NEED HELP! '91 ram need diagnostic help!

The SBEC (Single-Board Engine Controller) is located at the front of the driver side fender; you have to remove the battery to get at it. Find it by following the air cleaner snorkel duct; one end connects to the air cleaner and the other connects to the SBEC. Intake air is drawn through the SBEC housing to cool the computer. They rarely fail; it is probably not your problem, but it never hurts to inspect the 60-way unitized connector for corrosion or damaged/spread pins.

The distributor is not the ordinary Mopar electronic type with a reluctor and pickup coil. It uses a hall effect sensor. There is no mechanical or vacuum advance mechanism; all advance is handled by the SBEC. The hall effect sensor can get flaky with age and cause random stalling or no-starts followed shortly thereafter by perfect startup and fine running. The same can happen with a faulty hall effect sensor connector. But there is also the ASD relay, the fuel pump relay, the fuel pump, and other components that can cause this what you describe.

Go turn the ignition key on-off-on-off-on, leaving it in the "on" position and never going to the "start" position. Watch the "Check Engine" light. It will go on, then turn off, then flash out whatever trouble codes have been stored. Each code is 2 digits separated by a short pause. Each 2-digit code is separated from the previous code by a long pause.

So flash (pause) flash flash (long pause) flash (pause) flash (long pause) flash flash flash flash flash (pause) flash flash flash flash flash would decode as a 1 then a 2 for a "12", a 1 then a 1 for an "11", and a 5 then a 5 for a "55". Codes are not necessarily in ascending numeric order. "12" is "start of codes" and "55" is "end of codes". If all you get is a 12 and a 55, or just a 55, it means there are no stored codes.

The next time it fails to start, disconnect the battery negative cable for 60 seconds, then reconnect it, crank it unsuccessfully, then do the triple key flick and see what codes you get. In this case you're looking for that code 11, which means the SBEC has never seen a signal from the distributor (where "never" means "since the battery was most recently connected").

You really do need the factory service manual. The TBI system on these trucks is halfassed hardware sloppily controlled by halfassed firmware; everything has to be just right or the truck won't run well.

Your dash voltmeter is not causing your problem whether it's alive or dead.