Sorry for the long winded post, but here's the deal. Recall that I have one of the XS Power small AGM batteries, located up under the dash. After fighting hot starting problems all weekend in Springfield I came home and decided it could only be my crank fuel vs coolant temp curve, which leans out the crank fuel as the engine is hotter. This morning I went out, 84F coolant temp after sitting over night, and lit it off. My curve has values at 93F, 118F, 143F, 169F, 194F, 219F and then flatlines up to 320F (all coolant curves have the same range and breakpoints for consistency in adjustments). Brought it up to around 95F, shut down for five to ten minutes, and made very minor fuel adjustments to optimize the start at that temp - same thing up the range to 194F, stopping at each break point and thought I had it nailed. Let it sit for 1/2 hour or more, then was going to head up to get gas and check my trip mileage. Coolant was at 175F, unhooked the battery tender and the witch cranked and cranked, even with WOT to clear the fuel. Finally got it lit, but resorted to a little shot of ether for an easier ignition. At this point the battery was pretty well depleted, so I grabbed my jumper cables and hooked up my Jeep lead acid battery to the cables on the AGM battery.

With the jump, the starter cranks at least 1.5times faster than it ever has with the AGM, and the beast lit in two or three revolutions. With the jumpers hooked I made several starts at 192F coolant temp, and found that with a very small adjustment to lean out the crank fuel it would hit almost immediately, every time. This is telling me that my system voltage is dropping too low to provide a good hot spark, or maybe even too low to properly fire my injectors during crank. The answer may be to switch to a full size, lead acid battery, but that's a major issue for me as it would have to be in the trunk and I'm not going to do a shoddy install just to have it running.

I'm wondering if I may just have a bad AGM battery? Has anyone else running the small AGM's compared their crank speed and start with a bigger size lead acid battery? I'll be calling XS Power tomorrow, but thought someone here might have had experience to help me out?