Pfc. Parts

Hello List -

I'm preparing to test the injector harnesses on my '85, which seams to be missing on at least one cylinder following a complete intake, timing belt and ignition system refresh.

My question is how best to disable ignition while testing each connector. Pull the coil wires at the distributors?

I can't see any way to reach the injector harnesses without removing the intake again. Thanks for hints/confirmation.

dr bob

Scott--

You can listen to each injector with a stethoscope, a piece of vacuum tubing with one end in your ear, or in a pinch with a screwdriver with handle at your ear. You'll listen for the one that isn't clicking like the others.

Based on the work you did, I'd be starting at making sure the coil wires are connected and that the firing order is correct at both the distributor and the plug ends of each plug wire.

Pfc. Parts

Sound's like a better plan than pulling out the plenums right away and I do have a couple stethoscopes around. I'll see if I can get my ears to work

I have checked and re-checked plug wires and did find a problem on the re-check that was corrected. Then of course I checked again.

The plug wires are new and I can't exactly remember if I checked each one for impedance before they were installed but I think I did. That still worries me. Since my injector harnesses are old and feel brittle I thought I'd test them. I might have a bad injector too, but your test should pick that up.

Thanks,

davek9

you should be able to use a timing light to see if spark voltage is getting to each plug when running, remove the thin plastic air intake tubes.
Then set up a timing light using the jump post for power, get near/ touch each plug wire at spark plug with the "inductive pick up" of the timing light, it should light when the spark power is detected.

As for using a noid light, you will need to remove the intake plenums, however before you do that pull the spark plugs to see which one(s) not working, this will narrow down your search/work.
You will need to remove the plenums to remove the plugs
Remember the 928 is a "batch" injected system, so all injectors open at the same time.
12 v should be there, it's the ground that is switched.
Disable the coils by un plugin the power drivers to the coils.

Pfc. Parts

Great advice Dave. Thanks very much.

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The timing light trick led me to a bad connection on the #2 cylinder at the coil. After this was corrected the engine ran smoother but there's still minor vibration accelerating between 1000 and 3000 rpm. It's been several years since I drove the car and I can't remember if this is normal so I'm going to road test it.

I'm wondering if I should disconnect the battery first to reset the ECU? I don't know if a #2 misfire would change the map?

76FJ55

There is no memory in the EZF or LH on the 85. disconnecting and reconnecting the power serves no purpose. actually there is no permanent power supply to either one so turning off the key is as efective as disconnecting the battery.

Pfc. Parts

Thanks Simon, that confirms what I just experienced. I went ahead and disconnected the battery anyway before the road test and it didn't help.

Looks like I'll be pulling off the plenums to check the plugs. They aren't brand new now, they were replaced before I did the intake refresh and at that time I'm pretty sure all the injectors were working. I'm wondering what exactly to look for when trying to isolate a stuck injector? A dry plug? When the car is running right the plugs are dry anyway so I can't imagine that would tell me anything. Since the plugs have been used a bit, the color should be OK I'd think even if there was no fuel getting to the cylinder?

Maybe disconnecting the coils, cranking the engine, and looking for dry plugs then?

I can't quite figure out how to get a stethoscope into each of the injectors, not enough clearance with the plenums in place. I may try using a metal rod or long screwdriver but even getting one of those into each injector looks challenging.