My data on hard start diagnosis (Glow plug diagnosis)
Posted: Fri May 02, 2014 1:09 pm
Vehicle:
1994 Delica L300 w/4D56T
Symptoms:
Poor starting when cold
Profuse white/grey smoke from tail pipe for 5-10 seconds, improving immediately once combustion warms up
The colder the ambient temperature( > 0 celcius) the worse the start (chugging sputtering, long cranks etc...)
Cold combustion, Glow plug system fault suspected.
Removed common rail tested resistance at each glow plug: 5ohms each (glow plugs good)
Cleaned rail and contacts, installed common rail.
Tried jumping battery voltage to glow plug rail during cold start, significant improvement in starting observed.
Checked voltage at rail during cold glow plug operation: 10.4V (huh?) expectation is battery voltage (11.5 - 12 during glow plug operation)
Relay fault suspected
Checked voltages at relay:
relay open, hot side: battery voltage
relay operating: voltage drops to 10.4V (both sides of relay)
Voltage drop in system suspected ECU? Wiring? Relay contacts?
Checked red black wire from battery to relay: 0 ohms
Checked red black wire from relay to glow plug rail: 0hms
wtf...
I consulted this thread http://www.delica.ca/forum/glow-plug-cicuit-271.html
but could not match up my ECU harness or glow plug system to these diagrams, so I suspect I have a different system and am not going to start poking around the ECU without a proper diagram.
Please see the following photographs for reference. Can anyone identify this system?
I am considering bypassing this system using a manual switch to operate the relay just to make things easier, but I thought I would take a stab at the diagnosis regardless to see what can be done.
1994 Delica L300 w/4D56T
Symptoms:
Poor starting when cold
Profuse white/grey smoke from tail pipe for 5-10 seconds, improving immediately once combustion warms up
The colder the ambient temperature( > 0 celcius) the worse the start (chugging sputtering, long cranks etc...)
Cold combustion, Glow plug system fault suspected.
Removed common rail tested resistance at each glow plug: 5ohms each (glow plugs good)
Cleaned rail and contacts, installed common rail.
Tried jumping battery voltage to glow plug rail during cold start, significant improvement in starting observed.
Checked voltage at rail during cold glow plug operation: 10.4V (huh?) expectation is battery voltage (11.5 - 12 during glow plug operation)
Relay fault suspected
Checked voltages at relay:
relay open, hot side: battery voltage
relay operating: voltage drops to 10.4V (both sides of relay)
Voltage drop in system suspected ECU? Wiring? Relay contacts?
Checked red black wire from battery to relay: 0 ohms
Checked red black wire from relay to glow plug rail: 0hms
wtf...
I consulted this thread http://www.delica.ca/forum/glow-plug-cicuit-271.html
but could not match up my ECU harness or glow plug system to these diagrams, so I suspect I have a different system and am not going to start poking around the ECU without a proper diagram.
Please see the following photographs for reference. Can anyone identify this system?
I am considering bypassing this system using a manual switch to operate the relay just to make things easier, but I thought I would take a stab at the diagnosis regardless to see what can be done.