89 Taurus killer electrical ground

a 4.5 amp drain would not keep the car from starting, but at 4.5 amp drain at all times with the ignition off is not normal. How did you measure the current? What meter? What method?

You really need the shop electrical manual to continue. Keep in mind it was common for the ignition modules to fail (TFI) on those cars. Two ways to do it, Load shed and check for draw, or check resistances on the lines. It is not uncommon to have a wire harness that is worn through intermittently shorting. One Taurus i junked had such a condition in the distrubutor/transmisson area. Once i tore parts off of it, i could see bare wires. Did you disconnect the alternator? A shorted diode could cause a constant draw. The computer is behind the glove box.

BOB

No special measurements; I just put a Ammeter right off the batterys negative terminal and it reads 4.55. I've got a copy of the 94 shop manuals which I bought for my SHO, which seem to work good enough. There doesn't seem to be that much electrical difference between the 1st gen and 2nd gen. They don't really seem to offer that much. All the tests just sort of end up with "check for physically damaged wires". I was sort of hoping i wouldn't have to take the whole harness out of the car, but i'm slowly resigning myself to the fact. Are there any places that offer pre built harnessess?

----- Original Message ----- From: "BOB URZ" Newsgroups: alt.autos.ford Sent: Friday, October 24, 2003 5:32 PM Subject: Re: 89 Taurus killer electrical ground

I hope you meant to say you removed the negative cable and put the ammeter leads in series with the battery and removed cable. This is the only way you can check current draw with a normal meter. ( Assuming it reads current and has a scale that high) You can read voltage without disconnecting the battery, but not current. And most clamp on meter's do NOT read DC amps. Only AC amps. (if you might have one of those)

If ir was truly drawing 4 amps, you would have a dead battery the next day. Is that what is happening?

Assuming you are using the ammeter correctly, you need to load shed to determine where your problem is. Did you try to disconnect the alternator completely and see if the load dropped? Ar you sure your reading the meter correctly? If the battery is NOT discharging overnight, you don't have a 4 amp draw. Buy the special tool and take off your TFI module from the base of the distributor. Take it to autozone or such and get it tested for free.

I would take the battery out of the car and Charge it overnight. Then have it tested also. If its ok, put it back into the car. Do the headlights

work now? Dim? Bright? What voltage does the battery read? Light on/off?

The schematic you have should be similar. If you truly have a high current draw, something should be getting warm. Did you feel the alternator, distributor module, computer when you think this is happening? Anything smell?

If your truly doing the tests right, you need to remove the computer and disconnect loads and use the ohm meter function of your meter to find the resistance to ground of all the leads. Trouble shoot the problem. Don't shotgun it.

BOB

Take a good look at that big power box rear the radiator. It has relays for the ECM and fans if I remember right. Maybe the one(s)for the ECM is sticking on........

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Bob,

I have to agree with you. 4.5 amps at 12 volts = 54 watts. if it were a wire fault, it wouldn't be warm, it would be smoking. OR, something is continuously running when it shouldn't be. With 18 years of electronics tech and electrical background, my gut feeling is that misguided troubleshooting may be taking place.

Are you saying the computer and sensors are pulling the power ? The cars starts/runs when you jump it? If so check the big black box mounted by the radiator (on top i think) (I think its called a power module or something like that)for stuck on relays. Unplug that box and then check for your 4 amp draw. The box is just a bunch of relays for the computer/cooling fans/ and other things, cant remember.

The box you're talking about is the IIRC (integrated relay control box) It has (4) 30 amp relays in it. Cooling fan, Fuel Pump, computer and ?? Don't remember the other one

Man that was AFU. Its an IRCM integrated relay control module. It must be too early in the morning. My brain is fried.

LOL, Ya thats the box Im talkin about.

The ground off the battery should be fine. I replaced the cable from the battery to the starter, and the starter to the frame, and cleaned up the spot it connected the radiator support. Right now I have every connector off the main wiring harness disconnected, except for the three prong that provides power to the EEC (a yellow and two Blk/Org), the EEC itself, and occasionally the ICM. This includes the Realy module up front, the alternator, and everything else you could think of. I took the ICM and did some tests. The shop manual had some resistence checks for the pins, which all tested sat. I hooked up the battery and the EEC, and plugged the ICM to the connector (not bolted onto the distributor), and the four amp draw was gone. But as soon as I touched the metal back of the ICM to the mounting plate of the distributor, it came back. Comments, questions, concerns?

Well, first we need to get your nomenclature correct. The module bolted to the base of the distributor is the TFI module These are a known failure part. Did you take it off and have it tested for free at a auto parts store like i suggested?

The relay module can be know by a few names. IRM (integrated control module) or (integrated relay module). This is the module above the radiator. This module supplies power to the cooling fans, fuel pump, a/c clutch, and such.

Now, if i understand you right, if you disconnect the TFI module form the base of the distributor and turn the battery power on, the high current draw goes away. (I assume the key is off when you do this?)

If this is the case, something around the tfi module, the module itself maybe, the ignition suppresser resistor or the EEC could be bad. The ignition resistor is between the motor and the radiator on the drivers side. check out its wiring in that area for shorts. As i recall on one of my donors, i found shorts around that region a little higher up in one of the wiring harnesses. I would unplug the TFI module from the distributor (after you check it of course) and check all pins to ground. You may have to remove the intake plenum and other stuff to get to that area for a closer look.

I think you are getting closer. Keep at it.

