Piston compressor starts up then trips

Questions & AnswersCategory: GeneralPiston compressor starts up then trips
Guest Staff asked 2 months ago

Here in estyrenics plant we have an air compressor (diesel). When it starts up, it works for 5 seconds then trips and giving pressure fault. It trips when it actually start to compress. The solenoid valve on the second stage opens when I start up and when it compresses the solenoid closes then opens again when the compressor trips. I don’t know if it’s normal or no, or what is the problem?

1 Answers
Cas Staff answered 2 months ago


It looks like this compressor monitors the outlet pressure, and when the pressure doesn’t increase when the compressor starts, it gives an error (because something must be wrong).

So please check if there is any pressure built up during those 5 seconds?

What can also happen is that the pressure sensor is broken, that’s why the compressor gives this error, because it thinks that there’s no pressure.

The fact that the solenoid opens, then closes and the opens is normal I think.

At first, it’s open because the compressor is starting up (blowing off any pressure, to make for an easy start).

After that it closes, so the compressor starts to built pressure

But there’s an error, so the compressor stops again and the pressure is blown off (solenoid open).

So please check what I said in the beginning: is it building pressure? And check the pressure sensor.

Good luck! And please let me know the outcome!


Guest Staff replied 2 months ago

Dear Cas,
I think the problem is not with the compressor.

When i put the key in the start panel of the diesel engine and make contact then start, the compressor works for like 10 seconds then it stops and give me an error in the panel (Pressure Fault).
I also tried to make contact without starting, and again after 10 seconds the pressure fault come again and i can’t start the engine again.i opened the panel and tracked the pressure fault alarm to find it connect with another wire called (oil pressure timer)

So, i changed the oil and the oil filter and the same result every time i try to start the engine (10 seconds then it dies again and the pressure fault alarm works).i wait your respond

Cas Staff replied 2 months ago

Hi,Maybe the alarm is coming from the engine oil pressure?It’s common for a diesel engine to have an oil pressure sensor/switch, together with a timer.. During engine start, there is no oil pressure but after a few seconds there should be oil pressure. If not, the engine will shut down to prevent damage.If we assume for now that it’s the engine oil pressure, it can mean two things:1) There really is no engine oil pressure: Check the oil level in the engine, check the oil filter, if possible, check the oil pump, etc.2) There’s some sensor or electrical problem.Probably, the engine has an oil pressure *switch* (not sensor). It simply switches from ‘open’ to ‘closed’ when a pre-set pressure is reached.For testing (and testing only!), by-pass the oil pressure switch by connecting the two wires together. Check if the alarm still comes up. If not. Quickly shut down the engine yourself, to prevent any damage if there really is low engine oil pressure.But then you know at least where the alarm is coming from.(you can also check the switch by connecting a multimeter and see if it closes when the engine starts, if it does, it means the oil pressure is OK and the switch is OK).
Maybe the pressure is OK, and the pressure switch is OK, but the problem is with the timer. If you by-pass the oil switch, but the timer still gives and alarm, then probably the time is the problem. Or the wiring between the timer and the sensor.Long story 🙂 Hope this helps.. please let me know, I am curious what the problem is/was…

Guest Staff replied 2 months ago

Dear Cas,The diesel is working now ! At first, i removed the cable of the oil pressure sensor to stop the signal coming from it.

Then, we started the engine and it worked well. So, we took the sensor and cleaned it then start again.It worked normally with no problem.
I thank you for the advice.