View Full Version : Low pressure error on Diesel

11-13-2013, 11:16 PM
Not exactly "Transportation" but figured this was the best spot to ask a Diesel engine question.

We don't have to run our diesel genset a lot any more. So honestly it's sat for a good while without needing to be run.

It's China Diesel/ Hardy Diesel 12KW 295 engine diesel generator. It has the "Murphy Switch" on it.

That began reading "low pressure" and the pressure gauge was a good bit lower than normal.

Knowing next to nothing about diesels, where do I begin? Fuel system?

11-14-2013, 11:35 AM
If it's feul injected, there are two feul pumps. One is low pressure (from the tank to the engine), the other is high pressure (to the injectors). I've never had a 'low pressure' on a diesel, but my best guess would be one of the pumps. What's the brand of the genset?

11-14-2013, 11:41 AM
It's an old school Hardy Diesel, aka "China Diesel" back in the 1990's.

I'm gonna clear the fuel lines into a 5 gallon bucket, check the fuel filter and try that. Pulling a pump might be beyond my mechanical capacities.

If it is the fuel pump, I'm assuming they are repairable?

Looked on Hardy Diesel website last night and they don't even carry these models any more.

11-14-2013, 01:08 PM
The only other thing I could think of is oil pressure. How long has it been since the oil was changed? Correct viscosity?

Putting a feul or oil pressure guage on an engine is not too hard. You can pick either of them up pretty cheap at a local car parts store. They both come with pretty good installation instructions.

11-14-2013, 05:00 PM
Is it something you put inline? The pressure gauge I mean.

I should post a pic, that might help. There is some gauges that show pressure.

11-14-2013, 07:55 PM
Is the engine running up to speed, and generating 115v? Could be a couple of small things combined...

11-15-2013, 11:33 AM
Is it something you put inline? The pressure gauge I mean.

I should post a pic, that might help. There is some gauges that show pressure.

Pics and also see if the company still sells parts for it.

11-15-2013, 04:31 PM
1) Oil pressure. On most engines, there is an oil pressure sensor screwed into the block with two wires attached to it. To replace it with a guage, unscrew the sensor and screw in the sending unit for the guage. It has a pipe (either copper or plastic) that runs to the guage (mechanical setup).

2) Fuel pressure. That goes inline after the low-pressure fuel pump in in the fuel line.

Fuel Pressure Guage...inline with fuel line.

Oil Pressure Guage. Notice plastic line and sending unit that screws inot the block.

11-18-2013, 11:37 AM
Thanks for all the help.

I got it running well yesterday.

Just went through that building re-organizing things and putting wires that were run helter skelter over the years into flexible conduit. So I'm guessing that possibly this is the problem that caused the next problem-

Meters on inverter showed the hertz correct from the generator, once they synched the AC1 in showed 115 from the generator, yet no power seemed to go in to the battery bank. Voltage on bank showed 24.5 the whole time. Usually it starts immediately shooting up and puts a float charge in the bank in no time (Genset is 12KW).

However the voltage never changed on the bank. Genset showed correct hertz and once they synched, correct voltage.

Only thing I'm questioning is perhaps the comm wire between the inverter and the murphy shut off and gauges on the genset wasn't connected correctly. When it's not connected at all, the genset and inverter never synch.

11-18-2013, 09:54 PM
Gonna take this time also to upgrade and improve some things on the genset also.

Looking for the quietest muffler I can get and thinking of changing out the old radiator.

The engine part is working out fine, but there are some things in the exhaust and cooling parts I'd like to work at.

11-18-2013, 09:57 PM

This is the old gal.

11-19-2013, 09:29 AM
Thanks for all the help.

I got it running well yesterday.

So, did you figure out what was causing the low pressure error? Inquiring minds want to know ;)