diesel motor help please!

[WA hunter14]

i read on the internet that if the cps is bad than the tac will not work, the tac never worked properly the whole time i owned the truck but it would always come up some and still does when i turn it over. Do you know that if the cps doesnt work that the tac wont move at all? some of the diagnosis stuff is confusing for me are you saying that i should take it somewhere like napa and hook it up to diagnostics?

[DRobnsn]

I have seen them fail to the point the tach would work while cranking but the truck wouldn't fire. I don't believe that scenario is common but it can happen. Its possible for the sensor to operate under a starting condition and fail during a running condition causing it to die. I had one that would start and idle but would intermittently cut out at high RPM it was a aftermarket sensor and the updated Ford grey sensor fixed it.

As for the diagnostics you need to find out if the truck is equipped with an OBD connector. The last OBS ford I worked on the connector was under the dash just to the right of the trans hump on the passenger side. I can't post pics so google OBD connector to see what your looking for. It's a bit of a shot in the dark being the truck is 94 but it sure would be easier to diagnose if it has one.

I would also try the HPOP oil pressure sensor trick previously mentioned before you buy anything. Its easy and free.

How many times have you had it fire and die at this point? 

[WA hunter14]

Ok it looks like i do have a OBD connector right where you said, it has started probably 7 times but the last three times it only ran for like 2 seconds. ill try the hpop oil tomorrow after work.

[Mossy]

I had a cps go bad in a 97. Sounds pretty similar but I was able to make it close to home from the woods. Hard to tell how many dozens of restarts it took before it finally gave up the ghost.

[syoungs]

The high pressure oil pump is not a sealed system, no need to change the oil, it compresses oil, sends it through the injectors, and it drops back to the oil pan.

What you could do, is fill the resevior to within 1/4" of the plug on top, and try to start it, I suspect a hpop that I'd leaking down oil, or has lost its prime, which makes these engines a real bear to start if they aren't in perfect working order already.

You do have diagnostics, but a cheap obd reader will not work. You need auto engunity, or a snap on etc.
The cheapest way is a scangauge2, and that won't spell out your problem.

I'd be curious how many times it's actually started and how long it's ran as well.

Did you check the tin nut on the ipr? That's a free check, and I've seen more them 1 power stroke crippled by it.

Do you have a way to get the front end pointed down hill? Sometimes the oil pickup tube cracks, and pointing it downhill will make it start with all the oil in the front of the pan.

Have you plugged in the block heater when your trying to start it?

[whacker1]

At this point I am pulling for you.  this looks like a tremendous opportunity for a reliable rig once you get it fully operational.

[Mudman]

I will clear up hpop oil I mentioned.  The oil doesn't circulate well and becomes old and sludge.  Oil does this in all of em.  The pump circulates oil for injector pressure but does not clean itself well. I don't think this is your problem but you should clean it.  I really think its a fuel filter/flow problem.  Likely air in heads still.  Bleeding the back of head is a PIA but I had to do it many, many times after changing injectors.  Inj. harness in valve cover resulted in a miss when I dealt with that problem.  Sensor it quit running.  I had many issues with my old 7.3 years ago. Yes make sure the Batts. are always charged as well.  Good luck.

[WA hunter14]

i havent plugged in the block heater while trying to start it yet, ill do that from now on. I'll check that nut very next and the oil in the hpop is about a inch below the nut so ill fill that too. The truck is pointed downhill all the time, i do have some kind of draw on the battery very slight but i noticed it when i hook and unhook the batterys. Maybe that is a short in something? im determined to do what i can to get the truck running it really is the perfect truck for me if i could get it reliable. thankyou guys for sticking with me and working me through this stuff.

[WA hunter14]

I will clear up hpop oil I mentioned.  The oil doesn't circulate well and becomes old and sludge.  Oil does this in all of em.  The pump circulates oil for injector pressure but does not clean itself well. I don't think this is your problem but you should clean it.  I really think its a fuel filter/flow problem.  Likely air in heads still.  Bleeding the back of head is a PIA but I had to do it many, many times after changing injectors.  Inj. harness in valve cover resulted in a miss when I dealt with that problem.  Sensor it quit running.  I had many issues with my old 7.3 years ago. Yes make sure the Batts. are always charged as well.  Good luck.

ok ill change the oil in the hpop its easy enough to do, i bleed the lines going into the heads but only once and im not sure how well it actually worked? can i bleed right at the injectors? maybe i need to re bleed the lines going into the heads i just felt that it didnt get me anywhere and there was plenty of fuel going through

[syoungs]

When I tore down both my 7.3s, there was maybe 5cc of sludge in the bottom of the resevior, one had 330k miles on all stock components, one had 110k on all stock, so I don't bother with doing it anymore. Pull the plug on top and crank it over, that's a hard lesson on how much oil it'll flow lol.

The more I think about this problem, the more I think the lpop went dry, the hpop sucked out the resevior and let it run briefly, and it hasn't been able to re-prime....

Before you turn it over again, pull the upper plug and see if there is oil in the hpop res. If it's below approx 1/2" there may be supply problems, below 3/4 or 1" there def is supply problems. If it's low, fill it, and try starting, after 20ish seconds of cranking, check the level again. Might have to pull the lpop and pack it full of Vaseline to re-prime. Or it might have a cracked pickup tube, which means motor has to be lifted, preferable to remove, to fix.

[syoungs]

At this point it's probably oil related.
Can't bleed at the injector on these.

[WA hunter14]

alright well the motor really could just use a oil change no matter what so i can do that, ill do everything i can tomorrow after work and update but i also have a toyota steering knuckle to rebuild after work so im not sure how much ill be able to do.

[brush hunter]

yea id love to get rid of it other than it is the perfect truck if it would run right, didnt kill an elk but did have a bull at 75 yards bugling at me until he winded me and busted. I couldt shoot him though because it was so thick i could only see about 20ft

That sucks, but at least you got some time in the forest.

[DRobnsn]

If you have access to some fittings and at least a 3000psi gauge you can remove the ICP sensor and check the high pressure oil manually to be certain on what is going on in the system. Just make sure if you do this you have good connections at the fittings and a quality gauge.

As for scan tools you will need a good one to see whats going on. The others mentioned work as does the matco determinator, and the autel maxiSYS. Maybe you can find someone who will loan you one for a few bucks.

Once you've exhausted all the free easy checks it may be worth looking to see if you have a mobile mechanic in the area that can come run diagnostics on it. As you've seen the 7.3's do have several things that can cause starting issues and paying for a diagnostic check can put you money ahead depending on the issue. Throwing parts at a 7.3 can get spendy quick.     

[Mudman]

Reading your post confused me as to what you meant?  There is a plug in the back of the head for air bleeding.  By the firewall.  This is what you open not as line goes into head.  If your not doing this we have likely found your problem-air.  Maybe I misunderstood you?  Also these engines NEED clean oil or injectors run like crap.