When driving Engine turn off and does not start
10-13-2020, 01:21 PM
#1
Track Day
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When driving Engine turn off and does not start
Hi, I have Porsche 928 s4 1987,engine runs perfectly but after high hill driving or long distance driving Engine cuts off and does not start after 15 minutes, engine crank sensor is new, engine wiring harness is new(ordered from kroon) all relays are new LH, EZK, and fuel pump.ground points checked.
When the engine cuts off I checked with noid light no pulse from LH control unit to fuel injectors, also no spark from the spark plug wire,all power supply for both control units present that mean relays are good, rpm flactutes that mean crank sensor is good. Lh control unit can be defected? but why I don't have spark, LH control unit also controls the spark?as I know EZK is responsible for spark.
When the engine cuts off I checked with noid light no pulse from LH control unit to fuel injectors, also no spark from the spark plug wire,all power supply for both control units present that mean relays are good, rpm flactutes that mean crank sensor is good. Lh control unit can be defected? but why I don't have spark, LH control unit also controls the spark?as I know EZK is responsible for spark.
10-13-2020, 02:19 PM
#2
Instructor
"Lh control unit can be defected?" yes and might only happen when hot, common to need them refurbished. The LH sends load signal to the EZK (pin 9), I'm not sure but likely no load signal = no spark
"All power supply for both control units present"- have you checked to be sure key on power (15) - pin 29 on EZK is not dropping out when this happens, if so ignition switch could be issue.
"All power supply for both control units present"- have you checked to be sure key on power (15) - pin 29 on EZK is not dropping out when this happens, if so ignition switch could be issue.
10-13-2020, 02:52 PM
#3
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Check all the connections at the battery. At the positive post, there are several smaller red wires that need to have clean and tight connections. This power the injection, ignition, fuel pump, oxy sensor, and cooling fans.
Replace three critical relays in the central electrics panel. Replace the LH-Jetronic, EZK Ignition, and the Fuel Pump relays. These are common Bosch 53b relays, and should be available locally to you.
The alarm system/immobilizer disables the ignition system, which then disables fuel from injection and prevents the fuel pump from running. These don't randomly fail while driving. If you suspect a problem with the alarm, close the doors and turn the drivers door lock to lock then unlock using the key from the outside. Then open the door and try to restart. If that allows the engine to start, you can look deeper into the alarm.
Replace three critical relays in the central electrics panel. Replace the LH-Jetronic, EZK Ignition, and the Fuel Pump relays. These are common Bosch 53b relays, and should be available locally to you.
The alarm system/immobilizer disables the ignition system, which then disables fuel from injection and prevents the fuel pump from running. These don't randomly fail while driving. If you suspect a problem with the alarm, close the doors and turn the drivers door lock to lock then unlock using the key from the outside. Then open the door and try to restart. If that allows the engine to start, you can look deeper into the alarm.