my friend has a 1996 7.3 turbo F450 that stopped at the lights and then failed to ever start again. There is fuel in the filter and the pump is working, cracking the injector lines also reveiled plenty of pressure there. The computer codes were checked and showed crank angle sensor (or cam angle?) and air temp sensor was faulty. These were replaced but still no start. An entire processor was borrowed from another truck and tried but still no luck. Running out of ideas and where to look next.

 

There are 2 likely posibilities: (1) the cam position sensor. You said you've already changed it. Did the code for it go away? If the computer is not getting a signal from the cam sensor it won't run. (2) you may not have any injection pressure. You need about 500 psi to start. If you don't have it there are 3 possibilities: (1) the sensor (ICP) in the front (top) of the L/B head is bad (unplug it and see if it starts). (2) you've got an injector dumping and (3) the injection pressure regulator (IPR) is dumping. If you've still got the cam position sensor code you could have a problem with the wiring harness. If it is an injection pressure problem, because the parts to fix it are expensive, you'll probably have to take it to a dealer or qualified repair facility to get it diagnosed/fixed. Is there power to the ECM? Also the IDM (injector driver module) could either be bad or not getting any power. These things aren't so complicated that people of average intelligence can't fix them but you're going to need a Ford Engine Emissions manual and some specialized equipment to diagnose it. Tow it to a qualified Ford or Navistar dealer and get it fixed.

 

>There are 2 likely posibilities: (1)
>the cam position sensor. You
>said you've already changed it.
>Did the code for it
>go away? If the computer
>is not getting a signal
>from the cam sensor it
>won't run. (2) you may
>not have any injection pressure.
>You need about 500 psi
>to start. If you don't
>have it there are 3
>possibilities: (1) the sensor (ICP)
>in the front (top) of
>the L/B head is bad
>(unplug it and see if
>it starts). (2) you've got
>an injector dumping and (3)
>the injection pressure regulator (IPR)
>is dumping. If you've still
>got the cam position sensor
>code you could have a
>problem with the wiring harness.
>If it is an injection
>pressure problem, because the parts
>to fix it are expensive,
>you'll probably have to take
>it to a dealer or
>qualified repair facility to get
>it diagnosed/fixed. Is there power
>to the ECM? Also the
>IDM (injector driver module) could
>either be bad or not
>getting any power. These things
>aren't so complicated that people
>of average intelligence can't fix
>them but you're going to
>need a Ford Engine Emissions
>manual and some specialized equipment
>to diagnose it. Tow it
>to a qualified Ford or
>Navistar dealer and get it
>fixed.

 

Well the camshaft position sensor is working well. It logs no codes at all and never has. I have a genuine Ford Rotunda monitor and can test all the sensors. The VPWr reading is 11 volts (needs to be minimum of 7 volts), the RPM reading is 168 RPM while cranking ( indicates that the camshaft position sensor is o.k) the FUEL PW is 1.68 ms (also indicates the camshaft position sensor is o.k), the ICP sensor is reading 2500 psi (needs to be minimum of 550 psi but i think 2500 psi is too much) I have done an injector electrical buzz test which is system pass, I have changed the PCM and the IDM but it still wont start. If there was no power to either of these then it would not be able to carry out an injector buzz test. There is plenty of fuel pressure at the fuel regulator block, the glow plugs are working, there is no KOEO codes. The engine has no injector pulse until after about 20 seconds of cranking but there is plenty of oil pressure. When I disconnect the ICP the PCM should recieve a reading of 725 psi but it still reads 2500 psi. I have carried out voltage tests and continuity tests and the results are fine. I believe I am a technician of reasonable intelligence and I have a genuine scan tool and emission books. If you could shed any further light I would greatly appreciate it.

 

2500 PSI is about all you'll get at 168 RPM's of cranking speed and I don't think it will go into open loop until it runs for a predetermined time with the ICP unplugged. From what you discribed, all systems seem to be go. You need 5 things to run this engine: (1) air, (2) fuel, (3) compression, (4) injection pressure and (5) electricity to run the injectors. You have already done all the normal diagnostic routines. It is 4:30 AM here in Indianapolis. I'm going to bed and I'll check the Engine Emissions manual in the morning to see if there is anything either of us missed and get back with you. Also, it should start even if the glow plugs aren't working. Have you sprayed anything into the intake tract (don't use starting fluid) to see if it will start? (WD 40 or a similar product)

 

[font size="1" color="#FF0000"]LAST EDITED ON 25-May-01 AT 01:34 PM (EST)[/font][p]OK, here's what I think: Just because you have fuel pressure in the filter doesn't mean you have fuel pressure in the fuel rails. I don't think you can check rail pressure in the rails after the engine is installed in the truck. So, there are 2 things to check at this point: (1) there is a small protruding tip on the underside of the fuel filter that presses open a disc-check valve in the fuel filter stand pipe. It is there so that you can't run without a fuel filter. Make sure it is there. And (2) make sure the disc check valve is opening and closing properly with a small screw driver, and that there aren't any other defects in the fuel filter housing. That's all I have at this time. I'll continue to research this and if I come up with any ideas I'll post them here. (These automatic censures are a pain in the ****)

 

You can probably ignore that last post. Since fuel pressure is regulated on the return side, that probably ensures the fact that if you have pressure at the connecting block, you also have the same pressure in the fuel rails. Find out if this truck has an inertia switch and if so if that switch is tripped. Failing that, I think you're going to have to start over -- something has been missed. Disconnect the air inlet tube from the air filter to the air horn that attaches to the turbo. Have someone crank it while you spray WD 40 or some such product into the intake tract and see if it starts. You are going to have to install a break out box to see if all the information is getting back to the ECM (ICP, CAM sensor, etc). I'll check with the guys at work to see if they have any ideas. If everything is as you say I don't see any reason why this thing won't start/run.

 

Hello;
I too have a 99 7.3 stock Diesel on occasion will not start, I live in NC where the temp. is Moderate in the Winter, when it is cold or Cool I cannot get a start, I have had it towed to a Dealer 3 times and they cannot find anything, after it is moved and delivered to the Dealer it will start for them.
What I have observed is atomized Fuel, [white Smoke]from exhaust, I let the Glow Plug Cycle, I have checked the Fuel Filter for full it is, If I finally get it started it surges, I have to hit the Peddle to stop the Surging.
This is a regular winter and cool spring day problem, I just don't know when it might not start in the AM or first start.
Any ideas?
Do you think a preformance chip would improve this, I have 39,000
Miles on it.

 

Hello
I had the same problem a few moths ago.
Checked everything replaced alot of things. Finally by pure accident found the EEC POWER wire disconnected. On my 91 F-350,7.3 it is located next to the water resv. I plugged it in and after four days it fired right up. No problem since. Good Luck!