buzzingrub
New member
Subject: Suzuki DF20A (EFI) Aggressive Hunting at High RPM & Hard Start - Pumps Replaced
Hey everyone,
I'm fighting a severe, worsening high-RPM hunting/surging issue on a Suzuki fuel-injected outboard (DF20A block platform). The motor drops and spikes RPM rapidly under load at wide-open throttle.
Additionally, the engine has developed a hard starting condition. It will not fire up or catch at normal starting idle speed. The only way it will start is if I advance the throttle lever far forward into high-RPM territory to clear the path.
Here is what has been done so far to troubleshoot:
Since the fuel delivery pumps are brand new and the engine won't start unless it's given maximum air via a cracked throttle plate, I suspect it's still pulling a major unmetered vacuum leak or there's a sensor conflict confusing the ECU.
Has anyone dealt with a hidden air leak or a specific sensor failure (like the MAP sensor or IAC circuit) on these EFI Suzuki port blocks that causes this exact high-speed hunting nightmare? Any advice on what to target next would be highly appreciated.
Thanks!
Hey everyone,
I'm fighting a severe, worsening high-RPM hunting/surging issue on a Suzuki fuel-injected outboard (DF20A block platform). The motor drops and spikes RPM rapidly under load at wide-open throttle.
Additionally, the engine has developed a hard starting condition. It will not fire up or catch at normal starting idle speed. The only way it will start is if I advance the throttle lever far forward into high-RPM territory to clear the path.
Here is what has been done so far to troubleshoot:
- Low-Pressure Fuel Pump: Brand new OEM mechanical lift pump (15100-89L21) installed. No change.
- High-Pressure Fuel Pump & VST: Brand new internal high-pressure pump assembly installed, meaning the micro-filter and the internal fuel pressure regulator are brand new.
- Primer Bulb Test: Squeezing the fuel line primer bulb vigorously while the hunting occurs does absolutely nothing to smooth out the surging loop.
- Air Intake System: Disassembled the intake silencer housing and found that the soft rubber silencer throat seal (13832-89L00) wrapping the wire flame arrester screen was badly bunched up, crushed, and rolled completely backward out of its track. This was causing a massive unmetered air leak bypassing the throttle body.
Since the fuel delivery pumps are brand new and the engine won't start unless it's given maximum air via a cracked throttle plate, I suspect it's still pulling a major unmetered vacuum leak or there's a sensor conflict confusing the ECU.
Has anyone dealt with a hidden air leak or a specific sensor failure (like the MAP sensor or IAC circuit) on these EFI Suzuki port blocks that causes this exact high-speed hunting nightmare? Any advice on what to target next would be highly appreciated.
Thanks!