Engine electrical help

Topic: Engine electrical help (Read 2122 times) previous topic - next topic

Engine electrical help

Reply #15 – June 20, 2010, 12:31:14 PM

Quote from: 86caprirs;326000

Well the little wire to the battery is connected and also connected to the body. I checked the connector that is between the little wire and the body to make sure no corrosion is there. It was good.

?? does the connection to the "body" look like stock factory wiring??
The EVTM doesn't show it that way but it could be wrong. Are there other wires on this "body" grounding point?
On the EVTM diagram C434 is your little one wire connector. Splice S533 should be on the "RH Fender Apr0n" and X goes to the ground side of the heaters on the HEGO's.

Engine electrical help

Reply #16 – June 20, 2010, 01:18:12 PM

Blown::: Line is dissconnected. I am not sure about the sample tube as I bought the meter and 24lb injectors of a guy together. I suspect that it is right but I don't know what the sample tube should look like.

Badshoe:::: I tested signal to battery from the self test connector and got an got nothing. And this is a stick shift pcm to a Automatic harness. I will do the check to see if 60pin to 46 pin has continuity to ground. I make sure they are dissconnected from the pcm or do I just undo the pcm connector and touch one lead to the other on the ohms scale?
(((A damaged PCM on pin 46 may be caused by a stick shift PCM hooked to an automatic EEC wire harness. The stick PCM's don't always have a diode in the pin 30 circuit to protect it during startup (which can short out the sig. return))). This could be my no start condition. After it ran for 20 min or so, I shut it off and it would not restart for almost an hour.

Softtouch::: Yes the wire to the body is stock. It comes from the body harness to a single pin connector in a round black connector. It goes to the battery. Then from the battery to the body. We are talking about c434 right?

Engine electrical help

Reply #17 – June 20, 2010, 02:17:29 PM

Any time the 60 pin harness is off the PCM or checking continuity, the key should be off but understand the harness pin 46 will be open to gnd. at this point. You should have continuity from harness pin 46 to the TPS sig. return wire as well as that wire on the Baro and EVP on the EGR if your still using it as well as the self test connector. When you plug the PCM back in, the sig. return wires at the TPS, Baro, EVP will now have continuity to battery gnd. because the pin is grounded internally in the PCM. Are you running a stick or an automatic? If you running a stick, the auto harness shouldn't be a concern as long as the pin 30 is left unhooked.

Engine electrical help

Reply #18 – June 20, 2010, 04:01:07 PM

I am running a Auto.

Ok. I am sorta getting it. So pin 46 all attatched and plugged into the respected spots, should have continuity to battery? Or it will be open? I know I went self test to battery with key off and got nothing.

Engine electrical help

Reply #19 – June 20, 2010, 04:01:24 PM

Sorry. I am terrible at electrical.

Engine electrical help

Reply #20 – June 20, 2010, 06:41:43 PM

Yes, the BK/W wires coming from the TPS, EVP, Baro, ECT, ACT and the BK/W wire at the self test connector are all spliced together at splice S151 somewhere in the harness, therefore you should have continuity between all of those sensors on that wire. However, you will only have continuity to battery ground when the EEC connector is bolted to the PCM since it grounds to pins 40 and 60 inside the PCM. If there's no continuity to battery ground or pin 40 and 60, the PCM is bad. There's no self test with an open pin 46 as well.

Engine electrical help

Reply #21 – June 20, 2010, 07:25:27 PM

A follow up to my last message is if you find there is an open in the PCM on pin 46, it's likely caused by using a stick PCM with an automatic tranny. In a stick car the pin 30 goes gnd. through the neutral switch and pin 46 when the tranny is in neutral. However, in an automatic car, pin 30 also is grounded in park and neutral but goes to 12 volts during startup (stick car does not). The PCM's for automatic cars are protected from this 12 volts internally but I understand many of the stick PCM's are not, causing a short circuit internally on startup in a swap like yours. So if you get another donor PCM for testing, it should be from an automatic car.

Engine electrical help

Reply #22 – June 20, 2010, 09:16:34 PM

I know Ken knows his "stuff", but I'm running a early(has a '88 date code) '89 A9L stick PCM without issue...

The '86 Mustang EVTM shows a isolating diode externally connected to pin 30, so likely there would be issues if a '86 stick computer were used in a automatic application ... Unfortunately I don't have a later Mustang EVTM to check to see if there was one included in the harness in newer models...

Engine electrical help

Reply #23 – June 21, 2010, 12:32:22 PM

I hooked up a good A9L and it all works now. So i have a bad pcm. Thanks for the help guys.