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2002 7.3 dies like you shut the key off

6K views 40 replies 4 participants last post by  Railroad 
#1 ·
Stock truck. Replaced camshaft position sensor. And fpr housing with diesel o rings part.
The truck will start up and run good for a couple minutes without pushing gas pedal. Then without warning it turns off like you cycled the key to the off position. It will not start after that for about 20 minutes.
If I keep pushing the throttle after starting it it will run for quite a while but once I return it to idle it will run for a bit and die out again. Got any ideas?
I do have a Bluetooth scanner with car gauge pro.
 
#5 ·
So I don't know anything about the car gauge pro. Might not be what you need for this.

But if the PCM is really seeing "0" rpm while cranking it won't even try to start the engine (this is usually a CPS issue as it's where that rpm signal comes from). When it runs can you read rpm?

If so, I would think something's going on with the CPS (I know you replaced it already, is it an aftermarket or from Ford/IH?). Or possibly something to do with the wiring/plug maybe?

Again, you can't read any HiPres Oil sensors when running either? When it won't start, do you get a WTS light when you first roll-on the key? (shows the PCM is running)
 
#6 ·
I replaced the CPS with a NAPA brand part. I will get one from ford today and see if that changes anything. Your are right about the engine not trying to start. I dont even get a sputter out of it most times. Then it will just start up and run perfect for a couple minutes.
I will start with replacing the CPS and see if I get RPM's.
The program I am using might not be the correct one. But it does give me alot of other information and I am fairly new to using it.
I will post more information when I get the part replaced.
 
#7 ·
Another thing you mentioned. The Wait to Start light comes on momentarily then shut off. I do notice that when the truck starts the WTS light comes on for about 10 seconds. When it comes on momentarily and shuts of is when the truck just cranks with no start.
 
#8 ·
That could be important!

A healthy PCM will have that 10sec WTS. What you describe might indicate that the very short WTS is an indication that the PCM isn't "booting-up" all the way. When not running you wouldn't be able to read things like rpm and sensors either. Not sure how waiting 20 mins would cure anything though...

The place to start would be to check all the connections (fuses are tight, PCM connector is too, take a look at the transition point where the Fuseable Links go from B+ to feed the fusebox, even the ground straps). In most cases PCM trouble turns out to be power related and doing all this doesn't cost anything (as opposed to replacing the PCM).

Check that rpm as another good indication of a viable PCM. Be sure of what you can read from it when running and compare that to when it won't. If it doesn't communicate Only when it doesn't Start you've narrowed to being PCM related.
 
#9 ·
To you and OP... have you tried replacing the crankshaft position sensor and not just the cam position sensor... a bad crank sensor can cause the same problems your having
 
#10 ·
^ A bad crank sensor would also explain why its not registering any RPM
 
#15 ·
We're actually talking about the Crank Sensor (there's only One on a 7.3) The term "CamPositionSensor" is an OBD-II definition and calling a sensor Crank~vs~Cam is really just semantics for us now... :wink[3]:


OH!!! and speaking of CPS's LOOK WHAT I JUST STOLE on eBAy -> Ford F7TZ 12K073 A Synchronizer | eBay
Oh okay good info :)
 
#12 ·
i replaced the camshaft position sensor last night and it was trying to start. It was showing RPM's. But after the second time I tried to crank it over to get it to start it stopped showing them again. I am going to look at the pcm and look to replace the crank sensor. tonight. When it quit showing RPM's it stopped showing signs of starting. I did not write down the value of the RPM's while cranking thinking I would have time to read them after the initial start of the truck.
 
#13 ·
The deal is,,,, the PCM has certain criteria that it needs met before it will signal the IDM to fire the injectors. For rpm that <100 (normal is @150). So you go to 0 and things have gone BAD...

But, which "end" is the problem on? That is, has the CPS stopped sending signal OR has the PCM quit being able to receive it?

You've now had 3 CPS's in (with the original) with the same problem. Time to concentrate elsewhere maybe ;)

So, you're still seeing a short WTS? If so, I'd wanna resolve that. Try this, over the dr side valve cover is a big square electrical connector that's the connection for all the engines sensors. See if this happens, while plugged-in you have that very short WTS and if you unplug it the WTS acts normally (10 or so seconds on a warm day). If this happens you likely have a bad sensor that's causing the PCM to fail to boot (usually because it's drawing-down the 5v reference line).
 
#16 ·
yeah definitely give the all the wiring for the CPS a good look and the connector.. my guess is that's where the problem lies
 
#19 ·
Also I forgot that the 7.3 has all information read from one sensor... A 6.0 for example has both a crank and cam position sensors.. they are 2 different sensors..
 
#20 · (Edited)
Ok I just unplugged the wiring harness you described. The WTS light doesn't stay on. It just comes on breifly.
BUT WHEN I UNPLUG THE MIDDLE RELAY ON THE LEFT HAND SIDE OF MY FUSE BOX IT STAYS ON EVERY TIME AFTER THAT. Main wiring harness still unplugged.
Maybe that means something.
You can hear the fuel pump kick on and the vacuum box blow out also.
 

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#21 · (Edited)
To add to the previous comment the A/C clutch coil wire had stopped working about 2 weeks before these problems started happening.
With the sensor plug refitted in its spot, and the fuse box relay removed the WTS light stays on.
If I plug it in only 1 in 20-30 attempts does the WTS light stay on.
Is the PCM bad?
 
