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Discussion Starter #1
I just finished the install of a reman 7.3 engine into my 2000 Excursion. I've gone through all the pre start up steps and am not getting any oil pressure at all. Have cranked the engine for ~10 seconds at least 12 times and still do not have any oil pressure. I installed a manual pressure gauge into the port near the oil filter and it does not register any pressure. I've filled the res and it stays relatively full, in that it doesn't drain.

Could a bad IPR cause a no oil pressure at all condition? Where could the issue be? I also suspect the LPOP but would think it was replace with new one when the engine was rebuilt.

I seem to be getting oil circulation, in that the oil passages seem to be getting oil, at least the port where I plumbed the pressure gauge was running oil out when I pulled the plug.
 

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Did you pack the pump? Any issues with the pickup tube connection? The IPR default is open which will bleed off pressure, but it shouldn't bleed so much that it prevented all pressure from forming. Did you fill the HPOP?


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Discussion Starter #3 (Edited)
I don't believe there were any issues with the pickup tube but it does concern me.

I did fill the HPOP and it stays full. The engine acts like it wants to start but I'm hesitant to push it further until I can verify that I have low oil pressure.

What do you mean when you ask if I packed the pump?

Could I get any circulation if there was a problem with the pickup tube. If it was a pickup tube issue there wouldn't be oil in the system would there? When I open the port by the oil filter oil pores out. I wouldn't think there would be oil in the passages of the engine if it couldn't pick up oil.

Could the LPOP circulate oil yet not build enough pressure to register on a pressure gauge?

If it circulates oil but doesn't build pressure, what component in the system would allow/cause this?
 

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I don't think the LPOP could work and generate no pressure reading. I always pack the pump with petroleum jelly to help prime the pump. How did you tighten the HPOP pulley.


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The 7.3L has a two-part oil system.
Low pressure is supplied by the LPOP to the bearings, piston oil jets, lifters, and the HPOP reservoir.
The HPOP takes the oil from the HPOP reservoir and boosts the pressure and delivers it to the injectors. It depends on the IPR to close off a relief port to be able to build pressure, and if you don't get over 500 psi on the HP oil system, the engine won't start. But if the HP oil system hasn't been primed with oil (on the high pressure side of the HPOP - meaning the oil rails in the heads), then it'll just be trying to compress the air in the system. It may take a long time cranking if the rails are totally empty of oil. What I usually do on an injector replacement (which drains the oil rails) is to leave the glow plugs out and crank the engine with the starter till I feel/hear the HPOP load up. That's an indication that the air has been bled out.
The other problem may be with the IPR or ICP sensor. If the sensor isn't sending a good signal to the PCM, it may not control the IPR correctly, or if the signal isn't getting to the IPR, it won't close off.

I would recheck all your wiring connections on the engine harness, and maybe try cranking with the ICP sensor unplugged. That will make the PCM use a default signal to control the IPR.

Don't worry about damaging the engine. If there's no oil getting to bearings, etc, there won't be oil to the HPOP and the injectors won't fire. But be careful about overheating your starter by cranking too much without letting it cool off.
 

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Discussion Starter #6
I filled the HPOP res and cranked the engine multiple times until the res stayed full and didn't drain while the engine cranked. This took about 5 cycles.

I then cranked the engine for 10 - 15 seconds while looking for oil pressure to build. I would then let the system rest for ten to fifteen minutes to recharge and cool down. I did this step another 6-8 times but never got LOW oil pressure from the LPOP. The oil level in the HPOP res stayed full, I never had to add oil to the res again. But never registered any oil pressure on the LOW system. I'm not even ready to make sure the HPOP system has High oil pressure. I want to get over the low oil pressure hurdle first.
 

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Discussion Starter #7
So If the IPR was not behaving correctly could it cause a no LOW pressure condition? Where the LPOP can circulate oil but not build pressure?
 

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Discussion Starter #8
Is there a component in the engine or heads that could be left out during the rebuild that would let the LPOP circulate oil but not build oil pressure?
 

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If you're not getting oil pressure from the LPOP, that's a problem. Are you measuring it at the port on the HPOP reservoir or down on the filter housing? You might try to prime the LPOP by pulling the quick fill check valve in the valley below the fuel bowl toward the driver's side. Pull the plug and the check ball and spring and pour some oil into it with a funnel. That would fill the pump and the lifter gallery IIRC. The other thing you could do is overfill the pan by about a gallon and jack up the rear of the truck. That submerges the entire pickup tube and is the way that the service manual says to check for aerated oil caused by a cracked pickup tube.

There's a pressure relief valve in the oil filter housing that would lower pressure, but I think there would still be some pressure and circulation built up. Another thing might be one or more piston oiling jets left out, although in early engines they used to break off on occasion, and there weren't serious problems other than the jet rattling around in the oil pan. I would think that the rebuilder would have checked those.

