Voltage @ alt. and Battery Vs ECM/ScanMaster. Electrical bug or not???????? HELP

[TURBOPOWERED68]

I Noticed that the Voltage reading was low on my Logger File - thanks to Paulie, i was looking for it.
Anyway i checked the ScanMaster and it is also reading low. as low as 11.90 to a high of 13.30 but averaging about 12.30s - 12.50s
BUT at the back of the ALT. it reads from 13.5 to 13.9 and at the battery it reads from 13.40 to 13.7
the car has a Brand new battery.
where do i start looking and Do i really need to look for anything.

Do i need to ground the ECM??

My fuel pump is Hot wired so i am not worried about fuel.
but
worried about ECM functions - Driving injectors, sensors and Ignition.
thanks for your help guys....

 

[TurboBob]

the ECM reads voltage from the wire that comes from the ignition key. This same circuit also feeds the ignition module. So there are voltage drops that occur in the harness and fuse box.

Ground issues can also cause this.

Grab your shop manual (you DO have one, right?)

and your voltmeter (You have one of those also, right?)

and go snooping.

Measure voltage from ECM case to engine

from battery+ to engine

from battery+ to body

check the voltage at the ECM's Ignition voltage pin.

etc....



Bob

 

[TURBOPOWERED68]

will do
thanks for the reply
What would be considered a normal deference between the ALT and ECM?

 

[Rich Gio]

Before you go crazy.... check the ECM connections at the fuse box. Mine were loose and corroded at the fuse "stab" terminals. Just by cleaning that up I regained .5 volts at the scanmaster. Start simple and follow the circuit drawing connection by connection as Bob suggested. You'll find it!

 

[TURBOPOWERED68]

my BIG problem is that this is on my hybrid with a 43 year old ignition switch and wiring going into a Casper's dash mating harness going into a OE Buick engine harness.
So its going to be a challenge.

 

[TURBOPOWERED68]

after a quick look
i turned the car on and while the car was cold the alt was charging at 14.50 plus and the ScanMaster was reading in the 13.8 range BUT once the car got to full temp the Scanmaster voltage reading had dropped to low 13s high 12s.
Bad Alt ????
Also i did find that the ALT to battery cable has a bunch of broken strands
i'll get to that today and post the results.

IF i need an ALT
I am considering an ALT out of an Impala SS, Are these direct bolt in?
Would the plug from the GN plug right into the this ALT?
this one from Advance - "Remy New Alternator - 140 Amps
Part No: 91408"
thanks for your help guys.

 

[1KWIKSIX]

Impala alternator

I Noticed that the Voltage reading was low on my Logger File - thanks to Paulie, i was looking for it.
Anyway i checked the ScanMaster and it is also reading low. as low as 11.90 to a high of 13.30 but averaging about 12.30s - 12.50s
BUT at the back of the ALT. it reads from 13.5 to 13.9 and at the battery it reads from 13.40 to 13.7
the car has a Brand new battery.
where do i start looking and Do i really need to look for anything.

Do i need to ground the ECM??

My fuel pump is Hot wired so i am not worried about fuel.
but
worried about ECM functions - Driving injectors, sensors and Ignition.
thanks for your help guys....

Yeah the 94-96 Impala SS is a direct bolt in. It does have a smaller belt pulley (so it will spin at a higher rpm), but goes in easily.

Puts out a bit more ams (140amps vs 120amps for stock unit).

I installed it in mine with no problems.
At the same time installed larger cables from alt to battery and from battery to body ground (inner fender) & installed a grounding cable from alternator to frame.

Seemed to do the trick for me and brought the voltage up.

Carry on!

Dave

 

[turbo96max]

has anyoone run an additional power source to the ignition module/coil direct rom the alternator (relayed and fused)?? kinda like a ignition hotwire kit?? i have a similar issue which maybe causing some weak ignition so kinda curious if this is even possible

 

[TURBOPOWERED68]

still having this issue a year and different ALT later. I hope to have found a solution.
update - checked just about every connection, had the ALT tested off of the car, Had the alt. tested on the car and it tested great both times and yes the alt. was HOT.
Anyways talked to Doc. and he suggested that i look at the belt tensioner and belt.
the tensioner is holding the belt pretty tight so then go and try to spin the Alt. and it spins real easy with the belt on and tight. anyways i am going to drop in a new belt and put some paint on the Alt's. pulley and see how this works out and if that doesn't work the next step is a new belt tensioner.
BTW the big problem is off idle and on any good pull, as the rpms climb and the load increases the volts start to drop off.

 

[TurboBuRick]

has anyoone run an additional power source to the ignition module/coil direct rom the alternator (relayed and fused)?? kinda like a ignition hotwire kit?? i have a similar issue which maybe causing some weak ignition so kinda curious if this is even possible

Yep, My ignitions hot wired along with every accessory in the car. The biggest improvement came when I took all accessory load away from the fuse panel. Boom, ecm voltage is now steady in the 13's.

RL

 

[TURBOPOWERED68]

Yep, My ignitions hot wired along with every accessory in the car. The biggest improvement came when I took all accessory load away from the fuse panel. Boom, ecm voltage is now steady in the 13's.

RL

is there a write up on Hot wiring everything?

 

[TurboBuRick]

There are some threads that talk about it. Basically you would use a relay (or 2) to switch power to the accessory's. Scott sells a neat little aux fuse block that could be used with a relay to switch power. I have 2 relays running accessory's. Made up my own hot wire's and fuse-able links.

Target the things that draw more power. Are you running alky? That draws allot. The more load you take away from the factory fuse panel the more ecm voltage you will see at wot.

RL

 

[TURBOPOWERED68]

There are some threads that talk about it. Basically you would use a relay (or 2) to switch power to the accessory's. Scott sells a neat little aux fuse block that could be used with a relay to switch power. I have 2 relays running accessory's. Made up my own hot wire's and fuse-able links.

Target the things that draw more power. Are you running alky? That draws allot. The more load you take away from the factory fuse panel the more ecm voltage you will see at wot.

RL

Ok, time to start another wiring project

 

[TurboBuRick]

Keep us posted.

 

[TURBOPOWERED68]

OK
1-Feed the ALKY unit via relay
2-Module and coil ?
3-What else?

My fuel pump and fans are already being fed via Relay
Do i also feed the ECM via a Relay.
Does it make sense to use one BIG relay or multiple small relays?
i already have this http://www.installationproducts.com/s.nl/it.A/id.2973/.f just need a distribution block.

 

[Chuck Leeper]

Ohm testing for resistence across the connections will help verify/deny the quality of the connections....
http://turbobuick.com/forums/thread...oltage-deatchwerks.377992/page-2#post-3027085

 

[TurboBuRick]

80 amp relay is pretty overkill. 1 40 amp relay can run both ignition and alky. Leave the ecm. Focus on things added aftermarket.

Great advice from Bob and Chuck as well.

RL

 

[TURBOPOWERED68]

80 amp relay is pretty overkill. 1 40 amp relay can run both ignition and alky. Leave the ecm. Focus on things added aftermarket.

Great advice from Bob and Chuck as well.

RL

This a hybrid everything is/was added to this car.
Thanks for all the advice guys.