#22 ·
Ummm.... I'm not sure I understand what could be going on :(

As I look at your pic you're showing Relay #302 missing. That's what you unplug to get a normal WTS ~ is that right? That's the confusing part because 302 is the PCM Power Relay! Now I know there are several pins in the PCMs plug that bring power to it and certainly these are not all going through that relay but WTF?

Not sure what that could mean...
 
#23 ·
Yes that's correct. When I unplug the 302 relay is when the WTS light stays on.
I am not sure where to go from here also. It will not start with this relay unplugged. But when plugged in it does not tell the motor to start. I checked the connections on the back of it and they all seemed to be tightly connected.
These two codes repeatedly come up also.
I am going to put up pictures of the information I can get off my car gauge pro app. Maybe something will stick out as not normal.
 

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#26 ·
Your duty cycle looks way too high to be just idling.. shouldn't be over 15% and its just about at 25%... ICP looks okay but it just idling not a WOT... Check and make sure that your CPS is registering RPM correctly because it should at least register when you are cranking the motor over .. A bad CPS can cause these problems for sure as well as making the truck die and not want to start.
 
#31 ·
I think the ICP pressure was a little high because I had the truck running a little higher than idle, because I was afraid it would die on me before I could get a picture of the value's. Once it starts if I continue to rev the motor it stays running. Once I return to idle it shuts off within a few minutes.
 
#27 ·
What does WOT stand for?
What should injector pressure be when turning on the key?
I have put in two separate CPS'S
One from NAPA one from FORD.
They initially work but soon fail.
Either there is something shorting out my CPS'S or my PCM just will not read them. My truck is acting kinda weird. Every great once in a while I show RPM's and the truck will start.
But most of the time it does not show any RPM's and won't start.
Is there a way to test the CPS to see if it's bad?
 
#28 ·
I have another CPS showing up this afternoon and a new pigtail for it from ford.
I am going to start with replacing the pigtail and CPS to make sure there is no short in the connection. The clip on the trucks CPS is broken. I will put my meter on it and check to see if it's grounded.
I need to know where to go from there.
Again Thank you guys for helping with this.
 
#29 ·
OK, coupla things...

First the 340. Are you "Clearing All Codes" after you read them? Could this be a old code from the first CPS?

Next, the 1280/1211/1209 ICP codes. You want to be sure to clear those too. Sometimes excessive cranking/NoStart can cause that. You want your codes to be "fresh" ;) The ICP pressure you show is good.

I don't see any real problems with your sensor readings. Yes, the IPR is a little high but certainly nothing that should prevent you from starting and, again, these are unusual circumstances at present.

Also, I just pulled the 302 relay on My '02 and found, but I think I misunderstanded the situation you had, just what you did. That is, the WTS light comes on (wo/GP operation) but it stays ON, doesn't "time-out" like a healthy PCM would. This might just be the cluster doing that. So, it's not significant as I thought it was.

So, let's Step-Back and look at what we know.

1) Somethings wrong with the CPS signal in either getting to the PCM or the PCM isn't able to handle it and sees "0" RPM (and won't ever start without it)

2) That WTS light, why does it short-cycle (accompanied w/NoStart)? What does it tell us about the state of the PCM? Could it be getting improper (low) Voltage? It's OK when you first turn the key but drops-out? Measure the voltage in the fusebox, maybe at the OBD-II port/CigLtr too. What about the Grounds? Look at the under dash ground straps & connections. Maybe the PCM itself is just Bad? (there's no test I know of where you could determine that without swapping it with a good one)

And lets say the RPM isn't being read from the CPS sensor because the PCM isn't capable of reading it because it's in a "confused" state. How then does it produce a code? (IF that code comes right back after clearing). Wouldn't the PCM be at a non functioning state, with the WTS acting like that, and not be able to recognize anything? Including the lack of RPM?

As for the ICP, pressure should be "0" when first turning the key ON. The PCMs criteria for starting is around 500lbs (you've met that). You could always unplug the ICP, as a test, and the PCM will take over for it by setting a preset value for the IPR to run with (that will set ICP codes so, expect to reclear those if you do) BUT, I think you've narrowed it down to the RPM as the No Start issue...
 
#30 ·
The codes are Fresh. I can delete them and they will return after trying to start..
I do delete my codes every time. I normally will log them and then delete them.
I dont save them because normally I will first check them log them and delete them, before starting any work. Then after working on the truck I will start it up and run for a bit and check them again to see if they have gone away or not.
The WTS light does stay on continuously after removing the 302 relay. I think your right about the cluster causing that.
I am going to measure the voltage in the fuse box, obdII, and cig lighter/powerpoints.. to see if low voltage could be a problem. Batteries might be getting weak. Ground straps looked ok but I will look at them a little more closely tonight.

I think once I get RPM's to show up I will be able to fix the rest of the problems. So that will be my main focus tonight. If I don't get RPM's after tonight I am sending my PCM off to be fixed.
Does anybody recommend a good place to send it to? Would a salvage yard PCM work or does it need specific programming for my truck?
 
#34 ·
I got the truck started and running again finally. Last night after going through alot of sensors and wiring without finding anything shorted or unplugged. I unplugged the fuel heater at the bottom of the filter housing. After doing this I cycled the key and everything came on like its supposed to. My codes cleared up and it started. I let it idle for a while thinking it was going to die. It didn't, so I pulled it outta the shop figuring it would die when I drove it. It still did not die. At this point I don't care.
Don't get me wrong I care but I am sure glad its at least running. I am going to check out the connector to see if it was grounded. maybe it was back feeding to the PCM?
 
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