I was driving and my car just quit. I replaced the main relay checked the fuel pump, ecu,fuses... my cel stays on fuel pump does not prime unless I jump the main relay. I recently added a stereo that was a tight fit and not sure if I'm pressing up against a harness behind it.

Turning the ignition switch to ON (Position II), not START, does the CEL come on and then go off after 2 seconds? If not, the problem is with the ACG (ALT) (S) 15 amp 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 (Position II). 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. Many Hondas parked for several years are now back on the road. "The K-Test creates massive value, by providing a low cost solution where one did not previously exist."--TxGM

There is no voltage at the map sensor. The check engine light stays on and won't thow a code plus the ecu ran another car just fine. Tried testing the ignition and all seemed fine. If I jump a wire from 1 on the main relay to five the pump will prime but the car still won't start. I will double check the fuses.

The ecu could have went bad even though you just replaced it

If you turned the ignition switch to ON (Position II), and you didn't have MAP Sensor reference voltage, then there's a problem with the ECM. Be sure there's a fuse in the ACG (ALT) (S) slot and that it's good.

You are a genuis. I guess when this all started I pulled that fuse while checking them and it was broken. I never really paid it any mind thinking it was a spare. All of these other forums are so far off. Now if you could only tell me why I have two map sensors? One on the firewall and one on the intake.

Someone installed the throttle body from a newer Civic on your car, which had the MAP Sensor installed on top of it. The original MAP Sensor was on the firewall. You need to install the MAP Sensor connector to the new MAP Sensor.

You only want to check fuses with a test light or multimeter--it prevents creating fuse problems.

Do you have 5 volts now, after performing the K-Test?

Yes I do have five volts now. I put a jdm d15b vtec in my car and rechipped the ecu to a p28. Now I have a code 6 and 21 the dash gauge reads the temp pretty good so idont know why and I have not tesyed the vtec I think it might be a problem in the wiring. What would cause that 15 amp fuse to blow in the first place? And am I able to hook up an indicator light that will let me know when vtec engages?

. Code 6--Engine Coolant Temperature (ECT) Sensor.

. Code 21--VTEC Spool Solenoid Valve.

Hopefully, you have the correct ECM and harness for the new engine.

The temp gauge on the dash seems to be working just fine. I still have not checked the vtec will do today

The ECT Sensor is a two-wire sensor, likely located under the distributor. It's totally different from the temperature gauge. The ECT Sensor affects fuel injector pulse width. The ECT Sensor is a temperature dependent resistor (thermistor), whose resistance decreases as the engine coolant temperature increases. It provides a richer mixture when cold, leaner mixture when hot. They become corroded, due to not changing the coolant frequently enough, flood the engine, and waste a tremendous amount of fuel.

That would explain a lot. Because when I first start the car I have to give it a min to warm up or it bogs when I press the accelerator. I will check this, any clues on what to change

Just replace the ECT Sensor--super simple to do.