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87 Chevy Pickup 350 EFI "Blown ECM Fuse"

I replaced the battery in my truck last week. In the middle of this process my wife told me she was going into labor with our first child. Paying little attention to the polarity on the battery I hooked the leads up backwards and things began to smoke. I cooked the alternator as well as the voltage regulator lead off the alternator wiring. I have since replaced the alternator, and the connector for the above said wiring. 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?

Reply to
pode
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Pode, 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)). Elliott

pode wrote:

Reply to
Elliott

Could have taken out the computer. Kids will always cost you money.....

Reply to
Steve W.

Elliott,

Thanx, I will give it a try. Just curious to why the engine would fire w/ me pouring a little gas into the intake. Does the computer not control the firing of the electronic ignition? On this old of a pick up, is the computer located inside under the dash, or under the hood next to the firewall. I know sounds kinda lame, but the only experience I have with automotive cpu's is on a 94 vortec Blazer. I will also see if I can find a wiring diagram online.

Thanx again,

Daniel

Reply to
pode

No. At RPMs under appx. 400, the ignition module is in by-pass.

Passenger side, under the dash.

Reply to
Neil Nelson

Re: " From: snipped-for-privacy@ckt.net (pode) I replaced the battery in my truck last week. In the middle of this process my wife told me she was going into labor with our first child. =A0=A0Paying little attention to the polarity on the battery I hooked the leads up backwards and things began to smoke. I cooked the alternator as well as the voltage regulator lead off the alternator wiring. I have since replaced the alternator, and the connector for the above said wiring. 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. =A0 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. =A0 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? "

--------------------------------------------------------------- Before giving this problem any more thought,go ahead and take the poor woman to the hospital in another vehicle.

Reply to
Brian Orion

I thought 87's had carbs.... I have a Haynes manual sitting next to me that is for TBI/CPI/etc. machines, 88-98..... Was 87 a bastard year as well?

~KJ~

Reply to
KJ

KJ,

My 87 S-10 is TBI. So I guess that's an indication. And Pode labeled this email as an 87 350 with EFI and discusses an ECMB fuse.

Meanwhile We've not heard from Pode. He must be busy with the baby and have alternate transportation (or maybe just had it fixed somewhere).

I was thinking about his fuse-pops and figured that the ornge wire that comes out of the ECMB fuse must have a short on it somewhere. My computer on my truck powers that wire. You may remember me hotting it with the old computer prior to finding out it didn't have a chip. Thus I'm thinking it's possible his computer is ok, but something else on that circuit is not. Maybe the ESC.

Elliott

KJ wrote:

Reply to
Elliott

Yes '87 was a bastard year too.

Reply to
JR

yup...

trucks under 8500lbs got TBI motors, 8501lbs+ still got a carb...

Bret

Reply to
Bret Chase

LOL :) Sorry guys, I didn't mean to keep you all hanging. The baby is here and looking great! 8lbs. 8.5 oz. and 20" long. I fixed the truck. Thanx to you guys. 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 damn thing fired up like it use to. Thanx to you and the board members I save a ass load of money. I payed $165 for a new alternator and ECM. I got more questions on down the road for you all. I will be checking in more!!

Thanx again.

Daniel

snipped-for-privacy@ckt.net

Reply to
pode

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