Just had a problem Im diagnosing with my 92' Prelude...

Im about 75% sure its my main relay (car driving reasonably well one moment, dies 100% the next, CEL comes on w/o code just a solid light - indicating an ECU fault)

I know the relay sends power to the fuel pump (which I dont hear buzz when turning the key to the on position) but does it also send power to the ECU ?

Im reading through my diagrams and I see about 3 wires going to the ECU but dont see anything marked with power in. The CEL is on and unable to be reset which leads me to believe the ECU isnt powering up. Id put a volt meter on it, but my brother ran off with it a while back

 

I vote ignition switch.

 

Nope, not ignition switch, and now Im only 20% sure its the relay. Yesterday I put my hand on it and felt it switching over. Still havent put a voltage to it though....

Tried clearing off the CEL on the ecu (pulling the fuse & removing the ECU entirley for an hour), but it is still throwing the CEL, and I am unable to pull a code by jumping the wire ...... Bad ECU maybe

Also, pulled the timing belt cover, and noticed the Timing belt (havent looked at the counter balance belt yet) had sliped abit to the side and was rubbing the side of the housing cover. Im also thinking if the belt was rubbing that much it may have skipped off a few teeth and lost compression.

Pushing it into the garage tonight so I can do a complete teardown rather then poking at it in the driveway. Im thinking I have a combination of BS to fix. Whomever put this new enigne in the car should be drug out into the street and shot...its a brand new block but everything is out of spec and falling off of it... but thats anouther story

 

check your ecu fuse under the hood. its probablly blown.

 

The ECU powers up the main relay for about 2 seconds when the key is first turned to run, then re-energizes it once it gets a signal from the distributor that the engine is turning.