Curious fuel pump relay problem (93 Camry)

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Danny Beardsley - 18 Feb 2008 07:53 GMT

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

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Ph@Boy - 18 Feb 2008 14:22 GMT

> Here's the current problem: The "circuit opening relay" above the
> glove box that controls the fuel pump isn't engaging for the two
[quoted text clipped - 21 lines]
> Thanks,
> Danny

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.

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Danny Beardsley - 18 Feb 2008 18:27 GMT

> > Here's the current problem: The "circuit opening relay" above the
> > glove box that controls the fuel pump isn't engaging for the two
[quoted text clipped - 39 lines]
>
> - Show quoted text -

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Ray O - 19 Feb 2008 03:07 GMT

On Feb 18, 6:22 am, "Ph@Boy" <u...@example.net> wrote:

> Danny Beardsley wrote:
> > Here's the current problem: The "circuit opening relay" above the
[quoted text clipped - 40 lines]
>
> - Show quoted text -

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.

Signature

Ray O
(correct punctuation to reply)

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Ph@Boy - 19 Feb 2008 15:23 GMT

>>> Here's the current problem: The "circuit opening relay" above the
>>> glove box that controls the fuel pump isn't engaging for the two
[quoted text clipped - 41 lines]
> 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.

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.

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Danny Beardsley - 19 Feb 2008 18:18 GMT

> >>> Here's the current problem: The "circuit opening relay" above the
> >>> glove box that controls the fuel pump isn't engaging for the two
[quoted text clipped - 66 lines]
>
> - Show quoted text -

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.

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