YAY... now another problem!

[69camarokid]

ok so heres the new problem.... seems like i get one every week! oh, wait... thats cus i do. So most of you know my car setup by now, but for those that dont its a 69 camaro with a 95 trans am LT1/t56 setup.



after using my volt meter i discovered that the PCM memory is losing power everytime the car is shut off. This explains why the PCM wasnt learning to idle right. Becasue when the PCm loses power the memory is wiped clean.

So i took the wire for the PCM memory and removed it from its switched power source ( where it was spliced to a few other wires) and wired it to a constant battery source so it would always get power. theoretically this should solve my problem. But with the setup like this the engine wont start!!!! itll try and try but wont turn on!!!! i checked the original wires that the memory wire was sliced into, thinking maybe they had lost power. But they were still getting 12.5 volts with the power on and 9.5 while cranking.

I then wired the Memory wire back to its original spot, with the switched power wire and the car started up immediatly! it makes no sense. nothin lost power. and the memory just was given power all the time, like its supposed to!

my uncles coming over to check it out on wednesday, but im stumped.. any ideas?

[Jim Nilsen]

Could have been as simple as a bad connection. Sometimes just going back to the beginning and starting over solves the problem !!!

[6'9"Witha69]

Bad conn to the const or the const loses power during cranking. Like when your radio, etc. doesn't turn on during cranking. Check that the source you used (I am assuming right off the fuseblock blade) is hot during cranking.

[cad]

Or, hook it straight to the battery if you cannot check it while cranking....just use a long temporary jumper wire.

[69camarokid]

the memory wire still pulls a good 9.5 volts while cranking so its not losing power... oh, so annoyed and confused.

[72Z/28]

I know how it feels, I have been having problems with my 72 camaro ever since I bought. I completely rebuilt the engine( car mechanic did), everytime I run into a new problem, timing, valve adjustment crap, fuel gauge inaccurate reading, even with the stupid new fuel sending unit, and so on...

You need to find the right person who knows what he's doing, that's hard nowadays. I tried to fix some problems by myself, but I get frusrated and mess up everything..

[69camarokid]

even hooked directly to the battery it wont start, unless i feather the wire on it and start an arc..... killing me!

[6'9"Witha69]

I think you need to check the grounds on the ECU. I don't think it is getting the proper voltage due to a grounding issue it seems.

[6'9"Witha69]

Also, since you recently painted the car, are all the engine to frame and body, body to frame grounds etc all connected properly?

[69camarokid]

I think you need to check the grounds on the ECU. I don't think it is getting the proper voltage due to a grounding issue it seems.

checked all the PCM grounds with my trusty volt meter, nad they are all good. Alot of people had mentioned the bad grounds idea but all were tested and found to be fine. Theres got to be something i missing because logically there is no reason the pcm memory shouldnt want to start when taken from a ignition power wire to a battery power wire. this is killlling me!!!!!

[gearheads78]

Is the VATS programed out of the PCM?

[69camarokid]

yes the vats have been removed.

OK, so here what i know for sure.
The two orange PCM wires need a constant power source so that the PCM always has atleast a few milliamps of power to keep the memory system alive.

When those two power wires are hooked to battery power tohe car refuses to start. When those two power wires are hooked to a switched power wire, hooked to the ignition, the car will start up just fine, but when it does or is turned off the memory system will lose pwoer and be wiped clean.

[Damn True]

I wonder if those wires are supposed to be getting something less than 12v.

It could be that it is supposed to be getting +/-5V and it's shutting itself off when exposed to more than that.

Just a WAG.

[69camarokid]

I wonder if those wires are supposed to be getting something less than 12v.

It could be that it is supposed to be getting +/-5V and it's shutting itself off when exposed to more than that.

Just a WAG.

The schematics on shbox.com show that the two pcm power feed wires go to B+... which assume to mean battery, but i could be wrong.

[Jim Nilsen]

If I remember right B+ is a connection that goes to your distributor if you have one, or if you don't it probably goes to the ignition module. On my 89 camaro I had starting problems and it was the connection at the distributor that was causing the problem and one of the connections was labeled like that in the schematics. and the code actually told me the exact connection that was bad. I didn't put the code with the wire designation until I found the bad plug in connector.

So check your codes to see what you get? You might actually be getting the fault delivered to you with the wire you are looking for?

[69camarokid]

If I remember right B+ is a connection that goes to your distributor if you have one, or if you don't it probably goes to the ignition module. On my 89 camaro I had starting problems and it was the connection at the distributor that was causing the problem and one of the connections was labeled like that in the schematics. and the code actually told me the exact connection that was bad. I didn't put the code with the wire designation until I found the bad plug in connector.

So check your codes to see what you get? You might actually be getting the fault delivered to you with the wire you are looking for?

i cant look for codes right now as my wiring harness didnt come with the plug in thing ( cant remember what it is called) but im going to pick a part this wednesday nad going to look for one.

[holschen]

i cant look for codes right now as my wiring harness didnt come with the plug in thing ( cant remember what it is called) but im going to pick a part this wednesday nad going to look for one.

B+ is 12v battery black connector pin31 ignition is for 12+ ignition its black connector pin30