Cylinder four missing

[BammBamm]

My little 82 FI car is quite the character. So many things wrong and sometime symptoms just fade away. So I had her running great. Had being tearing around the neighborhood for many many miles. I had logged at least 20 hrs of it running in the driveway with the cooling fan cycling. It started right away and sounded great. I take it on my first out of neighborhood trip. About 7 miles down the road doing about 60mph I noticed the smell of oil. I look in my rear view mirror and smoke is billowing. when I pop the hood the spark plug wells are full of oil and it pouring down the back of the engine onto the exhaust. I was guessing the valve cover gasket. I had started it to move it and it didnt sound right. After a tow home I cleaned up the engine. Tightened up the valve cover and started it. It didnt sound right, like it was missing. I warmed it up and no oil leak.
So I start with checking the plug wires. While it running i remove each plug wire from the distributor to see if it makes a difference. When the plug wire for cylinder 1,2 and 3 were removed the rpm slowed and it sputered. But when I remove #4 it runs as it was. I used an inline spark viewer and she has spark. I checked compression which is even over all cylinders. I swapped plug wires and different spark plug. Still no power is being made from cylinder 4. When a spark plug is connected to wire 4 the arc is bright and crisp. It should be firing but appears it is not.
Im running out of ideas... Please assist..

[kilrwail]

Well you've checked spark and compression - the only other ingredient is fuel. You need to test whether that injector is working and/or plugged. I'm a carb guy but I'm sure an FI guy can direct you. You may need what I think is called a "noid" tester, to see if the injector is working.

[76was124]

No fuel in #4, would likely be one of three things.
1. Bad connector/wire
3. Stuck injector.
4. Clogged or failed injector.

I would test in that order.

Item 1: All injectors fire at once, so swapping the connectors between two cylinders would tell you if it's in the wiring or the injector. The only problem is the harness isn't long enough to swap the wires so moving #3 wire to # 4 injector will leave you running on three cylinders if the #4 injector is good, or two cylinders if the injector is bad. Therefore a trip to the auto parts store for a Noid light is the best/easiest way to determine wiring or injector. Digital volt meters are too slow.

Item 2 can be fixed sometimes by taking a dowel or heavy screwdriver and GENTLY tapping on the injector body while the is engine running. Getting the fuel flowing sometimes cleans it out.

Item 3 requires removing the injector so the most work. 1/2 hour + job, but make sure you read up and follow the proper safety procedures to dump the fuel line pressure before you disconnect anything.

[wizard124]

Remove the injector wire connection.. The ECU sends a grounding pulse. If you have a multimeter, use the 12vdc scale. You should see fluctuations in the reading while the engine is running. Next, remove the injector. 1 nut and it pulls out. There are 2 rubber o rings to retain. Could be pretty snug fit.

See if it sprays into a jar. no? separate the injector from the fuel line. Try cleaning the screen with spray cleaner. Look for obvious damage. Etc. I bought re-manufactured injectors from RockAuto.

If you are this far along, good idea to replace all fuel lines.

[RRoller123]

Alternatively, you can use a simple and inexpensive mechanic's stethoscope (a couple of bucks at HF) to hear the injectors fire. They make a very clear distinct click when they fire.

Pete

[BammBamm]

I have a 12vdc led is use as a noid. I will try that next. The spark plug was wet but it could be minimal fuel so low combustion heat. I rebuilt the whole intake system and cleaned the injectors. I have some spare injectors so I will check that next. Thanks guys.

[BammBamm]

Thanks guys. I guess I assumed the injector was working because the plug looked wet. The injector plug had a bad contact. Repaired it and the car is running great again. Thanks.