Jim Clark

Having a problem with #4 not firing.
All Injectors replaced
All new injector wiring
Compression 180 on all cylinders
Fuel is good
Electric is good
Unplugging injectors during idle provides feedback on all but #4.

Any ideas would be greatly appreciated.

Thanks

The DareDevil

Weak plug?

Kevin Baker

Do you mean that you are not getting a spark on #4 or is the fuel injector not "pulsing"?

If electric is "good" do you mean that you have 12v at the coil?"
"Fuel is good" You mean pressure at the rail? And volume at the rail?

More information, N/A, turbo, S S2 what 87 car is it?

What work have you done recently?

SoCal Driver

Clogged injector screen. Blow shop air backwards through it with a solvent charge.

Broken ignition wire. The stock BERU wires will break inside the ends where it is screwed in. The weather boot will hold it in so you think it's still attached. Could also be a bad end at the spark plug.

badcoupe

check to make sure you havr injector pulse at #4 injector by using a noid light, or jumping the plug with a testlight and running the car. The bulb flash on and off very fast. Inspect the spark very close as well. Could it be that perhaps one of the valves isn't opening, I haven't seen this on one of these, but that would contribute to your normal compression yet still a dead cyl. How's the dist cap? it could be internally arcing . Of course the ignition wire set is always another poss. Switch #4 and another on the cap and see if your miss goes to the other cylinder. Hope this helps

Jim Clark

foregive me if I'm duplicating here, new member.
I appreciate all the comments and help.
The only thing that comes to me as well is the valve not opening. Have you heard of a busted lob or cam with the engine still running well?
Listed is just a few thing that have been modified.
Fuel pressure good. Have adjustable regulator.
Spark is 12 volts MSD Coil
MSD ignition 6AL new 8mm wires
New head with 4 angle, new valves, guides, turbo springs, seals, and retainers.
MSDS header
Full 2.5" pipe back to a flowmaster
New rod bearings with life time bolts
New fuel rail, injectors and witing clips
New belts every event.
Fully adjustable suspension with 30mm bars and 400 lb springs and Koni's
Car is dedicated track use only, SCCA and PCA.
87 n/a 944

SoCal Driver

If only one cylinder is not firing then look at the spark plug cable or the injector.

Bad injection harness and/or connector.
Clogged injector.
Bad injector.
Bad spark plug connector.
Bad spark plug wires.


As the other three are firing this has to a local problem.

No you don't see a bad cam lobe if you have the compression you relate.

Jim Clark

But if the lobe is off or cam broke, would the valve not be closed and have good compression. The only time a valve would not open is if it is not pushed, correct? I've tried everything I can think off besides pulling the intake and exhaust and following the valve action.

badcoupe

Had you previously ran the car with the msd? If not you know you have to cut the little wires inside the round cover on the side? Made this mistake on my car when I put the MSD and 2 step on it.

Jim Clark

Yes....All modifications done correctly. This issue seems mechanical, just wondered if anyone had had the same issue.