Case cx160b no fuel pressure

I have been scratching my head on this for a while. We have a case cx160b in the shop with no lift pump pressure. So far I have tried multiple lift pumps, bypassing the tank and all the filters using a jerry can. Used all new hoses. I have put a new pressure relieving bolt in the lift pump lines. No luck.

If I block off the return line I can make it build pressure... the only part between the feed side and return is that bolt. I have tried 2 new ones. There has to be something stupid going on here I just can't find the problem.

This is all with the engine turned off so there is no draw on the feed side.

The original problem was the machine going into limp mode because of fuel starvation code 0087. It took out the high pressure pump so we put a new one on and we are still having the lift pump pressure problem. I feel like if this was a cat or deere it would have been fixed by now. But there doesn't seem to be to much out there on case.

Anyone have any ideas?

It sounds like you might be focusing too much on pressure. If that bolt is just a restriction, then you need volume to build the pressure. Do you have a spec for the lift pump volume? Any chance there's a screen in the intake that's still in the system in your tests, or when it's been running? Maybe it won't build pressure during testing but would at engine RPM.

Sorry, just general thoughts, I don't do newer stuff.

I have been toying with the idea that the pump isn't pushing enough volume. But I have tried multiple pumps all with flows over the stock pump.

The way I have it set up is jerry can, electric lift pump, pressure bolt, mechanical gauge, high pressure pump. There are no restrictions or even filters. I can get volume to the high pressure pump but no pressure. It isn't bleeding through the high pressure pump because I have checked the return from the common rail. If I pinch the hose between the gauge and the hp pump still no pressure. If I pinch the return line on the relief side of the bolt I build 14psi on the feed line to the pump.

The other though I had about volume was the banjo washers may let some fuel seep between the feed and return side. But clearance is pretty minimal. I have ordered new washers but the more I think about it I don't think this is going to fix the problem. The surface tension in the fuel should be sufficient to reduce losses to the return side with the clearance that is there.

I have attached a picture of the fuel relief bolt. Feed line comes in on the left then the supply line to the hp pump and on the right is the return to tank with the common rail billed off

Has this fuel starvation always been there or just appeared.
Looks like that fuel relief bolt may have a spring and valve under that hex head and depending on the way its set up, the pump feed and return lines may be on the wrong way around. Just a thought, as you have replaced relief
bolt with two new ones ,same result, unlikely to be all duds.

Someone else has done work to the machine so I don't really know what the original issue was. It came to us with a lack of fuel pressure.

The original Mechanic was a hack. He didn't time the cam and pump, bent a bunch of valves on the other machine.

I thought he might have switched the hoses also. But we went direct with the lift pump into the fees of the bolt. Took the bolt off and blew through it. It works as it should.

It sure seems like there's parts missing or assembled wrong...

As you mentioned earlier, possible fuel migration between pump feed and return banjos. New washers will seal the faces but there must be an o ring to seal one of those banjos to the relief bolt shaft to stop any migration. Any chance of a picture of relief bolt removed

I will take a picture of the bolt when I get to the shop tomorrow. I didn't see any oring in the parts diagram. Not that it means anything. The banjo washers just seemed loose. I think the spec on them is 10.4mm it is possible they were slightly oversize because they had some movement on the relief bolt.

This is a picture of the pressure bolt. There seems to be plenty of volume going to the pump and the return. But just 1 psi of pressure at the inlet of the high pressure pump.

There is no place that is apparent orings could be placed.

Does it make sense that 1 psi would be enough supply pressure to the hp pump?

I was thinking it could be a bad pressure sensor in the common rail after the hp pump sending a bad reading to the ecm. I would like to rule out the possibility of supply side issues before buying this as it is non serviceable. I would have to buy the whole common rail at about 600

10-12psi TO the HP pump..!!!

I take it when you blew through the bolt air came out the first holes just above the thread, and if you blocked those nothing came from the next lot of holes just under the bolt head.
I would try an o ring on the shaft of that bolt, quite tight in fit and compress it between pump feed and return banjos and see what you get.

You are correct.
I blew though the bolt at the bottom of the threads and air comes out the holes closest the threads. If I block these ports no air comes out of the ones closest to the heads. Blow harder and the relief will open and air will come out of the holes closest to the bolt head.

I tried all new banjo washers thinking they might fit a little tighter and stop any blow by on the bolt. Didn't work.

I put an oring in the banjo fitting but without a grove it won't stay in the right position to block fuel to the next fitting. If I use the oring in place of the banjo washer I don't think it will seal an external fuel leak.

An o ring in place of the washer will seal both internal and external leakage, as long as its big or small enough to be compressed between bolt and banjo internal bore by the other banjo, you may have to put a light counter sink
on those two banjos where they mate to get the compression onto the bolt shaft.

I have made some progress. I tested all the relief bolts and they open with only 1psi of air pressure. So I know that everything is OK as far as the supply system is concerned. So is this bolt supposed to be like this and the scv is supposed to regulate fuel into the hp?

When the machine is off and the lift pump is running i don't have any return from the hp pump past the scv.

I'm thinking maybe it's the hp common rail pressure sensor causing the issue.

Does anyone know for sure what the supply pressure to an isuzu 4jj1 should be? Just flow with minimal pressure?

We got it all taken care of. Still no pressure to the hp pump but apparently this is normal. All the tests want volume without pressure.

The issue ended up being a bad common rail and pressure sensor in the common rail.