I have the VX200TRLY. Let me start by saying that this motor has been rock solid for the 8 years I've had it. I did have the main relay go out and regular maintenance items, but nothing too serious. I wanted to share in case others are chasing gremlins on the Ox66 in the future.
This all started with a no start at the ramp one morning. The motor would start and then quickly die. I just couldn't get it to catch. The time before this, it was fine. I figured no big deal. It was due for low pressure pumps, and that was probably it. I had an extra set waiting for the day. Replaced the low pressure pumps, and it was still a no go. The high pressure pump didn't seem right, it would run intermittently so I replaced it. Still not like it should be. Figured why not just do a low pressure pump delete and replace it with an electric pump. It would start now, but just didn't seem completely right. I ran it for a couple of trips trying to understand what the problem was. It would start fine, but stumble from around 1200 to 3000 RPM. Once I got it over 3000 RPM, it would run but just seemed a bit gutless. Checked the TPS, did a link and sync, adjusted the throttle cable, etc. TPS was a hair low and adjusted that. No matter what I did, it kept doing the same thing.
I started digging deeper. Now the high pressure pump wouldn't activate when keyed on. That was new. I had 12v to the hot side, and when I completed the ground with a jumper it would run just fine. I got a fuel pressure gauge on it and when I did run the pump, it would go up to about 30 lbs but would immediately drop to zero once the power was off. But it still was not activating when keyed on. I had a funny feeling I may have a ground issue at this point. Here's the punchline. There are two ground points at the top rear of the block. On the port side, it is the termination point for multiple grounds that had some corrosion. I cleaned both of them back to shiney, and now the pump would activate when keyed on. I'm making progress now. The moral of the story here is if you are having gremlins appear on these motors, check those grounds and any others you can find. These motors are now getting up in age, and things can get corroded over time.
To close this out, on the high pressure pump, I didn't recall putting an o-ring around the center port on the pump. Pulled the VST apart again, and sure enough I didn't. When I took the original pump off, I didn't see an o-ring because it fell out into the bottom of the cowling. Put an o-ring on there, and now she would build and hold fuel pressure back to spec.
I always felt like I knew this motor pretty good, but this one stumped me for quite a while. I still need to do the complete lake test, but she is back to starting on muffs like the old days, so I'm pretty sure I finally solved the issue. Did some stuff along the way that I had always wanted to do like the low pressure pump delete. I even threw in some Chris Carson reeds since I wanted to check them anyway. If I had known to check those grounds first, I would have saved a lot of time, but I might not have gotten as much done that I wanted to do anyway.
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Originally Posted by JoeFriday
