Technical flamestart glow plug

[cumbriangeorge]

My 8140-47R engine (96 ducato motorhome) has the flame start system which I understand. About 2-3 years ago i replaced the glow plug which was showing open circuit. Tested the new glow plug on the bench, it heated up well and quite quick. I have rarely had to use the flame start since i also have a coolant pre-heater which works well, 30 mins on pre=heat and the engine fires up very well. Today I thought I would take advantage of the zero temperature to check that the flame start system actually works.

So pulled off the intercooler return pipe to give visible access to the glow plug, turned on the ignition, confirmed 12 volts to the glow plug but it did not heat up. Removed the supply cable and confirmed that the glow plug is showing open circuit.

New glow plug ordered, easy enough to fit but why would it have failed (open circuit) given that it has had little or no use?

I would add that the engine started anyway so this is not a show stopper.

 

[varesecrazy]

I suppose it is subjected to engine vibration .. no matter if it is actually Heating or not.. for all those miles it has covered.

I dont know the set.up

From my Early Diesel days:
I would change all 4 glowplugs at a time

When bench tested.. 90% would still glow Cherry

Leading me to believe that 'Somehow' they were not Earthing properly in the block

Food for thought..maybe

 

[cumbriangeorge]

Update.... new flame start glow plug fitted and appears to be working. Flame observed. The supplier of the glow plug, Coastal Motorhomes, has advised that the glow plug relay has a sturdy resistor in series with the glow plug to drop the voltage a little. The resistor is by passed when cranking to compensate for the voltage drop during cranking. The glow plug should NOT be tested by connecting directly to a battery. The new glow plug has a resistance of about 0.5 ohms. One interesting observation on this 96 Fiat is that the accelerator will be disabled if the airpipe is disconnected (to look for a flame). The MAF sensor will not pick up an airflow so the ecu disables the accelerator.