Cat D5G oil pressure problem

[Ncjetskier]

Serial number MHK07347

My oil pressure normally reads 40 lbs while working the machine. Now the gauge is pegged to the highest reading. The machine runs fine without any problems.

I changed the oil today and before even starting the machine (the machine had not run at all today) the oil pressure was almost as high as it can go - this was just turning the key but not starting the machine - just after changing the oil. Something must be stuck (sensor?).

The first picture is the gauge after just turning the key (machine not running). The second picture is the machine running.

Can someone give me some help in where to start to pinpoint the problem. Thanks!

 

[Nige]

before even starting the machine (the machine had not run at all today) the oil pressure was almost as high as it can go - this was just turning the key but not starting the machine - just after changing the oil. Something must be stuck (sensor?).

Electrical problem by the sounds of it. I think the oil pressure on those runs off a sender and IIRC disconnecting the wire (or a broken wire) will peg the gauge at maximum.
Do you have an electrical shcematic.?

 

[Ncjetskier]

OK, so I downloaded the service repair manual (all 6700 pages). Needless to say it is not much help. Can someone give me "short bus" instructions on what to check and where? I am not very good at reading electrical schematics. Thanks for any help!!!!

 

[heymccall]

#9 is oil pressure sender for gauge.
#7 is oil pressure switch.

You fault is at #9. Disconnected, gauge goes one way. Grounded, gauge goes other way.

 

[Nige]

I am not very good at reading electrical schematics.

Well in that case you need to learn. They are not hard to understand once you can comprehend the basics behind them. Cat schematics are some of the best available.

Post a Serial Number so I can locate the correct one.

 

[Ncjetskier]

Serial number MHK07347

 

[Nige]

Serial number MHK07347

Sorry, should have mentioned that is the engine Serial Number, not the machine. Electrical schematics are identified based on machine S/no.

 

[Ncjetskier]

IS it possible to get the part numbers for the pressure switch parts? The diagrams really help!!

 

[Ncjetskier]

Aaah ok, I need to go back to the machine and look that up.

 

[Nige]

IS it possible to get the part numbers for the pressure switch parts?

Again, a machine S/No is the key. There are different electrical schematics for D5G and it depends on S/No which one is the right one.

 

[Ncjetskier]

I will look at the engine tomorrow. Is it possible to take the two switches out and clean them with "brake cleaner" and re lubricate them to get them to work?

 

[heymccall]

RGK01401

 

[Nige]

I will look at the engine tomorrow. Is it possible to take the two switches out and clean them with "brake cleaner" and re lubricate them to get them to work?

I wouldn't have thought so, although the possibility exists you could have an dodgy electrical connection rather than the sender itself being on the fritz.

RGK01401

Thank you. Schematic on the way to the OP.

 

[Ncjetskier]

Engine serial number MHK07347

Ok, so I took the wire off the sending unit. The gauge went to zero. When I connected the wire to the engine block (ground) the gauge went to the max reading (over 80 PSI).

When I reconnected the wire to the sending unit, the gauge (briefly) read 40 PSI before going to the maximum PSI again.

BTW Thanks for the email!!!! Now I need to educate myself in reading schematics.

 

[Nige]

Bad sending unit - replace.

 

[Ncjetskier]

Would the part number be the same as listed in the email - based on the engine serial number being different? Thanks for all the help.

 

[Nige]

Would the part number be the same as listed in the email - based on the engine serial number being different?

It will be the same, but the Part # has been updated. I just pulled the number off the electrical schematic originally, never checked if it was current.
155-4032 is replaced by an improved Part # 295-0759

 

[Ncjetskier]

GREAT! Thanks so much for the help. Now I know I won't blow the motor until the new part comes in. Again, thank you for all the help!!

 

[Ncjetskier]

OK, I try to reply what the final outcome is when I have a problem. I replaced the oil pressure sensor and the high pressure reading remained unchanged. I ordered a new gauge and that fixed the problem and the pressure reads as it should. Thanks