LH 2.2 740 Turbo No Injector Pulse/Ground

Post by **bmdubya1198** » 23 May 2018, 15:36

I've been chasing my tail with this issue for probably 2 months now, and it's driving me insane.
I have an ongoing thread over on Turbobricks, but I have yet to find a solution. I figured I'd post over here and see if anybody has any other ideas.

My main question here is what would cause LH 2.2 to not ground the fuel injectors? I have checked and tested just about everything, and can't find anything wrong. I've tried two different LH ECUs and two different EZK ignition ECUs and the issue persists. I've checked all wiring as well as checking proper voltage on all of the ECU terminals, and everything appears to be just fine.
All ground points are clean and tight. All are making good contact with the surface.
The car is a 1988 740 Turbo M46, LH-Jetronic 2.2.

All 4 injectors have 12 volts, so the radio suppression/injector relay, fuel system relay, and ballast resistor are all GOOD. They have been mentioned several times already, but they are not the problem with my car. The problem I have is a GROUND issue, NOT a power issue.

If anyone would like to see the original TB thread, here's the link: https://forums.tbforums.com/showthread.php?t=341911

93Regina · Post by **93Regina** » 23 May 2018, 22:29

bmdubya1198 wrote: ↑23 May 2018, 15:36... what would cause LH 2.2 to not ground the fuel injectors?

1. With a tach, use pin 13 at LH 2.2 as the negative source (like for a coil setup) for the tach. I don't recall if this can be probed at LH 2.2, without splicing or back probing...but iirc, there is a way to use a "needle" type probe.

Crank engine

93Regina · Post by **93Regina** » 23 May 2018, 22:57

Footnote - I don't know which ignition box you have, but most likely it must send a signal over to LH 2.2...which one is it?

Post by **bmdubya1198** » 24 May 2018, 07:03

It’s the EZ117K ignition.

93Regina · Post by **93Regina** » 24 May 2018, 09:46

bmdubya1198 wrote: ↑24 May 2018, 07:03It’s the EZ117K ignition.

LH2.2 must know that the engine is running....

In this diagram here, LH2.2 (217) is using pins 1, 12, 24, which is connected to pins 8, 15, & 17 on EZK117.

Point being here is LH2.2 receives a RPM signal from ignition box...this is what is needed to be traced out....I'm busy right now...will check another resource later today. On earlier LHs, it was just a tach signal via coil, but on LH2.2, this was changed, iirc.

Post by **bmdubya1198** » 24 May 2018, 11:16

I can't find specifics on testing for RPM signal, but I used DC voltage on my multimeter to test at LH pin 1. I got a fluctuating 4-8 V while cranking. I take it LH is getting the signal from the EZK box.
However I also tested for ground on pin 13 (injector switched ground) while cranking and it came up open circuit. My meter shows 453 ohms with the key off or in position 1, and when I turn to position 2 it goes open circuit, and stays that way while cranking. Is this an internal problem with the ECU or is there a reason the ECU would cut fuel in that manner?

93Regina · Post by **93Regina** » 24 May 2018, 13:16

bmdubya1198 wrote: ↑24 May 2018, 11:16I can't find specifics on testing for RPM signal

On LH 2.2, pin 1 is where RPM signal is, as based upon this photo.

That said, my PDF Volvo manuals left out (not copied) specific details.

Sidbar - At volvowiringdiagrams.com, he has a "pinout for LH2.2," but I think this is for Regina, not LH2.2. But on Regina, Pin 17, as based upon this pinout, suggests a Hz signal would be observed. If you know him, could you inform him of this error?

Now, via "This information is for 1987 to 1995 Porsche 928s"

c Testing the EZK spark module RPM Output: The EZK module provides the signal to turn on the LH fuel injection module; it is the circuit from EZK connector pin 13 to LH connector Pin 1. Check for circuit continuity, if the wire is broken or the connection isn't clean, the car will not start.

: ezk_to_lh_rpm_pulse_trace_web.jpg (9.97 KiB) Viewed 2809 times

The waveform above is what the EZK pin 13 output looks like on an oscilloscope.

Hence, a scope is needed...on Pin 1 LH 2.2

Post by **bmdubya1198** » 24 May 2018, 16:07

Unfortunately using a scope isn't really an option. I'm going to assume there is a signal based on my reading.
I have checked continuity on all wires between EZK and LH, and they all zeroed out.

93Regina · Post by **93Regina** » 24 May 2018, 16:26

bmdubya1198 wrote: ↑24 May 2018, 16:07Unfortunately using a scope isn't really an option

ZVOLV said "Labscope."

Or slap another EZK117 ignition box in vehicle.

Reading a Hz signal might inform if RPM is in sync with engine rotation, but that waveform has a peak, which tapers off slowly, then it drops. Which LH2.2 may be expecting this waveform...where it drops off may be LH2.2's trigger signal.

Post by **bmdubya1198** » 24 May 2018, 16:53

93Regina wrote: ↑24 May 2018, 16:26 ZVOLV said "Labscope."

Or slap another EZK117 ignition box in vehicle.

Reading a Hz signal might inform if RPM is in sync with engine rotation, but that waveform has a peak, which tapers off slowly, then it drops. Which LH2.2 may be expecting this waveform...where it drops off may be LH2.2's trigger signal.

Gotcha. That’s a tool I need to get eventually, because I’m sure this won’t be the last time I need it.
The EZK (much like the ECU) seems to be fine, and I’ve already replaced it. I know a computer “seeming” fine isn’t really a good gauge of its condition, but I don’t know what to do at this point.