Inertia Switch ('85 EFI dual tanks)

[Nemesis F150]

The inertia switch was just an easy place to start, kind of in the middle. So if you don't have power to it then you need to move upstream. Check out the wires to the relay. The yellow wire should have power and when the relay closes the Pk/Bk is powered. But not if the relay doesn't close.

Good news: We have 12+V at the Fuel Pump (FP) Relay, Yellow 37 end.

Also, There is a circuit diagram on the back side of the made-in-china relay:

And for comparison, here is a picture of the pin layout of the china and OEM Ford Relays (complete with some dielectric grease):

The horizontal top-right horizontal pin is opposite the Yellow wire. [Green relay = Ford]

China relay has two horizontal pins

The three vertical pins, #3, 1, and 2 correspond to the china relay diagram.

 

[Gary Lewis]

Good news: We have 12+V at the Fuel Pump (FP) Relay, Yellow 37 end.

Also, There is a circuit diagram on the back side of the made-in-china relay:

And for comparison, here is a picture of the pin layout of the china and OEM Ford Relays (complete with some dielectric grease):

The horizontal top-right horizontal pin is opposite the Yellow wire. [Green relay = Ford]

China relay has two horizontal pins

The three vertical pins, #3, 1, and 2 correspond to the china relay diagram.

That is good news. Now, do you have power to the Pk/Bk wire coming from the relay to the inertia switch? If not we need to know if the computer is telling the relay to pull in.

[Nemesis F150]

Now, do you have power to the Pk/Bk wire coming from the relay to the inertia switch?

Can't figure out where to test to find out.

At the Fuel Pump Relay, the Yellow is obvious, and its 12+ Volts.

The Red is "probably" obvious because it is most likely "R" on the wiring diagram.

There are two other wires listed in the wiring diagram that I can't make a "wire code" connection with:

1) T/LG D 97 that goes to the EEC

2) 787 PK/BK H that connects to the C118 (connector?) and then connects to the 37 Y running to the Inertia Switch.

There are two colored wires of unknown color: One is a very light color in the picture, a very light shade of pink???, and the other that looks like a shade of brown.

Tried to find the location of the C118 connector but was unable. The yellow "37 T" that goes to the Inertia Switch is wrapped in electrical tape and then disappears into a wire harness that is also wrapped in electrical tape, and then it disappears into the dark underside of the dash.

Is there a table that says where the connectors, like C118, are located? (other than somewhere between the Fuel Pump Relay and the Inertia Switch?)

Or, maybe what color wire of (1) and (2) would be the 787 PK/BK H?

Thank you for all your help so far, this is progress.

[ArdWrknTrk]

Now, do you have power to the Pk/Bk wire coming from the relay to the inertia switch?

Can't figure out where to test to find out.

At the Fuel Pump Relay, the Yellow is obvious, and its 12+ Volts.

The Red is "probably" obvious because it is most likely "R" on the wiring diagram.

There are two other wires listed in the wiring diagram that I can't make a "wire code" connection with:

1) T/LG D 97 that goes to the EEC

2) 787 PK/BK H that connects to the C118 (connector?) and then connects to the 37 Y running to the Inertia Switch.

There are two colored wires of unknown color: One is a very light color in the picture, a very light shade of pink???, and the other that looks like a shade of brown.

Tried to find the location of the C118 connector but was unable. The yellow "37 T" that goes to the Inertia Switch is wrapped in electrical tape and then disappears into a wire harness that is also wrapped in electrical tape, and then it disappears into the dark underside of the dash.

Is there a table that says where the connectors, like C118, are located? (other than somewhere between the Fuel Pump Relay and the Inertia Switch?)

Or, maybe what color wire of (1) and (2) would be the 787 PK/BK H?

Thank you for all your help so far, this is progress.

97 is tan with light green dots

787 is pink with black hash marks

The pink wire goes to the inertia switch.

You could test for continuity from the relay socket to the inertia switch plug... (the location of the connector (C118) is irrelevant if there is continuity)

But my guess is that the EEC is not bringing wire 97 to ground and completing the pull-in coil circuit.

My understanding is that the computer should initially ground this for a couple of seconds, then it waits for a PIP signal from the distributor pickup.

The rising side of the PIP signal resets the countdown.

If the engine is turning and the ignition is on, the EEC never times out and the relay stays closed.

Additionally, the heavy EEC ground at the front of the battery negative terminal needs good connection.

But if you've used a noid light to check injector grounding pulses already then that ground from the battery negative terminal should already prove good.

[Gary Lewis]

97 is tan with light green dots

787 is pink with black hash marks

The pink wire goes to the inertia switch.

You could test for continuity from the relay socket to the inertia switch plug... (the location of the connector (C118) is irrelevant if there is continuity)

But my guess is that the EEC is not bringing wire 97 to ground and completing the pull-in coil circuit.

My understanding is that the computer should initially ground this for a couple of seconds, then it waits for a PIP signal from the distributor pickup.

The rising side of the PIP signal resets the countdown.

If the engine is turning and the ignition is on, the EEC never times out and the relay stays closed.

Additionally, the heavy EEC ground at the front of the battery negative terminal needs good connection.

But if you've used a noid light to check injector grounding pulses already then that ground from the battery negative terminal should already prove good.

Thanks for the help, Jim. Good suggestions.

 

[85lebaront2]

Thanks for the help, Jim. Good suggestions.

