Hi all,
I have a 1996 E350 7.3l. The engine has about 160K on it. Recently one of my employees was not checking the oil on the truck and ran it dry. (It has a small rear seal leak) so over time it became bone dry. Anyhow the engine is now semi seized. It will start only on ether (GP's Disconnected for the ether) but takes a long time to start and has a loud knocking noise and runs really rough. My first thought is maybe a bearing or two on the crank has seized, but I can't seem to tell if its bottom end or top end. Without pulling the engine and tearing it down is there a way I can narrow if its Bottom end (crank) or cam or valves. I want to avoid pulling the engine at all cost and my goal is to possibly change a bearing if its bad from in the truck? I know I should rebuild it, but I only need another 25K out of this truck and its a bucket truck so I don't want to junk it just yet.

 

I doubt its the bottom. These truck will shut down way before the crank runs dry

 

Does it sound like two hammers hitting together ?
You oil leak is most likely on the top draining down the back of the block.
How long have you been starting it with starting fluid ?

 

Yes it sounds like two hammers hitting together. Any idea's?

Never got to look fully into the leak so that could very well be.

Starting fluid I just used it recently, but again with the GP's disconnected and its diesel starting fluid.

 

Your knocking could be the injectors from low fuel pressure which can cause rough running.
If the oil was run that low then you could have air in the oil system.

I'd start with checking the fuel pressure.

 

Thank you, I will check this out once I get back to the truck and let you know. Is there a way to bleed the air? Run it and crack the line slightly?

 

Run it like you stole it to get the air out and it takes awhile.

Once I lost all my oil because my oil pressure line to my gauge broke. The computer is designed to shut the motor down before any damage occurs!

 

Actually, it's not the computer. It's the mechanical design of the engine that shuts it down before damage occurs. When the oil level drops too low to supply the HPOP, the HPOP can't supply sufficient injection pressure to fire the injectors. So even if you could fool the PCM about the injection pressure and "convince" it to fire the injectors, they wouldn't shoot any fuel and the engine would stall. Still, it means it's virtually impossible to do bottom-end damage to these engines.

 

You guys are giving me hope. This weekend I will give it a whirl. I wonder how long it will take to clear the air

 

So did you add oil to the full mark after all that?

 

Yes, I added the oil........ I closed the gate after the horse left the stable

 

It seems different for different vehicles. Mine never took too long to clear out, but I haven't had as much as you might have gotten. The "drive it like you stole it" adage seems to be the correct way to purge it, though.

 

After reading your post I’d agree as well it highly unlikely your bottom end, and would also suggest its probably not the top end either. Like others mentioned when these trucks run down 7 or 8 qts low they will shut off, and it’s simply due to the sump being above your low fill level. It’s unable to supply oil up to your HPOP, which cuts it off to your injectors, and in simplicity of a 7.3 Heui injector, your oil is its fuel to fire diesel into your cylinder, without oil its kinda like a car out of gasoline. Yes you can suck in air, but I personally wouldn’t think its causing the clacking you speak of. Only when the rails are drained have I heard this and its not for long, or at least that’s the case for me, usually hiccups and stutters but doesn’t become prominently loud.

I had an oring issue on my injectors that was so bad that it caused my truck to pass almost 7-8 quarts of oil into the fuel in less than 40 miles of driving. I thought it was mixing with my coolant or burning out the tailpipe via a turbo leak. Well it was burning out the tail pipe! I was burning it directly in the cylinder. After 5 or 6 iterations of this and a ton of T6, I pulled the injectors and sure as **** it was the orings. I noticed I was getting high to mid twenties for gas mileage though. Problem solved.

What I’m getting at is in the 5-6 times this happened, the truck tripped a CEL till it would become so sluggish that there was next to no throttle response and it would finally die. I’d fill it up with oil, and she would fire right over, no clacking, and we would be on our way under full power as if it never happened. So from my experiences I’d say no on the air in oil, but that’s me. Yes air in the oil will cause a clacking, but from my experience when running the truck out of oil this has never happened to me.

Now if you are starving injectors out of fuel, holy crap does it sound like every valve is slapping the top of each piston, or a bag of rocks just was dumped through the intake.

Easiest place to start is at your shrader valve on your fuel bowl. Check it to get a fuel pressure reading, it looks just like the shrader valve on your tire valve stem, you can use a tire gauge. Should see nothing less than 50 psi at idle. It will pulse a bit as well since it’s a mechanical pump. If you check out there then I’d check you filter and make sure it’s not completely cruded up. Check your fuel lines going to the bowl to see if they could be cracked sucking in air to your fuel. I would then assume you are getting oil and fuel correctly to your injectors and would move on to the electrical aspect. Most common problem are the pig tails, valve cover gasket plugs, and under valve cover harnesses that plug from the valve cover gasket to your injector. If any of these plugs are melted or shorting, it will cause injector misfire than can sound as bad as hammer smacking the top of a head. It sounds horrible.

The fact you are not getting her to fire under glow plugs may be due to a few of these connections melting and shorting, Glow plugs may be fine, but can only be tested by ohming them all the way through the harnesses back to your IDM.

Hopefully this is an easy check, at least a cheap place to start if anything. If all doesn’t check out after a solid 50 miles of driving to purge any air in oil per say, then get back to us and we can go from there…

 

Like Dan said, they are all different. Mine took 180 miles to get the air out.

 

Thank you for the information. After you mentioned to check the harness for the valve cover I realized that I posted in the wrong year. I have four of these vehicles from all different years. Mine is a 93 so I appologize this should have been posted there. The banging noise is so loud so maybe it did run dry of fuel I will check. I converted the low pressure mechanical pump a long time ago to electric so maybe that blew a fuse and is starving her of fuel. The glow plugs have always been an issue with this truck. I literally replaced EVERY EVERY component including wiring harness, controller several times and tried EVERY brand of glow plugs. It consistanly blows them like candy. Thats a seperate issue so we just disconnected them and use starting fluid. I was told that may be a timing issue that may be causing them to short. The glow plugs themselves look fine from the outside when you pull them. Getting back to the noise issue though I have replaced the injectors about 16K ago.