Bad ECM?

Topic: Bad ECM? (Read 20715 times) previous topic - next topic

Reply #15 – March 05, 2015, 12:45:07 PM

again,
out of the car the fuel pump relay works fine.

Bad ECM?

Reply #16 – March 05, 2015, 01:16:52 PM

How's the ignition switch look?

All gauges dead, fuel pump and ecm not working. All point to a lack of power, or lack of ground. Ignition switch turns all of them on, so in my mind it seems most likely.

Bad ECM?

Reply #17 – March 05, 2015, 01:33:36 PM

Ignition switch is new. I ordered it a few months ago from latemodelresto. I went over today to tinker some more ....found that pins 40 and 60 weren't grounded like they should've been, so I properly grounded them to the battery negative cable. Tried it then, still no lights, no fuel pump, no spark. Maybe I'm missing another ground somewhere? I read that a way to see if the ECM is powering up, is to turn key on, and probe the Orange wire on the tps. If you have 5 volts, then the computer is powering up. Is this a correct statement? In which case, the computer is "powering up" but I still have no fuel pump priming, warning lights, or spark. Could I be forgetting a ground somewhere?

Bad ECM?

Reply #18 – March 05, 2015, 01:35:52 PM

These are pics of the ground connection for 40 and 60 that I didn't have grounded to the battery before. I now have them grounded, but still no difference.

Bad ECM?

Reply #19 – March 05, 2015, 02:23:59 PM

The ignition switch powers your dash lights. It is two yellow or orange wires sliced into a single pin. If one wire is off, you have no dash lights.

A bad connector or splice can carry a light load, then overheat and fail under load. Imho, same thing happened to my 86 cougar. I replaced the ignition switch, my entire dash went dead and the car would randomly not start. Id hit a bump and the dash would light up for a bit till the next bump.

I think the ignition is sending 12v's to the relays, then when you try to start it the wire or connection overheats and fails. This would also explain why you only have momentary spark.

Check this link, http://sbftech.com/index.php?topic=588.0 if you can't find any problems with the ignition or 12 positive supply.

Bad ECM?

Reply #20 – March 05, 2015, 03:56:01 PM

Quote from: FOX-XR7;445622

Ignition switch is new. I ordered it a few months ago from latemodelresto. I went over today to tinker some more ....found that pins 40 and 60 weren't grounded like they should've been, so I properly grounded them to the battery negative cable.

This is an important ground for the EEC. And according to the EVTM it is needed to energize the EEC power relay. I am surprised it didn't make any difference.

Quote

Tried it then, still no lights, no fuel pump, no spark.

I think the lights are a separate problem.

Quote

Maybe I'm missing another ground somewhere?

Hard to say.

Quote

I read that a way to see if the ECM is powering up, is to turn key on, and probe the Orange wire on the tps. If you have 5 volts, then the computer is powering up. Is this a correct statement?

Yes, this is the EEC reference voltage. Did you have this before you fixed the ground?

What kind of cluster do you have, buttstuffog or digital?

Bad ECM?

Reply #21 – March 05, 2015, 04:12:59 PM

Check fuse 18 for the lights problem.

Bad ECM?

Reply #22 – March 05, 2015, 06:29:19 PM

full buttstuffog cluster,,
but from what he told me its from a TC...

I brought up ckt 787 parallel branch because while dealing with auto lamps in my sons 88,, it lead me to so many incorrect things for 88 inside the evtm.

Waiting for the original poster to chime in to confirm if "pin8 has that wire" on the computer or not.... and if he does, then that means yet another 1988 EVTM mistake I will note.

if its present on the 88 5.0L like it is on the 88 3.8L,, then it might be supervising spark and fuel... since we know the fuel pump relay itself is good.

Bad ECM?

Reply #23 – March 05, 2015, 06:53:27 PM

Scott, the 88 3.8 is a big change. all the older models are CFI. It looks to me like 88 3.8 EEC is checking for error code 95.(secondary fuel pump failure) . Since the 5.0 EEC doesn't check for that, they didn't run the wire back to the EEC.

Bad ECM?

Reply #24 – March 05, 2015, 07:03:31 PM

FOX-XR7
I am curious about the NGS & CSS wiring you did. I see it involves EEC pin 46 which is the EEC signal return (logic ground)
The stock set-up for this car puts 12v on pin 30 with the ignition switch in START. If 12v got to pin 46 through the NGS, that is a problem.
Jcassity's post 4 shows the pin out for the test connector. See if you have 12v on the "sig rtn" with the ignition in start.

Can you post a link to the instructions you used for the Mass Air conversion.

Bad ECM?

Reply #25 – March 05, 2015, 07:44:34 PM

When I get back over there, I will check fuse 18 for the lights, and pin 8 on the eec. I used a fiveology racing maf conversion from ebay. I read the directions and I cross referenced them to coolcats, and all the pins they had to swap over matched. So because coolcats matched the instructions, I went for it. I was definitely thrown by the fact that the ground didn't do anything different. when I go back to the shop, I will unplug the ground at key on and check the tps ref. Vol. Along with checking pin 46 voltage while cranking. My father in law checked continuity from a ground strap between the negative post and the fenderwell. And it beeped with key off. Then with key in run, the coil sparks once, and he loses continuity on that same exact negative wire. Wtf?!? How does that work?

Bad ECM?

Reply #26 – March 05, 2015, 07:55:32 PM

I also wired my ngs and css in series. Pin 30 goes to my css, then to ngs, then to pin 46. I thought that's how it was supposed to be wired, but I have Ben wrong before. Haha

Bad ECM?

Reply #27 – March 05, 2015, 09:29:43 PM

Yeah, the gauge cluster is out of an 87/88 tc. All the gauges are the tc gauges less the tach. The tach is the original one from the car. I changed clusters because my circuit board In the original was all torn up and peeling.

Bad ECM?

Reply #28 – March 06, 2015, 06:06:08 PM

This 93 5.0 Mustang diagram looks like what you are doing.
If you removed the stock AOD wire and added your new wire to pin 30 you are good.
If you spliced your new wire into the stock wire, you have a problem.

I am guessing you are using 88 Cougar 5.0 wiring harness.

Bad ECM?

Reply #29 – March 06, 2015, 07:26:32 PM

LOL, so you guys are wayyyyyyyyyyyyyyy over there and im still over here saying........
"why doesn't the relay have output power" ~as in what I posted earlier~ I thought someone else would have found this to be impossible as well

I mean,,, the darn thing works,,
it clicks ,
it has continuity when manually triggered,
we provided a manual ground to it when re-installed in the car.... and it clicks over when in the car
it doesn't pass power out?