Hey honda-tech! Long time reader, first time writer.
I've searched for an answer to this question, but I have a very specific set of circumstances and problem, so I haven't found an answer yet. I do apologise if this question has already been answered.
The car: Eg civic w/ b16a1 obd0 (pr3 ecu)
Ok, THE QUESTION! What would cause the voltage to drop at the injector clip, from 9v~ to 3-4-5v when an earth is applied, but the injector DOESN'T operate?
I've tested the continuity of the 9v injector wire to the ecu, which is solid, plus all the wires to the resistor box, and took an ohm reading of the injector, 2-3 ohms from memory. I've checked power to the resistor box, spark, fuel (at the rail), and checked that it fires after using a starting spray. I also checked a few of the grounds to the ecu, but if someone knows all the ones relevant to the injectors, please post, I will check again!
The history of the problem; I removed the fuel rail etc to paint the inlet manifold, and due to a few wires not having a connector (the car is custom wired) I had to cut about 8 wires on the LH (outlet) side of the fuel rail. Since connecting everything back up, the car has crank-no start. I got spark, fuel in the rail, ground to the ecu, timing hasn't changed (the car was running before I cut the wires), etc etc.
If you can, please help. This is driving me nuts... :/
I'm sorry if I have garbled the post, I tried to be as clear as I could. Please don't flame
Thanks guys!! I totally owe HT, some of your posts have saved my ***
If you are not running an injector resistor, voltage at the injector power lead, [lead that is the same color at all four injector] should be 12.5V, [or the same as it is at the batt. +/- .2-3 volts, if not, ch4eck the PGM-FI Main Relays fuel injector output, voltage there should also be the same as batt. voltage, if not, replace the PGM-FI Main Relay or try the fix... http://techauto.tripod.com/mainrelay.htm.
A voltage drop is normal when a load is applied, but not by 50% .
The injector will not operate at voltages that low, your already low at 9V, 5V is really low, making me think you have a connection problem, either into or out of the PGM-FI Main Relay and if voltage is low at the injectors it is most likely low at the heated O2 sensor, and IGP1 and IGP2 of the ECU/ECM. 94
RIP Zack 2001-2013, my best friend.
Keith; nah I used a multimeter to check spark, I took the spark plug out and grounded it to the block, and cranked...
I'm familiar with that site, it explains things very well
Grog; I've checked all my connections a million times, but unfortunately they are ok
I don't think I took any grounds off (it got painted while still bolted on) but I will check it anyway
Hey Fcm I've read quite a few of your posts before...
I am running a resistor box, so I should be getting about 9v, right?
I'm keen to check that relay, but I have no idea where it is or what it looks like :/ what would it be directly connected to?
Re voltage drop, yeah I agree, especially when the injector still doesn't operate!
What is IGP 1 and 2?
Oh ok... I can't find this elusive relay, is it possible that another relay of a different type has been used? Due to the custom nature of the car.. It used to have a carbie, now its got an injected engine... I know where the relay for the fuel pump is. Its still good lol
So I did a little test... The voltage at the resistor box drops to zero when one injector is earthed. However the voltage at igp 1 and 2 stay the same (11.9 v) :/ is this a sign of a bad earth in the injection circuit? What other earths are there, aside from the four at A2, A4, A16 and A18? (cause those are all good :/ )
I made a wiring mistake, coupled with a bad wire :/ pin A15 from the ecu goes to the resistor box, and supplies the current for the injectors to function. I mixed this up with another wire, and to top it off, the correct wire had quite a high resistance (thus didn't beep on the setting I had my multimeter on for testing continuity), so it had me stumped for a fair while. I found a fantastic diagram for the function of the injectors AND the ignition system, but I don't know how to post a picture...
Anyway, wiring mistake, my bad, but I learnt something in the process... And I'm a HT member now :D
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