Surely you all knew this was coming some day, so here are some questions.

I'm looking at building a tester that will plug into the 42 pin connector to test each UVCH, glowplugs, and injector.

As part of this test, I need to know what the specs/readings should be for resistance of each, and how many amps needed to trigger each injector and (if) there is anything I can test upon trigger to help diagnose....

...and most importantly, if there is any risk to electrically triggering an injector without HPOP/engine running? Maybe a limit to how many "triggers" can be performed in a single run?

Resistance of glowplugs?

I have a few other things in mind, too, but this will get me started.

Thanks!

 

Resistance between the common and injector leads should be less than 5 ohms, but the real key is to look for differences in the readings across all 8. I've seen a bad injector solenoid that ohmed out within spec, but was 0.2 or 0.3 ohms off from the rest of them. Glow plugs should ohm out between 0.6 and 2.0

Yes the injectors can be commanded to come activate without the HPOP or engine running. It's called a buzz test. This is strictly an audible test that lets you hear the poppet bouncing around so a semi-quiet poppet becomes troublesome to distinguish. I'm also not sure of what power to use to do a home made buzz test since I've always used a scanner to do it.

Pulling the valve covers and watching for oil discharge on a cold engine is a better indicator of injector condition in my opinion.

 

I believe you'll need to make an injector drive module a piece of your breakout tool.

buzzing injectors is kind of hard on them. The fuel is the lube, when you buzz them it is a dry fire.

 

Question,
does the injector actually fire on a buzz test? I'm asking because I'm genuinely not sure.

My basic understanding was that high pressure oil caused the injector to do it's squeeze, spray, bang thing. And that the poppet valve controlled the flow of oil. So without high pressure oil, they shouldn't move any fuel. Or am I missing something like residual high pressure oil in the galleys? But even then without a lot of entrapped air I wouldn't think there could be enough volumetric expansion to do much.

Am I somewhere near base?

 

1. The GP power never passes through the 42-pin connector, or the forum would be fraught with burned-up 42-pin connector threads. The GP power goes directly from the GP relay or GPCM and to the 9-pin connector on the valve cover gasket. The ohms on a good GP read like a dead short on many inexpensive meters, but they are typically less than 1 ohm.

2. The buzz test activates the solenoid - which does nothing more than open a poppet valve that would allow High Pressure Oil into the injector - if there was any ICP. Since the buzz test is not to be done on a running engine, there is never any ICP. Injector Control Pressure is what powers the injector. No oil pressure? Nothing there to hydraulically actuate the injector (fire fuel into the cylinder). The poppet valve is soaked in oil, and it didn't just go away. While I wouldn't want fire a buzz test for an hour and walk away, the short duration of a typical buzz test isn't likely to hurt anything.

3. The IDMs since the early 7.3l PSDs use anything from 100 volts to the later SD version with 120 volts - and my Swamps IDM kicks things around with 140 volts. That doesn't mean you line up 10 automotive batteries in series and throw a switch to activate the solenoid - nor do you plug it into the wall outlet. The solenoid packs are engineered to take an activation signal that lasts nothing longer than single-digit milliseconds. You'd be amazed at how fast that is. There are 1000 milliseconds in one second, and one frame of 60HZ Hi-Def video lasts 17 ms. One frame of gaming-quality video lasts 5 and 1/2 times longer than one firing of an injector solenoid. I think it's best we leave that kind of control to the PCM/IDM with a buzz test - initiated by an easily-attainable OBDII tool (link in my signature).

 

Thanks for the clarification tugly. Thanks for all the solid info, and help, you've given all of us over the years.

Thanks,
Joe

 

The distilled core is this: The Solenoid is a "Gatekeeper". This is true on any injector, HEUI, Common Rail, Gas, Diesel, propane, etc., It determine what gets in (fuel), and how long the gate is opened (time). Open/Closed - On/Off however you say it.

Activating an injector while an engine is running could (will) do anything from nothing to breaking the Crank if it were a companion cylinder.

You may get by with it the first time on a Gasser. But, Diesel is a much more uncontrolled explosion. Something will give.

REMOVING power actuation is a good troubleshooting process. It allows one to determine if the problem worsens or does nothing at all. The one affecting it the least is predominately the strongest suspect. You're interrupting the programmed signal from reaching the actuator.

 

Great input guys!

This is the kind of info I'm looking for. The tool I envision is microprocessor based, so milliseconds aren't an issue.

I'm considering OBDII commands, too, but that is down the road a bit- IF I decide to tinker with it sometime.

Even thinking about Wifi-remote diagnostics. Maybe the OBDII would be easier...

Good point about the GPs and the GPR (or Calif). Have to think about that a bit.

I am thinking of making something decent and simple, with a screen and stuff, that can be used repeatedly for troubleshooting and testing.

Unplug 42 pin connector, run tests to check the connector, UVCH, GPs, and Injector connections.

OBDII/scantool use would be great...if our systems had the necessary sensors and test subsystems. Unfortunately...

As these systems are getting more familiar to me, I'm starting to understand some of the systems. Not all the numbers and nuances, which is where all your collective knowledge is invaluable

Too many times, tests and tools come into being, but only test "book" things, not real-life/practical items.

I've seen the breakout box some have made to disable injectors. Pretty neat, but manual. No sense recreating the same thing- looking for EXTRA capabilities

I am testing out some technology and it has a bit of a learning curve for some of the items, so looking to do something that has a practical benefit afterwards.

Tips, ideas, suggestions....?