Isuzu 4jb1 oil pressure (starts 60-70psi, gradually drops to 20psi)

[John V]

Hey, I just swapped an Isuzu 4jb1 into my Ihi excavator. 4jb1 manual says the oil delivery pressure is about 56psi. I have the machine hot wired to get it to run right now (big wiring mess to sort out), so I have an analog pressure gauge hooked up to read the oil pressure. First start up in the morning and it reads about 70psi. From there it gradually drops down as it heats up. After about 15-20 min, it steadily runs at about 20psi. Is this too low? What should I first look into if it's not acceptable? I did change the oil and filter after swapping the motor in.

Thanks,
John

 

[Kenskip1]

Hey, I just swapped an Isuzu 4jb1 into my Ihi excavator. 4jb1 manual says the oil delivery pressure is about 56psi. I have the machine hot wired to get it to run right now (big wiring mess to sort out), so I have an analog pressure gauge hooked up to read the oil pressure. First start up in the morning and it reads about 70psi. From there it gradually drops down as it heats up. After about 15-20 min, it steadily runs at about 20psi. Is this too low? What should I first look into if it's not acceptable? I did change the oil and filter after swapping the motor in.

Thanks,
John

How many hours are on it? What weight of oil is in it? How high does the water temperature get? If the water temperature gets to high this will make the oil thinner and pressure will drop. Can you hear any engine noises besides the obvious? Check the radiator for any obstruction. This could become a over heating issue and this will lower the oil pressure. Ken

 

[John V]

I’ll get an analog temp gauge this week and check on that. There is a minor leak at the thermostat but seems to be moving water well.

no obvious noises to me. It’s running well now that I’ve put an hour or so of use into it moving some dirt piles. It’s jury rigged together right now with a 12v remote start switch from harbor freight, and to turn it off I reach back there and toggle the fuel cutoff. The dash panel is missing on the excavator so no dials to read off.

I did an oil change with rotella t4 15w-40 and a Baldwin oil filter.
Unknown hours on the engine. I bought it from China as a used excavator engine (excavator spec genuine Isuzu engines are a bit rare on the used market).

 

[Vetech63]

I bought it from China as a used excavator engine

YIKES!!!

 

[John V]

For $1500 it's about your best option. Even doing a full rebuild on it is cheaper than buying a new aftermarket 4jb1

 

[Kenskip1]

Sir, From your description I would simply go ahead and run it. Any blow buy when removing the oil filler cap when hot? I would get the temperature and oil pressure gauges fixed so you are able to monitor the engines vitals.

 

[John V]

The filter cap pops around when unscrewed and left on the filler neck, but it's no worse than my other diesel engines. Still working on getting a mechanical temp gauge; assuming that is good I'll just run it. thanks for your advice @Kenskip1