diesel jumpstart question

[hitcher]

my ride on lawn mower is having some starting issues so ive been going redneck style and jump starting it with my 85 truck (gas) . however today i was jumping it with my 88 6.2 diesel and got absolutly nothing . both batterys on the truck are new and i have no problems starting the truck every day . i was jumping off the battery that isnt connected directly to the starter motor . i left the truck running for a good 5 minutes but the mower didnt wanna know . put my 85 gas truck on the mower which i hardly use and the mower started up right away . so what the heck is going on with jumping from the diesel ?????? .

thanks