Alright, I did a search and all the main relay probs i found on here was everyone saying they were having fuel pump problems. Well here is my problem. 90 Honda Civic B20b. Double checked my MPFI conversion and everthings good (done the dpfi-mpfi a dozen times so i know that is good. Ok here goes...I am getting gas all the way up the fuel rail and that is it. Does the main relay control the injector pulse too. I checked and I am also getting a 12volt signal at each injecotr wire but no start. what else could be my problem?

 

what injectors (obd0 or obd1-2) and ecu are you using?

 

obd0 injecotrs and a pr4 ecu

 

an obd0 or obd1 pr4?

 

Its an obd0 ECU and they are obd0 injectors. I thought for a while i had a bad ecu so i stuck in a PR3 that i had and still the same issue. You think the relay controls the injector pulse?

 

why not use the multimeter to test the relay?

 

if you are getting fuel all the way to the rail, i doubt it is the main relay. Was your fuel pressure correct? cause if the pressure isnt high enough, then that might cause the problem also.

The ECU is what controls the injector pulse width.

 

not sure about fuel pressure. I have been meaning to put a fuel psi gauge on it. Stock pump, Regulator, and injectors.

 

alright guys gettin good fuel pressure. I spoke with a honda technician and he said even though the fuel pump is priming the main relay could still cause the injectors not to pulse. Anybody else ran into this situation?

 

bizzump

 

you want to know if ur main relay and fuel pump are working? its very ez and u dont need to even get your hands dirty.

1. sit in the driver seat
2. turn the key to position 2 (not engine, but a/c and stereo on)
3. u will hear a click (main relay) and half second hum (fuel pump) while the engine light is on.

if u dont hear either one of those, there is ur problem. hope its an ez fix, good luck!

 

Just a silly question, but you have checked the resistance on the injectors to verify that they are between 2-5 ohms and you are running a resistor box right? If your injectors have more resistance (10-12 ohms) then you should be running without the resistor box.

 

If you have pressure in the fuel rail then your relay and pump are fine. You have 2 wires coming out of each injector. The red/black wires go to the resistor box, the order doesnt matter. The colored wires are going to your ecu now. Your problem lies either within your connection to the resistor box or maybe you hooked the wires up to the ecu pins in the wrong order. Stock injectors?

 

Yes stock obd0 injectors, wired into a resistor box, with an obd0 pr4 ecu. I have not ohmed the injectors out yet (will do that when i head over to the car in a sec) but the fuel pump is def humming when i turn the key to the acc position. I cracked the line on the fuel rail and gas is also coming out so i am pretty definite my main relay is good. I did put a multimeter to my injector plugs and they are receiving a constant 11-12 volts when i turn the key. As i said before a technician told me that the injectors should not receive a constant 12 v because that way they wont pulse. Man, this car is getting to me..... any more advice? Thanks again for all the help so far!

 

I believe that you should be seeing a constant 12V to your injectors. The ECU controls injector pulse by grounding the injectors through the ECU.