Also what I did was swap a vortec 350 in place of the TBI 350 with the adapted plenum to keep the TBI throttle body and the ems7427 ECM was the ECM I had to buy from rock auto and install just to get this thing to where it would start i even had to cross match the serial numbers to make sure I got the right one
Greetings MANIAC,
For me the engine swap changes the troubleshooting approach. To explain, if we are working on a
GMT400 that's completely factory original in the engine bay, and is suffering a malfunction, our default
mindset is to find the one component/wire/signal that is not working per specification. (Assumption is
everything is innocent until proven guilty.)
On the other hand, when we are dealing with an engine swap, a single detail difference can create a
difficult to sort out project logjam. Or worse, overlapping showstoppers hide progress, and can really
discourage the DIY'er. In other words, when troubleshooting an engine swap, the assumption needs
to be that
everything is bad until
proven good. (Not calling out your workmanship, just an observation
based upon helping with getting engine swaps up & running over the years.)
Okay so I'm in the process of trying to diag the obd1 port and so far here's what I got white/blk stripe has a little less than 5v and the tan wire has about 5.5v I don't know what those are supposed to be but i imagine it's supposed to be 12 so now I gotta start either tracing those wire to find a break in the wire or I gotta run new wire and save myself a major headache I've been researching all night and I'm just barely starting to comprehend the electrical diagrams the only problem is I can't find the specific information as far as what wires are supposed to have certain voltage but I do think I'm getting close to figuring it out thanks in advance for anymore information guys
First things first. Let's define a couple of voltages, who makes them, and the hints that these discrete voltages mean to you.
* Approx. 12.6v-14.5v -- Battery Voltage. ~12.6v = fully charged battery, engine off. ~14.5v = engine on, alternator at goal voltage.
* 5 volts -- Regulated computer voltage used inside ECM/PCM. Also used as a reference voltage for most sensors, and also to communicate
with the scan tool via the under dash DLC. (Data Link Connector) Note: Also referred to as the ALDL or (retroactively named) OBD1 connector.
So here's a wiring diagram for the PCM (7427) equipped vehicle taken from the '95 Factory Service Manual:
You must be registered for see images attach
So when you jumper Pin A to Pin B in the underdash connector, what you are actually
doing is grounding Pin B on the connector so that we can tell the computer (via Pin A1)
to go into diagnostic mode. So according to this diagram we need to ensure that the
all-critical PCM to Engine grounds are good. If there's any flakiness with these grounds
then we may or may not be able to control the computer to communicate with your scan tool.
NOTE: Pin A to Pin B puts us into diagnostic mode. But on the PCM the serial data
is sent to Pin
M via the
TAN wire, and if this isn't wired to pin F9 then no joy.
Now, since we're doing an engine swap, we can't assume that Pin M is wired correctly.
Why? Well, if at some time in the past there was an ECM installed (think gas engine/5-spd manual)
then Pin
'E' on the DLC connector is what was used on one end of the
ORaNge wire to Pin A8 on the computer:
You must be registered for see images attach
****
I'll stop here and give you a chance to verify that your wiring matches your computer setup.
Once we get reliable communications between your computer and your scan tool, then we
will be in a much stronger troubleshooting position.
Best of luck --
PS -- I posted these pages from the '95 FSM for Driveability, Emissions, & Wiring -- as
mentioned previously, downloading the '95 FSMs is like cheating to win -- it will be really
helpful for a project like yours.
