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Toyota Service
Toyota Service, Toyota Expert
Category: Toyota
Satisfied Customers: 4599
Experience:  30+ Yrs of auto experience, Award Winning Svc. Manager; Just Answer Customer's Choice Award Winner
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I have 1992 Toyota pickup v6, I have no fuel pressure when

Customer Question

I have 1992 Toyota pickup v6, I have no fuel pressure when key is on not running. b+ to f1 jump test made fuel pressure when key was on not running
Submitted: 1 year ago.
Category: Toyota
Expert:  Toyota Service replied 1 year ago.

Hello. Welcome to Just Answer. Please allow me to assist you. If I understand your statement correctly, you have no fuel pressure when the engine is cranking, but you do have fuel pressure jumping B+ to Fp. Does the engine start B+ to Fp jumped?

Expert:  Toyota Service replied 1 year ago.

Note that the fuel pump is not designed to run with the key in the ON position.

Customer: replied 1 year ago.
engine starts when jumping b1 to fp, but when not jumped I crank motor and it builds fuel pressure slowly and will eventually start
Expert:  Toyota Service replied 1 year ago.

Ok. Thanks for responding. What you most likely have going on here is a weak relay. On this vehicle, a 'fuel pump' relay is not used to control the fuel pump. Toyota calls the relay that energizes the fuel pump the "Circuit Opening Relay " (or C-O). The C-O relay gets power from the EFI fuse in the fuse panel. When the engine is cranking (or running), the little door on the Air Flow Meter closes a microswitch. This switch allows a ground signal to be sent to the coil of the C-O relay, which allows it to energize and close the relay contacts; this sends power to the fuel pump. When you jump B+ to Fp, you are sending power straight to the fuel pump, bypassing the C-O relay. Failure of the C-O relays are quite common on these vehicles these days, especially if they are original/never changed. On this vehicle, the C-O relay is hidden behind the kick panel on the passenger side footwell. The recommendation I have for you on this request would be to visit you local Toyota dealership's parts department and purchase/replace the C-O relay in your truck.

Expert:  Toyota Service replied 1 year ago.

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Customer: replied 1 year ago.
ok, thanks, ***** ***** passenger kick panel, I see ecu and plug ins behind ecu, can not locate C-O relay.
also when idling up motor, is it normal for fuel pressure to drop? I have 33 psi when idling
Expert:  Toyota Service replied 1 year ago.

They hide this relay pretty good over on the passenger side. It is not low like the ECU is. it is higher up on the inner panel

Expert:  Toyota Service replied 1 year ago.

fuel pressure at idle is supposed to be 30-32 psi

Expert:  Toyota Service replied 1 year ago.

on the relay, look for these wire colors:

white/red

Solid blue (this goes to the fuel pump)

Black/White

Green/yellow (this is the wire from the air-flow meter

White/Black

Customer: replied 1 year ago.
found it
, will replace to see if it solves problem
Expert:  Toyota Service replied 1 year ago.

You can jump the White/Red wire to the solid blue wire; if it starts up you have found the problem.

Expert:  Toyota Service replied 1 year ago.

If it stays the same, look under the passenger side of the front seat for a melted or corroded wire connector. This is where the cab harness sends power to the under-bed harness.

Customer: replied 1 year ago.
put new C-O relay on , working a lot better .
got a knock sensor code. drive truck, has no power , manually advanced distributor but truck still falls on its face, got new knock sensor, prolly tomorrow installing, tough day ahead.
Expert:  Toyota Service replied 1 year ago.

On this engine there is a small sub-harness that goes between the engine room harness and the knock sensor. You would be best advised to replace this short harness too. The harness itself may be part of the knock sensor code. In my shop it is standard operating procedure to replace this harness whenever we have a knock code. We do not want to have to do the whole job over because the harness was the problem and not the sensor.

Expert:  Toyota Service replied 1 year ago.

Also make sure your timing has not jumped a tooth on the timing belt. Set the engine to TDC and pull the distributor cap. The rotor should be directly under the number one cylinder tower on the cap. Perfectly under the tower. Not a bit before, not a bit after. If so, you need to fit a new belt.

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