I have a thread about this no-start going on another forum but there seems to be much more Powerstroke activity over here. If anyone wants to comb through that play-by-play I can provide the link. For now I will summarize where I’m at with it and start fresh here. This is my first 7.3 no start diagnosis.

Owners of the truck bought the truck after taking it for a test drive that satisfied them as to condition. On the drive home it lost power and eventually stalled with lots of white smoke out the tailpipe and in the crankcase (coming out of the oil fill when removed). The temp warning light was seen shortly before the stall. Nothing about the history of the truck is known. No maintenance records. It’s pretty dirty, obviously hasn’t been pampered.

I was called to help figure out the problem. Owner drained oil and described significant sludge. Old oil somehow disappeared so oil analysis was not done. May yet attempt to siphon some out of the HPOP reservoir and send for analysis. Compression test has been performed, showing numbers around 300 psi. Not great but should be enough to fire. Batteries are brand new NAPA and spin the engine at 150 rpm or so. Glow plug relay inop but we have jumped it and tried to start with no change. IPR duty cycle goes to 65% while cranking and ICP reported rises quickly up to 3000-3500 psi. This number has been confirmed at the head with a mechanical gauge. Fuel pressure is 64 psi at the fuel bowl. The PCM is attempting to fire the injectors. A known-good IDM has been swapped in with no change. No smoke has yet been seen out of the tailpipe when cranking. No oil has yet been seen out of the injector spouts when cranking, although I finally know what to look for as far as oil spouting.

My latest move has been to revisit the injector buzz test, which was done before, but I counted as ok due to all 8 injectors sounding about the same during the test. However, I’m thinking now that they may be very quiet compared to good injectors. It is about 90 degrees during the day where I am. I posted the following video to YouTube so that anyone who is interested can listen and offer thoughts on the buzz test:

https://youtu.be/lVqX4e1RYRQ?si=mvKTMPf6obofmmsTIn the next video, it is stated that the truck with the quiet buzz test will not start when hot. I think this quiet buzz test is probably a similar volume to the test I did today:

https://youtu.be/lVqX4e1RYRQ?si=mvKTMPf6obofmmsT

So, did something take out all 8 injectors at once, and to similar degrees? Isn’t this deemed very unlikely to happen on 7.3s? Did a bunch of sludge from the oil pan that had settled while the truck sat for a year get kicked up as soon as it started moving again and slowly made its way into the injectors, where it still sits, too thick for the injectors to fire and manifesting as a quiet-sounding buzz test?

Or are the injectors getting low but equal voltage for a reason besides a faulty IDM? Or do all of these conditions actually seem fine? And in that case, could the breakdown just be symptomatic of the truck sucking air at the fuel tank and stalling due to aerated fuel?

Those are all the observations and suspicions that I can currently think of. Your thoughts are most appreciated!

 

White smoke usually points to a lack of fuel.

What is the fuel tank level? The pickup is notorious for breaking off and leaving many vehicles stranded with 1/4 tank on the gauge.

What does the fuel filter look like? Was the pressure read on the pre or post filter port?

It obviously needs oil to fire the injectors, a low level would make them not fire, draining it without knowing the level won't help diagnostics

Tho unlikely due to color of smoke, a rag has been known to be forgotten in the filter housing and stop up the turbo. Usually a lack of air is noted by black smoke, but being a vehicle with unknown history it's worth a look

 

Tank level is technically unknown, it’s thought that temp and fuel gauges are inop on the truck. However, the fuel bowl has been drained and filter removed and inspected and the fuel pump has refilled the bowl and pressurized to 64-65 psi.

Fuel pressure reading was taken at the upper port. Am I correct that this is the pre-filter port? Reading on this thread. I will try post. Have also changed the fuel filter since last attempt to start as the o ring that seals the cap was too big to sit down inside the lip. Made quite a mess of diesel in the valley when I discovered that. But yet again an indication that it was not simply out of fuel. I do intend to remove the line to the tank and put it in a gallon of diesel and attempt to start it then, though.

Filter looks ok. Not black or any reason that I see to think it is clogged. There is a not huge but significant amount of small rust-looking particles sitting in the bottom of the fuel bowl. Some drain out when the bowl is drained.

Oil was drained before I was called. New oil sits within spec. HPOP reservoir is full to 3/4” or so below top.

Air filter housing has been pulled to aid access to top of the engine, no obstructions found.

 

Post filter is always preferred when possible, but access isn't as easy since that port is next to the drain valve. It will help diagnose a fuel filter stand pipe that has been rotated and locked closed during a filter change, pre won't show that

Fuel pressure doesn't necessarily mean adequate flow. You can have 100psi of 1 oz per minute vs 100psi of 10gpm

is the IPR nut right?

Unplug the fuel bowl heater wire and pull and replace fuse # 30 under the dash

Have you tried starting with the ICP sensor unplugged?

Voltage while cranking?

