90 eclipse won't start

We checked the timing belt and spark plugs. Checks seem to point to changing the cam/crankshaft position sensor but we hesitate because of cost. Any suggestion would be appreciated.

Verify you have compression. I'm in the process of rebuilding my 4G63T engine at present. It was fine one night, but the next morning it jumped a couple of teeth and bent all the inlet valves. Result is no compression.

Yes, but do you have spark? Get a timing light and connect to #1. Crank the engine and see if there actually is a spark. If so, its not the cam position sensor (the round can on the end of the intake cam).

If not, if still may not be the sensor. Most of the engine sensors are run by +5 volts from the ECU, while the spark coils (in the bend of the intake manifold) are driven by the +12v. Turn on the IGN and pull the 6 pin connector on the air cleaner. One of these should be + 5V. If so, it means your ECU is OK.

Just below the spark coils is a large 1x8 or 1x6 (varies with year) connector to the spark power transistor assembly. This may be the problem.

The MPI relay is behind the radio in the center console, and have been known to fail. This relay provides +12v to the engine sensors, fuel pump and ECU. If the ECU has power, when you turn on the IGN, the Check Engine Light (CEL) should turn on for about 5 seconds then turn off. If this does not happen, your MPI relay is probably faulty.

Find the ECU test connector under the dash, drivers side. Connect an analog multimeter or 12V led across the diagonally opposite pins. If the ECU is working, you shouls get some meter pulsing or flashing lights.

Look on EBAY to find parts you need. Note that the 1990 parts have different connectors vs the 91-94.

Stewart DIBBS