I know this has been discussed before, but I would like some opinions. My 2003 7.3 dies when running, or won't start. After it sits for a few minuets it usually starts. Then a mechanic tried rapping on the under dash computer, and it started right away. I replaced the crank sensor last month, so I don't think it's that. Do I need to replace the computer? It's a pretty pricey ($800) item, but does anyone have a different option?

 

You have been around here long enough to know that you need to purchase Auto Engunity so you can get data and help us help you.
You have also been here long enough to know that we need to know HOW MANY MILES ON YOUR TRUCK.
How many miles on your oil?
Do you put any additives in your oil?
When you are cranking and it does not start, do you have any smoke coming from tail pipe? If so, what color is the smoke at tail pipe?
Do you have any gauges? If so what are they reading when the truck shuts off?
Do you have a SES(Service Engine Soon) or CEL(Check Engine Light)????
Can you give us any conditions like... is it running ok cold then stops when warm? What is the voltage on your battery when cranking? You need at least 10.5 volts to start it and keep it running. What is the voltage on the battery when it is running?
Have you pulled the ICP connector and tried to start it that way?
Is there oil inside the ICP sensor connection?
Do you have any HPOP lines leaking?
The CPS that you replaced....was it a OEM part or aftermarket? If aftermarket then go get an OEM from the stealership or order from Tousleypartsdepot.com
What it your location so we can see if anyone from FTE can hook up AE to find out what is going on with the ICP, IPR and battery voltage when cranking and when it dies.
What is the oil level on the dipstick?
If the oil level is low then top it up and see what happens.
After 6 more post you can post a picture if you need to.
Get a meter and give us some info on the battery.
Just because some mechanic was tapping on your computer does not mean that it the problem. Your mechanic might just need some of your hard earned $$. Could just be coincidence that he tapped and it started.
Go get some more info and report back.
We want to help you but you have to help yourself first.
Dwayne

 

Sorry. Here is the info requested.
132,000 miles.
Less than 2,000 miles on this oil change, no oil additives, but I do use Diesel Kleen in fuel.
No smoke coming out of tail pipe when it cranks but won't start. Feels like there is no fuel getting to the engine.
I only have stock gauges, but no SES or CEL lights are on.
It has died when running for about 2 miles from my home, in town. I had earler that day run it 100 miles pulling a 10,000 lb RV and it did fine.
Don't know the battery voltage when running or cranking. I had to replace both batteries with Napa batteries last month.
Oil level is full.
No leaks noticeable in any fluids.
Will check the CPS part that was replaced, and don't know about the ICP connector. Will try and check it out.

Thanks for your patience and help. I am in Brown County, Texas

 

The ICP is located on the drivers side head on the top and on the front. It is the only sensor mounted in that location. This sounds like a dirty IPR or it may be the Under Valve Cover Harness has worked it's way loose on one or both sides. Have you done the 50 cent mod on your truck? If you don't have any way of pulling data then it will be really hard to diagnose if it is the IPR or something else.
Have you had your valve covers off before?
I will post up the 50 cent mod or the UVCH mod, which ever you wish to call it.
Have you been having any problems with power or getting up hills that you used to be able to go up just fine?????
Here is the 50 cent mod. I just copy and paste from one of the other threads that I post in.
In short. The 50 cent mod is done to keep the Under Valve Cover Harness (UVCH) plugged in properly, clipped into place and a quarter(25 cent piece) placed under the plastic clip to keep it clipped. This is classic of the 7.3L problems. Now the details below. It KEEPS ALL INJECTORS and GLOW PLUGS plugged in and FIRING when necessary. You can be running on 3-7 cylinders based on wether the plugs under the valve covers are plugged in all the way or NOT. You can also have very hard starts from the glow plugs not being plugged in and only a few heating up.

You know I have to pop in here and ask if the Under Valve Cover Harness (UVCH) connector has been looked at and the 50 cent mod done? 50 cent mod video here
2001 F350 7.3L Turbo Diesel, UVCH - YouTube

How to do it written down from my post in another thread. The video above is not my video but is a great training tool.

