Cylinder 2&3 not firing on 1984 fi azzurra

[searya]

My car runs real rough and based on heat from my Vick’s stainless headers cylinder 2&3 seem like they are not firing.

This was also confirmed by pulling the injector wires for 2&3 which had no impact on how the car sounded.

I don’t think it is the wiring harness as I tried a spare I have with no change.

Anyone know what would control those two injectors versus 1&4 which are fine?

[Daddio]

I'd do a compression check. A failed head gasket can let them pump back and forth instead of build compression.

[searya]

I'd do a compression check. A failed head gasket can let them pump back and forth instead of build compression.

Compression looked good on both cylinders at 140psi each.

I also tried a new Coolant Temp sensor and it didn't help. Spark plugs are new Champions and gap is .31

Any chance it could be wiring from the ignition to the FI relay under the passenger side dash? And if so any ideas there?

[spider2081]

I would suspect the fuel injectors. Have you used a car sthethoscope or a long screw driver and listened to the injector click?? All 4 injectors fire at the same time but each has a separate pin and wire from the ECU. It is not too uncommon for fuel injectors to be stuck shut cutting off fuel supply to the cylinder.

[searya]

I think that was it. I pulled the fuel rail with injectors attached, unplugged all of them from the wiring harness then took turns plugging one at a time back in, putting the live one in a mason jar and then having my wife crank the engine. 1 and 4 definitely put out more fuel than 2 and 3.

I have had issues with the injectors before but they were all brand new. A few months ago I was able to get the car running well again by replacing them. Probably put 250 miles on the car and the problem came back. So I pulled the head and there was lots of oil in chambers 2 and 3. I took the head to the machine shop where he installed new valves and smoothed out the surface.

The machinist said the valve seals were basically non-existant before he replaced them.

So here is my theory, oil leaked in through the valve seals was my problem all along. It caused my first set of new injectors to go bad and now the second set as well (or at least cylinder 2&3).

So two questions:
1. Does my theory hold water. That is would a bad valve seal be a reason for an injector to go bad?
2. Assuming it would make them bad then all I have to do now to finally be done with my issues is get new injectors (as there should be no more oil getting past the new valve seals)?

[tima01864]

I sent my injectors to be cleaned and tested, The injector service told me these injectors sometimes stick and if they do try tapping them and also use a gas additive on every fill. He recomends a product from Redline but I have used Stabil and a few others. For what it is worth https://hurstinjectorservice.com/faqs.html

[GeorgeT]

The connectors to the fuel injectors can be tested for firing by putting a jumper between the terminals with a bulb in-line (incandescent). Crank the motor and the bulb should flicker if the wiring is good.

[spider2081]

The connectors to the fuel injectors can be tested for firing by putting a jumper between the terminals with a bulb in-line (incandescent).

I have heard of doing this with a Noid light but haven't heard an incandescent The ground supplied to the injector from the ECU has a duration of a few milliseconds. Incandescent bulbs might not react fast enough to be seen.

Have you actually tried this??

[spider2081]

A rusty fuel tank and lines could be clogging the injectors filter screens. Have you changed the fuel filter and looked into the gas tank. ??

[redcars]

Oil going into the engine though the valves won't hurt the injectors, but trash and rust from the fuel tank and lines will. I would take the fuel filter off and cut it open. If it is clean then I am wrong. If it is loaded with rust you will need to clean or replace your tank and maybe the lines. I hope you get to the bottom of this so you can enjoy your Spider. I am going through mine now to put them away till next season.

[searya]

I was afraid oil may not have been the culprit.

When I had the problem the first time I change the fuel filter but didn’t look inside.

I will do that this time and also look in the tank to see what I find.

Thanks for the tip,

Assuming the tank looks good is there a good way to clean out the lines?