Spark Plug Reading Anyone?

[Tom]

Changing my spark plugs in preparation for a smog test. Any spark plug whisperers here?

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[dr bob]

3 looks a little lighter, so might get a harder look. Maybe a borescope shot of the top of the pistons for some correlation. If you fail on NOx or are even a little unexpectedly high, initial focus might go to that injector.

There might be a case for a DIY test fixture with a fuel pump or cannister, a simple pulse controller with timer, and a graduate cylinder you can use to measure the flow mass. I might be tempted to use a good scale that reads to grams, and just weigh the output flow. I've used paint thinner for the test fluid to reduce the chance of fire-or-worse, and do it outside. Do each injector individually for flow in the same amount of time. Compare.

Do you have EGT on each pipe?

[Tom]

3 looks a little lighter, so might get a harder look. Maybe a borescope shot of the top of the pistons for some correlation. If you fail on NOx or are even a little unexpectedly high, initial focus might go to that injector.

There might be a case for a DIY test fixture with a fuel pump or cannister, a simple pulse controller with timer, and a graduate cylinder you can use to measure the flow mass. I might be tempted to use a good scale that reads to grams, and just weigh the output flow. I've used paint thinner for the test fluid to reduce the chance of fire-or-worse, and do it outside. Do each injector individually for flow in the same amount of time. Compare.

Do you have EGT on each pipe?

Funny you mention that. I've had my eye on these cheap testers for a while now -- they all seem to come from the same place and get pretty good reviews.

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Problem is I'm eleventy-two percent sure these plugs split time between the stock injectors and the bigger Five-O injectors I've been running recently. And the stock injectors are a mixed set -- 3 of them were professionally cleaned a few years ago, but one is an older used one I cleaned myself with carb cleaner and home-hacked controller to open and pulse it for cleaning. Smog results have been quite good this way (knock on wood). Once I'm done with the smog test, maybe I'll install new plugs with the new injectors and see if the same pattern develops. I have a single EGT sensor, but could try an IR gun on the header pipes.

[dr bob]

The DIY Fronkensteen tester/cleaner I cobbled isn't nearly as fancy. I looked hard at the one you show when it was less than half the cost in your link, and it was marginally more than the Five-O injectors at the time. I just went with new injectors. I did clean and sprep/store the originals in case a savvy concours judge spots the different colors. It's hard to justify another bench monument for something I use so infrequently. Anyway, mine started life as a regulated air over liquid cannister similar to the BG-44 and Snap-On on-car setups. I use a 556 (dual 555's) timer and a small transistor to pulse a relay 50% duty (adjustable) for fifteen seconds (adjustable), and push test or cleaning fluid through into a graduate cylinder for the volume measurement. For just cleaning the injector sits in the opening of a plastic detergent bottle, to be poured back into the cannister for the next injector. I do them one by one because I'm too frugal to buy a used fuel rail and do more at once. A bit Rube Goldberg but for my needs it does the job. Next time I have it out for something I'll snap a few pics, post them when I get the film back from the drugstore.

I push ATF through the ones I'm going to store. I should probably use MMO instead of ATF, but almost anything will do so long as it stays inside for a while.

I'll suggest that just pushing a little cleaner offers a pretty dramatic visual if the nozzle is at all obstructed. Rather than a nice clean cone, it looks like individual pee streams at all angles.

[Tom]

I also just realized there is one mismatched pintle cap so the spray pattern could be affected too. Would love to see your test rig when you next have it out. To pressurize the test fluid, did you use air pressure? I was close to making my own when trying to calculate dead time on the new injectors (until they showed up with a detailed dead time chart), and the thoughts of wiring up a pump and fuel pressure regulator started making the Ali-express testers pretty appealing. Because I have lots of spare parts, my plan was to use a fuel rail, fuel pump and fuel pressure regulator, and that started becoming quite the contraption. Didn't think of air pressure...

[dr bob]

Simple air over fluid with an air pressure regulator. Cannister holds a couple gallons. I can connect it at the fuel rail test cap, pinch the return hose from the FPR (only one of the two fuel hoses in the car it's OK to pinch that way), and push clear though all injectors at the same time. In your case with a possible flow imbalance, testing them out of the car is the only real option.

The very sophisticated electronics are breadboarded and run on a 12V power supply. Two small pots for timing adjustment, a couple caps and IIRC 4 resistors for the timing side, a couple small filter caps for the power inlet. The injector under test gets a separate 9V battery for the opening duty via the relay contact. The cycling relay and injector coil pulses were messing with the timer functions. The 556 is an astable multi-vibrator on one side for the pulses, the other side determines the delay/total run time. It's still a little breadboard with TC busbar for connections on the back. Very high tech. SMD and PC boards are for sissies.