• Hello Guest, welcome to the initial stages of our new platform!
    You can find some additional information about where we are in the process of migrating the board and setting up our new software here

    Thank you for being a part of our community!

740 No Pulse to Injectors, Has Spark

Okay just making sure. AFAIK that’s the only lh2.2 turbo ecu (could be wrong). And I’ve read they’re extremely reliable. I doubt either of your ECUs are bad.
 
I was reading more last night, and I agree, they’re probably both fine. I found a thread with an issue similar to mine, but as usual the OP never posted the solution...
I read something about the ignition coil continuity to ECU pin 1, but I can’t find the page. I tested that and found high resistance, over 1,100 ohms. After looking at the diagram though, I don’t think there is supposed to be a connection. Anyone know about that?
 
What does the legend say?

Why would a power wire go to ground!? Do you have power on pins 18 and 9? Is that diagram LH 2.2?
 
What does the legend say?

Why would a power wire go to ground!? Do you have power on pins 18 and 9? Is that diagram LH 2.2?

Well, I thought the same thing, but both injector wires have power, don't they?

Pins 18 and 9 both have power. ~11.94V at 9 and ~12.12 at 18. Strange there is discrepancy in voltage, albeit a small one.

Yes, the diagram I posted is LH 2.2 B230FT.
 
Well, I thought the same thing, but both injector wires have power, don't they?

Pins 18 and 9 both have power. ~11.94V at 9 and ~12.12 at 18. Strange there is discrepancy in voltage, albeit a small one.

Yes, the diagram I posted is LH 2.2 B230FT.

One of the wires for each injector is switched to ground by LH2.2. The other is connected to 12v through the rsr.
 
As I have said, you confirm power , ground, and signal to a computer before condemning a computer.

I can think of many tests. I have a $80 oscilloscope which is about the cost of one or two missed shots with the proverbial parts cannon.

With the scope I would confirm a clean square wave from the hall sensor into the EZK box.

Next I may jump over to the LH box and see if it's pulling the injectors to ground. I would be doing my checks directly at the LH box which would eliminate any problems with engine bay wiring.

Or lower tech would be the damn test light. Your thread title is no injector pulse. Connect test light to a positive source, connect the other end poked into the back of an unsheathed LH connector at the injector control terminal. Blink?
 
Last edited:
I’ll see what I can do about testing that the ECU is grounding the injectors. I’m pretty sure the EZK is getting a good RPM signal from the hall sensor. It’s a new sensor (yeah yeah, I know that doesn’t mean much) and if it wasn’t getting a reading, I likely wouldn’t have spark.
Now, whether that signal is getting to the LH box, I couldn’t tell you. Nobody has given me clear directions on testing for those signals, and it’s hard to crank the car over and hold meter probes on things without a helper. I’ve been doing 95% of this alone. And I do not have an oscilloscope.
 
Notice how I skipped the explanation of looking at the signal from the EZK to the LH box. I honestly don't know what kind of signal it is. The greenbooks were written before scopes were cheap and available, so they likely tell you to look at an AC voltage reading, I guess. It may be an AC voltage signal with varying frequency. Ipdown in Estonia did well at reverse engineering all the signals and code on the 2.4 system. His website is still up.

Regardless, that's why I said skip that part of the circuit and focus downstream. You gotta figure out where the signal goes missing, or if it's a dead box or a wiring issue.
 
I would think there's probably a way to test with ACV. I tested for DC voltage at pin 1 (signal from EZK) and it was fluctuating between around 4-8 volts. I assume that's a good sign?
Also tested for ground at pin 13 while cranking. With the key off or in position 1, my meter shows 453 ohms. When I turn to position 2 it goes open circuit, and stays that way while cranking.
I take it the ECU isn't grounding the injectors.
 
Idk man I'm busy at the shop. Interpreting others' reading without a diagram right in front of me means almost nothing. Sorry.

I use software flow charts that would point me towards which circuits to check and what the reading should be.

Find the greenbooks is my suggestion at this point. Or buy a scope, or just keep firing away.
 
Got some new info...
I tested the ECU terminals one by one per the typical values document from volvowiringdiagrams.com. I noticed some issues...

At pin 9 while cranking, my meter shows 7-8 volts. It's supposed to be between 11-14V. Pin 17 is supposed to be between 0-1V while cranking, it was 5 volts. Pin 21 should be 11-14V key on, it was 1.6V.

Those are the values with my spare ECU. My original one had even more values that were incorrect (like 12V on pin 19, a ground wire) but those 3 above are the only ones that concern me.
My original ECU showed the same reading on pin 9 while cranking, 0.05V while cranking on pin 17, and 0.51V on pin 21 with key on.
Interestingly, all of those pins are related to the fuel relay. Probably related to the lack of ground on pin 13.

I tested once again for injector pulse with this ECU and sure enough, nothing. The readings I got could have been low because of the battery, but the other things that were supposed to be 11-14V were within range. The battery was still over 12 volts.

The throttle switch signal on pin 12 seemed off too, but that may be a bad switch for the WOT signal. It showed 0.31V both with the throttle closed and and fully open. It's supposed to be 0 fully open and 5V closed. I'm leaning more towards the fuel relay pins being the main issue.

Is this still the ECU, or is it a wiring issue? Or a problem with the fuel relay itself? The relay looks to be working just fine, so maybe I just have two ECUs that failed in different ways, or I just have an issue with the wiring at the fuel relay.
 
I'll go ahead and add what those pins show on my LH diagram/pinout...
Pin 9 is the ECU power supply from the relay (low voltage, could be an issue)
Pin 17 is control signal to fuel relay
Pin 21 is control signal to main reay
 
I’m not saying your ECUs are for sure good, but the odds of 2 very reliable ECUs both being bad is very slim. Unless of course they were thrown in a pool or something?

Also, the fuel pump relay is easy enough to swap out, have another laying around? Takes about 30 seconds. Try a couple different ones.

But also if it for sure doesn’t start on starting fluid then you have issues. Are you 100% sure the engine is timed correctly?
 
Back
Top