Ok, got too busy to post this after the Challenger engine arrived. Was up until 3:30am Saturday finishing the Challenger engine install so I could take it to the lake over the weekend. It ran great!
Anyhow, back to the GTX DI...
I put the rebuilt engine in the DI and had a HECK of a time fitting the exhaust in and getting it appropriately tightened. I thought that the gas system had been drained before it sat for a couple of years. I didn't realize until AFTER I had spent about 5 hours fighting to get the exhaust in and tightened that there was still a bit of gas in the bottom of the tank. Based on the receipt still in the glove box, it would be from 2007.
The fuel system was taken apart in 2011... with the fuel rail in a box, the cylinders in another box, & the fuel hoses still in the boat.
It was already about 4am and I had to get to bed (I had 3 really late nights last week). The thought of pulling EVERYTHING back out to pull the fuel tank was too much for me. I tried to syphon out the gas from the tank but is was so little that I couldn't get the hose to stay in the right place to suck it out... except for the one time that I got a mouth full and had gas shooting out my nose.
uke: I jumped and tugged the hose in the process, which broke vaccuum. After that I gave up on syphoning and put 5 gallons of fresh gas on top of the gallon that was already in there.
And I also pre-mixed it to 32:1
At this point I'll point out that in post #7 of this thread JHJESSE very wisely advised me to take out the entire fuel system and clean it... and I didn't. I was thinking that the Challenger engine would not be back in time and was rushing to get the GTX ready in case I needed it for the weekend.
That brings me to that nervous moment when I pressed the start button.
On the carburated (sort of... I think it is more of a mechanical direct injection... it doesn't even have a float) 787 in the Challenger I got used to how it usually needs a few seconds of cranking to get the gas flowing so it will start and run. With the GTX it actually startled me that it fired INSTANTLY the first time I pushed the start button.:cheers:
I didn't have the jet pump hooked up, so with no resistance it idled really fast. After a couple of seconds it started surging. Not sure if that is the right term, but RPMs increase, then fall off in roughly 1-1.5 second intervals. It reminds me a touch of how the challenger wouldn't idle smoothly the first time I put the carbs on and didn't notice that one of the carb gaskets had rotated and was only on one bolt, so it was blocking part of the carb throat on one side, and had a gap on the other side. That massive air leak in the fuel circuit burned up the top end of that motor in a couple of hours. :facepalm:
So, now I've got the GTX back together and am trying to get my head around all of the possible causes of this surging so that I can prioritize them by likelihood and impact and start working through the list.
What I'm thinking now:
1) an air leak in the fuel circuit. My first thought is to pull the reeds and throttle bodies and reinstall, making sure there are no leaks. I like this, as I can do this without taking the exhaust pipe off, but I don't think it is very likely that it will solve the problem.
2) the old gas in the fuel system has gummed things up and it isn't getting enough gas to one or both cylinders. I'm sure there are threads on here telling how to clean the fuel system. I will check the manual and search the forums for info.
3) ??
Any other ideas of things I should do or check?
