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Curious fuel pump relay problem (93 Camry)

Here's the current problem: The "circuit opening relay" above the glove box that controls the fuel pump isn't engaging for the two seconds or so when the ignition is turned on like it's supposed to.

If I manually active the relay (press down on the top of it to close the contacts) to turn the fuel pump on for a few seconds while I start the engine, then the car will start and the relay will stay activated when the engine is running.

I've tested and I'm getting constant power to one coil on the relay (there are two) and the other coil is only energized when the starter is running.

I've tested the relay outside of the car and it activates with the

12.5 volts directly from the battery just fine (perhaps I should try 11V.. perhaps it's just getting weak and there are losses in the wires going to the relay)

Perhaps the relay is weak AND the compuer only turns on the relay for

2 seconds if it senses the fuel pressure is low...

any advice?

Thanks, Danny

Reply to
Danny Beardsley
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It may be a bad relay but I am suspecting the socket/bad connection at pin 3 (black/white wire), or 6 (white/black wire) ground. If I understand your post correctly, you are pushing on it to get it to work, and unless you have the relay exposed, it would be almost impossible to close the circuit inside the relay just by pushing on it. That is why I suspect the socket connections.

Check for any corrosion or bad connections at the socket base. On an outside chance of a bad relay, look closely at the base of the relay for any suspect pin connections.

Check for corrosion on any grounds as well (pin 6 white/black wire).

Check for voltage at pin 2 and voltage when the circuit is closed at pin

1 that feeds the fuel pump.
Reply to
user

I took the cover off the relay to manually close it. the relay and it's sockets are clean and free of corrosion. I can't say the same for the ground connection points at the other end of the wires. If I recall... I think I was seeing about 11.5V at pin 3 and 6, and the same on pins 2 and 4 while the starter was turning. I'm not sure how it's supposed to function though. The relay stays closed after I close it while the car is running, soperhaps it's just too weak to close on it's own, but strong enough to stay closed once it's closed.

Reply to
Danny Beardsley

I took the cover off the relay to manually close it. the relay and it's sockets are clean and free of corrosion. I can't say the same for the ground connection points at the other end of the wires. If I recall... I think I was seeing about 11.5V at pin 3 and 6, and the same on pins 2 and 4 while the starter was turning. I'm not sure how it's supposed to function though. The relay stays closed after I close it while the car is running, soperhaps it's just too weak to close on it's own, but strong enough to stay closed once it's closed.

***************

It has been a long time since I looked at the specs, but there is a minimum battery voltage for the EFI system to work properly, 11 point something volts. Try giving the battery a jump and see if everything works properly.

Reply to
Ray O

Maybe I missed it in your posts, but did this problem occur suddenly or did you experience intermittent failures over a period of time?

I would say that if it was a sudden failure, it might be the relay. If over a period of time, it could be a voltage/battery/charging system issue.

There are two relays (you are working on the circuit opening relay) in that system but if it is working while the car is running it is not the other (EFI main) relay.

11.5 vdc might not be enough cranking voltage to actuate the plunger to close the relay contact. Check your battery (old?) and charging system function.

The relay is energized through the ignition switch while you hold the key to "start".

When you release the key to "run" it basically is energized through the EFI main relay system.

It might be several issues contributing to this problem on a fifteen year old car.

Reply to
user

I was thinking along the same lines and I cleaned of the negative terminal on the battery and tried to clean out the plug that connects the fuel pressure sender to the wiring harness. Everything seems to work reliably now. It was an intermittent problem, so no telling how long this fix will last. After lots of testing, fiddling around, and measuring I determined that the root of the problem was not the relay, but the Computer not telling the relay to turn on when it was supposed to... The only reason the computer would mess up would be if it didn't have the right info (the pressure sender was malfunctioning, or not connected well). So we'll see how that goes. Thanks for the advice.

Reply to
Danny Beardsley

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