so if I pull a line off of and injector and spin it over it should be a fast shot right?

 

Sort of. It'll be "fast", but because once the line is free from backpressure the pressure drops very very quickly only a little squirt will come out.

Keep in mind any time you crack an injector line that the pressures you're dealing with are enough to pierce your skin and rumor has it that it's pretty easy to die from getting diesel in your blood stream. So keep your hands away from the area when cranking, wear eye protection and probably wear leather gloves too.

 

well i get a little squirt, just can't figure this issue out.

 

If I am following this correctly, you have verified fuel out of the IP to the injectors. Assuming that you have not touched the IP as far as timing goes, and the starter is spinning the engine fast enough, the GP's are functioning correctly, and you have decent compression, the your problem is IP output pressure or injector pop/flow issues. I once smoked an old IP with new injectors and it took 4 new injectors with it. I have never tried it but maybe you can pull an injector, connect it, and crank to see if it pops. Fuel could/will spray under pressure so be careful how you do this. The IP is not terrible to replace if needed for a check. Just do not remove the gear housing. Take the little plate off to access the IP bolts. No telling if it starved for fuel and got trashed or what. It is still pumping at least. Good luck, report back if you find something.

 

wont be until next weekend again. I'm back to work on the island. how would that work with the return lines? i suppose i could turn up the fuel a little on the IP. think i'm going to open that plate and see if I maybe lost some teeth on the timing gear maybe?

 

I would complete checks before jumping into mechanical problems. Timing teeth are not likely to be broken and the fueling rate of the pump certainly didn't change itself. By making changes on a non-running engine you are going backwards as you have no way to determine whether it helped or further hurt the situation. On the injection test you could pop the return cap back on and run a little longer hose to the return. During cranking it probably doesn't matter if it is hooked up as there shouldn't be a whole lot of fuel being returned. You're just checking for spray out of the nozzle. Alternatively, you could remove the GP's and see if fuel blows out of the GP holes when cranked. Place paper towels to catch any fuel and identify if it is missing on any cylinders. Fuel, Air, Heat(compression) is what's needed. Air is a given, fuel is looking promising, compression requires some more specialized tools.

I'm not sure how hard it revved or for quite how long, how many miles are on it, etc. but it could have damaged the compression rings if there was a ridge or carbon built up that it was contacting at higher than normal speed. This is not likely but could be possible. Possibly heat damaged valve leaking could be another loss of compression. IIRC that little plate won't allow you to see much. Maybe with a mirror/flashlight. Maybe try the gas soaked rag trick for starting. Gasoline surely has a lower auto ignition temp, so if it wants to start with that it may be a loss of compression issue.

These are just my ideas and what I would do if I was stumped.

 

it wants to start on wd40 and carb cleaner. have alot of tools, don't know what i'd need for a compression testing.

 

main thing i'm trying to do is get this info before i mess something up haha. worked on alot of diesel tractors, loaders, but never got to do the rebuild of my old man's 7.3... why we ended up with the spare old motor. main reason I bought my 7.3. have an old 6.9 laying around too haha. 276k miles on my motor.

 

In your original post you stated that it acted like it lost compression or something to that effect. What made you think this? Did it spin over faster on the starter? If you have or can locate another IP, maybe try that. What you described doesn't seem too catastrophic for the engine. They are pretty dang tough engines. You need a compression tester to test compression. It consists of engine specific adapters, a high pressure hose, and a gauge. I have seen posts on here stating that the more expensive of the two testers that Harbor Freight sells has the correct fitting. Use the search feature here to learn more about that. A quick look in my Chilton's manual didn't show what pressure to look for.

The same principles apply to our IDI engines as they do to a tractor engine and in terms of mechanical operation they are not very far removed at all. Problems like this are frustrating but remember to start with the easiest and free fixes first. Check everything and use a methodical approach based on what you know about working on tractors. You being away from it should give you some time to think about what happened and what you are seeing trying to start the truck.

 

Almost sounds like the cam slipped a few teeth.
never heard of that happening though.

 

yeah that's my scary worse case scenario or cam breaking but yes I'm going through getting rid of all possibilities before i get to the scary one haha. it'll run again. just take time. glad I have a spare parts motor.

 

new question now. if all else fails and I'm unable to get this motor running, how hard would it be to swap in an old 6.9L? have a spare one with very low miles on it.

 

Take out the 7.3, drop in the 6.9....
Recommend that you use the newer style glow plug system off the 7.3. Everything else is pretty much the same. The return line system is may be a different size, but thats also trivial.

 

What tune you got loaded on it?
Ahh just kidding.

You said the turbo was starting to spin a bit while cranking, so air must be getting moved through the engine.
Have you cracked injection lines yet to see if the fuel pulses out? Carefully?

I wouldn't be thinking of swapping engines at this point.

 

Ummm stupid question, but did you check fuel filter?

Is it not possible that the wide open throttle run maybe caused a greater than average fuel use, and a semi-clogged filter caused the fuel pump to suck some air into it?

I would replace the filter and purge the lines before doing anything else.
I'm not a master on these trucks, not even way back when I drove one.
But I would entertain the thought that maybe that hard run at wide open throttle air locked the pump from a plugged filter. It's worth looking into before tearing stuff apart.