What does the ECMB fuse control it keeps blowing on me and now I'm stuck in the hills. It did this once and I put a new fuse in and I drove home from work about 45 miles drove around town for a few days and everything is fine. Now I can't get a fuse to hold in that spot. Anyone know or has had this happen to them? This is on a 90 blazer with the TBI 350.
CK5
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ECMB fuse
- Thread starter de3en16
- Start date
I vaguely recall it also powering the cigarette lighter, which is prone to shorting out if stuff gets caught inside. Like your mother's hearing aid batteries. 
More common, the little metal tip on the end of an auxiliary plug, like the one from your GPS or radar detector or whatever. I had one come loose and made all kinds of fun sparks down in the lighter, and trying to fish it out with very long needlenose only made it worse
-- A
More common, the little metal tip on the end of an auxiliary plug, like the one from your GPS or radar detector or whatever. I had one come loose and made all kinds of fun sparks down in the lighter, and trying to fish it out with very long needlenose only made it worse
-- A
I vaguely recall it also powering the cigarette lighter, which is prone to shorting out if stuff gets caught inside. Like your mother's hearing aid batteries.
More common, the little metal tip on the end of an auxiliary plug, like the one from your GPS or radar detector or whatever. I had one come loose and made all kinds of fun sparks down in the lighter, and trying to fish it out with very long needlenose only made it worse
-- A
Pennys fit in there perfect too.
black dawg
1/2 ton status
try unplugging the connector at the trans for lock up
I made it home. I'm thinking its one of the 3 wires going to the starter I've got a heat shield that the wires are in and I think I can see where the wires have been rubbing on to of the heat shield. I'm hoping this is my problem. Thanks to everyone for the quick replies any idea or suggestion was very appreciated thank you all!!
A fuel pump locking up will also pop this fuse
The oil pressure sender can short out sometimes and blow the ECMb fuse, unplug it and see what happens. If it still blows the fuse then it probably is the fuel pump.
I found on my '90 that the plastic wire loom had crumbled away on the within harness as it came around the top passenger side of the engine. The wires had rubbed against a bracket there. Fixed them up with heat shrink, and routed them so they wouldn't rub.
This problem originally started happening to me on the Rubicon. took me a long time to find it. Like months.
This problem originally started happening to me on the Rubicon.
took me a long time to find it. Like months.Good more places to check out. The biggest problem I have with electrical problems is where to start thanks to everyone I think I can figure this thing out now. What was happening is the truck would just die like it was just shut off no warring. I noticed when I turn the key on the fuse would hold so I don't think it's the fuel pump or oil pressure sending unit but I'm going to check them out to be sure. It's when I start turning the key to start the truck that the fuse blows. That's why I'm thinking its the stater wires shorting out on a heat shield. I'm have to work so its going to be a few days till I can work on my blazer. Thanks to everyone again for all the idea and recommendations.
Start by looking for the ECM B fuse in this diagram available in the Injection Section! 
Ok correct me if I'm wrong. The ECMB fuse gets power at the ECM and gives it to the oil pressure switch. And if it has pressure there it goes to the fuel pump relay. Does that make sense at all? It seemed that night if I turned the key to on the fuse would be fine it's just as I turn the key to start the fuse would blow I would turn the key slow and watch to see when it would blow.
It's my understanding that when you turn the key to on the fuel pump comes on to prime then shuts off because there's no oil pressure. Then as the engine cranks the fuel pump turns back on because there's now oil pressure.
I'm just trying to understand the this all works. Wiring and chasing down shorts is my biggest weakness.
It's my understanding that when you turn the key to on the fuel pump comes on to prime then shuts off because there's no oil pressure. Then as the engine cranks the fuel pump turns back on because there's now oil pressure.
I'm just trying to understand the this all works. Wiring and chasing down shorts is my biggest weakness.
The power comes from the fuse to ECM in 2 places, Fuel pump relay and oil pressure switch.
The oil pressure switch is redundant, look at wiring, it's not needed to make fuel pump prime or run when key on. It will supply power when oil pressure is high if fuel pump relay fails. Aftermarket harness don't use oil pressure switch, just a relay.
I've told guys this before but they don't believe me because most other diagrams are wrong. Disconnect the oil pressure switch and the vehicle still runs fine.
Most light duty trucks do not have the Hot Fuel Module.
The problem of short is likely from firewall to fuel pump relay or oil pressure switch. Or from fuel pump relay to pump, could also be pump.
The wiring from fuse box to ECM is all under dash, through firewall on a 91 is a large epoxy filled block and very unlikely to ever go bad without human intervention.
The oil pressure switch is redundant, look at wiring, it's not needed to make fuel pump prime or run when key on. It will supply power when oil pressure is high if fuel pump relay fails. Aftermarket harness don't use oil pressure switch, just a relay.
I've told guys this before but they don't believe me because most other diagrams are wrong. Disconnect the oil pressure switch and the vehicle still runs fine.
Most light duty trucks do not have the Hot Fuel Module.
The problem of short is likely from firewall to fuel pump relay or oil pressure switch. Or from fuel pump relay to pump, could also be pump.
The wiring from fuse box to ECM is all under dash, through firewall on a 91 is a large epoxy filled block and very unlikely to ever go bad without human intervention.
Ok I started looking for a short and I found 3 places the wire harness could rub. When it quite on me the other night it kept blowing fuses till I started moving wires around. So I'm sure the problem was on the back of the engine. I put tape on the rough edges and on the wires and zip tied them back so the wouldn't rub anymore. I took it out on a test drive and a tail next to my house and it ran good. Thanks eagle mark for the wire diagrams and thanks to everyone else for all the ides.
