I couldn't tell you. The past week it hasn't been blowing the first and the circuit shows no continuity to ground. And since it's so intermittent I'm leaning towards a wire instead of a sensor. I have measured my o2 sensors which both read 13 ohms. And when it was blowing the fuse i disconnected the vsv and maf which didn't get rid of the short.
Hot/Melted EFI Fuse
- Thread starter fj40toycruiser
- Start date
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LFD2037
TEXAS LEXUS!
My EFI relay is always hot. Like burn your finger hot. It's been this way for 3 years that I know of, & it's like this on the other 2 1FZ's I checked. It doesn't seem right BUT is it not normal? It's 3 for 3 on the ones I checked.
Time for my update. This evening i finally got some time to work on the truck. At this point i decided to just yank the wiring harness and inspect it with all the loom stripped. I started disconnecting the wires at the ecu and noticed a burnt smell. Further snif tests led me to the ecu. I pulled The ecu and took it apart and found my issue. A pin came lose and shorted out on the cover to the ecu. Never thought id be this happy to find a ruined ecu but I'm glad to have finally tracked it down. Once i figure out how to post pics i will add photos of the ecu
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I'm not trying to be a wet blanket, but could the damage you see in the ECU be caused by some other short in the EFI circuit? I'm not a 12v genius and not looking at the EWD, but I could see too many amps going through there could pop it because of another short elsewhere. Do you know what that blown IC does? I would want to triple check the circuit before putting in a new ECU.
Looking at the underside of the board, it looks like the pin stuck out significantly further than everything else on the board. Surely that's a manufacturing defect, right? Or did it actually get so hot that the solder melted and allowed the pin to move?!
Personally I'm leaning towards that pin being a manufacturing defect as it was only that one pin sticking up past all the rest. If the IC got hot enough to melt the solder i would expect all of those pins to be out of place.
That's pretty interesting. If I understand correctly, that ECU lasted from 1993 until 2017 with a single pin cut too long that finally contacted the case. I recently inspected my 1994 ECU and was surprised to see that it's pristine. Seems to have a coating (presumably epoxy) over the whole board. That thin layer must have been all that was between that pin and the case for decades.
ppc
M Go Blue
In my opinion it doesn't look like a manufacturing defect but a component failure. The picture of the component side of the board is not very good but there seems a lot of discharge covering the area. On the foil side there appears to have been enough heat to melt the solder. The solder on the longer pin looks like a cold joint with discoloration surrounding and has wicked solder from the adjacent pins. The automated insertion equipment would never have had one pin protrude more than others.
bloc
SILVER Star
I agree with @ppc
no way a single pin on that component would have been that much longer than everything else and make it past toyota QC. However, if that pin melted and separated from the component and the solder was hot enough it could get pushed out. The other pins remain because they are still attached to the component.
Personally I think your root problem is elsewhere.
no way a single pin on that component would have been that much longer than everything else and make it past toyota QC. However, if that pin melted and separated from the component and the solder was hot enough it could get pushed out. The other pins remain because they are still attached to the component.
Personally I think your root problem is elsewhere.
Does anyone have information on what these IC's control inside the ECU? It would be much easier to confirm the circuit is good if I knew the specific circuit that this IC is on. From the diagrams I have found, the components connected to the EFI fuse are: EFI Main Relay, ECU Bat +, MAF, EGR VSV, Fuel Pressure VSV, IAC, Heated O2's, Circuit Opening Relay, Fuel Pump Relay, Fuel Pump Sender.
I am going to start with checking these sensors connected to the circuit. I already confirmed O2 sensors are fine. And the wiring harness leading up to the O2 sensors looks fine.
I am going to start with checking these sensors connected to the circuit. I already confirmed O2 sensors are fine. And the wiring harness leading up to the O2 sensors looks fine.
have either of the people working through these efi circuit issues come across any new info or tips? i'm about to start pulling the efi circuit apart myself looking for where it's grounded out and i'm hoping for some luck. previous things that have restored connectivity: messing around in the glove box with the harnesses in there, one of which has the efi circuit running through it; jiggling the relay and jostling the fuse box briefly restored continuity; replacing the relay the one time i did that restored continuity for a few days. All this leads me to believe that something is intermittently shorting out. Any other tips before i start getting up to my neck in tearing the circuit out?
This happened to my 80 over the summer. Was only time I've gotten a tow in my 80.
It was a faulty fuel pump relay. The big one mounted to driver inner fender.
Mine too melted the efi fuse
Mine bench tested fine as per fsm but was momentarily bad.. replaced and has been fine since. Bought from rock auto. Came in factory Toyota box.. paid like 75.
I too went crazy troubleshooting. Hard part was everything tested ok. The fuel pump main relay should be replaced as part of pm. My old one still worked if I tossed back in there......sometimes. somehow. old relay made it take a long time to start and shut off while going up hill. Also crank but no start randomly. new ome cranks fast and fires right up.
It was a faulty fuel pump relay. The big one mounted to driver inner fender.
Mine too melted the efi fuse
Mine bench tested fine as per fsm but was momentarily bad.. replaced and has been fine since. Bought from rock auto. Came in factory Toyota box.. paid like 75.
I too went crazy troubleshooting. Hard part was everything tested ok. The fuel pump main relay should be replaced as part of pm. My old one still worked if I tossed back in there......sometimes. somehow. old relay made it take a long time to start and shut off while going up hill. Also crank but no start randomly. new ome cranks fast and fires right up.
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