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

[Luke_IDI]

I am trying to diagnose a crank no-start on a 2003 E-350 7.3. I have another thread detailing the convoluted diagnostic process here if anyone is interested: https://www.oilburners.net/threads/slow-crank-after-possible-overheat.92706/

This new thread is for clarification on the simple issue of testing my ICP sensor.

When cranking, IPR duty cycle goes to 60-65%. ICP correspondingly climbs and climbs to 3700 psi.

Is this IPR reading a real or inferred reading? I have read that the PCM will disregard the actual ICP reading and report an inferred value if the actual ICP reading is vastly different from the desired. If this is the case, one could see high ICP on the scan tool while still having low ICP.

I have seen it suggested to monitor voltage at the sensor itself. I back probed the wires and interpret the following:

Black with white stripe = ground

Gray with pink stripe (?) = 5v ref

Blue with green stripe = signal

I get 5v KOEO at the reference wire. I get 4.6v at the signal wire. According to a chart I found, 4.6v is pegged high. There is no change in the signal wire voltage when cranking. Therefore I infer that the sensor is bad, and the PCM is making up values for ICP.

I hope someone can corroborate my understanding so that I can feel confident spending $150 on the new part.

If the sensor is indeed good, if anyone has an explanation of how it works electrically speaking, and any other thoughts on why the injectors are spitting no oil (not firing, I assume), they would be most welcomed.

 

[u2slow]

Unplug the icp sensor. The idm assumes a default value for starting. If it starts fine then, the icp is usually the culprit.

 

[XOLATEM]

How about the ground side..? what is it showing..?

I would start with going through every ground connection you have with a fine-tooth comb...

The high signal reading can result from no place for the current to go...

No ground or insufficient ground will just absolutely ruin your week...

 

[Luke_IDI]

Unplug the icp sensor. The idm assumes a default value for starting. If it starts fine then, the icp is usually the culprit.

No start when the sensor is unplugged. There may also be a problem with actual injection control pressure, or even fuel supply. Trying to answer the question here so that I can accurately monitor pressure to help the rest of the diagnosis.

 

[Luke_IDI]

How about the ground side..? what is it showing..?

I would start with going through every ground connection you have with a fine-tooth comb...

The high signal reading can result from no place for the current to go...

No ground or insufficient ground will just absolutely ruin your week...

My results were measured using the ground wire at the connector for ground.

It sounds like you are saying that my signal readings, while possibly inaccurate, are not simply values that the computer has “made up” due to an unreasonable ICP signal reading. When I unplug the sensor, I do see the ICP reading on the scanner default to a single value.

 

[Rdnck84_03]

If there is oil in the icp sensor connector, it is bad. Since it won't start with it unplugged, it is also not the smoking gun your looking for.

If you do replace it I would strongly recommend spending the extra and buy genuine Motorcraft. I don't remember what brand it was but I bought 1 at O'Reilly that blew the guts out, put a dent in the hood, and covered everything under the hood in oil.

James

 

[u2slow]

I agree, it's prob not the icp. Have you tried plugging in the block heater? (Some problems are lessened with heat).

Other tips ...

Can you swap/borrow another idm to try?

Ensure the hpop reservoir isn't draining down, and is filling (via lpop).

What is the age/miles of the hpop and ipr?

Fwiw, I had a miserable time with a '97 van for starting. A new lpop changed nothing. Preheat helped a little. Replacing the hpop ( with used) and a new ipr made the van run reliably again.

 

[XOLATEM]

I bought 1 at O'Reilly that blew the guts out, put a dent in the hood, and covered everything under the hood in oil

I would characterize that happening as a 'catastrophic failure event'...in todays parlance...
Back in the day...when things were closer to the truth...and people dealt with the truth...instead of trying to dress it up...it would have been something along the lines of...

'The thing just blew up...that ain't no ****...!!'

So...what did the manager at O'Really's say about it..?

 

[XOLATEM]

My results were measured using the ground wire at the connector for ground.

you did not get the whole story if you did not run your meter directly to battery negative...you only got the ground signal after it has run with other sensors...

It is advantageous to check the ground at the sensor first and note if it looks good....or only fair to middlin'...it would help you see the whole electrical picture...

A lot of times...IMHE...the ground line is fed through a number of other sensors in series...or else each sensor would be pigtailed to a ground on the engine or chassis or body...

They are all ganged together IMHO to save on parts needed to attach all of the extra grounds

You could have a sensor pulling down the ground or reference voltage somewhere along the line...and...with the adverse operating environment of a diesel engine...sensor degredation is inevitable and a fact of life...

It the truck totally stock...? or has any aftermarket equipment or programming been added..?

 

[Rdnck84_03]

'The thing just blew up...that ain't no ****...!!'

The way they are designed, the steel case is crimped at the top holding all the plastic internals together. Either the crimped wasn't good, or the Chinese steel was so soft that it couldn't hold the 4,000 psi that can be seen in the rails.

I didn't even bother to take it back since it only had a 1yr warranty to begin with and it had been on the truck about a year and a half. That and even if they did warranty it I wasn't going to re install it. I upgraded to the Motorcraft and never had another issue.

James

 

[Luke_IDI]

Thanks for all the suggestions…. If you are interested in seeing more of the picture of what I have done to the truck so far, I’m keeping that going in my other thread, “Slow Crank…”:

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

Regarding where to measure ground, I would think it would be an issue if I were getting low voltage as opposed to high voltage, but it appears my signal voltage at the sensor is pegged high. I will check again, isolating the wires from each other, and see what happens.

What is the function of the IDM as it pertains to my question of ICP operation? I have electrical pulse at the injectors while cranking, I assuming this means the IDM is doing its job.

HPOP reservoir is full and stays full (3/4” from top).

200,000 miles on the vehicle. I have no maintenance history. No mods that I know of.

I was really just hoping to use this thread to find the answer to my original question: does a changing ICP reading on a scan tool necessarily indicate a functioning (to some degree) ICP sensor/circuit? Or can that changing reading be something that the computer infers?

Definitely interested in any and all ideas, just worried that it will become too confusing if split between two threads. So if you want to follow along, check out the other thread.

 

[u2slow]

What is the function of the IDM as it pertains to my question of ICP operation? I have electrical pulse at the injectors while cranking, I assuming this means the IDM is doing its job.

What magnitude/voltage is the pulse? I don't know the right value, but if it low, the injector may not fire. (Like low voltage to a solenoid.)

My understanding is the ICP provides the pressure signal feedback for the IDM to control the IPR.

Years ago was troubleshooting another PSD van (no start) and I swapped my own IDM over.... then it started fine.

 

[Luke_IDI]

What magnitude/voltage is the pulse? I don't know the right value, but if it low, the injector may not fire. (Like low voltage to a solenoid.)

My understanding is the ICP provides the pressure signal feedback for the IDM to control the IPR.

Years ago was troubleshooting another PSD van (no start) and I swapped my own IDM over.... then it started fine.

I will try a scope if ICP and fuel pressure check out. I do have a friend who would probably loan me his known-good IDM.

 

[Rdnck84_03]

I'm not sure where the idm is located on the e-series superduty, but the f-series is in a real pita location. You have to remove the driver side inner fender to get to it. Its rite behind the fender badge. If possible try to borrow an idm from an obs truck, they are under the hood and easy to get at.

James

 

[u2slow]

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.