Help me with my very very low BLM problem

[turbonut85]

May sound silly....and you may have already done this, but...Check the 4 grounds under the AC compressor. I was having major drivability issues and was running way rich as well. Turns out, those pesky grounds were loose---causing all sorts of goofy stuff. It was throwing off the o2 readings to the ECM, it would try to compensate for the false readings. Then it would just snowball from there. Worth a try. I felt like a big dumb dummy when I found them. HTH ---Keith

 

[Waco84GN]

Already been there :-(

Took a dremel and polished the bracket off where the grounds go, put di - electric grease on the grounds and snugged them down.

Good guess and thanks for the help.

Jerry

 

[Waco84GN]

PL log file

I checked the two pink / black wires to the module and they has 12.16 & 12.14 with the key on.

1. Should they have battery voltage? I've heard the pink wires are resistance wires, is this correct?

Here is a PL file that I pulled from the car when I put my 87 ecm and a stock 87 chip.

The BLM's are better yay

The car is still choppy at idle and the blms are still rich at idle.

The injector PW goes to 0% after I let off the throttle, is this normal?

Seems as though the car is definitely running better I think.

The map sensor and maybe something else may be whack because I have a 3 bar map.

The boost gauge shows 15 in Hg.

 

[Waco84GN]

Ign module positives

These are the two pink / black wires on the ign. module.

Key on voltages

P = 12.16

N = 12.14

Back probed engine running voltages

P = 12.6

N = 13.24

Ran the engine up the rpm range thinking the alternator may not be charging at low rpm, but basically little change in either wire less than .4 volts + or -.

Brand new (3 day old) duralast gold

battery resting voltage = 12.65

Checked voltage at orange wire ecm connector on inner fender = 12.63

Checked ecm pin c16 batt + for voltage = 12.4 (.2 voltage drop?)

Checked ecm pin a6 ign - ecm fuse key off = 0 volts key on = 12. 07

Wiggled the ignition switch a little and the voltage for the ign / ecm fuse pin went down to 11.87. Ignition switch resistance due to contacts?

Well let me know what you think about the ign. module power wires.


Thanks,

Jerry

 

[Waco84GN]

Was looking at this ecm pinout...

http://www.engraver1.com/help/ecm.gif

On pin a6 it shows key on voltage to be 12.3 my key on voltage was 12.07 - 12.11

The same chart also shows an open circuit reading to be 12.15.

So do I have a bad ground on the ign / ecm circuit?

Thought the module grounded through the bracket.

All of the computer grounds are under the a/c compressor correct?

Anyways getting interesting.


Thanks,

Jerry

 

[Jerryl]

http://www.engraver1.com/help/ecm.gif

On pin a6 it shows key on voltage to be 12.3 my key on voltage was 12.07 - 12.11

The same chart also shows an open circuit reading to be 12.15.

So do I have a bad ground on the ign / ecm circuit?

Thought the module grounded through the bracket.

All of the computer grounds are under the a/c compressor correct?

Anyways getting interesting.


Thanks,

Jerry

I really don't think you have a voltage issue, at least not the kind you are thinking.
Sure, battery voltage could be higher, but at idle, the car should not be doing what it does. The voltage drop you are/have - seeing/measured are somewhat normal.

If you truly had a "misfire" due to low voltage, the O2 would read the oxygen, and "think" the car is running lean, and add fuel (Increase BLM)
So in your case, the opposite is true.

Also, don't like the "0% DC" you are seeing on decel. That tells me that there are some more serious issues.
What that means is that the ECM is shutting the injectors off, because something is telling it to do so.
I will look at the file tonight and need to think about that one.

Here is a good pic of the ECM pin-out. Wire colors may be differenct, but it is close, until the ignition module . . . . .
http://www.gnttype.org/techarea/ecmsensors/ecm3.PDF

Have you tried another injector harness?
Put a test bulb on #4 and see what happens while you crank it, or run it (idle)
One more thing after looking at the wiring; Is the oil pressure switch connected?

 

[alb84]

Did you change out the plug wire?

 

[Waco84GN]

Plug wire

As far as the #4 injector firing I listened to it with a stethoscope and it is clicking so I assume it is getting pulse. I cant get to the plug to put a noid light in the socket without some major surgery (turbo off etc.).

Did not exchange wires because the only other wires I have the clip is too deep for it to clip on the plug I believe. I cant feel a positive engagement (click) onto the plug.


Good side is the BLM's have been as high as 121 with the 86-87 ecm and they're not 105 (i think) havent gone through the whole log yet.

Just FYI the first bit of the log is at idle and then I do several gradual accel. cycles.

Thanks,

Jerry

 

[Jerryl]

....... Good side is the BLM's have been as high as 121 with the 86-87 ecm and they're not 105 (i think) havent gone through the whole log yet.

I thik you may be on to something. :tongue:

 

[Waco84GN]

Swapped #4 wire

Swapped #4 wire was an acdelco wire on there.

Took a Jacobs brand wire off of my 84 and put on there.

No difference.

Thanks,

Jerry

 

[Jerryl]

Had a chance to review the log.
Nothing really sticks out other than the PW/DC and LV8.
Could possibly a chip program thing on those.

Everything is starting to point to a wiring issue in the #4 injector.
Disconnect the wire at the injector, and the ECM harness.
Put an ohm meter on the #4 injector wire @ the ECM, wiggle all the harnesses (Main and injector) in all directions and every way possible.
Ohm meter should continue to read "open circuit".
If it indicates/reads a resistance at any time, you found your answer.

 

[charlief1]

I've got a harness if you need it Jerry. Can send it Thursday with Richard if you need it. Everything from the firewall foward including the injection harness.

 

[alb84]

My next best guess would be a leaky#4 injector. The fact that it seems to be gettiing slowly better could mean that with use it is cleaning itself out. I might be inclined to take it out and drive it around for a while. I know what a pain it is to get that injector out to clean.

 

[Waco84GN]

I know it doesnt mean anything....

But all injectors were cleaned, flowed, and balanced before install into this motor.

They were power cycled and all checked within stock factory flow ratings.

Fuel filter changed twice already.

Guage on rail slowly drifts down over probably an hours time.

Thanks,

Jerry

 

[alb84]

A leaker is just what it sounded like to me. I have had injectors that worked fine on the bench, and had immediate problems when installed. You might also want to check compression again on #4. I hope you get it figured out soon. I have confidence you will.
Danny

 

[charlief1]

This may help you some Jerry. Found it while surfing a little tonight.
Extreme Heat - TurboBuicks.com

BTW, Richard was a great help today so please tell him so. Thanks.