Starting from start... need guidance

**AzDon** · 09-19-2021

It's been awhile since I gave the final spark and fuel scheme in the 69 van I'm building much thought because it was important to get the mechanical remodel completed into a functional shell first. I now have a complete TBI L03/700r4 drivetrain installed from a 91 Olds wagon.... I saved everything including the wiring harness and 6965 ECM, but I'm conflicted about whether to buy a new custom harness and chip from Affordable EFI or to try to prune and use the stuff I saved....The harness layout needs to be a bit unconventional to be a good custom fit and I am pretty good with a soldering iron.... My concerns are: 1) That I will accidently prune something out that is not negotiable to the ECM 2) That I won't know which wires need some kind of RFI shielding (or run in separate harness) 3) That I will get too deep and invested in the DIY and get to a point where the technical help I need to finish is not available ....... I have some ideas that I want to simplify a couple of items that I'm hoping to run separately of the ECM, so I have a couple of questions... 1) Can the electric in-tank pump be run completely divorced from the ECM? 2) Does the ECM require pulses from a DRAC module, or can I just run a cable speedo? 3) Can TCC lockup be run on a single wire divorced from the ECM? 4) will the clipped and terminated ECM wires for these divorced items and the ECM wires from EGR, A.I.R., and purge cause disfunction of the ECM? 5) Will I need a reprogrammed chip or modified ECM (?) and who would be a good source?  The knowledge base on this site is mind-blowing and mostly over 30 years ahead of me (maybe 40) regarding electronic engine management and I'll likely never catch up, but you guys have been patient with me (so far)...... Thank You!!

**tayto** · 09-20-2021

My advice on pruning a harness: don't do it. i have pruned stuff that "i will never need" only to come back years later and need. now I unpin the wires from the connector and put heat shrink (with out glue kind) on the terminals then tuck it back into the loom. things like EGR and AIR will need to be disabled in the calibration.

use the ecm to control lockup, again you will need to change in the calibration. the "old school" way sucks. locking up everytime you shift into 4th gear, bleh. manual switch even worse IMO.

**AzDon** · 09-24-2021

I've kind of decided on the pruning scheme....
I printed a pinout schematic, but I'm confused about what certain ECM pins are looking for and whether they are "power output" pins or if they are "ground control" wires for the item being controlled....
The schematic I printed was from the GearheadEfi knowledge base (I think) and it's for the 16136965 ECM...
There are several systems that I want to run divorced from the ECM, but I want to satisfy those pins, if required, so I need to know what they want.
First pin B10 park neutral.....Is this pin powered and looking for a ground or a ground looking for power?
A/C and power steering (pins b8 and c8) same question
Does the ECM require VSS input? (A10) TCC lockup (A7) ? or 4th gear input (C7)?
I also want to simplify fuel pump power, so I'm curious about (B2) fuel pump input (?) and whether A1 will know or care if it's not triggering the pump relay

**tayto** · 09-24-2021

sounds like you're over thinking this. hook it up as it was it was. When I did my first EFI swap 15 years ago I found all my questions/answers in a factory shop manual. to give you a short answer: most inputs/outputs from the ECM are ground. ECM does not require VSS, but if you want TCC control you will need it. I don't understand about simplifying the fuel pump circuit? A relay needs power and ground to work. usually one would be battery or ignition voltage and the ecm grounds the other to active the relay.

**AzDon** · 09-24-2021

Thank you Tayto for your reply!...
I have a FSM for the 91 Old Custom Cruiser the harness came from
I also drive a 91 OCC as my daily, so I can experiment some to learn answers to some of these questions....
I currently know that the ECM operates fine with the A.I.R., EGR, and TCC disconnected.
I want to just run the fuel pump from a toggle switch off of the ignition switch on this van unless there is some kind of frequency control provided by the ECM or if the ECM might refuse to operate without the presence of an operational fuel pump electrical feedback...
The FSM tells me that the neutral/park pin (B10) is powered and sees ground in park and neutral, but uncertain what the ECM does in response to open or closed positions of the switch. (maybe nothing since Neutral safety is generally addressed on the starter wire side of things)
FSM also indicates that power steering pin (C8) is powered and the switch is normally closed to ground and opens under high pressure.....Since I won't have power steering, I guess that means I should ground this wire....

**tayto** · 09-24-2021

when the park/neutral switch is grounded The ECU knows its in park or neutral, when it sees NO ground it will know it is in reverse or drive range. even if you run the fuel pump off a toggle switch I would Still have it relay activated. do not veer too far from how the factory did things as far as circuit design. it might seem easy to hack it out now and make your life "easier". But time spent now on a nice install will make for easier troubleshooting and less thinking while driving. The factory fuel pump circuit is often miss understood, but provides TWO means to get voltage to the fuel pump. 1 is the relay controlled by the ECM and the other is the oil pressure switch. if your relay was to die, and you crank to start once the oil pressure switch is over 3psi it sends power to the fuel pump. when both circuits are working correctly, IMO, the oil pressure switch shares some load from the relay contacts (which In theory means longer contact life).

You will need an additional relay to turn your van neutral safety switch into a ground switch to send to the ECU. I had to do this on my '64 Impala. I thought i posted a drawing on another post here sometime ago but I may be wrong.

**AzDon** · 09-26-2021

So I'm guessing that the engine will start and run whether it's in neutral or in gear, but that the ECM bumps the idle speed up when it's in gear?
The fuel pump relay being operated by the ECM and/or oil pressure switch seems to be about making sure fuel is shut off when the engine isn't running which is probably a good idea and easy enough to set up...
The van was stick shift, so setting up a neutral safety switch will be a royal pain requiring some engineering. I'm thinking of just putting a toggle switch on this feature...

**tayto** · 09-27-2021

My recommendation would be to find an automatic column. I like original stuff but you may be able to buy a bolt in aftermarket one. Your other option is an aftermarket floor shifter, again not my style but they should come with park/neutral switch. I am curious why you dont want to put a manual with OD in?

**AzDon** · 09-27-2021

Configuration of steering and shift columns is unique to these vans and really not adaptable to something else.... I'm just trying to understand what each pin wants to see and what it's function is so I can accommodate it one way or another....