my 99 7.3 wont start. this graph on forscan doesn"t show any change while cranking on the cps does that mean its not working?

 

I blew that pix up big, and I do not see CPS on the chart.
ICP, IPR, and others, but no CPS.

if it is not working, it would be a straight line.

 

You're right! For some reason I was confused thinking CMP (cam) was crank and that's what I circled in the picture. As far as I know, there's no CAM position sensor. Thus no data. I'm not sure if Forscan offers Crank Position Sensor.

 

The CMPStat PID is one I have not tried, but appears to be just an "OK" output. Look at RPM and see if it shows a value while cranking - that will tell you if the Cam Position Sensor is working.

Does FORScan report any codes?

Recommend changing any PIDs with kPA to PSI. More on this in the FORScan Q&A thread.

 

The tach does indeed move when cranking (about 250 rpms).

 

My CPS was having an intermittent failure. Sometimes it would be fine and run down the road for hours, sometimes it would not allow the engine to start and every running and non-running scenario in between.

My story about how sometimes it is actually the CPS: https://www.ford-trucks.com/forums/1...-the-road.html

I'm not saying that is your issue though.

 

Sounds like you've got a cam signal, and from your pic it looks like you've got sufficient hpo. Next step would be fuel. Do you hear the pump kick on when the key is turned to run. How about smoke, see any at the exhaust during a long crank? Checked the bowl has fuel no water? Any recent repairs or maintenance that might be a starting point to look at?

 

I've been through Ponca City many times on trips from MO to Alva, OK. Nice drive!

Yes, can hear the fuel pump. It would be a good idea to check the fuel pressure. There is some smoke sometimes but not even thinking about starting. Compression sounds even when cranking.

My son started the thread here (he's at work now). But he had the truck start missing about a mile from home and sputter out. We thought maybe low on oil but that doesn't seem to be the problem. The only work done was a new dip stick to oil pan fitting. He wasn't sure the oil level was reading correctly after the job (not sure what led him to believe that).

My thinking is maybe low compression. When it was running, his exhaust with engine hot smelled like a cool burning or poorly fueled engine to me (not a clean burn). Especially when he steps on it. The truck is hard starting even in warm weather. Injectors were supposed to have been replaced before he bought it, but the seller wouldn't give a builder name. So reputation of injector rebuilder is suspect. It's always been low power and only gets up to 2200 psi oil pressure max and very low boost. He had a respected 7.3 shop look at it and they couldn't figure it out in a few hours. Would have been big $$ to diagnose further so he gave up at that point. I keep encouraging him to replace the dead glow plugs and check compression. Easy to do and the best diagnostic info at this point.

EDITED to add: We also buzz tested to rule out IDM, PCM, etc. The injectors all buzz. #3 was weak sounding but all others sound ok.

 

How ,much fuel is in the tank? Signs are pointing to it not getting fuel . Do you know if the Hutch mod has been done yet? It's where you delete the mixing chamber and pick up foot in the tank and replace it with a simple tube and an external in line filter pre-pump.

 

Once it's running we'll be able to investigate the other issues and at the least figure out what the cause might be.

If the truck doesn't have a working glow plug system try plugging in the block heater for a few hours before trying to start it. That should help.

 

Was reading through and planned to say this. ⬆️

They will run out of fuel at around 1/4 tank if the pickup is broke off.

And this too!

If the glow plugs aren’t working it’s difficult to say what’s causing the hard starting. Plugging it in is a great idea.

Folks around here will do their best to help get it sorted out.

 

I don't think anything is different than usual as far as fuel tank level and he's had it plugged in. This truck won't start unless plugged in (even in moderate to warm weather). So there is definitely something not right (compression or injectors I'd guess).

I believe you all are right. Fuel is the best thing to check at this point. I wish he had a fuel pressure gauge plumbed in. That solves a lot of problems fast.

 

An easy way to test fuel pressure is to slide the drain tube off the valve on the fuel bowl and clamp a 5/16 hose, long enough to reach the drivers mirror, in it's place. Rig a gauge to the other end and open the valve. It works temporary but I wouldn't leave it like that. If you disable the glow plugs completely it is safe to hit her with some girl scout water(ether), but if even 1 plug is still lighting up it could destroy the engine. So if you're going to try it I would disconnect the relay so no chance of them getting power.

 

It could be injectors but I doubt it unless the whole set is flat wiped out. Same goes for compression, nearly every cylinder would have to be circling the drain for the engine to not at least try to start. I've literally no BS driven home on half an engine. I blew a high pressure oil hose one night on my way home. It was late I had groceries in the truck and didn't feel like waiting for a wrecker. So I dug around and came up with a way to plug the port on the pump that fed the blown hose. A gallon low on oil and running on only 4 cylinders she drove home. Sounded terrible but still had reasonable power considering. This is why I'm thinking you've got fuel problem, cause the engines will almost always run. You just gotta give them what they need.

 

Quite an accomplishment finding a way to plug off 3000 psi.

I've never had that happen but I have had a full bank go out on the IDM and have driven on 4 cylinders that way. It did run. So you're right. It'd have to be pretty bad compression wise to just not start any longer. Probably very incremental and not from running and driving to dead. It is a hard starting truck though, and has been since he bought it a couple years ago now.

He's ran probably 3 cans of ether through it since he's owned it. I used to unplug the GP relay jumper on my OBS truck when I needed to use ether (last resort, almost dead battery and cold out). But I don't think he's bothered with unplugging it on his SD when he's had to use ether to start it in the past. We tried ether this time and it isn't firing.