I will throw a suggestion out on these and some of the later systems. Ford used (as shown) some very strange relay configurations. Their function is the same as the pretty much standard Bosch 5 pin relays. Before I would put a Chinese relay of indeterminate quality in my vehicle, I think I would buy a relay kit (fog lights maybe) that uses a standard Bosch cube relay. Ford went to these in the later trucks with the PDC. These are some common (I shared some pictures a while back of Ford, Chrysler and GM relays, all had proprietary numbers but were interchangeable). I have several boxes of the various relays as they are so common and rarely do I find a bad used one from a junkyard. Of the Ford ones I had, two brown skirt and one green skirt, they were all bad. If you need one for underhood where the skirt is needed as a shield, Chrysler minivans in the 90s had a row of them on the left side underhood on a long bracket. These also feature a lock tab on the socket for some applications. Some will be 4 pin, which will work fine, the normally closed contact (Bosch 87a) is not on these, but the normally open (Bosch 87) is there and that is what turns on.

 

[ArdWrknTrk]

Is there a table that says where the connectors, like C118, are located? (other than somewhere between the Fuel Pump Relay and the Inertia Switch?)

C118 is only identified as a brown 2 wire connector located near the inertia switch.

(I wanted to attach the page from the EVTM, but the forum will not open the "insert image" window for me today... )

[Nemesis F150]

97 is tan with light green dots

787 is pink with black hash marks

The pink wire goes to the inertia switch.

You could test for continuity from the relay socket to the inertia switch plug... (the location of the connector (C118) is irrelevant if there is continuity)

But my guess is that the EEC is not bringing wire 97 to ground and completing the pull-in coil circuit.

My understanding is that the computer should initially ground this for a couple of seconds, then it waits for a PIP signal from the distributor pickup.

The rising side of the PIP signal resets the countdown.

If the engine is turning and the ignition is on, the EEC never times out and the relay stays closed.

Additionally, the heavy EEC ground at the front of the battery negative terminal needs good connection.

But if you've used a noid light to check injector grounding pulses already then that ground from the battery negative terminal should already prove good.

Jim - Great information!

Spent a lot of time this morning on the wire colors. To me, the Tan wire looked Pink and the Pink wire looked Tan; however, the markings, namely the Black and the Green did not match the wire color. Maybe I'm becoming color blind?

Anyway, it appears the black markings are actually on the wire that looks Tan but must be Pink; and the Green markings are on the light-colored wire that looked Pink but must be Tan. The green markings are almost non-existent after 36 years.

Took a picture of the connector and labeled the wires:

[ArdWrknTrk]

Jim - Great information!

Spent a lot of time this morning on the wire colors. To me, the Tan wire looked Pink and the Pink wire looked Tan; however, the markings, namely the Black and the Green did not match the wire color. Maybe I'm becoming color blind?

Anyway, it appears the black markings are actually on the wire that looks Tan but must be Pink; and the Green markings are on the light-colored wire that looked Pink but must be Tan. The green markings are almost non-existent after 36 years.

Took a picture of the connector and labeled the wires:

Wires get crispy after 30+ years.

I spent yesterday afternoon chasing a bad wire in my parking lamp circuit.

After changing out the switch and pigtail I ultimately ran a jumper from behind the fuse panel to the new socket. 😖

I hope you can figure out if 97 is seeing ground and pulling in the relay when you first turn the key to 'Run'

Back probing that relay socket with a test light you can see from the driver's seat seems the easy way to accomplish that.

If the ECM isn't responding and you have some soldering skills replacing the capacitors on the board is inexpensive and worthwhile since those caps go bad over time, even just sitting on a shelf!

[Nemesis F150]

The pink wire goes to the inertia switch.

You could test for continuity from the relay socket to the inertia switch plug... (the location of the connector (C118) is irrelevant if there is continuity)

Continuity can be checked but I'll need a helper. Used to have a collection of short wires with alligator clips on the ends but don't know where they are.

At the moment I'm not seeing any voltage at the Pink terminal end on this green connector. This may be related to what you wrote below. Only been testing with the ignition key at the Run (w/ engine not running) position, not the Start position.

With the ignition key in Run position there is full battery voltage at the Yellow and Red wires, and a little over 1.0V at the T 97 wire.

Additionally, the heavy EEC ground at the front of the battery negative terminal needs good connection.

But if you've used a noid light to check injector grounding pulses already then that ground from the battery negative terminal should already prove good.

I don't have a noid checker and didn't know what it was until now. For what it's worth, the engine does run fine if it gets gas (don't use starter fluid, use only regular gas in a spray bottle)

Additionally, the heavy EEC ground at the front of the battery negative terminal needs good connection.

But if you've used a noid light to check injector grounding pulses already then that ground from the battery negative terminal should already prove good.

There are two ground wires on the battery, the large one that heads south, down below, maybe to the starter motor (?), and a small one that disappears into a wire harness that is wrapped in electrical tape. Unable at the moment to troubleshoot any further due to time constraints (thru today and tomorrow).

Aft of the battery there is a group of ... relays(?), or something, behind a semi-protective plastic shield. I came across a circuit diagram that showed them but can't find it. They don't seem to have been an important part in this process (yet), though.

Thank you very much for the explanation about how these things work so this was a good learning exercise. The old flat-head V-8s were much simpler. (FWIW, my first engine was a 4-cylinder Dort (car name) circa 1916, Model-T carb, on a set of Model-T rails. Hand-crank to start, manually adjust the spark advance, and no shop manuals or Internet. Things were simpler then.).