efi fuse/ starter

Hey guys My mystery efi fuse problem comes back. Battery reads 12.65, doesn't turn over the engine. I hook up a portable charger and it turns over nice. Today followed the same procedure and instaed of hooking up charger I put a yellow top in. Cranked the starter but engine won't hold a efi fuse. Is there any way in the world a starter or the wires going to and from could short out and cause the efi fuse to not stand.

Reply 1 : efi fuse/ starter

EFI fuse circuit totally unrelated to starter circuit. Most common cause of EFI fuse blowing is the O2 sensor wire touching the exhaust pipe, melting and shorting. Otherwise, could be tough to find the short since EFI fuse powers the circuit opening relay and fuel pump, powers the ecu and, through it, many of the sensors. Suggest finding a wiring diagram and start measuring resistance between various sensor leads and ground.

Reply 2 : efi fuse/ starter

Thanks very much for the reply. I thought I had the problem fixed because as I said it has been starting up in the garage once a week, and it was fine. All of a sudden it happens again. Could it be a efi relay. It is fairly new, but could be bad.

Reply 3 : efi fuse/ starter

Quote:

Originally Posted by marley119 Thanks very much for the reply. I thought I had the problem fixed because as I said it has been starting up in the garage once a week, and it was fine. All of a sudden it happens again. Could it be a efi relay. It is fairly new, but could be bad.

Could be, but probably isn't. Did you check the O2 sensor wire?

Reply 4 : efi fuse/ starter

Yes , O2 sensor wiring is out of way. This problem would go away and drive around nice, then all of a sudden, pop.

Reply 5 : efi fuse/ starter

Could an ingniter failure cause the efi fuse to blow

Reply 6 : efi fuse/ starter

Don't think so. The igniter is powered directly off the ignition switch. The ecu does send a spark triggering pulse to the igniter, but the worst the igniter could do to that wire is ground it, which is what it does anyway. That wouldn't blow the EFI fuse. You probably have a wiring fault. I'd search for a wire either loose or with damaged insulation. Check the wire that goes to the circuit opening relay. If your search doesn't uncover anything, you might consider opening up the ecu to make sure the circuit board is okay. I've seen some scary pics of ones that got water in them.

Reply 7 : efi fuse/ starter

Thanks I will look at these things. The fuse doesn;t blow when the efi relay is removed

Reply 8 : efi fuse/ starter

Quote:

Originally Posted by marley119 Thanks I will look at these things. The fuse doesn;t blow when the efi relay is removed

Not a huge surprise since most of the power that goes through the fuse also goes through the relay. There is one feed from the fuse that bypasses the relay, going to the BATT terminal of the ecu. But that's just for holding the settings and codes in the computer when ignition is shut off. The main power to the ecu is switched by the efi main relay, going into the +B terminal, and from there on to the various sensors. Also the feed to the fuel pump goes through the main relay, then through the circuit opening relay and on to the pump.



Wire colors to look at especially closely are the white wires with red stripe - that goes from main relay to five places: the circuit opening relay, the ecu, the VB terminal of the air meter, to all of the VSVs and to the O2 sensor(s). Actually, six places: one of the white/red stripe wires also leads back to the +B terminal of the check connector. Also check the blue wire going from the circuit opening relay to the fuel pump. Most likely, one of those wires is shorting out. It is theoretically possible for there to be an internal short in one of the components those wires connect to, but it's not too likely. Still, disconnecting those components offers a good way to troubleshoot. When you disconnect something and the fuse no longer blows, you know that there's probably a short in that component (or downstream from it in the case of the COR). The components include the circuit opening relay, the fuel pump, the air meter, all of the VSVs, the O2 sensor(s) and the ecu. POSSIBLY a short in one of the sensors that connect through the ecu (or the wires to them) could blow the efi fuse. Note that disconnecting a component won't tell you anything if there's a short in the wire leading to it. For example, if there is a short in the white/red wire leading to the air meter, that short will still be there if you disconnect the air meter.



I would first pull the COR and see if it still blows. If not, there is a short in either the COR, the blue wire leading from it to the fuel pump, or inside the fuel pump. Of those, a short in the wire is most likely. Next, try unplugging the ecu plug that contains the white wire with red stripe. If the fuse still blows, that eliminates any problem in a sensor connecting to the ecu. After that, try the air meter and then each of the VSVs. But again, that won't tell you if there's a short in one of the white/red wires leading to those components, and as mentioned, that's most likely where the problem will be.



A good way to check if there is a short somewhere in the white/red stripe wires is to pull the efi main relay and COR, disconnect the ecu plug with the W/R wire, disconnect the O2 sensor(s), air meter and all of the VSVs, and then use a multimeter to check for continuity between the +B terminal of the check connector and a ground. There should not be continuity. If there is, then somewhere on one of those W/R wires there is a short where the wire is contacting a ground. Pinched wire, abraded insulation, place where a connector is immersed in water, something like that.

Reply 9 : efi fuse/ starter

Can this problem be seen by a code

Reply 10 : efi fuse/ starter

Worth checking, but most efi fuse blowing threads report no codes.

Reply 11 : efi fuse/ starter

I should add that the wire that goes from terminal 10 on the ecu to some of the fuel injectors is also white with red stripe. That wire is unrelated to your problem, since that wire is powered by the ignition switch, is always hot when ignition is on, and the ecu grounds it to fire the injectors. So it has no way of blowing the efi fuse. Check the ecu connector diagram in the EFI SYSTEM - TROUBLESHOOTING chapter of the fsm to identify the +B terminal. That's the right white/red wire.

Reply 12 : efi fuse/ starter

sb5 I want to thank you for your help. I will get to this Tuesday and let you lnow.. Best to you

Reply 13 : efi fuse/ starter

Hey im not blowing fuses but the same thing with the battery. It's fine and I have a brand new starter, supposively the best one for yotas, well it was the most expensive. Today I was leaving work and nothing, no turn over no nothing....sat there kept flipping switch back an forth got out check battery checked starter still nothing all wires connected and everything got a coworker to try and jump me off to no avail then got him to bang on the starter while i was trying to turn it over and nothing stood back stratched my head figured i'd try it again and it cranks fine tryed it about 20 times when i got home an it just cranks right up no problem but something has to be causing it not to crank any suggestions? I'm not tryin to highjack your post btw jus looking for answers

Reply 14 : efi fuse/ starter

sb5 Dave, the mechanic went out to the truck, fuse was blowing when key turned to on, regular battery. The key was on , put in fuse , immediately blew. He put in the yellow top and it turned the starter strong, still fuse blowing. There are two wires coming off hot of battery. One goes to the efi route and the other went to some lights. The one for the lights was shorting on wheel well. He took wire off hot of battery and put fuse in, no blow. He put wire that was for lights and shorted out, on metal, fuse blew, So,he fixed and rerouted wire an the truck starts up strong, ????????????, WTF. AFTER ALL THIS HE WIGGLED EVERY WORE IN THE FUSE BOX AND FUSE STAYED GOOD. wE WILL SEE.