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Old 20 Aug 2011, 08:08 pm
Posts: n/a
Default Re: Which relay is bad when fuel pump doesn't work?

micky <> wrote in

> My next-door neighbor has a 2001 Honda Accord EX with a 4-cyl engine.
> It wouldn't start,

Exact symptoms?

Did it start, but stall as soon as the key was released?
Did it crank, but show no sign of firing?
Can you hear the fuel pump run for two seconds when the key is first
turned to "II"?

Did the MIL illuminate as the starter was operated?

> but did start when starting fluid was sprayed in
> the air intake.
> This indicates most likely the fuel pump or fuel pump relay.

Not too sure of that. By 2001, Honda had seen enough cracked-solder
situations to have improved the PGM-FI Main Relay. These newer ones are
pretty reliable.

Your issue could simply mean weak spark. When were the HT ignition
components last changed? I'll bet you're running original OE parts, or
cheapo aftermarket.

> The
> dealer told her he has never had a bad fuel pump, but the relay can
> overheat,

The dealer doesn't know.

Older traditional combined PGM-FI Main Relays did not "overheat", but
suffered from cracked solder. Letting the Relay cool down would
sometimes re-establish sufficient contact between the cracked parts to
allow starting.

> and she should leave the doors open to let the interior cool
> off. She tried that and the car started, less than 15 minutes later
> I think.

Probably coincidence, in this case.

Very important questions: When the key is first turned to "II", does the
MIL illuminate for 15-20 seconds, then go off and stay off? And does it
remain off after the car is started? Or is it on all the time?

> The dealer said the relay wasn't with the other ones but under the
> dash, and googling showed that the
> However severl people, maybe even by pros, called it the fuel pump MSR
> Main System Relay, and I think they are referring to the relay that
> shuts down after a crash to prevent a fire.

I think Honda uses the PGM-FI Main Relay for that purpose: Engine
stalls, fuel pump and injectors shut off. The engine must be turning for
the ECM to allow the fuel-pump and injectors to operate.

> But her main system is
> working, or the car would not start with the starter fluid.

If your model is one of those new enough to have the traditional single
PGM-FI Main Relay split into two (which I'm not sure it is), then you
have one relay for the injectors and one for the fuel pump. They are
always installed together, in my limited late-model experience. And the
split kind are utterly reliable.

> So is the url below, an Airtex Access Relay 1r1455, the relay she
> needs, or is there a separate fuel pump relay, that is different from
> the fuel pump main system relay?

Don't go replacing possibly perfectly good OE parts with stupid and
alarmingly unreliable aftermarket. Diagnose the problem properly
instead. Start with the HT ignition components.

If you absolutely must replace the Relay, go to your nearest U-Pull
wrecking yard and get a proper OE Relay from a vehicle there, for likely
much less than the Airtex crap.

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