Resolved 1G Injectors not firing (getting voltage) no start issue

[CrackedDSM]

I am at my wits end with this car. Details of car in build thread.

Issue: Car will not start. Has spark, has fuel pressure to rail. Does not have injector pulses. Activating injectors in link does nothing. Injectors are receiving voltage, just not completing the circuit or whatever. When I test the injector clip while trying to start (or when activating via ECMLink), it won't activate the test light.

TPS is tested and working, seeing proper voltage and signal. Nothing is unplugged that I can visibly see, ECU was taken out and no burned drivers or leaky caps were found. ECMLink connects to the ECU just peachy, and no codes are found or stored.

Relevant detail: The water temp gauge via the gauge cluster has not worked since I got this car. Now suddenly it's reading 1/4 of the way when I turn the ignition ON, and then drops down to zero when turning ignition off.

IDK what to do, or everything that controls injector function. I didn't see any wires chewed or missing when I crawled under the dashboard on the drivers side, but if you know more, by all means.

This car started and ran 24 hours ago. Now it's dead.

 

[CrackedDSM]

Update: checked resistance on the injector resistor box, all ohm'd out within spec.

 

[TerminalTalon]

Man I don’t know why I don’t have the schematic on my garage board. I’d have to verify the wiring but I believe the ECU is power and the resistor is ground. Is it bolted down?

 

[Tyeler18]

If you have power at the injectors than the resistor box is working correctly. It supplies the 12v to the injectors.

If you don't have a ground pulse on any of the injectors but you do have spark that generally means the Cam/Crank sensor is working, however, verify you have an RPM signal while cranking at the ECU via ECMLink.

The injectors share nothing other than the 12v feed so it's unlikely you lost the ground wiring to all 4 injectors. Does the engine start with starting fluid?

 

[CrackedDSM]

Resistor pack is definitely bolted down, and ECMLink logs RPM when cranking.

 

[CrackedDSM]

Is there a way to test the injector driver in the ECU? IDK what else it could be at this point. I’m gonna test the CAS later just for giggles. The MPI relay clicks on like it should. IDK.

 

[TerminalTalon]

Way off . So resistor pack is power side and ECU is ground? I finally see the MPI relay above on that side so it makes more sense. I don’t trust many google image diagrams for that reason.

 

[CrackedDSM]

@steve , please help.

 

[steve]

Does not have injector pulses. Activating injectors in link does nothing. Injectors are receiving voltage, just not completing the circuit or whatever. When I test the injector clip while trying to start (or when activating via ECMLink), it won't activate the test light.

The checkbox in ECMLink doesn't enable an injector, it disables it.

I didn't see a log...

Man I don’t know why I don’t have the schematic on my garage board. I’d have to verify the wiring but I believe the ECU is power and the resistor is ground. Is it bolted down?

As pointed out, the power comes from the MPI Relay to the Injector Resistors and from there to each of the injectors. The ECU grounds it's wire causing the injector to open when and for as long as the ECU thinks is needed.

Non-turbo cars don't have the resistors and the wires going directly to the injectors. Turbo cars running aftermarket high impedance injectors need the resistors bypassed and you'll often find a connector with all the pins shorted together to do that.

I'm not convinced all Noid Lights work on a turbo DSM.

 

[CrackedDSM]

The checkbox in ECMLink doesn't enable an injector, it disables it.

I didn't see a log...


As pointed out, the power comes from the MPI Relay to the Injector Resistors and from there to each of the injectors. The ECU grounds it's wire causing the injector to open when and for as long as the ECU thinks is needed.

Non-turbo cars don't have the resistors and the wires going directly to the injectors. Turbo cars running aftermarket high impedance injectors need the resistors bypassed and you'll often find a connector with all the pins shorted together to do that.

I'm not convinced all Noid Lights work on a turbo DSM.

