I had the wire harness of the dme while checking the impedance and voltage, of course. I don't have a clear picture of how all the parts interact, but the fuel pump would be running while cranking, normally. Would it not be running while cranking with the harness off? I smelled fuel pretty strong; I had the garage door down so it confined the smell more than it might otherwise.
sid

I'm not clear how all the parts interact, but I smelled the fuel when I had the wire harness off the dme and was checking the impedance and voltage. And, of course, the fuel pump does run during cranking. I also had the garage door down, which corralled the fumes making it easier to smell. After I put the harness back on the dme I tried it again just because, and it still does not hit.
Does the lack of voltage on both sensors indicate they are both bad?
Thanks again.
Sid

The DME controls the fuel pump via the DME relay.

When you crank the DME turns the 2nd stage of the DME relay on and that powers the fuel pump. With the fuel pump running the fuel rails get pressurized. If you disconnect the harness from the DME while cranking the fuel pump doesn't turn on during cranking. You can manually turn the fuel pump on by putting jumpers into the DME relay socket instead of the DME relay.

When you crank with the DME connected the following happens on a working system:

- the fuel pump turns on due to the key in START position
- once the DME recognizes at least one pulse from the reference sensor it is ready to look for the speed sensor signal.
- as speed sensor signals come into the DME it issues fuel and spark pulses.
- the fuel pulses open the injectors and let fuel into the engine (assuming there is fuel pressure)
- the spark pulses generate sparks (assuming the coil/distributor/cap is healthy)
- The speed sensor signals tell the DME to keep the 2nd stage of the DME relay on (keep fuel pump running) even after you let go of the key

If the reference sensor is dead (or disconnected) the DME will never issue a single fuel or spark signal ever. There are some famous threads where the pin in the flywheel is missing or of the wrong material preventing the engine from starting. If the speed sensor is dead same as above. If the speed sensor is intermittent, the engine will run rough, cut out, etc. If the reference sensor is intermittent the engine will start but not run well.

There is no sensor condition that produces one or the other signal but not both. In other words fuel and spark are the heart beat of the DME and both are always generated simultaneously. The only exception is at higher RPM and idle switch active (decel). This is the only condition where the DME only delivers spark signals but cuts out the fuel pulses.

If you smell gas during cranking chances are our sensors are O.K. and deliver fuel and spark pulses. In that case either your ignition system is bad (coil, distributor, cap) or the DME is damaged where the spark signals don't make it out of the DME. This of course assumes you don't have badly leaking injectors (now we are getting into corner cases)

I would go and pick up a NOD light (cheap) and an inline spark tester at the friendly auto parts store. This will tell you if your DME is seeing sensors or not. Diagnostics always beats changing parts.....

Best,
Ingo

Wow! Great information. Thanks for the great description.
As I go back over today's scene in my mind, I think it might have been the ether from trying that again in the throat yesterday. Suppose some could have been trapped yesterday and just made it out as I was cranking today? Seems fuel or ether, either one, would have been dissipated since yesterday, unless it "got trapped" somehow. I don't think the gas would linger, but not sure about ether.
Since I ran the impedance and voltage checks, and got only one of four readings, I'm not sure there is a way for the sensors to be working now (that would be a nice surprise). And, I have checked for spark at least three times, once yesterday again just for good measure, and nothing. That, along with ether in the intake, seems to say it never has gotten spark to the plugs. It never has hit, even one time, in the several weeks I have been tinkering and then trying to start. I may not have mentioned, but at one point, when checking basics, with the key on, there was voltage to the primary side of the coil. I just realized that I have not checked the coil, except to see if a plug wire would create a spark.
Sid

Power at the coil is correct. The DME provides momentary GND to release a spark. With the key in ON you will measure VBat at both screw terminals of the coil. To check the coil measure resistance between primary and secondary. I don't have the values on top of my head but do a search.

Ether is much more volatile than gas but depending how much you dumped in there it could remain in the engine. The smell should tell whether it is ether or gas.

Ingo

I believe I'll get a NOD and in-line spark tester tomorrow; would be nice to have them for future anyway. And, I'll check for primary and secondary impedance also on line.
Thanks again.
Sid