Ford Power Stroke Nation banner
1 - 18 of 18 Posts

·
Registered
Joined
·
1,568 Posts
Discussion Starter · #1 ·
anyone have hints on the common wiring issues that kill IDMs in a 1997?
or hints on how to find which harness has the issue?

I replaced the valve cover gaskets with Dorman SD style and there was a noticeable improvement in how it ran vs the nasty old stuff but it still kills the IDM in about 3 days.

I am thinking about unplugging the 42pin and the IDM plug and sending full 12V down each wire to see if it will show me a short

I am going out right now to do the GB#103 tests again but it has never failed those.

thanks in advance to any help you can provide
Michael
 

·
Registered
Joined
·
1,568 Posts
Discussion Starter · #3 ·
I got the harness spread out now searching.
I was assuming chafing would be through the loom but internal is the search now I guess... always something
chances are it will have to be inside the tinfoil and shielding bare wire, so whats the best for replacing the fragile tinfoil?
 

·
Registered
Joined
·
3,438 Posts
Hey Michael,

Can't provide any help buddy except for moral support, whats with the tinfoil anyways? Wonder if you could just use quality Alcan stuff that comes in the wide rolls. Been eyeing up the 97 harness as it's kinda nasty greasy looking, have bought a bunch of wiring harness covering as the stock stuff is pretty brittle. For now just leaving greasy dogs lay although with the chicken #### little stutter, miss I have, might be right behind you.

keep us posted....

jrc
 

·
Registered
Joined
·
424 Posts
The tinfoil is a shielding tape.

The tinfoil, along with the bare wire (called a drain) keeps the RF signals from escaping. The RF "noise" is generated by the high frequency signal that drives the injectors.

In the "olden days" you would get an annoying buzzing through the radio if you didn't have shielded spark plug wires. If the tinfoil and drain are removed you'll get that same annoying buzz.

In "modern days" I wonder if the RF noise could also affect cell and GPS operation??

The tape is easily aquired through a Google search for RF shielding tape. I bought a roll from Digikey recently when I needed to extend the engine haness during an engine swap.
 

·
Registered
Joined
·
3,438 Posts
Man I feel like such a hillbilly..... RF shielding tape.... For heavy gauge Alcan aluminum foil. Hahahaa.
 

·
Registered
Joined
·
1,568 Posts
Discussion Starter · #7 ·
thanks Mark.
it looked like Foilon I have seen in other industries.
with the nomenclature I can hunt it down, maybe SMI locally will have it
 

·
Registered
Joined
·
2,761 Posts
Did you convert to a SD UVCH? If you switched over to a SD harness, are the wires in the correct spot?

Also I would have never used Dorman UVCH. A lot of info on the harnesses failing.

Does the IDM fry or shut down a bank? Did you ohm out the injector solenoids?

Billy T.
[email protected]
 

·
Registered
Joined
·
1,568 Posts
Discussion Starter · #9 ·
issue predates harness work
yes converted to SD style thinking the issue was in the UVCH
runs good for about 3 days worth of trips to work, then seems to lose cylinders, then seems like the timing goes way late.

I am going to pull the Hydra out and see if it will run better without it, to rule it out. that just turns the truck in to a Dodge-like smoke machine
 

·
Squeezing out Torque...
Joined
·
157 Posts
So still no love on that? (Have many PM's in to you...)

I sent you to that bulletin... but I noticed it didn't check one issue that I saw somewhere else. One of the warnings I read in doing the test described in that bulletin, is that you check it at the connector pins instead of piercing the insulation.

I read the background story behind that warning is that if you pierce the shielding (insulation) of the wires in that harness, you will have problems from then on with the wires leaking high-voltage, arching out to a ground. I didn't realize until then, that those wires were shielded, nor that they carried a high-voltage frequency type of voltages across them.

So it makes sense that if you covered them with diy metallic sheilding, that if it had any leaks in that shielding before that... it would be like covering your spark plug wires (gassers) with aluminum foil, eh? That's why a trouble spot for them is usually were a pushrod wore into the shielding and intermittently shorts out... I guess if you did a mod'ed higher voltage IDM, that would show worse?

It also makes sense that in GB's doc's on IDM's, that the wiring shorting out, grounds and/or too low a resistance in the injector coils... seems to blow the diodes in the IDM. That's how my IDM went... Low resistance in 3 injector coils.

As I remember, your problem is on the driver's side = cyl's 2,4, 6 & 8... right? So if that harness, eh? Maybe strip off the plastic wear guards, drape it over some aluminum foil and let it run at night in the dark... (If an auto, with someone in inside, on the brakes with it in gear = a load.) I know the fireworks method seems old school, but it works in a pinch when looking for intermittent high-voltage arching..

Me? I'm on my own adventure also. I over-upgraded and went over that balance threshold. (Fricken' performance fell through the floor/backwards with an upgrade!!!) Backing that off until my other upgrades catch up to that step. (restoring that balance!!!)
 

·
Registered
Joined
·
1,568 Posts
Discussion Starter · #12 ·
does the IDM share the same connector pins as the PCM?
I just did a repair on the PCM connector involving replacing the plastic housing with a wrecking yard sourced harness
I have a slew of pigtails from the donor harness that if they are the same as the IDM I can use to make a bypass test harness to go direct from IDM to injectors bypassing the 42 pin connector.
I also grabbed a 42 pin connector from the wreckers.
the only 7.3 in the yard was in an Econoline that had been raped so the harness I hacked was from a gas pot f150
 

·
Squeezing out Torque...
Joined
·
157 Posts
does the IDM share the same connector pins as the PCM?
What do you mean by "share"?

It has some circuits that go from the IDM to the PCM, yes. Is it the same connector style, no. Are you thinking that your bad PCM connector is burning out your IDM's? ...??? Let me look at one of my wiring diagrams to see whet circuits they are (that go between the two) and get back to you with that...

EDIT:
Here's the circuit that go between the two (PCM to IDM)

CID Signal (PCM) pin 96 to #3 to pin 16 (IDM) CID Signal In
Fuel Delivery (PCM) pin 95 to #4 to pin 17 (IDM) Fuel Delivery
IGN Signal In (PCM) pin 48 to #6 to pin 4 (IDM) IDM Feedback
Signal Return (PCM) pin 91 to #7 to pin 2 (IDM) Signal Return
Power Ground (PCM) pin 51 to #8 to pin 26 (IDM) Power Ground

Note: the middle #'s are through an 8 conductor connector that is in the harness between the two.
 

·
Squeezing out Torque...
Joined
·
157 Posts
See Attached...
 

Attachments

·
Registered
Joined
·
1,568 Posts
Discussion Starter · #15 ·
can I use connector pins from PCM to build a harness from the IDM to the injectors :)
 

·
Squeezing out Torque...
Joined
·
157 Posts
can I use connector pins from PCM to build a harness from the IDM to the injectors :)
The individual pins themselves should be the same, but the wire is not. I can buy the individual female terminals at a electronics store here locally. I can get you a number from them s that you would have a brand/item number cross reference.

The wire itself is different. Form the IDM to the valve covers... high-voltage shielded wires. I would not have believed it, but they are.

Maybe I should stop by that same electronics supply to see if that type of wire can be sourced... Hmmm... I'll do that when I get out of class today.
 

·
Registered
Joined
·
1,568 Posts
Discussion Starter · #17 ·
PCM pins are smaller, maybe IDM are the same as the eecIV
 

·
Squeezing out Torque...
Joined
·
157 Posts
1 - 18 of 18 Posts
Top