PunchyTurtle
Cadet
- Joined
- Aug 4, 2023
- Messages
- 10
This is a 2005 50ELPTEFI.
It previously had been running fine but suddenly began having this surging RPMs issue. The video shows the issue pretty well.
The engine will run as normal and suddenly begin doing the surging at idle. Throttling up and getting up to speed causes the surging to stop. During throttling up, the surging continues until the engine reaches a medium RPM (I didn't specifically note a particular RPM) after which it flattens out and runs as-normal.
After throttling back down to idle, the issue will randomly occur after some time (either immediately or after minutes of idle time, though almost always after minutes of run time). The surging has never happened past about 3/4 throttle.
Also, before this surging began happening, the motor began dumping fuel out of the VST overflow after coming off plane two separate times. After we increased RPMs to maybe 1/4 throttle, the issue stopped. After some high-idle run time (we had to make it back to the ramp) nothing came out of the VST overflow after two times of idling for about 5 minutes after nearly full-throttle. This is what is really throwing me for a loop, because how can there be an excess of fuel in the VST while also clearly having starvation.
So far, I dug into the low-P fuel pump and found it to be quite corroded, and replaced it as a precaution, though I doubted it to be the issue or even contributing.
My immediate thought is this a fuel delivery issue. I have a pressure gauge that I will use to measure pressure on the VST later and will update.
I figured because this is a pretty unique set of symptoms, someone might have the golden ticket on what is going on and save me some headache on diag. Thanks ya'll!!
It previously had been running fine but suddenly began having this surging RPMs issue. The video shows the issue pretty well.
The engine will run as normal and suddenly begin doing the surging at idle. Throttling up and getting up to speed causes the surging to stop. During throttling up, the surging continues until the engine reaches a medium RPM (I didn't specifically note a particular RPM) after which it flattens out and runs as-normal.
After throttling back down to idle, the issue will randomly occur after some time (either immediately or after minutes of idle time, though almost always after minutes of run time). The surging has never happened past about 3/4 throttle.
Also, before this surging began happening, the motor began dumping fuel out of the VST overflow after coming off plane two separate times. After we increased RPMs to maybe 1/4 throttle, the issue stopped. After some high-idle run time (we had to make it back to the ramp) nothing came out of the VST overflow after two times of idling for about 5 minutes after nearly full-throttle. This is what is really throwing me for a loop, because how can there be an excess of fuel in the VST while also clearly having starvation.
So far, I dug into the low-P fuel pump and found it to be quite corroded, and replaced it as a precaution, though I doubted it to be the issue or even contributing.
My immediate thought is this a fuel delivery issue. I have a pressure gauge that I will use to measure pressure on the VST later and will update.
I figured because this is a pretty unique set of symptoms, someone might have the golden ticket on what is going on and save me some headache on diag. Thanks ya'll!!
