Ricks87chevy 2011-08-13 18:36:47
Hi everyone, I’m new to the site. I came across it when trying to figure out
why my 87 chevy pickup 350 EFI,,,refuses to start. A member named Pode had
the same exact problem I was having. Here’s what he said:
This motor normally starts with out a hitch. When I
tried to start the truck I got nothing, nada, zilch. I checked over
the fuses under the dash and found only one that was blown. It is
labled “ECM B”. When I replace the 10 Amp fuse it instantly pops. I
can’t recall hearing the fuel pump priming either. I did get the
engine to fire by pouring a little gas down the throttle body, but
immediatly dies. So at this point I know I am not getting fuel. So
what else could possibly be blown and or shorted out at this point?
In response to that, a member “Elliot” responded:
ECM-B is the computer’s battery output to the fuel pump. Sounds
like you blew the computer. Pull out the computer and replace the
fuse. If it doesn’t blow, measure the voltage on the socket (same
as the orange wire to the fuel pump relay. If the voltage is low,
measure the resistance from the ECMB fuse to ground (not sure which
side). If it isn’t shorted to ground
you probably isolated the problem to the computer. If that’s the case
you may have damaged the computer’s PROMs too (hope not) – but
just in case, a J-yard replacement w/ chips seems the way to go (AZ
has them w/o chips).
If it is still shorted w/o the computer, pull the fuel pump relay,
and do it again. If it’s still shorted (blowing fuses) try pulling
the Electronic Spark Module (ESM (a flat black box in the middle of
the fire wall with an hand full of wires to it)).
Looks like Elliot knew what he was talking about from Pode’s response:
I followed Elliotts instructions and he
was right. First I did test the ESC, and the fuel pump relay. All
were good. I then pulled the power on the fuel pump and the ECM-B
fuse would still blow when I replaced it. Last but not least, I
disconnected the Computer and BAM, no blown fuse. I picked up a new
ECM, move the PROMs and the d*** thing fired up like it use to. Thanx
to you and the board members I save a a.s load of money.
Man!!! Wish I had Pode’s luck. I’ve done the same thing to my truck, good
news is that by process of elimation, I too found that it was the ecm,,,,,
when I disconnected it, the fuse didn’t blow. So, fuse blowing problem fixed,,
,,,,,,The bad news is, I purchased a new ecm, switched the PROMS and the
truck STILL won’t start!!!! Now what??? ANY advice or suggestions, welcome!
Snoman 2011-08-13 18:36:50
There is still a chance that the fuel pump is going bad and the extra
draw from it shorted out ECM output and caused its failure. Those
pumps have a fairly high failure rate if you are one to run them low
on fuel a lot.
Ricks87chevy 2011-08-13 18:36:52
Hmm ok, we’ll have to check on that then. Also, since replacing the ECM, when
cranking, the check engine light comes on, blinks off once and then comes
back on and stays on?
Snoman 2011-08-13 18:37:03
A code is being set in ECM. Have you tried to read it!
Stormin mormon 2011-08-14 09:50:40
As I understand, the gasoline cools the pump. So low fuel
oveheats the pump. Try to keep at least half a tank.
Christopher A. Young
You can’t shout down a troll.
You have to starve them.
: >truck STILL won’t start!!!! Now what??? ANY advice or suggestions, welcome!
: There is still a chance that the fuel pump is going bad and the
: draw from it shorted out ECM output and caused its failure.
: pumps have a fairly high failure rate if you are one to run
: on fuel a lot.