I was waiting for this. On some trucks that gauge can take a pretty long crank to come up. Personally, I'd first try to retorque the injector with new copper rings - they don't cost much and it's the most likely problem since that's what you worked on. Sometimes the threads on the hold down clamp bolts get stretched a little. Is this the first time that injector has been out? You can buy a new bolt or torque an extra pound or two. If you know anyone with a SnapOn or IDS scanner that can do a cylinder contrib test, you might see the leak.

 

 

Oh yeah. Sat on the side of the road in Arkansas for a week tearing into stuff only to find it was the valve. They're about $300 from the dealer. Be nice to swap in a known good one to see if that fixes it before you buy a new one. I can pull one off one of my trucks if you're in the Houston area.

 

 

Check the junk yards for a used one, and if it fixes the problem just keep it as a spare if you'd rather have a new one.

 

 

 

Most people think they will hear something when powering the IPR. You won't. The valve is closed and the pressure
the pressure from the HPOP forces it open. Power is applied by the PCM in PWM format to hold it closed against the
pressure. That is how a digital device controls something analog.

To make this less confusing. The valve is closed and the power keeps it closed. Turn the power off and anything it was
holding back. Be it air or oil pressure. It gets dumped out the vent holed back into the crankcase.

Some times some tiny trash will get past the screen and block the valve open. When that happens you don't get the
needed pressure. There is an easy way to clean the valve. You take a awl or small punch. Remove the screen. Push
the tool into the small hole behind the screen and you will weel it hit a stop. Push on it and you will feel it move back.
Use some brake or carb cleaner to flush the valve out from where you have the awl pushing it open. The spring will
close it as soon as you let the pressure off. If you use something to catch what comes out you can check for trash if
you would like to see if anything was in there.



More info if you want to read about it.

A Pulse Width Modulation (PWM) Signal is a method for generating an analog signal using a digital source. ... By cycling a digital signal off and on
at a fast enough rate, and with a certain duty cycle, the output will appear to behave like a constant voltage analog signal when providing power to devices.
May 2, 2018

https://knowledge.ni.com/KnowledgeArticleDetails?id=kA00Z0000019OkFSAU

I looked for a good visualization of how this works and did not find one I liked.
Basically the longer the pulse on time the higher the pressure. You can see that
if you look at the signal with an oscilloscope.

 

Sean, the IPR valve is open until the PCM grounds it.

Many people hear it click when commanded closed, especially when air is flowing and the valve is closed (stopping the air flow). That said, I know people say they can't hear the click. I can hear mine click.

The valve is "duty cycled" closed w/ the PCM ground. It is a fast acting valve.

 

I disagree. I have two on the bench.

 

So why do we have to apply the power and ground to the IPR to seal the system and do the pressure test?

Edit - let me clarify .......

When I say "open", I mean open to the crankcase.

Another edit, I see what you are saying now ............... the valve has a return spring that will hold it closed to the drain (not a particularly strong spring), but the actuator isn't in the closed position until power and ground applied. B+ power is applied w/ key on (and is continually supplied), ground is applied in a duty cycled manner by the PCM when cranking,

 

Correct. Applying power/ground to the IPR manually CLOSES the valve to keep the produces HPOP pressure in the system. Take away the power/ground the generated pressure will force open the valve and bleed off pressure back to the crankcase instead of the system.

 

Sorry about that I got distracted and did not finish my thoughts.

If the valve were open then there would be no need to depress the spring so that you can spray brake cleaner spray in to wash out junk.
Electrically it is an open circuit until the PCM closes it by supplying a ground (current sink).

If I can get at the valves I have in the garage I will take a closer look at them and report back on it.

 

We're talking about it in a pressurizing state which easily over powers that spring. Power/ground to the IPR CLOSES it to build pressure.
If it was default closed and powering it opens it, then a failed IPR would build max pressure on a crank. We know that doesn't happen.
Also when an IPR screen breaks and gets stuck in the valve, the screen holds it open dumping all the pressure. The IPR tries to pull it closed @ the 87% DC to build pressure.

 

I see we are all now on the same page with this.

If I can find that valve out in that big pile I have out there I will see if I can take it apart for display.