I am having an intermittent issue with my Honda Civic SI 1987. I replaced the fuel pump as I thought that was my issue, a $120.00 guess that was wrong.

After running and then I turn car off it does not want to start engine cranks fine. The fuel pump does not power up nor does the "check engine light" ( it is really some injector light ).
Once it "rests for a time 5 to 10 minutes it will be fine.

According to what I have read here it maybe the "ALT - S fuse" or "ACG". I can not reference to those items in the manual or online. Again, from what I read it could also be the main relay, That I can find. But before I guess again for 70.00 bucks I was looking for some help in these other two items.

Any thoughts?

. Test all under dash and under hood fuses with a test light or multimeter:

https://www.askmehelpdesk.com/cars-t...tml#post252145

. Clean the main ECM ground, located on the thermostat housing.

. When you turn the ignition switch to ON (Position II), does the Check Engine Light (CEL) come on and then go off after 2 seconds? If not, the problem is with the ACG (ALT) (S) fuse, in the under-dash fuse/relay box; ECM (perform the K-Test, below); Main Relay; or the Ignition Switch. Perform tests in that order.

The K-Test: Remove the MAP Sensor connector and turn the ignition switch to ON (not start). Using a multimeter, check for 5 volts going between the MAP Sensor connector's reference wire (+) and ground. As you look at the connector, this is the socket on the right. Really press the black test lead into a cleaned main ECM ground on the thermostat housing. If the voltage is low, it's probably indicating ECM failure. Most failed ECMs will record a fraction of a volt. To me, the K-Test is simple, elegant, and accurate.

My focus would be on the ECM--it may be slowly failing.

TxGreaseMonkey thanks for the response. The issue happens intermittently. Before I changed out the fuel pump it was almost assured. Now the car runs better, I suspect the pump may have been on the way out. Now it is back to less frequent "Non starts".

When it does happen it is always after it has been running. The CEL ( actually some injector indicator on my Civic ) light does not go on nor do I hear the fuel pump engange.

I am not familiar with the terms you have used. Alt S or ACG or ECM. I have a repair manual and can trace these parts down that way and replace as necessary.

I will try your ground suggestion tonight when I get home.

With 260,000 miles and 20 plus years most things need replaced just trying to do this as fiscally smart as possible.