So realistically the only thing it could be at this point is the ECU? I’ll check voltages again at the injector clips but if they’re all getting voltage it’s the ecu that’s not grounding them?

Is there a ground the ECU uses that might’ve gotten cut?


This is the ECU. Can someone circle what the injector driver is?

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Here's a log BTW. As far as battery is concerned, even if I hook up a jumpbox to it, it doesn't start. So battery voltage doesn't seem to matter.

 

[CrackedDSM]

Okay this is weird. I tested the injector clips again.

Both pins on the clip are getting 12v. But only one pin lights the test light I have when I ground it.

How in the world can this be possible? How can it get 12v but not light a test-light??

When going to start it, I’ll have my multimeter probes in the plug, when key on not cranking it’s 0. (Both are getting 12v, so I assume it's an incomplete circuit). When cranking it switches and bounces from 3v-5v or so. While cranking it never sees full 12v.

 

[dwb]

What did you change before it stopped working?
On your ECU, what's all the brown coloring around the driver chips i.e. R38? I'm not sure if those traces affect the injectors or not, but this might help:

driver01 [ECMTuning - wiki]

www.ecmtuning.com

 

[CrackedDSM]

What did you change before it stopped working?
On your ECU, what's all the brown coloring around the driver chips i.e. R38? I'm not sure if those traces affect the injectors or not, but this might help:

driver01 [ECMTuning - wiki]

www.ecmtuning.com

I took a plastic pick to it and it came off, it looks like old flux or something. There's no smell to it and the board underneath is clean.

And I didn't change anything. I updated the timing map via ECMLink, it uploaded it and I started the car. It started, idled fine, and I shut it down. Next day I came out to drive it, and it wouldn't start. Been here ever since. Legitimately nothing messed with.

I just don't understand what could've happened. The OEM water temp gauge on the gauge cluster is now reading 1/3 warmed up every time the key is on. For the last three years I've owned this car the needle was dead/below the coldest mark. I swear I feel like that's related. Like, somewhere a ground for the ECU is receiving voltage.

 

[nice97civic]

Looks to me, from the log, that your injectors are firing when you're trying to start. Looking at "InjOn" and "InjDuty" values. Also your throttle position is 36% @285rpm.

Might all be irrelevant but doesn't look right to me.

Noting your omni sensor reading -0.1in/Hg as well seems odd but I don't know what that should show at startup

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[CrackedDSM]

Alright so, progress.

I pulled a spark plug and cranked the engine, looking in a single hole at a time.

Result was

Cylinder one injector is working/spraying.
#2 seems to be spraying, not as much as #1
#3/#4 not spraying.

In light of this I beat the shit out of the injectors with an extension as my wife cranked it and it actually started. It idles like complete shit at first, then became more and more manageable.

So on a whim I decided to drive it and see how it would do. It boosted great, no chugging, AFRs were perfect and the timing changes I made, made a huge difference in power.

So I found my issue. Injectors were clogged or frozen or something like that. It drives fine now and idled like normal. So yeah. Weird AF.

E85 life I guess. I need to send these injectors out and get them checked or run a tank full of 93 through this thing.

 

[steve]

So realistically the only thing it could be at this point is the ECU?

As you have discovered, no.

This is the ECU. Can someone circle what the injector driver is?

The red circled transistors are the injector drivers. The green transistor next to them is part of the voltage regulator.
The orange circled area is the snubber circuit for the injectors.

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[Drewpy Dawg]

A better way to free up stuck injectors: Put test clips on the injector terminals. Attach one to the negative of a 9v battery. Intermittently touch the other clip to the positive of the battery, sending pulses to the injector. Do this for a couple minutes and it should free up. It's the equivalent of gently working a seized bolt back and forth rather than hitting it with the biggest impact you can find.

 

[Drewpy Dawg]

Correction to my last reply: Don’t use a 9 volt battery, connect it directly to the car’s battery. I was testing something using a 9 volt battery last night and had a brain fart while typing that.