Yesterday after work I pulled the GTX to the local lake for testing with the jet pump on and the correct battery.
I ordered the battery online for in-store pickup... the battery that STS linked to. Advance Auto is on the way to the lake, so it would work out perfectly.
What I didn't realize is that the battery comes with the acid in 2 jugs, so you have to first fill the cells, then trickle charge it.
That completely wrecked my plan to test the GTX. I thought about getting one of the AGM batteries that is already charged and ready to go, but it cost nearly twice as much and they couldn't use the online coupon in the store... and I was running out of time before the light rain would end and the approaching storm would hit.
So I opted to take the battery I ordered and see if putting the jet pump on was enough to solve the issue. ie. still running on the lawn tractor battery.
The guy at the marina was nice and let me back the trailer in and run it on the trailer for a few minutes without the $7 launch fee... probably since I was the only one dumb enough to be out there in the rain.
Really not much different than the prior result.
It starts fine. Surges a bit while idling at around 1,400 RPM. Runs a bit smoother up to about 3k RPM, but still surges a bit. Revs fine past about 3k RPM. Dies when I let off of the throttle fast, or even sort of fast. I was holding out hope that even on the wrong battery, the load of running in the water with the pump on would solve the issue. At least I now know that it wasn't the lack of jet pump and/or water resistance that caused my issue.
I filled the new battery last night and put it on my trickle charger. Extra frustrated that the charge chart only shows times for down to a 1A charger (14 hours). Mine is a 500ma, so I have to guess it will take around twice as long... and may not be fully charged when we are ready to leave for the lake this evening. Found my old 2A trickle charger from my motorcycle this morning, but it is DOA.

I wonder if I can switch to the normal charger (I think it is a 10A charger) near the end of the charge cycle to top it off, or if that would cause a problem with the initial charge.
Anyhow, I am trying to be optimistic that the new battery will solve the problem, but I can't get my head around how it would. So I expect that I'll need to start troubleshooting.
The most logical place to start seems like it would be cleaning the injectors. I'll have to look up how to do that.
OH! I had a brain fart and just remembered something... what should my compression readings have been when I first installed the engine, but before I even installed plugs and fired it up the first time? I'm guessing that compression would be lower than normal until it has been broken in, as the rings haven't seated at all yet. I put maybe 5 or 10 drops of oil in each cylinder before I installed it and hand-spun it so that the cylinder walls weren't completely dry. Before installing the spark plugs and before the engine had been started even one time I tested compression and got about 91 on each cylinder. That seemed low to me, I chalked it up to having not been broken-in at all and moved on. When it fired up instantly on the first try I think I mentally discarded that info, as I literally didn't remember that I even did the test until this morning. I guess that is what I get for staying up past 4am working on the GTX.
I am dying to test it again since it has been run for a few minutes and see what it says, but I left the compression tester on the Challenger (along with most of my metric tools, doh!) at the lake.
As I typed the above paragraph I was thinking of my 787 engine at about 150 PSI, and that 91 seemed low. I just searched and see that 120 is considered good for the 951 DI.
Starting to worry that there may be bigger issues here.
I soooooo do not want to take that engine out.
Not sure if it is worth pulling the GTX 2 hours to the lake tonight or not. ugh:ack: