What is this noise, engine starts to die when it happens

[Brutacus]

I have an M818, which has the Cummins NHC 250. It idles fine at around 550 to 600 rpms, then a strange ticking sound starts and the engine rpm's drop to around 400 to 350, sometimes it just dies. I can hold my foot on the accelerator to keep the rpms up, then without notice the ticking will stop and the engine will idle normally. After a minute or two the noise will start again, and rpms drop with it. It keeps coming and going as if it is in a cycle. I thought it was the oil pump going bad, but my pressure stays at 80 psi when idling, and goes up from there. I have no idea what it could be. Any ideas would be appreciated. Thankx

 

[simp5782]

Post a video of it.

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[162tcat]

Probably the air compressor


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[grunex125]

agreed, air compressor would tick like that. not sure about pulling the rpm's down though, shouldn't do that unless maybe too high of pressure on the tank? Does it pull the rpm's down only when it's cold?

 

[Brutacus]

It pulls the engine down when it's warm, hot, or cold. I don't know if the pressure is high or low on the air tanks. My gauge has a very sticky needle, but it never makes it up to 120 psi. That's probably a gauge that need replacing. I have a new/spare air pressure regulator. I don't know if that's the problem though. I'll replace that and see if that fixes it. If it's the air compressor, how hard is that to fix?

 

[fuzzytoaster]

Air compressor for sure. It shouldn't be lagging the engine down enough to stall it, check your fuel filters and feel the temp of the compressor. If the compressor is going it may be hot to the touch.

 

[plym49]

I guess you can just loosen the outlet from the air compressor to see if anything changes.

 

[162tcat]

If you have an air leak in your fuel line or very dirty filters, the air comp will do that. Is it like that hot and cold or does it get better once the engine is warmed up? Does it do that after you have driven it? Does it stall or drop way down when you put it in drive versus neutral?


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[74M35A2]

Compressor sounds excessively difficult to rotate. Remove and inspect.