No power to the fuel pump and no spark to the spark plug
#1
No power to the fuel pump and no spark to the spark plug
All,
My 928 s4 has no power to the fuel pump and no spark to the spark plug
I have renew fuel pump relay and renew LH system relay.
What can I do to check or fix this problem?
Any reply will be appreciated. Thanks a lot.
My 928 s4 has no power to the fuel pump and no spark to the spark plug
I have renew fuel pump relay and renew LH system relay.
What can I do to check or fix this problem?
Any reply will be appreciated. Thanks a lot.
#2
Nordschleife Master
Possible causes:
failed EZ-K relay (the one with the tester in it - but can be swapped with any type 253 relay as they're functionally the same)
failed EZ-K ECU
failed Crank Position Sensor
My memory says the LH fuel pump circuit only energizes when it receives an rpm signal from the EZ-K, which is sourced from the crank position sensor.
IMO - most likely cause:
crumbled harness connector on the Crank Position Sensor
However - do you have access to an oscilloscope?
Before you get into the expensive parts-swapping phase, swapping the relays and also putting an o'scope on the terminals for the rpm signal at the EZ-K and LH harnesses connector is a great way to check whats going on
failed EZ-K relay (the one with the tester in it - but can be swapped with any type 253 relay as they're functionally the same)
failed EZ-K ECU
failed Crank Position Sensor
My memory says the LH fuel pump circuit only energizes when it receives an rpm signal from the EZ-K, which is sourced from the crank position sensor.
IMO - most likely cause:
crumbled harness connector on the Crank Position Sensor
However - do you have access to an oscilloscope?
Before you get into the expensive parts-swapping phase, swapping the relays and also putting an o'scope on the terminals for the rpm signal at the EZ-K and LH harnesses connector is a great way to check whats going on
#4
Nordschleife Master
Not really - its a hall effect sensor, so you can't check continuity/voltage on it with a DVM.
Did you start by swapping the EZ-K relay? swap it with the horn one (make sure horn works first ) and see if you get spark. Guessing you're in Hong Kong from your forum name? (i.e. access to another S4 to test your ECU in is tricky).
Did you start by swapping the EZ-K relay? swap it with the horn one (make sure horn works first ) and see if you get spark. Guessing you're in Hong Kong from your forum name? (i.e. access to another S4 to test your ECU in is tricky).
#5
Addict
Rennlist Member
Rennlist Member
Join Date: Oct 2003
Location: Gone. On the Open Road
Posts: 16,322
Received 1,542 Likes
on
1,006 Posts
No spark with good EZK relay means dead CPS, both coil amps or coils dead, or dead EZK. EZK rarely fails. CPS has limited life. 1 in a million for both coil amps or coils to die at same time.
Replace the CPS if the EZK relay is good.
Replace the CPS if the EZK relay is good.
#6
Nordschleife Master
Quick and dirty Crank Sensor test:
Watch the tachometer when you crank the engine with the starter.
If it twitches, the crank sensor is working. If not, not.
Watch the tachometer when you crank the engine with the starter.
If it twitches, the crank sensor is working. If not, not.
#7
Thanks for all replies.
For secure, which cause(s) (dead CPS, both coil amps or coils dead, or dead EZK) will also trigger another problem of no power to fuel pump, besides no spark?
For secure, which cause(s) (dead CPS, both coil amps or coils dead, or dead EZK) will also trigger another problem of no power to fuel pump, besides no spark?
Trending Topics
#9
Addict
Rennlist Member
Rennlist Member
Join Date: Oct 2003
Location: Gone. On the Open Road
Posts: 16,322
Received 1,542 Likes
on
1,006 Posts
#10
Addict
Rennlist Member
Rennlist Member
Join Date: Oct 2003
Location: Gone. On the Open Road
Posts: 16,322
Received 1,542 Likes
on
1,006 Posts
Or, in other words, the EZK will not activate the coil amps unless it sees that the motor is turning.
#12
Chronic Tool Dropper
Lifetime Rennlist
Member
Lifetime Rennlist
Member
The Hall sensor on the cam gear helps the controller know which revolution the crankshaft is on, so it can adapt ignition in specific cylinders when it detects knocking. A failed Hall sensor allows the engine to run OK but not full power. Timing is retarded some to protect all the cylinders all the time, but engine will still feel pretty normal.
Failed CPS is the most common cause of your symptom, but it can be other things like a loose power or ground for the EZK box. What did the tach do when you tried cranking on the starter? Tach depends on CPS, as does the EZK for ignition. Fuel injection gets the engine speed translated and relayed on by the EZK box. No tach points you to cps..
Failed CPS is the most common cause of your symptom, but it can be other things like a loose power or ground for the EZK box. What did the tach do when you tried cranking on the starter? Tach depends on CPS, as does the EZK for ignition. Fuel injection gets the engine speed translated and relayed on by the EZK box. No tach points you to cps..
#13
Rennlist Member
I experienced pretty much the same symptoms on my 89 GT a few years back. I changed out all the relays, jumpered the fuel pump, etc.
In the end, it was a the ECU which is prone to failure - a well documented Bosch flaw. I was fortunate enough to trade it out with a spare ECU from Motorsport here in SLC which showed a failed ECU was the cause. Ended up installing the improved Speake-modified ECU which also cures the Bosch flaw.
In the end, it was a the ECU which is prone to failure - a well documented Bosch flaw. I was fortunate enough to trade it out with a spare ECU from Motorsport here in SLC which showed a failed ECU was the cause. Ended up installing the improved Speake-modified ECU which also cures the Bosch flaw.
#14
Rennlist Member
Not really - its a hall effect sensor, so you can't check continuity/voltage on it with a DVM.
Did you start by swapping the EZ-K relay? swap it with the horn one (make sure horn works first ) and see if you get spark. Guessing you're in Hong Kong from your forum name? (i.e. access to another S4 to test your ECU in is tricky).
Did you start by swapping the EZ-K relay? swap it with the horn one (make sure horn works first ) and see if you get spark. Guessing you're in Hong Kong from your forum name? (i.e. access to another S4 to test your ECU in is tricky).
#15
Addict
Rennlist Member
Rennlist Member
Join Date: Oct 2003
Location: Gone. On the Open Road
Posts: 16,322
Received 1,542 Likes
on
1,006 Posts
In the end, it was a the ECU which is prone to failure - a well documented Bosch flaw. I was fortunate enough to trade it out with a spare ECU from Motorsport here in SLC which showed a failed ECU was the cause. Ended up installing the improved Speake-modified ECU which also cures the Bosch flaw.
OP has no spark which points to issues before the LH computer.