As someone that has spent a decent amount of time working on a 7.3l Ford Econoline van, I have grown to love the engine and its reliability. But I do remember a couple of problems being really pesky and taking a long time to figure out.
That is why when I read this post on facebook from a guy who got stuck on his boom truck due to his 7.3l diesel ford engine intermittently stalling, I wanted to be sure I wrote a post about how he fixed it. The post got 90 comments from professional technicians all over the country and in the end, it turned out to be the Cam Position Sensor (CPS) was faulty and causing intermittent stalling and hard-to-start symptoms. It is important to note as well that on a Ford 7.3l diesel engine if the Cam Position Sensor is only intermittently failing it may not be enough to throw a check engine code related to the sensor. Another important note is to NEVER put in an aftermarket CPS, if you’re on a budget go to the junkyard and pull another OEM one from a different truck. Aftermarket Cam position sensors can easily cause more weird problems, and used OEM is always better than cheap aftermarket. With sensors, especially ones KNOWN to go bad often (7.3l Ford CPM’s) do not ever RISK putting in an aftermarket sensor.
Ford 7.3l Symptoms of a Bad Cam Position Sensor:
This is what the guy who originally posted asking for help described as his symptoms. I am sure there are more, and that they manifest themselves in different ways, but this is a good list to start.
Here is what you may notice when your 7.3L Ford Diesel Cam Position Sensor goes bad:
- An Intermittent stalling issue
- It doesn’t always stall.
- Once it does stall and is restarted, it doesn’t stall again until I turn it off.
- It doesn’t stumble. It just shuts off out of nowhere
- once it stalls, I usually have to bury the pedal to the floor like its flooded to get it started
- On cold starts, you may also have to hold the pedal all the way down to get started.
What does the CPS Control on a Ford/Navistar 7.3l:
The 7.3l cam position sensor identifies which cylinder is at top dead center. This allows the PCM to adjust fuel injection timing to allow your diesel truck to start. If it isn’t working properly, then it will not tell the computer when to send fuel at the right time and you can have trouble starting your engine.
The CPS on a 7.3l is a magnet which basically senses gaps and spokes and those allow it to know where your engine is and what cylinders need fuel at what time. If it isn’t working properly once again it may just cause your truck to intermittently stall out, or have trouble starting. It also can cause the truck to just act up suddenly and shut off, then work totally okay the next minute.
I highly recommend checking your Cam Position Sensor if your 7.3l Ford Diesel is having any stalling issue. They also do NOT typically through a code, so just because you are not getting a CPS OBD2 code does not mean the CPS is working properly.
Tools Needed To Change the 7.3l CPS:
From what I can tell the space where you need to get to get the CPS out is pretty tight and a 1/4″ ratchet is the best way. People online talk about carrying an extra CPS in their glovebox and the tools needed to change it. These fail so often and are pretty easy to find at a junkyard, that I would highly recommend carrying the tools needed to change one. It is most easily changed working from underneath, and it sits near the oil pan. Here is a video about changing where you can see the steps and tools involved *Quick note, he is recommending an aftermarket CPS– I highly recommend not using any aftermarket CPS on a 7.3l:
Here are the tools needed for a CPS swap in a 7.3l Navistar/Ford:
1. 1/4″ ratchet– Here is a link to my favorite Amazon ratchet set for all purposes (Gearwrench 120xp Set)
3. An assortment of 1/4″ Extensions
Other Common Problems with Ford/Navistar 7.3l:
I won’t get into this too much, because this could be a whole huge post on this subject alone. The 7.3l engine is known for having problems with the CPS, as well as some other electronic issues.
Here is the list of other common failures that can cause weird problems on a 7.3l engine:
- Fuel injector wiring harnesses came stock with vinyl clips on the injectors that’d dry rot and crack. One came loose, burnt, shorted. Check to make sure injectors electrical connections are good.
- ICP (Injection Control Pressure Sensor)
- Injector Driver Module
- Do a fuel pressure check with a manual gauge. Pressure should be around 60 psi.
- Wiring at the injector control pressure sensor may be damaged or loose. Unplug it and check it as well and check the wiring for damage.
- Air in the fuel filter
- Check the injection oil pressure. It should never get below 550 psi at idle.
- Possibly wiring to the injection pressure regulator. Wiring short under the tape because of leaks. The insulation on the wiring does not like oil or fuel. It dissolves it and creates a random stall until it cools or someone wiggle tests them.
- Check your ICP (Injection Control Pressure). Unplug it check for oil in the plug.
- Aftermarket CPS causing problems. Replace with OEM Motorcraft (Ford) part.
How to Install the CPS:
If you’re experiencing an intermittent stalling on your Ford/Navistar 7.3l diesel engine make sure to check your Cam Position Sensor. It may be worth carrying one around with you and the tools needed to change it. It won’t take you long to swap it out if it does go bad, but it can leave you stranded or stall out on you at the worst possible time.
I spent a couple hundred hours researching all the tools needed to get started as a beginner DIY technician and I made a list with photos here. I highly recommend checking my list out, and seeing if you’re missing any of these tools. Also I wrote a post on my favorite top 10 cool automotive tools which you should check out!
Thanks for reading! Hope you get your 7.3l issues figured out ASAP.