Is my ICP sensor bad? Do I have low or high ICP?

[Luke_IDI]

Ok, finally managed to assemble a few different adapters, a grease whip, and a 3000 psi gauge to look at ICP manually.

The ICP sensor thread is M12x1.50. The seal is with an O Ring as with the sensor. My local hydraulic shop had this fitting to JIC, then JIC to 3/8” pipe, 3/8” pipe to 1/8” pipe, grease whip (rated 3000 psi), 1/8” pipe to 1/4” pipe, gauge.

As verified by the mechanical gauge, ICP does indeed rise to 3000 psi in a matter of a couple of seconds. So to answer the first part of my original question, the ICP is reading correctly.

Is it possible to see rising values like this when they do not correspond to actual pressure? I can’t say for sure. I have heard a mention or two that an electrical issue could cause that situation, but I’m not sure what.

Where this stays interesting is: why is the PCM commanding full IPR duty cycle?

Thanks to everyone who posted. I’m going to copy this into my other thread, “Slow Crank…” and continue updating about the diagnostic process there. To be continued…

 

[Luke_IDI]

The E-series IDM was easy to get at. Open the hood and almost stares back at you from the driver side. Biggest problem is rain ingress between the hood and fender.

Luckily my friend who may loan me one also has an E-series.

 

[Luke_IDI]

Again, here’s the link to the other thread:

Slow crank after possible overheat

I’ve been asked to take a look at a 7.3 Powerstroke that the owners recently purchased. They report that the truck (van chassis box truck) ran great for them on an initial test drive, then on the way home lost power and died. They noted white smoke in the engine bay and coming out of the oil...

www.oilburners.net

 

[Luke_IDI]

Ok, I finally assembled all of the fittings necessary to adapt to the ICP sensor port. The port is 12mm x 1.50. My local hydraulic shop was able to adapt this to JIC. I then went to a grease whip hooked to a 3000 psi gauge.

As verified by the mechanical gauge, ICP does indeed rise to 3000 psi in a matter of seconds!

To answer my original question, my ICP is putting out accurate readings.

I am not able to answer my secondary question: is it possible to see changing readings that do not correspond to actual ICP.

My third question: why would thee PCM be commanding max IPR duty cycle if there is plenty of ICP to fire the injectors?

I am going to continue the saga at my other thread, “Slow Crank.” Thanks to everyone who posted! And If I do swap an IDM to test, my friend who may loan me one also has an E-series.

Is there any risk of blowing my friend’s IDM by putting it in the no start truck?

 

[Luke_IDI]

What the double post, whoops!

 

[Luke_IDI]

Here is what the IDM is sending to the easiest to access injector. This is with the injector unplugged.

 

[u2slow]

How much voltage is that?

My understanding is the IDM feeds 100-130vac (depending on the revision).

Do you have fuel pressure?

 

[Rdnck84_03]

On an 03 I believe the voltage sent from the idm to the injectors should be 120v.

If I remember correctly
obs is 100v
Early 99 is 110v
99-03 is 120v

Any of those idms can be swapped around the voltage doesn't make any noticeable difference.

James

 

[Luke_IDI]

Ah! Interesting! I set the range for 50v in that shot. I’m still getting used to my scope, so I’m not sure if it’s showing -50 to 50 or -25 to 25. I assumed -25 to 25, thinking those would be 12v pulses. I did wonder why the pulse went up and down—AC would explain it! At any rate, what you’re seeing is definitely not 100+ volts. Suspect bad IDM?

 

[Luke_IDI]

It’s also not much of a consistent pulse, is it?

By the way, I did test fuel pressure at one of the bowl plugs today. 64 psi dropping to 60 psi while cranking. Someone suggested pulling the fuel line to the rail and checking for pressure at the rail. Think that’s worth doing?

 

[Luke_IDI]

I’m also reading that the IDM kicks the voltage up to 100+ DC volts. That would make sense too, but in that case I’m not sure what’s up with my up-down pulse.

I will try to get a good picture of what is going on with those injector pulses. Maybe I can get a good capture and zero in on them. I’m inclined to think this is a pretty good picture of what’s going on. I think it might be time to talk to my friend about borrowing his IDM!

 

[Luke_IDI]

I just hooked my scope up to a 12v battery. Pulses are the same height, approximately, as those in the screenshot I posted, with the same range settings. So the injectors are only getting 12v maximum from the IDM. Looks like we found our problem. Will swap with the other IDM ASAP and report back.

 

[Luke_IDI]

No change with the good IDM. I believe I misinterpreted the voltage my scope was showing earlier. Good IDM showed a similar wave form. Captures from IDMs 1 and 2 are attached. One vertical square is equal to 50v. These readings are taken at the injector connector. Do these pulses look adequate to fire the injector? I still do not see oil coming from the injector, even though I have verified ICP to be sufficient with a mechanical gauge. Is it possible the PCM is sending a weak signal to the IDM, and the injectors are not getting enough voltage for that reason?