Quick Test for a 7.3 IDM

[greasybob]

I was diagnosing a no start 7.3 2000 Excusion the other day and after fixing some electrical problems that were keeping me from communicating with the PCM I still had a no start with good oil pressure and cranking RPMs so I did an injector buzz test to see if every thing on that end was OK. I could only faintly hear them buzzing so I cam up with this test to check the operation of the IDM and the integrity of the injector cicuits. I put my low amp probe around the power supply wire to the IDM and back probed the IDM command (input) wire and captured the wave form during the buzz test. The pattern showed a fairly even draw during each injector cycle time and also confirmed that the PCM was doing it's job. I came to the conclusion that I had sticky injectors and thats what was keeping the engine from starting. The same test works equally well while cranking, Itconfirms that both the PCM and the IDM are working and that the injector circuits are good. It does not test the operation of the injector but atleast it quickly eliminates some key components as being the problem. Here is a video link of the test and a screen shot for the Utube impaired. http://www.youtube.com/watch?v=MnldO...el_video_title and http://www.youtube.com/watch?v=MnldO...el_video_title

[greasybob]

I just wanted to add that part of the reason I wanted to try this is that I often get asked from other shops and indivduals in the area if I have a good spare IDM laying around that they can borrow so they can see if theirs is the cause for their nostart or misfire. Maybe this is a better alternative method of testing

[USpMD]

I just wanted to add that part of the reason I wanted to try this is that I often get asked from other shops and indivduals in the area if I have a good spare IDM laying around that they can borrow so they can see if theirs is the cause for their nostart or misfire. Maybe this is a better alternative method of testing

In some cases, replace with known good part is the only answer, in the Dealer world thats not to tough, I have both the IDM and FICM in my lower tool box for just such times, however now being in the aftermarket world its very hard as there are so many makes and modules out there, replacing with known good part can save a lot of time......