I have a 1998 SR 330 EC with the merc horizon 454's and I've noticed when I start the boat both engines are dumping fuel out the exhaust last about 5-10 minutes and goes away..if I take a a couple hour ride and then shut the boat off and restart it after it sits for awhile their is no fuel in the water.. I've replaced the coolant system on both engines, also the risers and manifolds. The oil is clean, spark plugs aren't burnt or black.. I've read that the "engine coolant temp sender" could be a culprit. But before I start buying parts I'm wondering if anybody else has experienced this issue. thanks
running rich at start up need HELP!
- Thread starter mleone101
- Start date
JHornsby3
Well-Known Member
- Nov 10, 2020
- 1,392
- Boat Info
- "Steele'y Tutz"
1992 300 Sundancer
- Engines
- Twin 4.3L W/Alpha One Gen II
Have you checked the choke system? Sensors and such that provide the signal to the cold start. Most of the sensors can be checked for their resistance/ correct operation. A low cost to start out with.
would fuel injected motors have a choke system?
JHornsby3
Well-Known Member
- Nov 10, 2020
- 1,392
- Boat Info
- "Steele'y Tutz"
1992 300 Sundancer
- Engines
- Twin 4.3L W/Alpha One Gen II
It will have a higher idle at start up like a choke. All run by sensors and ECM until the motor warms up some. Sorry if I confused with "choke". But it will act as such.
Ericinmich
Active Member
- Dec 12, 2021
- 213
- Boat Info
- 48 Sundancer, 2007... formally PapaG's
- Engines
- Cummins
Assuming it's EFI/MPI, there are a few things that could cause the engine to run rich. Has any work been done recently (may point in a direction). Do you have a way to check codes or read data?
Engine Coolant Temp, sensor/connector/wiring. Plug in and read data from ECM would tell you if this is it.
MAP sensor, less likely. If it's reading a high MAP, then it will fuel accourdingly.
I'd find a way to read data from ECM.
<edit for not reading OPs post on rebuilding>
If it's running rich after your work, then I would look at that work!
These vintage of EFI systems run open loop, no feedback from O2 sensors. They also don't have a very smart diagnostic system. For example, if you don't have the MAP sensor hooked up correctly (wiring short, etc) then it defaults to a TPS based speed density controls which very well would be rich to keep the engine safe from lean conditions. If this was happening, there would be a code set.
I'd suggest (again) reading the ECM data and codes, it should point you in the correct direction. There may be a way to read fault codes by a jumper or LED across the connector. I'd need to know which ECM system boat has, etc... and google it (memory of each version of ECM has been displaced by more important stuff.. or got old).
(FYI, 30 years in auto ECM controls... actually had responsibility of a couple of marine ECMs in the late 80s to early 90s.)
Engine Coolant Temp, sensor/connector/wiring. Plug in and read data from ECM would tell you if this is it.
MAP sensor, less likely. If it's reading a high MAP, then it will fuel accourdingly.
I'd find a way to read data from ECM.
<edit for not reading OPs post on rebuilding>
If it's running rich after your work, then I would look at that work!
These vintage of EFI systems run open loop, no feedback from O2 sensors. They also don't have a very smart diagnostic system. For example, if you don't have the MAP sensor hooked up correctly (wiring short, etc) then it defaults to a TPS based speed density controls which very well would be rich to keep the engine safe from lean conditions. If this was happening, there would be a code set.
I'd suggest (again) reading the ECM data and codes, it should point you in the correct direction. There may be a way to read fault codes by a jumper or LED across the connector. I'd need to know which ECM system boat has, etc... and google it (memory of each version of ECM has been displaced by more important stuff.. or got old).
(FYI, 30 years in auto ECM controls... actually had responsibility of a couple of marine ECMs in the late 80s to early 90s.)
PlayDate
Well-Known Member
Did it do this prior to you replacing the manifolds and risers?
