink. Ask for a Ford or Bosch type.

123quattro

If you are running lean on a cylinder to the point of misfire, that fuel is going straight into the cat and combusts there. It can melt a cat solid in pretty short order. You'll know if that happens. Your car will make about 20hp.

ZEUS+

How does it run ? Does it idle smooth ? Any power issues ? You can check the resistance of the injector with an dvom, should be about 2.5 ohms. Injector 1,5,2 and 6 all receive power from afc relay XVI, red and black wire. Cyls 2 and 6 receive their ground pulse from terminal 33 of control unit, grey and black wire. You can supply power and ground momentarily and listen to injector with engine off. A noidlight as suggested will check for pulse. A lean misfire is when there is not enough fuel to support combustion. The unburned fuel gets passed on to the cat and raises hydrocarbons.

dr bob

John, I agree to the possibility. A single cylinder that's so lean it won't light off at all will pass that same too-lean-to-light-off fuel-and-air charge , unburned, to the cat. At low loads this won't melt the substrate since the total raw charge mass is so low.

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Another sometimes-forgotten tecnological breathrough method for finding the 'offending' cylinder is the now-common IR temperature gun. Shoot each exhaust port/pipe and you'll quickly see which cylinder isn't firing. Even a cheap one will do the trick for this test.