November 8th, 2009

#1803: It's not the fuel injector.

Friday afternoon I had a quick look at the fuel rail, and it turned out that I could swap the #1 injector in a couple of minutes, so I tried it.

Car ran exactly the same. Damn it.

The fuel rail is held on with two bolts, and in fact I only needed to remove one of them to get the #1 injector out. Remove one, loosen the other, unplug the injector and rock it loose. No problem.

But since the injector didn't fix it, now I'm going to have to consider other issues.

Fuel delivery is still not out: looking at the Fiero forum today I realized that it could be a fuel pressure problem. But it's not the way to bet.

So my next step--when I have the gumption to get after it--is to pull the timing cover off and triple-check the timing.

When I was assembling the engine, I recall noticing that the reluctor ring for the crank sensor seemed to be in the wrong position. One tooth is missing; that's the tooth which tells the engine computer that the crank is at top dead center (TDC) for the #1 piston. But there is only one way to install the crank pulley; I ignored the little voice and kept on working. Besides, the thing was way off, not just slightly--it's supposed to be in about the 10 o'clock position and it was closer to 8:30--but as I said, the shaft is keyed and you can't put the pulley on incorrectly.

BUT: if the crank isn't at TDC with the cam at TDC, the reluctor will be in the wrong place. I'm thinking this might be the case, as I don't recall double-checking the timing after getting the timing belt on.

If this is the problem, I will feel incredibly stupid, but at least it'll be easily corrected.

The problem is, I don't see how it can be: if the engine is out of time far enough that the #1 cylinder isn't firing (or not firing at the right time) how the hell can any of the cylinders be firing?

The answer to that may lie in the "lost spark" technique used in some ignition systems: the coil fires two plugs at once, only one of them is on the exhaust stroke rather than the compression stroke. If the "lost" spark is happening on the cylinder in compression, it would work. It might be out of timing far enough such that one cylinder doesn't fire.

This is a theory, and I haven't thought it through, and I'm not even sure the Escort's ignition system is based on the "lost spark" paradigm anyway.

You know, fuel injection and computer control of engines is a marvelous thing...but when you need to figure out why the hell a refreshed engine isn't working correctly it can be a royal pain the patochis.