I’m getting ready to put my intake back together and button up the top of the motor after a long and drawn-out FE refresh. I want to make sure as many of the critical things are working as I can before I proceed.

I resolved the no crank with key issue I was having. Now that I’m able to turn the motor over with the key I’m not getting any spark at the plugs or pulse at the injectors. I’m focusing on the injector pulse first. I have tested and have known good relays in for X-Bus (IV), EZF (XVI), and the LH (XXV). I’ve tested them both on the bench with power and an ohm meter to test continuity when triggered and I also swapped each one in for the horn relay and tested them that way. I’m seeing issues with the LH relay socket. My understanding is that I should have power at pins 86 and 30. I have power at 86 but not at 30. I read a post from @GregBBRD saying that pin 85 should ground when cranking. I’m not getting ground there when cranking. The CPS is new and I see the tach needle bounce when I crank the engine. I’m not sure what the next things to check are. Below is a list of the current configuration along with what I’ve done / checked so far. Let me know what you think.

• Grounds• Injectors• Relays• Things connected to the injector harness• Sensor

 

All "30" connections are 12 volt power, directly from battery. In this case, "30" connects to "87" when the magnetic coil closes the relay ("85" and "86" are the magnetic coil connectors.
Without power to 30 and to 87, once the key is turned on, you will not get voltage to the LH.

Start by checking the 3 or 4 main red power wires at the positive post of the battery. These send 30 power to the relay board. They must be clean and tight.
If these red power wires are clean and tight, you will need to remove the relay board and find out what is wrong with the 30 power buss at the top of the relay board/why there is no power to 30 on the LH relay.

 

Suggest you pull the EZ relay and check terminal 86 for voltage with the ignition switched on [if you have not done so already].

As best I can fathom out the alarm module when armed isolates power from the 15 bus that is switched. To test that the 15 bus is live pull the fuel pump relay and check for voltage on terminal 86 with the ignition switched on.

I have been chasing an erratic start problem that I suspect is caused by an ignition switch that has a mind of its own when powering up the 15 bus..

It also helps to have a line diagram of the system rather than jumping around the wiring diagrams- I have one that I prepared to help me- can post it if you think it may help at all- there may be slight differences with your MY but the principal will be the same I suspect.

If you are not seeing power with the ignition off on any terminal 30 then you need to resolve that before anything else.

 

Thanks Greg and Fred. I now have power at 30 on the LH relay and have a ground signal for it on pin 85 when the key is on and when cranking. Pin 86 had power before and still does. You were right on the money Greg. The red wires at the positive battery post weren't at all tight and the connection was not close to being clean. That was the cause of not having power at pin 30.

I have spark now but still no injector pulse. I can feel the LH relay click when I turn the key. I've also tried jumpering pins 30 and 87 on it and then cranking. Still no pulse. What do you think the next steps would be for getting the injector pulse? I have a spare new Bosh CPS. I've seen the tach bounce a few times when cranking. I'm not sure if that is a valid test. I have a small o-scope I could connect to it although I'm not really sure what kind of wave I would be looking for.

 

If the CPS is original I would replace it. Just do so carefully.

The next step if you have no injector pulse is to put your ECU in another 928 to see if it works, otherwise your LH may have failed.

They're all destined to unless they have been rebuilt with a new board to replace the hybrid circuit.

 

Thanks Blake. The CPS is 5+ years old but has zero miles on it. I put anti-seize on it so it shouldn't be too hard to swap out with the new Bosh one I have. I also have a spare EZF and LH that I was told were good. I could try the LH if needed as well.

 

You have solved one problem and based on your last post I would second Blake's advice that you now need to eliminate the LH unit from your line of enquiry.

 

Well I've found out what's going on that's preventing the injectors from firing, but I have no clue why it's happening. First here's what I tried this evening.

1. I swapped out the LH for one that was tested and working prior to it being shipped to me 7 years ago. Nothing at the noid light when cranking.
2. I disconnected my CPS and tested it with a small o-scope that I have. I got a sine wave when cranking the engine which is what I expected.
3. I took the previously installed CPS out and installed a new bosh unit. I got the same sine wave from it. I hooked it up, cranked the engine, and nothing at the noid light.
4. I tested with one side of the noid light hooked directly to the jump post and then connected the other side to each terminal on an injector plug one at a time. That's where things got interesting.

It turns out that one side of the injector wiring is always grounded. It doesn't matter if the key is on or off or even if the LH is hooked up or not. I then hooked it up to the other side and got nothing with the key off or on. I then cranked the engine and it flashed. One side of the injector plug wiring is getting the ground pulse that it needs but the other side is always grounded. This was with all injectors disconnected. I get the expected ~ 2.5 ohms resistance if check between the two pins on an injector plug with 7 injectors hooked up so I don't have a short between the two sides of the injector plugs. I'm not sure where to look to find out why the side of the injector wiring that should be 12v when the key is on is always grounded. Could that be the factory immobilizer?

 

the clue might be the CPS connector you replaced , you possibly got the wires swapped

 

It is not uncommon to swap the TPS and CPS connectors after a top end refresh. I've done it myself.

The CPS wiring jacket should have a grey cover while the TPS is black.

 

Good Call Stan. That's definitely something worth checking. I think it's wired correctly. The wire colors are different than the the same connector on my spare used motor. The spare has white, brown, and black where black is shield. It's white, black, and shield on my car. I should clarify that I'm not getting a dead short between what should be 12v+ to the injectors and ground. I believe it was about 78 ohms between what should be 12v+ and ground.

 

Hey Kevin. I thought of that as well. I believe I have the correct connector for the CPS. It has a shield wire in it and I'm not sure that the TPS does. Also, my LH is getting the signal from it when it's hooked up because I'm getting the ground pulse to the injector harness when I crank the engine.

 

doesnt the shield wire go to the center

 

I'm really not sure. It doesn't seem to be the center wire on the CPS connector from my spare. It wouldn't hurt to disconnect the CPS and test with the key on.

 

The shield is on pin 3. On the TPS connector the common earth is on pin 2- maybe that is what Stan has in mind.


Look familiar?