'89 CRX starts then stalls

I'm going to attach an LED (with resistor in series) to the fuel pump
connector and bring the led out where it can be seen during the starting
sequence.

The LED will tell me when the fuel pump is given power. Normally I would
expect to see 1. LED lights up for 2 seconds when ignition is turned then
goes off 2. LED lights up as I crank the engine 3. LED stays on when I
release key (once engine has started). Perhaps there could be a small
pause between 2 and 3?
The clicks method would do the same thing but I find it hard to feel the
click when the engine is been cranked. Also the relay could be clicking
but not delivering power to the pump (if the relay contacts are bad).

It will be interesting to see what the LED will show but I have to wait
until the problem happens again.

I will post the results of the investigation.

"ThomasE" > wrote in
lkaboutautos.com:

> I'm going to attach an LED (with resistor in series) to the fuel pump
> connector and bring the led out where it can be seen during the starting
> sequence.


Sounds cool, but all you really need to do is backprobe terminal 7 of the
Main Relay with an analog multimeter set to VDC. In fact, this would give
you an even more accurate result, revealing any low voltage condition or
hitches in power.




--
Tegger

The Unofficial Honda/Acura FAQ
www.tegger.com/hondafaq/

ThomasE wrote:
> I'm going to attach an LED (with resistor in series) to the fuel pump
> connector and bring the led out where it can be seen during the starting
> sequence.
>
> The LED will tell me when the fuel pump is given power. Normally I would
> expect to see 1. LED lights up for 2 seconds when ignition is turned then
> goes off 2. LED lights up as I crank the engine 3. LED stays on when I
> release key (once engine has started). Perhaps there could be a small
> pause between 2 and 3?
> The clicks method would do the same thing but I find it hard to feel the
> click when the engine is been cranked. Also the relay could be clicking
> but not delivering power to the pump (if the relay contacts are bad).
>
> It will be interesting to see what the LED will show but I have to wait
> until the problem happens again.
>
> I will post the results of the investigation.
>
it's a cool tool, but is there much point? fuel pump is on all the time
the motor's running. it's only off if the ignition [switch] is off or
the motor is registered as off for 2 secs [ecu].

ThomasE wrote:
> It so happens that I used the same exact soldering iron (the only one I
> got). Probably unlikely that resoldering would leave the relay contacts in
> the same borderline situation (sometimes working sometimes not).
>
-------------------------------

When you resolder a Main Relay, it's best to remove all the old solder,
add some resin, and put on some new solder, otherwise you may not get
good adhesion and a nice meniscus. The factory solder was very thin, BTW.

I wouldn't even bother if I only had a soldering iron but no solder
(unless I was stranded in another city).

'Curly'

I did remove most of the old solder and I did put new solder. Resin I did
not have but I assumed the resin contained in the new solder itself was
enough.
In any case, I attached the LED to the fuel pump power now so I will wait
for the malfunction to happen and get some more diagnostic information.
Unfortunately the problem is intermittent and did not happen yesterday.

You are right an analog multimeter would have been easier, I did not think
of that. But in any case I only have a digital multimeter which would have
been harder to read. If I had an analog one I would still attach it to the
fuel pump connector though because acessing the main relay is difficult.
Anyway, I attached the LED and it is working as expected but unfortunately
the car started fine all day yesterday. I'll wait for the malfunction to
happen again...sooner or later, then I'll have some more diagnostic
information.

I thought that if it is indeed the main relay that's causing the problem
then the fuel pump will not run (except for the initial 2 second priming).
Not?

Finally. I cought the engine not starting.
This afternoon the engine failed to start on 4 attempts. In all 4 attempts
the LED shows power to the fuel pump been cut off after I return the key
from the cranking position to the driving position.
So,
1. I turn the ignition and the LED comes on for 2” (I also hear the pump).
Here I feel the 1st relay click (relay goes on). Then after 2” LED and
pump go off and I feel the 2nd realy click (relay goes off).
2. I crank the engine and the LED comes on (cannot hear pump over engine
noise), engine starts. Here I feel the 3rd relay click (relay on).
3. I return the key from the cranking position to the driving position and
the LED goes off!! and I feel a 4th relay click. Engine then stalls about
1” later. This 4th realy click must be the relay going off again.

So this points to the main relay being at fault. I guess it could still be
the ECU’s fault for failing to maintain the relay closed but from what I
know blaming the ECU for problems is usually a loosing proposition.

So I will probably replace the main relay. If that fixes the problem I
will then take the older relay apart to see if I can determine where it
was failing, just out of curiosity.

ThomasE wrote:
> Finally. I cought the engine not starting.
> This afternoon the engine failed to start on 4 attempts. In all 4 attempts
> the LED shows power to the fuel pump been cut off after I return the key
> from the cranking position to the driving position.
> So,
> 1. I turn the ignition and the LED comes on for 2” (I also hear the pump).
> Here I feel the 1st relay click (relay goes on). Then after 2” LED and
> pump go off and I feel the 2nd realy click (relay goes off).
> 2. I crank the engine and the LED comes on (cannot hear pump over engine
> noise), engine starts. Here I feel the 3rd relay click (relay on).
> 3. I return the key from the cranking position to the driving position and
> the LED goes off!! and I feel a 4th relay click. Engine then stalls about
> 1” later. This 4th realy click must be the relay going off again.
>
> So this points to the main relay being at fault.

--------------------

If turning the key to another position kills the relay, does it really
implicate the relay, or the ignition switch?

'Curly'

Good point. The ignition switch is not out of the hook.
In fact the relay is demostrating that it is capable of getting
instructions from the ECU and closing sucessfully to give power to the
fuel pump. I say this because the fuel pump always comes on for 2 seconds
when I turn the ignition. So why would the relay not close sucessfully if
it is getting a signal from the ECU to close once the engine has started.
Perhaps the ECU signal for the 2" priming and the ECU signal for
continuous fuel pump operation follow a different path? I'm not sure I
understand the electrical schematic to anwser that. The honda shop manual
has a diagram on page 11-111 which shows the connections to each pin of
the main relay. But from that schematic alone I cannot figure out the
electrical logic. I will try to look at the full electrical schematic this
evening see if I can figure out more.