ecm problem? need help!

[jaredts]

The pictures Vile asked for would be very helpful.  I also wonder about the check engine light not staying on when you turn the key on...what do you mean by that?  Does it just flash on for a second or something more intermittent?  That and the fact that it flickers while driving make me think poor ground to ecm or poor connection to the bulb socket in the dash.

[ron85C10]

Here you go im also

[ron85C10]

Yeah it doesnt stay on when the key is in the on position with engine off. Hope these are helpful. Where would i check for proper grounding? Also the bulb to check engine is new.

[VileZambonie]

So key on engine off, the check engine light doesn't come on? Elaborate

The Assembly Line Communication Link (ALCL) is a diagnostic connector located in the passenger compartment (Figure 2). It has terminals which are used in the assembly plant to check that the engine is operating properly before it leaves the plant. Terminal "B" is the Diagnostic terminal, and it can be connected to terminal "A", or ground, to enter the Diagnostic mode.

If the Diagnostic terminal is grounded with the ignition "ON" and the engine stopped, the system will enter Diagnostic Mode. In this mode the ECM will:



Display a code "12" by flashing the "Check Engine"/"Service Engine Soon" light (indicating the system is now operating). A code "12" consists of one flash, followed by a short pause, then two flashes in quick succession. This code will be flashed three times. If no other codes are stored, code 12 will continue to flash until the Diagnostic terminal is ungrounded:
The engine should not be started with the Diagnostic terminal grounded, because it may continue to flash a Code 12 with the engine running. Also, if the test terminal is grounded after the engine is running, any stored codes will flash, but code 12 will flash only if there is a problem with the distributor reference signal.



Display any stored trouble codes by flashing the "Check Engine"/"Service Engine Soon" light. Each code will be flashed three times, then code "12" will be flashed again. If a trouble code is displayed, the memory is cleared, then the engine is run to see if the code is a "hard" or "intermittant" failure. If it is a "hard" failure, a Diagnostic Code Chart is used to find the problem. If it is an intermittant failure, the charts are not used. A physical inspection of the applicable system is made.
Energize all ECM controlled relays and solenoids (with some exceptions, as noted in "Component Systems"). The mixture control solenoid is pulsed for 25 seconds or until the engine is started, whichever occurs first.
 

[VileZambonie]

CHART A-6 - WON'T FLASH CODE 12



This step checks for short to battery voltage in wire to Terminal "C" or faulty lamp driver.
Normal voltage reading is 9-11 volts.



This step checks to see if problem is related to the ECM or the lamp driver.
Normally, grounding Terminal "C" should turn lamp "OFF". If it does, the problem is related to the ECM and its wiring. If not, it is related to the lamp driver and its wiring.



Grounding Terminal "G" at ECM and finding light "ON" indicates an open in the wire to Terminal "C" of lamp driver. Normally, grounding Terminal "G" should turn lamp "OFF".
This step checks for open in wire from ECM to test terminal in ALCL connector. The lamp should flash Code 12 when Terminal "5" is grounded.
Checks for proper voltage supply to ECM. Both should read over 9 volts. Terminal "C" is ignition and Terminal "R" is constant battery for long term memory.
Checks for a bad ground to ECM - Terminals "A" and "U" are connected together in the ECM.
This step distinguishes between a faulty ECM and PROM. Normal response is for Code 51 to flash even though the PROM is not installed in the ECM. If it doesn't, it means that the ECM is faulty.
 

[ron85C10]

Nice thats some good reference im gonna try to work on it tomorrow and check the alcl under the passenger side. Also i took some other pics and found some wire that is disconnected and i dont know what its from. But here you go maybe you could ID this conundrum.

Oh also the check engine light does not stay lit when the key is in "on" and engine "off" and from my own understanding isnt it supposed to stay lit? And when i try to ground terminals A to B to place it in "diagnostic mode" the light does not flash any codes. Hope that kinda makes my problem a little clearer.

[VileZambonie]

So the check engine light does not illuminate at all? Check the bulb

[ron85C10]

The bulb is new and flashes sometimes when i am driving.

[87454westernhauler]

the bulb could have a bad ground. that hapens to me all the time on my dash lights, and if u wiggle them or tap them they will start working again. it might be ok though, just another thing to check...

[ron85C10]

Well i finally gave up. It seems that the guy that igot the truck from had a really nice alarm with remote start so theres extra wires in the engine bay and all kinds of half way wiring. So i just decided to take the stock carb out and put in an aftermarket one. Any suggestions? I have a 305.

[jaredts]

A rebuilt regular quadrajet is probably best.  I love my Edelbrock 1406, though, and you can get them at most auto parts stores, slap it on, and be done with it.  It will run pretty well out of the box, but as you drive it you may find that you want to get a tuning kit to get it just right.  I did that recently and its much better than before.

[ron85C10]

Cool man thanks thats exactly what i want to do is to just be done with it. Im mainly going to be using my truck for work and right now the whole problem was getting it to not suck up so much gas. Im getting like 6-7 mpg right now and gas prices dont seem to be going down.