94 Ford Explorer Fuel Pump and scanner

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J Adams - 19 Apr 2007 20:55 GMT

I have now narrowed it down to the fuel delivery system (somehow) and
the scanner not working when fuel pump can not be heard to run with
ignition on.

Here's the symptoms and the scenario;

Last night I went to the store around 9PM, inside less than 5 minutes,
and when I came out to start the car, no luck. Outside temperture was
around 70.

1. With ignition on could not hear fuel pump run.
2. Hooked up scanner/code reader with ignition on.
3. Scanner would not cycle through tests. The square indicator icon
did not come on to indicate receiving any codes.
4. Replaced battery in scanner and results were the same.
5. This morning I turned on the ignition and heard the fuel pump run
and of course the engine started.
6. Hooked up the scanner and it cycled through all the tests and came
back with 111 "system pass"

It seems to be getting worse, which is good I guess, it happened 3
times in one week, whereas before these instances were months apart. I
did cancel my Mexico trip as that would not be the last place I would
choose to get stranded, even with a beach near by :-)

Before I start with the shotgun approach of parts replacement and
especially the fuel pump/strainer/etc, I would welcome any suggestions
of where to start. Since the problem seems to occur after I've driven
somewhere and the engine is warm, and not after having sat all night
or at least for many hours, say 6 or more hours.

By the way, I have replaced the fuel pump relay.

Thanks

Jim

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Happy Traveler - 19 Apr 2007 22:22 GMT

As you already found out , there is a fuel delivery problem. If your
'scanner' indeed cannot communicate with the ECU, there is a chance that the
ECU is not getting power, and the ECU relay is defective. Since the ECU
controls the fuel pump (and a lot more), it may explain the problem.

Incidentally, a '94 vintage vehicle uses EEC-IV. You don't really need a
'scanner' to access it. A test light, connected from the STO pin to B+ will
flash the codes just the same and will be a lot more reliable than your
'scanner'. You put the system in diagnostic mode by grounding the single pin
test connector. There are details all over the web.

>I have now narrowed it down to the fuel delivery system (somehow) and
> the scanner not working when fuel pump can not be heard to run with
> ignition on.

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Happy Traveler - 19 Apr 2007 22:35 GMT

By the way, on most vehicles of that era the EEC-IV test connector will also
allow you to force the fuel pump to run. Grounding the bottom pin in the row
of four (holding the connector with that row on the left) should cause the
FP relay to close, regardless of whether the ECU is functional or not. If
you still don't hear the pump running, either the FP relay or the pump
itself is bad.

Reply to this Message

J Adams - 19 Apr 2007 23:53 GMT

Hi Happy Traveller

The connectors from the car, as I'm looking directly at the end are as
follows;

On the left is a single, and separate, wire then the somewhat
triangular group with 4 on the bottom, and 2 -centered- above the
bottom 4.

Which of the connectors would I use to cycle the fuel pump. I replaced
the relay last week even though I did not suspect it was bad. I
swapped the AC relay and it made no difference.

That is really helpful that you point out I can cycle the fuel pump
this way. Also, I assume you mean grounding as inserting a wire into
the appropriate test connector and touching the other end to something
metal on the car. Yes?

Thanks

Jim

>By the way, on most vehicles of that era the EEC-IV test connector will also
>allow you to force the fuel pump to run. Grounding the bottom pin in the row
>of four (holding the connector with that row on the left) should cause the
>FP relay to close, regardless of whether the ECU is functional or not. If
>you still don't hear the pump running, either the FP relay or the pump
>itself is bad.

Reply to this Message

Happy Traveler - 20 Apr 2007 00:45 GMT

Just like I said: the FP test pin is at the end of the row of 4. Holding
this row vertically and on your left, it will be the one at the bottom. You
don't need to look for metal on the car, because one of the two pins on the
short row of 2 is ground. That's the one at the bottom, as you are holding
the connector the way I described. You will see that only one pin in that
row has a wire attached to it (most likely black). Just stick a piece of
wire between the FP test pin and the ground pin.
The STO (diagnostic test output) pin is the second from the top in the row
of 4.
If this explanation is still not enough, google for EEC-IV, and find a
picture of the connector, with all pins identified. Numerous websites have
this information.