BOB

Sorry about the poor nomencalture, i'll try to be more specific in the future. In either case, you did understand me right. I tried to take the TFI module it to my local autozone, but they basically told me to go f*ck myself, as is usual with my local autozone (Officially, their testing equipement was down, but it's like that whenever I go to get anything tested). So I just did what the shop manual said, assuming that was all the stoner teenagers at the autozone would do. Anyway, the Ignition resistor is unplugged (white ceramic thing bolted just forward and lower from the TFI?), and the EEC module was replaced with a new one, so that limits it to the wiring harness itself, right? I'll do some more testing when the rain stops.

thanks again for the guidance

I don't have anything to contribute here, but I do have a request: when you do find the short, will you post the solution? I've been following this thread with great interest and I'm very curious where the fault lies. No doubt you are as well.

I own no stock in Autozone. They just happen to be helpful usually in my neck of the woods. Most auto parts stores have a specialized ignition module test set. Unless your way out in the boonies, call around to a different store, find who has one, and get it tested. I just had the one one my 93 tested at O reileys when i thought it was bad. (turned out to be the coil, TFI was OK).

I assume you have this trouble shot down to if the TFI module is plugged in with the ignition off, then you get the current draw. The TFI is really a simple part. The three little terminals that plug into the bottom of the distributor go to a hall sensor to determine where the distributor is.

The other end has 6 wires on it. One of the wires is switched hot that comes from the ignition switch. It supplies power to one pin of the TFI, and one side of the ignition coil. The other side of the ignition coil go back to the TFI too. This wire is the one switched by the TFI to turn the coil on and off. Now the interesting part about this is the coil and the TFI only get power when the ignition switch is in the run or start position. So, if your getting power to the coil or TFI power terminal with the key off, something is funny right there. The other four wires go to the EEC module.

At this point, i would take the module off and measure voltage on all the pins with the key on and off. I would also measure the resistance to ground on all the pins with the battery disconnected.

TFI pins:

PIP profile ignition pickup SPOUT spark output FTO/IDM ignition diagnostic monitor ICM POWER power to module COIL IGN GND

BOB

I did some voltage tests at the end of the connector that plugs into the TFI, and found that three pins had 12 volts present: PIP, SPOUT, and the IGN ground. (pins 1, 2 and 6). If the wiring diagram is correct, then these three wires go directly from the EEC (pins 56, 36, and 16 respectively) to the TFI with no other connections. I tested those three wires for shorts, and they're all fine. So now I'm getting really confused; The path that I've found comes from the positive terminal, to the yellow power wire at the solenoid, continuing into the EEC, out through the three TFI wires, through the TFI into the distributor which is grounded back to the negative terminal. The EEC is replaced to no avail, the wires have been tested SAT to ground, and the ICM is supposed to be grounded. Since the only part of that circuit is hot at all times is the yellow power one, then that has to be shorted to something else, like the actually wires going to the TFI? If it ever stops raining i'll get out there and test the power wire to everything else I can find.

al

As if my car problem wasn't as complicated and stupid enough, I now have yet another random tidbit of information. On the front right hand side of the engine, almost right below the distrubutor, there is what looks like a ground strap from the engine block into the main wiring harness. I found out today that if I disconnect everything EXCEPT that ground strap and the EEC, then the 4.5 amp short is present, without either the TFI or the VSS connected. If I disconnect that ground strap, and just leave the EEC, it goes away. So I checked the continuity of all the wires in the EEC harness to that grounding strap, and pin 59 was the only one with continuity at all, and it was something like .3 ohms, which is a good sign. The 89 diagram from the chiltons book shows that pin 59 gets spliced out to Fuel injectors 3, 5, and

6, and then gets spliced back into the three other injectors, a couple sensors, and back into the relay module. Anyway, the newest theory is this: Since the line goes from pin 59 of the computer, out to three fuel injectors, then back into a line into the relay module, which is unplugged, it's a good bet that somewhere between those three fuel injectors is a pinched wire, touching the block, going to the grounding strap, and creating the 0K Ohm short. If anybody has any comments or flames regarding this, i'd certainly like to hear them. I'm going to get out there probably this weekend and start pulling off the intake and the the injectors. Again, everybodys help is greatly appriciated

Al

I am looking at my 90 manual, so it may not be the same, but it should be close.

All the injector harness loop around the front of the engine, around the passenger side (right) then back around to the drivers side (left). Although i cannot verify it, it looks like there is a connector where it goes into the main harness. If there is, pull it and then do your resistance readings again..

Now, remember what i told you before when i found a problem in one of my donors? Look real close the the left side (Drivers) on top of the transmission area. That is where the big fat harness comes around and jumpers off to other locations. On my donor, i found that harness wore through the bottom touching the area above the transmissions and the end of the engine. You may have to remove some stuff to get to that area, but you need to closely inspect the harness in that area for any signs of abrasion. Also, look over all the harness for any signs of melting and overheating. especially around the exhaust manifolds. My bet is you will find a cut in the wire and the insulation rubbed off between the distributor and the engine block on the fat wrapped cable. If you can affix your ohm meter, you can measure the short and then try to wiggle harnesses to see if it changes. Good luck.

BOB

It just sounds like the ECM is "on" when its not supossed to be. I think you are getting carried away here. Did you check that power module on the radiator yet? It powers the ECM through relays. The relay for the ECM could be stuck. That module is known for having problems. Unplug it and see if your draw goes away :) Doesn't the car run?

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This is what's killing me every time I read this thread. A 4.5 amp continuous draw at 12 volts is 54 watts. If this were a short circuit, it would be more than 4.5, to the point of blowing fuses. If not a complete short circuit, 54 watts would generate enough heat to melt everything around it. Most soldering irons are about 20-30 watts. This trouble shooting has gotten way too complicated.