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GT 40 Loss of Power/Surge at WOT
Experienced loss of power/engine surge when attempting WOT beyond 3500 RPM. Ultimately, the e-coil was the issue. I picked up a replacement at Advance Auto [part # 26C1038) for less than $40. Engine runs like new, has no issues at 4500 rpm and is smooth throughout acceleration. I am definitely not a mechanic and have very little experience beyond oil changes. The posts on this site are 100% the reason we are enjoying our old ski Nautique. I thought I would list some of the diagnostics/errors I made while repairing so someone else my be able to avoid and get back on the water.
Initially, I believed the symptom to be fuel related.
- changed fuel filter, it was dirty, but not terrible
- inspected FCC for leaks [none]
-replaced fuel pump relays [had spares] no change
-check fuel lines back to the anti- siphon valve, no issues
- checked fuel lines from low pressure pump to high pressure pump. [no issues]
- checked fuel pressure regulator at the rail [no issues]
-checked fuel pressure at the rail. +/- 35 PSI at idle, 40 psi at WOT
-ran sea foam and high octane fuel, no change
- put long screw driver on injectors to feel firing. Found one injector that was not firing [cleaned injectors and replaced one] surge/loss of power continues
***error at this step. During removal of the fuel rail, I had to remove the intake manifold. The ECM mount is partially secured with one of the bolts on the intake manifold. While manipulating the plate, I must have moved the wires under the mount, which connect to the starter solenoid. I was unaware and during subsequent water test, the engine would not shut off. The ONLY way I could kill the motor was to remove the spark plug wires. I had to take off 6 before the engine killed!
With the replaced injector, the engine defiantly came alive, but the loss of power was still prevalent. I could bring the engine slowly up to 3700 RPM and it would stay there fine. But if I went right to WOT, it would stubble along the way. It felt like it wanted to get there, but just didn’t have enough.
- I have spare ECA, replaced and the condition continues
- replaced MAP sensor, problem continues
-tested throttle position sensor, no issues
-tested idle air controller, no issues
- while replacing MAP sensor, I looked at the ignition coil and could see rust under a covered portion of the coil.
- before the start of the season, I replaced the cap and rotor, did not check, but was headed in that direction
-replaced coil, ENGINE RUNS PERFECT!!!
**The engine would rev in neutral easily to 4500 RPM. The hesitation was only present under load and beyond 3500 RPM. I was unable to see anything out of spec on a bench test of the coil. It definitely looked like it was time to replace once the cover was removed. My theory it that under load, the field was interrupted by corrosion and the rust would make a connection to the outside of the coil.
Initially, I believed the symptom to be fuel related.
- changed fuel filter, it was dirty, but not terrible
- inspected FCC for leaks [none]
-replaced fuel pump relays [had spares] no change
-check fuel lines back to the anti- siphon valve, no issues
- checked fuel lines from low pressure pump to high pressure pump. [no issues]
- checked fuel pressure regulator at the rail [no issues]
-checked fuel pressure at the rail. +/- 35 PSI at idle, 40 psi at WOT
-ran sea foam and high octane fuel, no change
- put long screw driver on injectors to feel firing. Found one injector that was not firing [cleaned injectors and replaced one] surge/loss of power continues
***error at this step. During removal of the fuel rail, I had to remove the intake manifold. The ECM mount is partially secured with one of the bolts on the intake manifold. While manipulating the plate, I must have moved the wires under the mount, which connect to the starter solenoid. I was unaware and during subsequent water test, the engine would not shut off. The ONLY way I could kill the motor was to remove the spark plug wires. I had to take off 6 before the engine killed!
With the replaced injector, the engine defiantly came alive, but the loss of power was still prevalent. I could bring the engine slowly up to 3700 RPM and it would stay there fine. But if I went right to WOT, it would stubble along the way. It felt like it wanted to get there, but just didn’t have enough.
- I have spare ECA, replaced and the condition continues
- replaced MAP sensor, problem continues
-tested throttle position sensor, no issues
-tested idle air controller, no issues
- while replacing MAP sensor, I looked at the ignition coil and could see rust under a covered portion of the coil.
- before the start of the season, I replaced the cap and rotor, did not check, but was headed in that direction
-replaced coil, ENGINE RUNS PERFECT!!!
**The engine would rev in neutral easily to 4500 RPM. The hesitation was only present under load and beyond 3500 RPM. I was unable to see anything out of spec on a bench test of the coil. It definitely looked like it was time to replace once the cover was removed. My theory it that under load, the field was interrupted by corrosion and the rust would make a connection to the outside of the coil.
Attached Files