Supa Dexta

So I've got the common EFI blown fuse, but I checked the wiring to my o2, and found nothing. I also tried jumping Fp and B+ in the diag and the fuel pump wont turn on this way.

(Does the fuse need to be in the EFI for that jumper to work?) Because putting a fuse in the EFI and then jumping the diag blows the fuse immediately.

I even ran jumpers directly back to my fuel pump from the battery and I can hear it run fine.

If I put a new EFI fuse it, it will start and run for 1-2 seconds and then pop the fuse and stall.

With no jumper in the diag I only get ~30mA across the fuse terminals but if I jumper the diag it will bounce around 10A-4A-6A..etc..with the Ign on.. So does that point to my fuel pump wiring? Or am I missing something else.

EFI relay gets warm also, swapping it with starter relay = same symptoms.

It was running fine, I parked it, it hesitated slightly so I gave it a shot of gas, it revved up and then idled right down and quit and hasnt ran since (more then a few seconds before fuse blows again)

waskillywabbit

iTrader: (-1)

Vehicle specs would help.

:wabbit2:

Supa Dexta

Sorry 1992 4 runner, 22re

ZUK

iTrader: (1)

I had a 92 regular cab.....the efi fuse kept blowing. Turns out the last thing I did to the truck was some exhaust work....sure enough, when I eyeballed the oxy sensor, I saw that the wires had melted onto the exhaust pipe. I know you said you checked yours but check closer....check for frayed insuation that's on a sharp bend also.

Supa Dexta

Mine was tied well away from the exhaust. But checked anyways. Im focusing more on why the efi fuse blows when I jump the Fp and B+...?

I've read of the 'circuit opening relay'... But its always mentioned in older rigs, does the 92 still have this? I looked by the ECU and didnt see it, but didnt dig way up there yet..

Also isnt the jumper supposed to bypass the COR and turn on the fuel pump anyways?

Which points me back to a short somewhere else giving me the EFI greif.

sb5walker

The COR is in the passenger's kick above the ecu on most of the 89-95 series trucks. I've read of it being behind the glove box on a few. The wire from the COR to the fuel pump (which is solid blue on most of the trucks in that series), has a splice with another blue wire leading to the FP terminal in the check connector. So if there was a short inside the COR, or at the connection to it, that would blow the EFI fuse when FP jumped, yes. (Power goes through the EFI fuse, through the switched circuit in the EFI main relay, to the +B terminal in the check connector (and also to the ecu).

If the EFI fuse blows when you jump FP, and yet you've determined the pump runs okay without shorting when jumped at the pump, then yes, there probably is a short either in the power lead from the COR to the fuel pump, in the lead from FP to the fuel pump power lead, at the connection of that lead to the circuit opening relay, or inside the COR itself. I'd check the COR and make sure the connections are okay and the fuel pump lead doesn't short to ground.

http://personal.utulsa.edu/~nathan-b...38circuito.pdf

When you jumped the fuel pump close to the pump and it ran, did you have a fuse in that jumper? You might use a 15A fuse in that lead to make sure the pump for some reason isn't drawing more amps than that.

EDIT: corrected COR location

Supa Dexta

My ECU is in the passenger kick panel though? The interior fuse panel on the drivers side however?

Ill try the pump with an inline fuse, it didnt sound like it was straining at all though.

scuba

COR is behind the PASSENGER kick panel.

sb5walker

OOPS! My bad - I meant to type "passenger's". I edited the post.

Instead of a fuse, since you posted some amp measurements, you could just check the amps.

Supa Dexta

Ok so I've done a bit of digging with my meter. Ill need some pointers on what I've found though.

> I'm getting continuity to ground thru my FP terminal in the diag port and from the B+ to battery ground I'm reading 250 ohms?

So at the fuel pump connector under the rear seat, white w/ black stripe appears to be ground and blue my power wire which seems fine. However on the pump side of that connector both wires are common to ground? So something is shorted from there to the pump? Dropping the tank doesnt look like its going to be fun with the rust under there. But that seems to be my problem at this point. I still havent found my COR relay, its definitely not out in the open anywhere by the ECU. but Im not too worried about it at this point until I sort out the fuel pump grounding issue...

TNRabbit

It's easier to pull the bed off than drop the tank~

Just be sure you remove the taillight connections before you yank the bed off~

Supa Dexta

Its a 4 runner..

Got it most of the way out, just have to fight with the fill neck some more..

Never fun using the mini grinder to cut bolts off around the fuel tank though.

Supa Dexta

Alright so I dropped the tank and removed the sending unit.. It appears to be the terminal that passes thru the top, that is supposed to be insulted - that is shorting out.

I disassembled both connectors, the one going into the top of the sending unit, and the one that plugs in to the pump itself to make sure it wasn't shorting in the connectors and its not. Its the terminal itself. I could remove that terminal and make my own pass thru connector, but the fuel lines on the sending unit are too rusted to bother.

So now I'm on the hunt for a good condition sending unit. My pump is good.

Supa Dexta

Also I can't post in the classifieds yet, so if someone reading this has a good sending unit, let me know! thanks for the help so far.

sb5walker

It's normal to get some continuity to ground on FP since it goes to the motor coil in the fuel pump and through it to ground. So you should pick up some resistance equal to whatever is produced by the pump coils. Same with +B except that goes through electronics in the ecu to ground.

You mention "fuel lines on the sending unit" The fuel lines are in the fuel pump bracket, and the fuel sender is a separate unit, AFAIK.

Supa Dexta

hrmm Ive always called that a sending unit, but in my past experience the fuel level float was also built into it.

So is a sending unit sending fuel, or fuel gauge signal? lol

Supa Dexta

So I've got it running again. I didnt really 'fix' anything.. But it did turn out to be the insulator pass thru in the sending unit. It was grounding out there somehow, all I did was turn it back and forth with some pliers and then it wasn't grounding out any more..? So who knows how long it will last.. That and some fake metal on the outlet tubes to keep them from leaking..

87 'runner boosted

fyi, fuel sending unit sends fuel level signal to gauge, pump does the pumping. Im searching for similar problem on my truck...just overhauled, wont start. fuel pump not kicking on. Do you by any chance have pics of the Fp and +B connector yall are talking about??

Supa Dexta

Its a small connector with a grey cover right next to the fuse panel on the passenger side fender /under the hood, pop the cap and it should be labeled under the cover as to what pin is what..

sb5walker

The gray connector on the passenger inner fender started with the 89 trucks. I know there is a place to jump the fuel pump on the earlier trucks, but don't know where it is or what it looks like. Maybe an 88 or earlier fsm will show it.