If there is a shortage of current to the start (ie just using jumper cables) there will be a click but no crank (with the starter still bolted on the engine), but I can't tell if the click is the solenoid moving all the way or just part way, I'm more familiar with starters that make a louder clunk when engaging. But the fact that it did once turn over slowly leaves me thinking you've got a shortage of current to the starter rather than a solenoid problem

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1978 300D, 373,000km 617.912, 711.113 5 speed, 7.5mm superpump, HX30W turbo...many, many years in the making....
1977 280> 300D - 500,000km+ (to be sold...)
1984 240TD>300TD 121,000 miles, *gone*
1977 250 parts car
1988 Toyota Corona 2.0D *gone*
1975 FJ45>HJ45
1981 200>240D (to be sold...)
1999 Hyundai Lantra 1.6 *gone*
1980s Lansing Bagnall FOER 5.2 Forklift (the Mk2 engine hoist)
2001 Holden Rodeo 4JB1T 2WD