Hoping someone with more knowledge of 4stroke outboards can help me out. I'm new to 4S having had 2 strokes to date.
I've been chasing a fuel issue, or I think fuel issue, in a new to me 2010 Merc 30hp EFI 4 stroke I bought a couple of weeks ago. It did stall once when we first got it when going from F to N, then not again until this final case which has persisted. A few days later, due to a stuck fuel sender I didn't realize it was very low on fuel and eventually it ran out of fuel on me. I discovered water in the tank and a bunch of junk. I pumped out whatever old fuel I could get out the tank that was left, purged the lines, and added 8 gallons of fresh fuel. I then added a Racor fuel/water seperator right after the tank but before the bulb, cleaned the low pressure fuel filter screen and bowl, replaced the high pressure fuel filter (old one was definitely restricted) and lastly, cleaned the VST and the filter screen on the bottom of the high pressure fuel pump. I checked the fuel pressure today, and it's 43psi regardless of the RPMs or when surging.
Unfortunately, it still isn't running right. It will start right up but it idles poorly. It will surge from about 800-1200, stay in one spot for a few seconds, then drop to 600 or 800, then sometimes catch and stay running, or sometimes stall. Pretty inconsistent on the behavior detail, but typically the same result, most times it will stall. If I advance the throttle to about 1200 -1500 it will stay running indefinitely, but still hunt a bit, but not as much. If I bring the throttle back to N quickly, it will almost always stall, but if I really gently bring it back slowly, I usually can keep it running, but again, it mat still stall as it drops to 400rpm or so, tries to catch and stay running, then just stop.
Given the above, I'm thinking it's likely not fuel pumps, as if I can keep it running at a higher RPM, it will run a while, much longer than I think it would if the low pressure pump wasn't keeping the VST full. I could be wrong though. Last weekend, I actually was able to take it on a 20 minute ride and it was perfect, and ran at WOT without issues (thought it was fixed, but it wasn't, as the issue showed again the next day).
At this point, I'm thinking the IAC valve is the likely culprit, unless it's something like an ECM issue, clogged injectors, or something else I haven't considered. I know I could get a Merc tech to hook up a diag reader to it, but I'd have to pull it from the water to bring it somewhere (which assumes I can safely get to the ramp to pull it in a swift current river), and at this point in the season, it's likely not going to get back to me in time to enjoy it at all before the season ends, so I'm trying to solve and test stuff myself instead of just replacing parts wildly.
Any tips or thoughts are appreciated. I read how to test the IAC to check for a vacuum on the open hose, but I'm not there tonight to try that.
Here's a video of the tach when it's jumping around, some of the higher RPM stuff being me advancing throttle. And the second video is the surging all on its own, showing the fuel pressure while it's doing it.
https://www.dropbox.com/s/ctx7fl6o1f5e0zh/Video Sep 02, 11 46 24 AM.mov?dl=0
https://www.dropbox.com/s/2x3o9qasxcm0cgi/Video Sep 02, 12 57 05 PM.mov?dl=0
Thank you very much.
I've been chasing a fuel issue, or I think fuel issue, in a new to me 2010 Merc 30hp EFI 4 stroke I bought a couple of weeks ago. It did stall once when we first got it when going from F to N, then not again until this final case which has persisted. A few days later, due to a stuck fuel sender I didn't realize it was very low on fuel and eventually it ran out of fuel on me. I discovered water in the tank and a bunch of junk. I pumped out whatever old fuel I could get out the tank that was left, purged the lines, and added 8 gallons of fresh fuel. I then added a Racor fuel/water seperator right after the tank but before the bulb, cleaned the low pressure fuel filter screen and bowl, replaced the high pressure fuel filter (old one was definitely restricted) and lastly, cleaned the VST and the filter screen on the bottom of the high pressure fuel pump. I checked the fuel pressure today, and it's 43psi regardless of the RPMs or when surging.
Unfortunately, it still isn't running right. It will start right up but it idles poorly. It will surge from about 800-1200, stay in one spot for a few seconds, then drop to 600 or 800, then sometimes catch and stay running, or sometimes stall. Pretty inconsistent on the behavior detail, but typically the same result, most times it will stall. If I advance the throttle to about 1200 -1500 it will stay running indefinitely, but still hunt a bit, but not as much. If I bring the throttle back to N quickly, it will almost always stall, but if I really gently bring it back slowly, I usually can keep it running, but again, it mat still stall as it drops to 400rpm or so, tries to catch and stay running, then just stop.
Given the above, I'm thinking it's likely not fuel pumps, as if I can keep it running at a higher RPM, it will run a while, much longer than I think it would if the low pressure pump wasn't keeping the VST full. I could be wrong though. Last weekend, I actually was able to take it on a 20 minute ride and it was perfect, and ran at WOT without issues (thought it was fixed, but it wasn't, as the issue showed again the next day).
At this point, I'm thinking the IAC valve is the likely culprit, unless it's something like an ECM issue, clogged injectors, or something else I haven't considered. I know I could get a Merc tech to hook up a diag reader to it, but I'd have to pull it from the water to bring it somewhere (which assumes I can safely get to the ramp to pull it in a swift current river), and at this point in the season, it's likely not going to get back to me in time to enjoy it at all before the season ends, so I'm trying to solve and test stuff myself instead of just replacing parts wildly.
Any tips or thoughts are appreciated. I read how to test the IAC to check for a vacuum on the open hose, but I'm not there tonight to try that.
Here's a video of the tach when it's jumping around, some of the higher RPM stuff being me advancing throttle. And the second video is the surging all on its own, showing the fuel pressure while it's doing it.
https://www.dropbox.com/s/ctx7fl6o1f5e0zh/Video Sep 02, 11 46 24 AM.mov?dl=0
https://www.dropbox.com/s/2x3o9qasxcm0cgi/Video Sep 02, 12 57 05 PM.mov?dl=0
Thank you very much.