If there's oil in the HPOP reservoir, it should be picked up by the HPOP and delivered to the injectors. If you can't get it to fire off, there may be something wrong on the HP side. You should try pulling the ICP sensor plug off and see if it will fire off. If it can run for even a few seconds (at faster than cranking speed) it may get the LP system primed up to build pressure.
 

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Discussion Starter #10
Thanks for the information.

First, I tested the sending unit on the HPOP res to verify it was working. I then testes the dash gauge to verify it was working as well. Both are working. I then tapped into the port on the filter housing with a mechanical oil pressure gauge for a second reference. I am not getting any pressure from either location.

I will do the things you recommend today and see what happens.

After cranking it about ten cycles I replaced the fuel pump fuse and cranked it to see if it would build enough high pressure to fire. It acted like it wanted to start but didn't. I didn't go any further with it but will try and get it to fire and let idle a few seconds to see if low pressure builds. Everything I've read tells me that it should build low pressure while cranking so I am a bit hesitant to start it until I can verify low pressure.
 

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You might try to prime the LPOP by pulling the quick fill check valve in the valley below the fuel bowl toward the driver's side. Pull the plug and the check ball and spring and pour some oil into it with a funnel. That would fill the pump and the lifter gallery IIRC.
Correct me if I'm wrong, but I'm pretty sure that's in the hpop reservoir

The other thing you could do is overfill the pan by about a gallon and jack up the rear of the truck. That submerges the entire pickup tube and is the way that the service manual says to check for aerated oil caused by a cracked pickup tube.
Definitely try this. Also look at the oil pan itself to see if it looks bent. Being a used engine, it could've been dropped on the oil pan.

There's a pressure relief valve in the oil filter housing that would lower pressure, but I think there would still be some pressure and circulation built up.
I would think if it was stuck closed, it could cause a no pressure situation. But I would try the overfill and Jack up the rear before pulling the oil cooler. Could also just drop the filter and crank it.
Points above are in bold.

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Discussion Starter #12
I cranked it this morning and she started up. I let it idle, very rough, for about 5 seconds... still no low oil pressure.
 

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I cranked it this morning and she started up. I let it idle, very rough, for about 5 seconds... still no low oil pressure.
The rough idle is pretty normal, because of air in the HP oil system, but if you're still not getting LP oil pressure (low oil pressure light still on, dummy gauge on the dash not registering, and your gauge not showing any) then you need to try the overfill/elevate the rear end test. You may still need to pull the engine and oil pan and investigate. :frown2:

79Jasper, the quick fill check valve isn't in the HPOP reservoir, but under a square recess plug in the front of the valley in the block proper. It lets oil thru a separate passage in the front cover into the reservoir. If you look straight down below the fuel return line connection on the fuel filter bowl, you should be able to see the plug.
 

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Discussion Starter #15
I wasn't able to get to any of it today, daughter had a gymnastics meet that took the whole day. I'll investigate the oil pickup tube issue first thing in the morning. In the event it is an oil pickup tube issue, would I be able to get the oil pan off by raising the engine or do I have to pull it? I have a 4wd and it looks like there might be enough room to raise the engine and remove the pan.

Should I fill through the quick fill plug before I do the oil pickup test?
 

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Should I fill through the quick fill plug before I do the oil pickup test?
Might not hurt, but probably not essential.

Some guys have had some success pulling the pan with the engine in the truck, but the problem is that it's stuck on with RTV and that's tough to get off and get cleaned up. Also, the pan and block surfaces needs to be clean and oil free to put it back on the factory way with the RTV. That's probably not going to happen (the oil-free part) with the engine upright. The service manual recommends doing it with the engine upside down, letting it cure for 24 hours.
I believe there is a conventional gasket set available now for the 7.3L, so that would solve that problem. But you'll still have to fight it with the crossmember in the way.
 

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Before you do any more work - let's take a step back. Since we all know a 7.3 will NOT run with no oil pressure, let's explore that. My first thought is your measuring port. There are two ports in the area of the back cover. Can you take a picture of where you have the line? I'm attaching one below. If you have your pressure gauge on that back port, you won't get any reading as that's just a return port.

oilline.jpg
 

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Discussion Starter #18
I attempted another start this morning before attacking the oil pickup check and the oil pressure did came up to normal level. I don't get why it took so long to get oil pressure. From everything I've experienced and read the oil pressure should come up relatively quickly. I'll definitely be keeping my eyes on the oil pressure for a while with this engine.
 

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Discussion Starter #19
I can get the engine to fire and idle rough. Have had it idle a couple of times for about 10 seconds. I am now getting both fuel and coolant dripping from the rear area of the right head. Any ideas of what could cause that? It's a pretty good amount, not a stream but enough to hear it dripping and see it dripping after I shut it off. I doesn't occur during cranking only after it idling.
 

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Is it in the valley or the outer part of the head? Pick one fluid and start investigating. Clean the area where the fluid is and restart the truck. Use clean paper towels and isolate the origin of the leak. Take pictures and post if it isn't obvious how to repair.


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