For the 50 cent mod you will need two quarters, a short 13mm socket, deep 13mm socket and a universal or wobble short extension to get the back bolt on the drivers side and a few of the bottom bolts on the passenger side, a 13mm wrench and a long(6-8 inch) extension. Various wrenches and sockets for pulling harness connector and Intercooler boot clamps.
Only takes 20-25 minutes to pull the Turbo intake hoses and Turbo pipe(metal) on the driver's side. Be careful with the boots. Just be easy with them.
Don't pay too much attention to all the oil inside of the inlet tube and metal pipe as you can clean them any time IN THE FUTURE.
Right now focus on taking the valve cover off. I take out the stock filter and all the inlet tubing going to the turbo then I gently shove a not so good towel into the stock filter box AND lay a moving blanket( very thick folded over several times) over the battery and stock filter box so I can lay on it while I take the Valve cover bolts out. Be careful of the towel in the stock box for the sensor in that box. They are fragile. I am short so please laugh and work with me at the same time.
Unbolt the 42 pin electrical connector on top of the valve cover. If you have an air compressor, now is the time to blow any debris around the valve cover down out of the way.
Take a PICTURE or take note which fasteners are bolts and which ones are studs with a nut to mount something else to. You will want to put it back exactly as it was. Get the 13mm socket and a 13mm wrench.
DO NOT TAKE THE Positive Crankcase Vent or CrankCase Vent(CCV) DOGHOUSE OFF UNLESS YOU HAVE THE FOUR ORINGS TO RESEAL IT
4 Viton O-rings to reseal the Crank Case Vent cover
OR THE ORINGS WILL SWELL UP AND BE NO GOOD AND YOU WILL LEAK OIL ALL OVER THE PLACE UNTIL YOU GET THE NEW ORINGS.
Using the 13mm wrench carefully remove the bolt just above the CCV dog house and leave the CCV in place. You will not be able to use the socket with the CCV in the way. Now you can use that 13mm socket and take all the rest of the bolts out. The hardest one is on the rear of the cover and you can not see the bolt without a mirror. Don't worry about the mirror, just loosen it and place the bolts to the side. I use a 5 gallon pail to put my fastners in. Slow down when you get the bolts loose and keep a tight grip on them unless you like fishing for metal in the pit of hell. I put a tarp under the truck for items I drop to easily find them.
When you pull the cover loose, be slow and easy so you don't put any debris in the VC area. If your harness connection is loose, very gently push the connector towards the top of the VC gasket and let the clips clip UPWARD into place. You could also unclip it and inspect for burnt connectors. Place the connector back firmly in place. Now take the quarter that you have shaved off right at the top of the hair line on the head and slide it in round side down and flat, cut side toward the TOP of the valve cover. DO NOT FORCE ANYTHING unless you have a fresh Benjamin Franklin laying around to spend on a new gasket/harness.
The clips should be clipped fully in and pushing up whilist the quarter holds the clips up. The flat spot gives the valve cover enough room to be installed and keeps the quarter from going anywhere.
If you want to you can now check the torque on the:
Lower injector hold down bolts at 120 INCH lbs.
Rocker arm bolts at 20 Foot lbs
Valve cover bolts when reinstalled will be 96 INCH lbs.
Verify all of the injector connectors are secured and clipped
Verify all of the glow plug wires are tight.
Do everything in the reverse order to put it all back together. Wipe the oil coated pipes down to remove any excess oil and start on the passenger side
Remove the intercooler pipe. You will figure out that you have to move it above the turbo to get it out. Lots of room above that turbo. I loosened my boost pressure gauge and tied it back with string or a small bungee.
Bungee cord the two heater pipes toward the passenger side fender. I put the Moving blanket on this side but did not lean on the A/C pipes. Same thing on this side except you have a bolt holding down the Engine Oil Dipstick so be careful with the dipstick. Only pull the dipstick high enough to remove it from the stud. The bolt near the AC compressor is tight but you can get to it with a few extensions and a deep socket. Same one as the oil dipstick. Note the stud positions again. Don't loose the heater hose clips because they are 28$ at the dealer. Loosen and remove the rest of the bolt/studs. Same thing as the driver's side from here.
Man, that is a lot of typing. Talking thru it is much less time consuming. LOL. Put a wrench in your hands and get to work. The sooner you get it done, the sooner you can drink that favorite cold beverage and relax that another inexpensive mod is done and you will feel better for not spending any money at the mechanic shop or Stealership It might even run much better or have gained some power back. Same torque values as mentioned above. Be careful whilist VC's are open. If it rains you need to shut the hood all the way immediately after you remove the blanket and slowly slip the VC in place. I hope this helps and is not too mundane. I prefer air tools but you need to put it back together with regular rachet/wrench and get torque values correct.
Dwayne

 

One other thing....Is your battery light flickering at all? If you post up what reading you get on the battery with the truck running then we will know if the alternator is charging your batteries properly. New set of batteries makes me wonder about this.
Do you get your Wait To Start(WTS) light when you cycle the key to the on position?
Can you cycle the key three times and wait for the WTS light to go out(ensure the glow plugs that are turning on get good and hot) and then see if it starts easier??
Dwayne
The minimum to start and FIRE the injectors is 10.5 Volts. You should be between 13.5-14.7 volts for it to be charging correctly while running.

 

Wow Fixitman...your thorough! EVen though I think the 50 cent mod is a great idea either way. your description of the truck actually shutting off would lead me to believe thats not your problem. I've had loose UVCH's on a few of my trucks and never had one actually turn off...for this to occur, Both sides would have to come loose at the same time. Typically, one side will come loose and the truck just runs very poorly due to cylinders cutting out. Your problem honestly sounds very similar to a CPS, tell tale-sign is to watch your Tach when it's acting up and see if it starts jumping around...any chance these problems are happening while it's raining outside?

As already mentioned...these trucks HATE voltage problems. Clean, tight connections and good ground(s) w/ a properly functioning Alternator are essential to these trucks performing as they should.

Cleaning/checking your IPR is free and never a bad move however I can honestly say in all my trucks when problems ocured....this was never the problem.

Out of all my trucks, most common issues with your symptoms was the CPS.
Most common issues overall w/ all my 7.3's were: Loose UVCH's, bad ICM (but only if I could shake it and hear water got in it!), injector o-rings, bad battery connections, HPOP lines, CPS ( a lot!). I've replaced IPR's before and they were never culprit (although a good idea to clean!).
Never had an HPOP, ECM, IPR, Injector (besides o-rings) or a turbo failure in any of my trucks and they all have high mileage.

 

I also (which amazes me...)never had a fuel pump failure!

 

Does this truck have a chip? Have u checked the harness connector attached to the pcm to see if it is tight?

 

Forgot about that X2! Did have a loose DP chip cause some prob's before.