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ToyotaTom
ToyotaTom, Toyota Technician
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Experience:  Toyota, ASE, MSE, MECP Certified
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93 toyota: 3.0 v6 no power to fuel pump all fuses and relays are..12v

Customer Question

i have a 93 toyota pick up 3.0 v6 no power to fuel pump all fuses and relays are good i have found the circuit opening relay and tried to test it by the book but it doesnt make sense to me where does it get its power from? the book says from the efi relay and the ing. but i only have one terminal with 12v with the key on and that comes from the efi relay should the circuit opening relay be getting power from anywere else?
Submitted: 3 years ago.
Category: Toyota
Expert:  ToyotaTom replied 3 years ago.

ToyotaTom :

Hello, and thank you for choosing Just Answer to help you with your questions!

ToyotaTom :

The white/red wire gets power from the EFI relay
The blue wire is the "output" to the fuel pump
The white/black is ground.
The black/red OR black/white (depending if you have manual or auto) should show 12v when cranking

ToyotaTom :

The green/yellow gets ground through the air flow meter when the AFM opens the door flapper on the inside of it

ToyotaTom :

So basically, yes there should only be 1 wire with power (key on) but another wire with power during cranking.

ToyotaTom :

A couple ground circuits. These grounds are equally as important as the voltage sides, as the two combined are what energizes the coil in the relay, closing the contacts to allow power to flow through the relay from the EFI relay to the fuel pump

Customer:

by the book the circuit opening relay tests ok and i got one out of a running truck so i know its good were should i look next?

ToyotaTom :

Check the green with yellow stripe at athe air flow meter. REmove the top of the airbox from the housing, and test for continuity to ground. Manually reach inside the meter, and slide the little door open. This wire should go to ground

Customer:

also when i jumped the fuel pump i wasnt getting any fuel at the fuel rail?

ToyotaTom :

When you jumped FP and B+ at the diagnostic connector?

Customer:

yes

ToyotaTom :

Ok, let's start over here, perhaps we have a bit of a miscommunication. In your original question it says that you don't have any power at the fuel pump. Have you tested for power at the blue wire at the fuel pump? Or does it just not turn on?

Customer:

no power at the pump. i ran a jumper wire to the pump to test it first and i didnt get any fuel at the rail.

Customer:

but im still not getting any power to the pump

ToyotaTom :

Have you actually tested for voltage at the blue wire at the fuel pump?

Customer:

yes first thing i did

ToyotaTom :

And it shows 12 volts?

Customer:

no

ToyotaTom :

ok

ToyotaTom :

In the diagnostic connector, do you have 12 volts at terminal B+ with the key in the ON position?

Customer:

yes, that comes from the efi relay correct

Customer:

wait

Customer:

when u say diagnostic connector do you mean the plug next to the fuse box?

ToyotaTom :

yes

Customer:

no didnt do any testing there

Customer:

just check at the circuit opening relay plug

ToyotaTom :

Ok first thing is first. You need to use a paper clip or jumper wire, whatever. Jump from terminal B+ to FP

ToyotaTom :

If you turn the key to the on position, you should hear the fuel pump turn on

Customer:

did that at the circuit opening relay and the pump came on

ToyotaTom :

It bypasses the circuit opening relay, afm, etc

ToyotaTom :

ok now we're getting somewhere. IF you jump the blue wire and the white/red wire, it comes on?

Customer:

yes

ToyotaTom :

good. And you swapped circuit opening relay from a known good truck and no change?

Customer:

yes

ToyotaTom :

good. Now we're on the same page at least. Are you testing wires with a meter, or a test light?

Customer:

meter

ToyotaTom :

Good. You've done a good job at troubleshooting. What it appears is missing is a signal source going into the circuit opening relay to activate it. It ALWAYS has power from the EFI relay. It's different ground signals that operate the coils in the relay, coming from different places.

ToyotaTom :

IS this a manual trans or automatic?

Customer:

manual

ToyotaTom :

Ok. There are 2 wires you need to check. At the circuit opening relay, there will be a black with white stripe. This will show power when you are cranking the starter.

ToyotaTom :

The other is the green with yellow stripe. You can check this at the air flow meter. IT should go to ground when you push the little flapper door open with your hand

Customer:

ok

ToyotaTom :

Both of these are what activate the circuit opening relay to "do it's thing"

ToyotaTom :

:)

Customer:

"there will be a black with white stripe. This will show power when you are cranking the starter." does this power come from the starter? may there be a bad connecton?

ToyotaTom :

This will come from the starter relay, activated by the clutch start cancel switch. If I were a betting man I would have to go with air flow meter, but it's good to give the information so you can cover all of your bases

ToyotaTom :

Alternatively, you could always just ground the green/yellow wire at the circuit opening relay and stt if it starts

Customer:

thank you for your help ive been racking my brain over this all day looking at schematics hopfully i can get it running first thing in the morning thanks

ToyotaTom :

It will be either the starter wire, or the green/yellow AFM wire. Those are the 2 inputs that energize the relay. So if you apply ground to the green/yellow (just use a jumper from the white with black stripe and green/yellow) it narrows it down to the AFM. I would put my money here

Customer:

thanks

ToyotaTom :

If this is the case, I would recommend scouring junkyards or used parts. New ones are, well, quite pricey to say the least

Customer:

i know the circuit opening relay was $90 at napa

Customer:

and they couldnt even get one

ToyotaTom :

The AFM is considerably more than that, only at the dealer as far as I am aware. Like close to a thousand dollars range

Customer:

:O

ToyotaTom :

It's really not common that they fail, but when they do it just won't run

Customer:

it just stalled at a light

ToyotaTom :

Ok, you can pretty much rule out the starter wire then. I wouldn't even consider that at this point

ToyotaTom :

I'd concentrate on the AFM'

Customer:

k thanks

ToyotaTom :

IF your buddy, or whatever donor truck you borrowed the circuit opening relay from has the AFM still, you could simply try just swapping it over, Quicker and easier than testing wires

Customer:

thats what i will do where is it? right at the throttle body?

Customer:

easy to get to?

ToyotaTom :

You know the "lid" to the air filter?

ToyotaTom :

That's it

Customer:

mint thanks

ToyotaTom :

It unclamps with the 3 clamps, loosen 1 10mm bolt to the clamp holding it to the intake pipe, and unplug the connector

ToyotaTom :

Takes about 20 seconds to remove it

ToyotaTom :

There's a vacuum line also, now that I think about it. IT runs to the baffle box just to the left of the air filter housing. (my baffle box has a big hole in it from an exploding fan on my 91... shortly thereafter replaced with electric fan)

Customer:

to easy thanks

ToyotaTom :

Good luck. Please let me know if there is anything else I can help you with

ToyotaTom :

Have a good weekend :)

Expert:  ToyotaTom replied 3 years ago.

I just wanted to follow up with you and see what you came up with

 

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