> Hi Happy Traveller
>
> Which of the connectors would I use to cycle the fuel pump.
> Also, I assume you mean grounding as inserting a wire into
> the appropriate test connector and touching the other end to something
> metal on the car. Yes?

Reply to this Message

J Adams - 20 Apr 2007 19:11 GMT

Thanks Happy Traveller

I tried that, shorting the 2 connectors, and it cycled the fuel pump.

Now the next time I don't hear the fuel pump cycle (and the car
doesn't start) and I short that circuit to cycle the fuel pump
hopefully that will work.

In the event I do just that , there are 2 possible outcomes;

1) The fuel pump does cycle - what component failure is implied

2) The fuel pump does not cycle - what component failure is implied

I suppose in case 1 that indicates the ECM/PCM is bad and in case 2
the fuel pump is bad. Do I have the assumption right?

By the way, when I short the EEC-IV connector circuit does that bypass
the ECM/PCM?

Jim

>Just like I said: the FP test pin is at the end of the row of 4. Holding
>this row vertically and on your left, it will be the one at the bottom. You
[quoted text clipped - 15 lines]
>> the appropriate test connector and touching the other end to something
>> metal on the car. Yes?

Reply to this Message

Happy Traveler - 20 Apr 2007 21:09 GMT

----- Original Message -----
From: "J Adams" <ujsa@yahoo.com>

> I tried that, shorting the 2 connectors, and it cycled the fuel pump.
>
[quoted text clipped - 5 lines]
>
> 1) The fuel pump does cycle - what component failure is implied

If it only works by forcing this and does not work otherwise, you either
have a bad ECM or the ECM is not getting power (perhaps bad ECM relay).

> 2) The fuel pump does not cycle - what component failure is implied

Bad FP relay, bad pump, or tripped inertia switch. If not familiar with the
latter, that's a switch which disconnects power to the FP in case of an
accident. It's not likely to be intermittent thing: once tripped, the pump
will not work until you reset it. Just to make sure, find it (probably
somewhere in your trunk - check the owner's manual) and push the reset
button. Could also be a bad electrical connection somewhere along the way.

> By the way, when I short the EEC-IV connector circuit does that bypass the
> ECM/PCM?

Yes, it does.

Reply to this Message

J Adams - 21 Apr 2007 02:18 GMT

In this same vein, would a bad ECM or relay cause intermittent failure
of the fuel pump to cycle upon turning the ignition switch? The good
thing is the failure of the fuel pump to cycle is increasing in
frequency so soon it will better/easier to isolate the source of the
problem. Is my thinking on this correct?

Jim

>----- Original Message -----
>From: "J Adams" <ujsa@yahoo.com>
[quoted text clipped - 24 lines]
>
>Yes, it does.

Reply to this Message

Mike Iglesias - 19 Apr 2007 23:21 GMT

>As you already found out , there is a fuel delivery problem. If your
>'scanner' indeed cannot communicate with the ECU, there is a chance that the
>ECU is not getting power, and the ECU relay is defective. Since the ECU
>controls the fuel pump (and a lot more), it may explain the problem.

Could be an intermittent problem with the ignition switch. My wife's 92
Acura developed a problem where you could start the engine, but as soon as
you let go of the key the engine would die and there were no lights on
the dash. Some of the grease in the switch had hardened over the years and
had settled right where it needed to be to block power to the engine
computer. Cleaning the switch contacts fixed it.

Signature

Mike Iglesias Email: iglesias@uci.edu
University of California, Irvine phone: 949-824-6926
Network & Academic Computing Services FAX: 949-824-2069

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J Adams - 20 Apr 2007 00:04 GMT

The ECU and the PCM are the same thing I assume. How would I test that
to determine if it is not getting enough power.

This does seem like it could be the source of my problem as it is
intermittent, especially as the scanner did not always communicate
with the ECU/PCM.

Thanks

Jim

>>As you already found out , there is a fuel delivery problem. If your
>>'scanner' indeed cannot communicate with the ECU, there is a chance that the
[quoted text clipped - 7 lines]
>had settled right where it needed to be to block power to the engine
>computer. Cleaning the switch contacts fixed it.

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