The back story to Volvo Penta Hard Starting is that towards the end of this year’s autumn twilight series we had something strange happen, the engine started “First turn of the Key” (as is normal) in preparation for the evening’s event, however after the race when I started the engine it took quite a bit of cranking and when started it idled poorly then stalled, started again same thing, a third time I gave it some throttle, it started but would not come off idle, it ran as if it was on only one cylinder then eventually came good. Note that my normal starting procedure involves about 10 seconds of glow plug before cranking, as per the operators manual.
After many “Google” searches I could not find a solution to our issue, or at least one that appeared relevant to our situation.
Googling and talking to a number of folk could come up with just about anything that could hamper the starting of a diesel engine:
Water in the Fuel.
Air leak in fuel system.
Blocked Air filter.
Poor cylinder compression.
Injector pump timing etc.
Further discussion went along the line that if for any of these reasons the engine was difficult to start then run roughly, why would it come good after a few minutes and why did it start occurring so quickly without any over time indications of things getting worse? That is that the first start of the day was normal, the second start was not! Could it be that a warm engine could handle these difficulties better than a cold engine? Could it be the glow plugs?
Now the filters (all of them) were less than 50 hours old and while I run the fuel tank fairly low for racing I am paranoid about fuel cleanliness and water contamination, Fuel Doctor (a fuel conditioner) is used liberally and fuel is sourced from known high volume outlets. (Yes even in Sydney that can be an issue). A blocked air filter would manifest its self over time as probably would an air leak, low cylinder compression surely would not become a problem within 30 minutes of engine operation. We were back again at the glow plugs, but why would all 3 fail at the same time?
The glow plug indicator would light up on the instrument panel which sort of threw me off that line of thought, then a perusal of the wiring diagram in the workshop manual revealed that the instrument panel indicator light is illuminated on the same circuit as the low current relay coil activation. Not the high current switched circuit.
A check of the two relays, one for start and the other for glow plugs, in the little black box on the side of the engine revealed that the one switching on the glow plugs was open circuit in the coils, fortunately these relays a standard Bosch mini relays that are universally and inexpensively available, either as genuine Bosch or from a myriad of other suppliers (Probably a myriad of quality levels as well), The relay was replaced with a cheap unit that was sourced from a nearby electronics store and the Volvo Penta Hard Starting issue was solved.
It is also interesting to note that the DI-30 loves its glow plugs, even in Sydney in autumn with water temperatures around 20c and ambient air temperatures in the low to mid 20’s it won’t start properly without a fix of pre-heat. Confirmation is in a quote in the operators manual:
“⚠IMPORTANT Always pre-heat the engine (even when it is warm).”