No CEL or scanner communication

[Shannen Durphey]

Cameano at aol.com wrote:
> 
> Hi, all,  my name is Darren Pferdehirt, I'm new to the list, although I was
> subscribed about a year ago for a couple of months.  I've come back seeking
> some help with a friend's car.  It's an 89 Pontiac Firebird, 2.8l PFI, manual
> trans, a/c car.  The car was running fine until this last Sunday.  It was
> shut off, and a couple of hours later, when he went to restart it, it
> wouldn't start.  I took a look at it, and determined that it wasn't getting
> any fuel.  So I went to hook up my Snap-On MT2500 scanner, but when I hook
> up, and turn on the key, it won't communicate with the ecm.  Also, there is
> no Check Engine Light, but I've pulled the dash and verified that the light
> is in fact good.
> 
> Not having a good reference manual on this car, I went to Alldatadiy.com and
> subscribed for this car.  From the info I've gotten off the site, the only
> problem I can find is the ckt 340 (fuel pump oil pressure switch) is open.
> Tracing the circuit, I see that it leads back around to the fuel pump signal
> terminal on the ecm.  Is this a good indication that the ecm all of a sudden
> just took a dump?  One note, when I had the scanner hooked up the first
> couple of times, the car would start, but it was in "limp home mode", very
> rich, poor running.  As soon as I would unhook the scanner from the aldl, it
> would die, due to the fuel pump shutting down.  Now, it won't even to this.
> 
> I do have another ecm from an 85 Firebird, with the 2.8 PFI, but auto trans.
> I've tried swapping ecms with the same results, also swapping PROMs between
> ecms and trying both, with the same results.

I show 2 different ecm part nos. for those years.  Prolly not a good
idea to try Plug-n-play with ECMs.  No CEL can be caused by no power,
no ground, bad ecm, bad prom, poor cel connections at ecm.  Verify all
power and ground circuits first.  If it was running well a couple of
days ago, look for corrosion and broken wires.
I haven't looked at the diagnostic charts, but a faulty oil pressure
switch is an unlikely cause for no CEL.
Shannen

> 
> Anyone have any suggestions?  I'm at a loss here.
> 
> Thanks in advance,
> 
> Darren Pferdehirt
> Waipahu, HI