EspritS4s

Well, my motor is back in the car and everything is hooked up (I think), but she won't start. I'm not getting any fuel or spark. Could someone tell me if the LH controller turns on the fuel pump to pressurize the fuel system before the starter is engaged, or does it wait for a signal from the EZK? Rich Andrade posted a good spark and fuel diagnostic procedure in which he states that the LH is a slave to the EZK which is looking for a signal from the RPM sensor. I'm going to double check the sensor tomorrow, but I'm also looking for other ideas.

Thanks,
Gary

Rich9928p

Could someone tell me if the LH controller turns on the fuel pump to pressurize the fuel system before the starter is engaged, or does it wait for a signal from the EZK?

>> After the ignition is turned on, the fuel pump should run long enough to pressurize the system prior to the engine turning over, after that it doesn't run until the engine starts. The chain of events is:

1. The EZK must see input from the "engine speed sensor" before it will start spark. These inputs are from the Hall sensor to EZK pins 5 and 22. Pin 5 is a 12 V supply for the Hall sensor. You'll need an 0-scope or LED testor for the Hall sensor.

2. Once the EZK starts, it provides engine speed information that the LH needs to start running via the circuit EZK pin 13 to LH Pin 1 .

3. The LH controls the fuel pump relay, and turns the fuel pump by a signal from LH pin 20 to circuit to fuel pump relay XX pin 85.

To start, check to see if your fuel pump is running. This is accomplished by removing the fuel pump relay and inserting a jumper connection between sockets for 30 and 87. This turns on the fuel pump regardless of ignition or controller output. If the pump runs, then you have a problem somewhere in the circuits mentioned. If the pump doesn't run, look to the circuits to the pump or the pump motor itself.

EspritS4s

Rich,
Thanks. I'll try jumpering the relay tomorrow. I'm not getting any fuel pressure at all. Since I just finished installing the motor, I'm assuming that I either left something unconnected or mixed up a connector somewhere. I was pretty careful, but obvously something isn't right.

Thanks,
Gary

EspritS4s

Well, during the process of pulling and inserting relays, the fuel pump started working. I get fuel pressure, but I'm still not getting any spark....

-Gary

Rich9928p

One step at a time. You need to verify that each relay (LH and EZK) have battery voltage at relay connection # 30.

EspritS4s

Rich,
I've already checked that. I'm getting voltage at pin 30 of relay 25 & 16.

Rich9928p

You should have schematics, if not you are flying in the dark (send me a PM). Just to restate the obvious, did you plug everyting back together?

These are kind of generic tests, since you've disturbed all the systems there are many more tests.

a. Testing the engine RPM sensor. The EZK spark control is the system master, if engine rotation signals are not provided to the EZK, spark will not be generated and EZK will not provide a turn-on signal to the LH Jetronic fuel injection system. The RPM sensor input to the EZK is from an inductive RPM sensor. Inductive RPM sensors generate voltage so a VOM can be used for testing the sensor. EZK pins 23 and 6 are connected to the RPM sensor; pin 6 is ground and is connected to master-ground pin 18. EZK pin 24 is the shielding of the sensor cable and is connected internally to pin 18.

b. The Hall Effect engine position sensor can be tested with an LED tester. The EZK provides the power supply for the Hall Sensor at pin number 5 (12V). The EZK provides a 5V level at pin number 22, which the Hall sensor can pull down to ground. Pin EZK pin 22 is the "hot" signal cable and therefore is shielded. The cable shielding is connected to EZK pin 4, and pin 4 is connected internally to master-ground EZK pin 18.

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

d. The circuit from LH Pin 20 goes to the Fuel Pump Relay XX pin 85, check for continuity between these two points.

e. From the Fuel Pump Relay XX pin 87 the circuit passes through fuse 42 then to the fuel pump motor. Pull the fuse, check the fuse, and clean the connectors. Check the continuity of this path. Bridge Fuel Pump Relay XX socket points 30 and 87, the fuel pump should run.

f. There should be 12V (nominal battery voltage) at the fuel pump and LH relay pins 30 at all times. This same circuit connects to LH connector Pin 4, check for 12V there too.

g. The LH relay XXV pin 85 connects to LH connector pin 21, check for continuity between these two points.

h. The LH connector pin 18 connects to all the fuel injectors. The LH functions as the switch from the fuel injector to ground. With the LH relay jumpered between pins 30 and 87, there should be 12 V at pin 18. [Model Year 1989 and newer 928s have a spark monitoring system, consult the wiring schematics and workshop manuals.]

i. Power and Ground connections are key points to inspect and clean. The LH is grounded via Pin 17 to chassis ground point VIII. Use an Ohm meter to measure the resistance between LH connector Pin 17 and a chassis ground point. It should read as close to zero as possible. If it reads a high resistance, a corroded ground connection at MP VII or cut in the wire could be the problem.

j. If all of these items check out OK, and the fuel pump is functioning, then potential problems could be:
- The system fuel pressure is too low; fuel filter or pipes are restricted, fuel injectors are not functioning correctly
- The LH Jetronic fuel injection module is not functioning correctly and requires a rebuild.

EspritS4s

Rich,
Thanks for the info. I have the factory wiring diagrams if those are the schematics that you're talking about. Right now I'm suspicious of the crank sensor because we attempted to remove it while the motor was out, but we couldn't get it out. It's very possible that we damaged it. With the crank turning, what voltage levels should I expect to see. I took a look at the sensor leads with an automotive specific meter that has limited o-scope functionality, and it looked like I was getting a waveform but the amplitude was under a volt.
I agree that the most likely culprit (outside of the RPM sensor) is an incorrect or missing connection. I'll go down your check list and validate the connections you mentioned.

Thanks again for you help!
-Gary

EspritS4s

Rich,
Thanks again for your help. The car is now running. It turns out that all three of the wires from the EZK to the crank sensor were open somewhere in the wiring harness. I suspect that a previous splice came apart while I was pulling the harness through the firewall since all three of the wires are open. I didn't want to completely open the harness to find out, so I ran a new set of shielded wires.

Thanks Again,
Gary

Rich9928p

Good news, hunting down broken wires is a very time consuming job. Time to get the shark on the road!