Unburned fuel in the air manifold

Engine failing to deliver load



Let me ask you if a top end overhaul had been completed on one of your engines, then it wasn’t able to take full load, you’d be questioning the engine overhauler, right?

That’s the situation we’ve been in and following the investigation, I thought it would be useful to share our findings as an extra check in case you have a similar issue.

Having changed the pistons and liners and rebuilt the engine, the preliminary checks were carried out and it was ready for test. Once on test, there were no real issues up to 50% load, but then that’s as far as it got.

To find out why, our engineer started by looking over the fuel system, the governor control system and air intake.

Whilst checking the air intake system, it was found that the air flap valve on one bank was closed, so the engine was running, but performance limited because of the lack of oxygen preventing ignition in the right bank.

Following further checks, it wasn’t the valve sticking, but instead, the inhibitor switch had been wired incorrectly, only allowing the engine to start with the right bank air flap in the closed position.

And the result of the lack of combustion was this… unburned fuel in the air manifold.

Unburned fuel in the air manifold


Having pumped out the unburnt fuel, and re-wired the switch, the engine was retested and successfully met all performance expectations on test.

On review, this issue hadn’t been picked up before and the electricians were resetting the flap (closing it) to be able to start the engine, which seems madness as a diesel engineer, but shows the importance of different disciplines working together, to get an overall understanding of the complete package.


If you’re after a trustworthy engine specialist with an excellent track record for your job, email us info@bartechmarine.com or call +44 (0)1206 673101.

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