 

You can check voltage to the injectors from the center pin of the harness connector. With KOEO they should be hot and waiting for a ground signal from the IDM. The more I think on this it's sounding like a PCM problem. I mean you got hpo, you likely got fuel, cranking speed is good. The only thing not showing up to the party is the PCM to pull the strings. You might message DToC for an opinion. Here's a link to their website if you want to check them out.

https://www.dieseltechchatt.com/

 

I will try checking fuel pressure at the post port. Also perhaps more difficult as this is a van chassis but I will give it a go.

Do you have a link about the IPR nut? Not sure what that means.

I have WTS light, I understand that means the PCM is getting power so fuel bowl heater is not shorting and blowing the fuse.

I have tried starting with ICP sensor unplugged. Reported pressure defaults, still no start.

 

I’m starting to think it is PCM problem too. The main thing that doesn’t line up is the rising ICP. When cranking the IPR duty cycle goes to 65% and the ICP correspondingly goes over 3000. I have heard it mentioned (in post #13 of this thread for example) that IPR duty at 65% means the PCM is compensating for a high pressure oil leak. It seems most people see around 600 psi while cranking. I see well over 3000 psi with that duty cycle at 65%. The reported ICP reading has been verified to be reasonably accurate with a mechanical gauge. Consequently, the system is generating pressure correctly, the PCM has control over the IPR, and the ICP is reporting the correct pressure to the PCM, which is showing in the scan data. If the premise of 65% IPR duty being the PCM’s number to compensate for a major high pressure oil leak is correct, and if this over 3000 psi number I am seeing is too high for cranking, the only source of the error must be an internal miscommunication inside the PCM.

However, the PCM is attempting to fire the injectors, as I have monitored voltage at the injector connector while cranking and seen pulses on a scope (though I need to do a better test as my resolution on the scope was not great when monitoring). Also, the PCM is able to command a buzz test. I would think too much HPOP pressure would dump too much fuel while cranking if the injectors were able to fire, and I’m not seeing smoke when cranking.

Thanks for the link, I’ll check it out.

 

Also, I intended to monitor data on a friend’s 7.3, but his truck would not connect to the scanner.

Are there compatibility issues between PCMs? I could possibly swap my friend’s PCM into the non-starting vehicle as a test. I believe both vehicles are 2002-2003 E-series.

 

One more thing. Now that I think about it—the driver during the breakdown described some kind of transmission weirdness shortly before the loss of power and stall, like the transmission dropped out of gear and the engine revved without putting power down for a moment. The PCM controls the transmission….possibly this was the first sign of PCM failure?

 

Have you tried swapping the CPS? I hate to be the CPS guy but if the PCM is firing the injector's and you've got all the other parts of the equation you gotta ask is it firing the injectors at the correct time. Also the 65% and 3k psi is normal during a no start. Any of these trucks should read that way if the engine isn't firing.

To my understanding PCM's w/ the same X code will swap fine. There are some other cross compatible PCM's but I forget the particulars and I'd hate to give you bad info and make things worse.

 

Thanks for the clarification on 65% and 3000 psi.

My understanding of Hall effect sensors is that they pretty much work or don’t, and this can be intermittent, but that it would never produce a
wrong or wrongly timed signal. Am I wrong in thinking that a faulty CPS will always stall the engine immediately due to the PCM not seeing RPM signal and ceasing to command the injectors? Is firing the injectors at the wrong time a known failure mode? Is it possible for the fueling event on these engines to somehow get out of time?

 

I won't claim to understand 1/4 of the possible failure modes of any of the engine management sensors. I operate under the idea that anything is a possibility when electronics are involved.

 

Given that I have injector pulse in time with the engine rotation, I think I’ll focus on other possibilities for now.

 

My first thought was bad IDM but it buzzes so not sure that’s possible. I can’t say if the buzz is normal or not. But I can make the link easier for others to watch so maybe you get more feedback on it.

You Tube

It sounds like you’ve got fuel pressure & HPOP pressure which are needed to run. But the PCM requires seeing certain things while cranking before it says to fire the injectors. I can never remember the list but I wonder if that may be happening here.
ICP > 500psi
Engine speed > 150 rpm
Battery > 10.5 volts
Those are my guesses of values but don’t put a ton of faith in them. If you can watch these things while cranking it may give a clue.

Unless you find something soon, I would consider sending the IDM and PCM off to dieseltechchatt. He will run diagnostics on them and either give you the all clear or fix the issues. I’ve never heard a bad review of that company.

 

Thanks for the repost of the video! I hope someone who is more familiar with the buzz test will be able to chime in and tell me if that is definitely too quiet. Based on the comparison to the video I included above, though, I think it is.

Thanks everyone for the replies. I believe I am satisfying all of the basic parameters the PCM needs as it is sending a pulse to the injectors while cranking.

I am going to work on the truck some tomorrow. I’m going to focus on making sure I have fuel at the rails (testing fuel pressure on the post-filter port and cracking the fuel lines at the heads) and trying to get the block heater plugged in, hopefully thinning the oil enough so that the injectors will be able to fire.

If neither of those work, I may send the IDM and PCM to Diesel Tech. Thanks all for the suggestion.