sv21 fuel pump problem - Toyota Nation Forum : Toyota Car and Truck Forums

phild01 · 10-13-2009, 04:01 AM

Hi
Desperate for an answer and hoping it is simple.

My sister's '87 SV21 3SFE Camry stopped and it has been discovered that the fuel pump is not getting any power after cranking over. So the fuel pump pumps fuel to the rails while cranking but stop cranking the engine and the power supply then cuts off to the fuel pump and the engine stops shortly after. I am guessing there may be an ECU problem but hoping for something else.

Anyone know why the battery power would not continue to the fuel pump after the starter motor stops and do you think a power supply bypass to the fuel pump could be put in and not create other problems.
???
any help with thanks

Just been reading up and now suspect the air flow meter which may have a fuel pump switch. Anyone familiar with this device?

white90dx · 10-13-2009, 01:43 PM

It could be the AFM or the Circuit Opening Relay (or possibly wiring).

Check if the car stays running with a wire connecting the "FP" and "B+" connections inside the check connector in the engine bay.

You can check the AFM by verifying that there is continuity between the Green wire and White with Black tracer wire when the flap inside the AFM is held open.

If the AFM seems to be working, you can just grab a replacement from the junkyard. It it located next to the ECU which you can find by pulling back the carpet in front of the passenger footwell near the center of the car (its behind the radio/AC controls).

-Charlie

phild01 · 10-13-2009, 06:36 PM

thanks Charlie

The AFM is now being looked at. It seems when the choke is operating the petrol (gas) flows. Car started from cold and kept running until choke was no longer operating? Could this be a function of the AFM or is there something else as well controlling the fuel pump? ......just had a call from the associate looking at it some 150 kms away and he held a flap open inside a shoebox sized box and said it is all working properly now. I assume this is the AFM inside the airbox. So he is wondering if the AFM needs replacement? Unfortunately he has no internet and depending on me a bit.

white90dx · 10-14-2009, 01:43 PM

The AFM sits on top of the airbox. The air flowing through it opens the flap different amounts depending on how much air is flowing to the motor.

It is possible that the flap was stuck closed, I suppose.

Does the car run normal again, or does it only run when the flap is held open?

-Charlie

phild01 · 10-15-2009, 05:18 AM

The pump will only work if flap held open or when the starter motor is kicking over. These AFM's cost quite a bit ($300+ reconditioned). A wrecker has one for $45 so I have had this couriered to him. I spoke to a Toyota mechanic who advised that the car will run rough if the flap is permanently held open and we found this to be true. In a few days I should know how this all works out.
Thanks Charlie.

phild01 · 10-23-2009, 06:55 AM

Charlie
In your earlier post you indicated a relay may be an issue. You were directing me to under the carpet next to the ECU. Just asking because the swapped over AFM did not resolve the problems we are having. Manually holding the flap open allows the car to start and run but very rough running with too much petrol pumping through. I suspect the AFM may well be fine. Is it normal for the fuel pump not work while the flap is closed, but operates only if the flap is actually open even if just open?
The ECU, is this another name generally for thye cars computer.
Is there any way of applying 12volts to the AFM terminals to see if the flap activates as a conclusive way to see if it is working? I am assuming the ECU drives this flap open or am I wrong and perhaps it is a totally mechanical device operated by air pressure (this would mean an air leak I guess)
thanks Charlie if you can offer any advice.

drugal · 10-23-2009, 08:08 AM

The AFM flap is a mechanical device. When the engine is running, the air being sucked in moves the flap. It is not electrically moved.

Power for the fuel pump goes through a relay called the Circuit Opening Relay which is located under the ECU. This relay has two solenoids inside to activate it. Either one will activate it. One solenoid is energized when you have the key in the start position, providing fuel pressure when cranking the engine over to start it. Once the engine starts, the first solenoid is de-energized, and the other solenoid is then energized when the AFM flap opens (even a little bit). The AFM has an internal switch connected to the flap for this. The idea behind this is that if the car is in a bad collision, the fuel pump will not continue to pump fuel if the engine is stopped.

So, holding the flap open or having the engine in start mode will provide power to the fuel pump. I would check for a major air leak, possibly a crack in the flexible intake hose.

You can bypass the fuel pump safety stuff by jumpering two connections in the diagnostics terminal. This is a little black box mounted on the strut tower next to the AFM. If you jump terminals "+B" and "FP", power will be sent directly to the fuel pump with the ignition on. You can use this to keep the car running while you search for leaks.

white90dx · 10-23-2009, 02:08 PM

Yeah, it does sound like an torn intake tube. A large vacuum leak anywhere between the AFM and the intake valves would cause what you are describing - so it could be a problem somewhere else farther down the line.

Oh yeah, when you are testing the motor, make sure that the intake tube and the AFM are hooked up - otherwise the motor won't run for more than a second or two...

-Charlie

phild01 · 10-24-2009, 05:49 AM

Well, I am near the car for the moment and went and had a look today. Try to explain to the person trying to fix this problem the AFM function. I had a play with it and with the engine running (screwdriver stuck in flap for the start) and revving the aFM flap clearly worked. I removed the screwdriver and the engine ran well for about 5 minutes and then choked to a stall. Restarting I observed just the slightest touch to the flap improved the engine idle revs and it ran very smooth. i left it idling untouched, no screwdriver and after about a minute it suddenly choked to a stall again.
I am not sure what specific hoses to look at but did not find any that seemed split or broken and not hearing any hissing sounds.
One thing I have done is look at the resistance measurements at the terminals to the AFM. All checked ok except E2-Vc which I read should be between 200-400ohms. I get varying readings for this but then is consistent with two other AFMs I checked from sepearte wreckers. Generally I might get an instant reading of 80ohms that retreats to next to nothing. As I say this was consistent with all 3 AFM's checked so I doubt this is the issue. Can't get my hands on a new AFM. The terminals I refer to are the third ones in from each end of the 7 pin socket on the AFM.
Thanks for the input so far as it all makes sense to me now but I wonder if a very small air leak might be causing the problem. It is though the AFM flap could do with an extra 1mm or 2 of being open???

TUBEJUNKE · 10-31-2009, 01:03 AM

It is possibble to remove the plastic cover. Then you can verify visually how just a small touch of the air door controls a set of relay contacts. While you are in there you can take a pencil eraser and clean the contact area of the potentiometer (volume control) which you will see is turned by the rest of the air door's travel. All potentiometers get electrically noisy with time due to eratic increases and decreases of resistance caused by non conducting contaminants. Point being, it can never hurt to make sure a potentiometer is clean, especially if something electrically whacky is going on. In this case it's super easy to do but DONT try to pull the harness plug by removing the two screws holding the socket. No need to unplug anyway....