Engine swap computer & wiring question

[Tim De Coster]

Steve,
Thanks for the tips.  Man, that Blazer must fly!  The reason this swap may
get a little bit hairy is because I don't think I'll be able to use the
entire harness out of the donor car because it will be an OBDII computer,
and from what I understand, it's not easy to get a OBDII computer to
function in an older car.  So do you think that my existing computer could
control this new engine if I get a new EPROM module for it?  I already have
one from a '91 Z24 (It had a 3.1 v6), and I am hoping that it will work.  It
may because the 3.4 is basically the same exact engine as the 2.8, except it
has revised heads, among a few other things.

I know that the Cadillac Cimarron's digital dash does talk to the ECM,
because I was going to put the Cimarron digital dash into my Sunbird...
until I found that most of the info. for the gauges goes through the ECM
before it gets to the dash.  This probably would mean that the Cimarron
wiring idea is out of consideration, right?  The only reason I thought of it
was because the dash is physically the same in it, and it has a 2.8 mpfi v6
engine.

I'm not sure exactly where the vss signal comes from in the Sunbird, I'm
still working on getting a GM manual for this car.  I know that the digital
dash in my Z24 does, but that's a different application.

Thanks again,
Tim De Coster
'89 Z24 Conv.
'88 Sunbird GT Conv.
'98 Intrepid
www.sunbirdconvertible.com


----- Original Message -----
From: "steve ravet" <sravet at arm.com>
To: <gmecm at diy-efi.org>
Sent: Wednesday, July 12, 2000 12:31 PM
Subject: Re: Engine swap computer & wiring question


> Tim, I'm not familiar with those models, but I have been through an
> engine swap (replace 2.8L w/ 5.7L in my Blazer).  What is the concern
> with the dash?  Is it electronic, and wants to talk to the ECM to get
> MPG info or something?  If not then I don't think it matters too much.
>
> I'll talk about my swap some, it's probably similar to what you'll
> find.  There are two places where wires cross from the engine
> compartment to the inside of the vehicle.  One is the ECM harness, which
> runs from the engine thru a hole in the firewall to the ECM behind the
> dash.  This bit of wiring is almost completely isolated from dash/body
> wiring.  Exceptions that I can recall are ALDL signals like data, TCC,
> etc. that have to run over to the ALDL connector.  VSS also comes from
> the dash in my app, not sure about yours.  Anyway, as long as you use
> the ECM that comes with the engine there is no problem here, just splice
> in the handful of wires for ALDL/whatever and the rest plugs right up.
>
> The other connector is the bulkhead connector.  The car side is anchored
> to the firewall, the engine side comes from the engine bay.  When you
> get your new engine it'll have it's own bulkhead connector, and there is
> basically no chance that it will plug directly into the existing car
> half of the plug.  Wires and signals here can be different even on the
> same year model cars, depending on options etc.  Fortunately there is
> little/no engine wiring through here.  Typical things here are wiper
> controls, A/C controls, power to and from fuse box, engine sensors that
> go to dash gauges (but NOT ECM sensors, they are in the ECM harness),
> etc.
>
> What you'll have to do is go to the junkyard and buy an engine side
> bulkhead connector that is physically the same as yours (from the same
> model car), and all the wires attached to it as long as possible.
> You'll cut off the bulkhead connector from the new engine, and connect
> the wires to the appropriate places on the junkyard bulkhead connector.
> Use crimps, and then solder them, like the service manual shows.  The
> junkyard connector may have blank places in it where yours has wires, in
> that case you'll have to add pins and wires.  You could re-use your
> current bulkhead connector but I wanted to leave the old engine as
> intact as possible so I could sell it.
>
> You'll need a service manual/schematics for both the donor engine and
> your car to properly match these up.  I spent probably 20 hours or more
> sitting in front of the computer, going over the schematics, typing in
> what went where, and double/triple checking all of it.  Then I printed
> it out and started cutting and twisting wires together.  I wrapped all
> the twists with bright green electrical tape.  Lots of time but I had no
> wiring errors to track down later.  Once it's working, take off all that
> green tape, crimp and solder the wires properly, put them back in the
> loom, tape it up nice, and off you go.
>
> All bets are off if the dash wants to talk to the ECM via ALDL, though,
> like the digital dash vettes did.  hope yours isn't like that.
>
> You'll make the swap easier if you get the new engine intact with all
> it's wiring, accessories, sensors, etc.
>
> write back if you have more questions.
>
> --steve
>
> Tim De Coster wrote:
> >
> > Hello,
> >
> > I'm new to this list, and have to admit that much of what goes on here
is a
> > little over my head.  I do however, have some advice to ask for.
> >
> > I have an '88 Sunbird GT with a 2.0 OHC non-turbo engine and am
eventually
> > going to install one of the '96+ 3400 OHV v6's.  My question is:  what
is
> > the best way to handle the wiring and computer change-over?
> >
> > Ways I have thought of:
> >
> > Getting the complete dash wiring and engine wiring from an '87 or '88
> > Cadillac Cimarron (it had the same style dash and a 2.8 mpfi v6 engine).
> > This way I would have the v6 wiring that I need, though the computer
will be
> > programmed for the 2.8.  I think it would work, but I'm not sure in
> > real-life what sacrifices would have to be mad going this route.  I'm
sure
> > that I would have to run the engine in MPFI mode like the 2.8 is, unlike
the
> > SFI mode that the 3400 was built for.
> >
> > Another idea was to use the existing dash wiring and computer that is
> > currently in my Sunbird and getting the wiring out of a '91+ Chevy Z24
that
> > had the 3.1 v6.  I would then have to change the EPROM, but I'm not sure
if
> > the engine wiring will plug right into the existing harness and
computer.  I
> > think the computer itself is the same, but this isn't confirmed.
> >
> > Getting a computer for the '96+ GM minivans or other GM vehicles the
3400
> > came with is probably out of question because they use the OBDII
computers
> > which I understand are a pain as far as engine swaps are concerned.
> >
> > Any comments or suggestions on this would be VERY appreciated!
> > If you're interested, check out my website listed below.
> >
> > Thanks in advance,
> > Tim De Coster
> > '89 Z24 Conv.
> > '88 Sunbird GT Conv.
> > '98 Intrepid
> > www.sunbirdconvertible.com
> > www.z24convertible.com
> >
>
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> --
> Steve Ravet
> steve.ravet at arm.com
> ARM,Inc.
> www.arm.com
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