Fuel pump relay part number?

[amengineering]

I've been having problems with my car stalling lately. I hear a clicking sound on the rear firewall while driving and then it dies. I researched it last summer and ended up replacing the main relay but it is still happening. After the car dies if I pound on what I believe is the fuel pump relay and I can get it started again so I assume that is the problem. Its the one behind the drivers seat that says, Mitsuba Retracter Control 12V, RK-0238. Tried to upload a pic but its not working. Does someone have the part number for it so I can order a new one?
Thanks for any help!

 

[Jeff@Carbon6]

I believe it is 39797-SE0-003

#11

 

[amengineering]

Thx, what is number 7 then? I think that is what is clicking when it dies.

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I found it actually. It is for the headlights, so that cant be it. hmmmm, id swear that #7 is clicking but must be something close to it.

 

[michaelbrat]

Thx, what is number 7 then? I think that is what is clicking when it dies.

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I found it actually. It is for the headlights, so that cant be it. hmmmm, id swear that #7 is clicking but must be something close to it.

Did you ever figure this out? Thanks.

Mike B

 

[amengineering]

I replaced main relay. Everything seems ok now.

 

[michaelbrat]

I replaced main relay. Everything seems ok now.

Weird, so you had to replace the main relay twice? You had mentioned in the original post that a new main relay didn't fix it.

It seems Jeff Carbon6 was right about the fuel pump relay part number (39797-SE0-003). I've ordered one to see if it fixes my accel delay issue.

Mike B

 

[amengineering]

Yes. I guess I haven't driven the car that much but it hasn't happen. Maybe 1000 miles since then.

 

[nsxtasy]

I've heard that the main relay runs off the fuel pump relay. Or is it vice versa? Something like that. Bottom line, it can appear that the fuel pump relay is to blame, when in fact it's the main relay that's causing the problem, so that's the one to try replacing first. This sounds like confirmation of what I was told.

 

[Briank]

The fuel pump is run by the main relay, the fuel pump relay just bypases the fuel pump resistor above 5000 rpm to keep the fuel pressure from dropping off.

 

[Old Guy]

Briank and nsxtasy are correct. The main FI relay enclosure is a two for one special. It has the main relay for powering up the ECU along with the relay for powering up the fuel pump (not to be confused with the fuel pump relay in 'Honda speak'). The fuel pump relay (in Honda speak) just by-passes the fuel pump resistor to apply higher voltage to the fuel pump. A dead fuel pump relay (Honda speak) will not prevent the engine from operating, just cause the potential for high load fuel starvation. A dead main relay will stop the engine from operating.

 

[Kaz-kzukNA1]

For your reference, fuel pump relay is activated to bypass the fuel pump resistor not only under high load (about 4,000rpm with WOT and higher rpm region mapped against the intake manifold pressure) but also at the time of cranking the engine.
Once the engine starts, ECU will switch off the fuel pump relay and the fuel pump will be in lower speed mode.

Therefore, depending on how much fuel pressure is left since you stopped the engine last time and how quickly you tried to turn the IG key from P2 (On position, lot of light on the dash) to P3 (Start position, cranking), you may require much longer cranking if the fuel pump relay has failed even with the healthy Main Relay.

Kaz

 

[michaelbrat]

I'm getting a acceleration delay under WOT between 2-4k rpm, and it clears up after that. So it sounds like the function of these relays are not related to this condition.

I've been reading a lot on prime about this. It has been said it can be the main relay, fuel pump relay, fuel pump resistor, regulator, or fuel pump. What do you guys think? I'm about to install a fuel pressure sensor so that I can monitor my pressures while accelerating. Hopefully that will give a clue as to what is going on.

Mike B

 

[jwmelvin]

Because in many conditions, the fuel-pump relay bypasses the fuel-pump resistor at 4k rpm, having a change in misbehavior of your car at that rpm can indicate a problem with the resistor. The easy way to test is to bypass the resistor, either at the connector to the resistor itself (in the engine compartment against the firewall) or at the relay (on the passenger-compartment side of the firewall, slightly driver's side of center). With my non-OE fuel pump and pressure regulator, I replaced the fuel-pump relay with a jumper.

 

[Old Guy]

For your reference, fuel pump relay is activated to bypass the fuel pump resistor not only under high load (about 4,000rpm with WOT and higher rpm region mapped against the intake manifold pressure) but also at the time of cranking the engine.
Once the engine starts, ECU will switch off the fuel pump relay and the fuel pump will be in lower speed mode.

Therefore, depending on how much fuel pressure is left since you stopped the engine last time and how quickly you tried to turn the IG key from P2 (On position, lot of light on the dash) to P3 (Start position, cranking), you may require much longer cranking if the fuel pump relay has failed even with the healthy Main Relay.

Kaz

That is a useful piece of information. Is that something you acquired with your employ with Honda because I don't recall stumbling across it in the service manual?

Does that by-pass of the fuel pump resistor on start occur just during that 1 - 2 second prime of the fuel system (when you turn the switch to P2; but, not all the way to P3) or does it extend beyond that?

 

[Kaz-kzukNA1]

Hi, Old Guy.

The ECU will activate the fuel pump relay to bypass the resistor in order to run the fuel pump at max speed for 2sec after turning the IG key into P2.
This is to prime the fuel system as quickly as possible.
If you don’t go into P3 within this 2sec period, then the ECU will switch off the fuel pump as well as the fuel pump relay.
The primed fuel pressure is retained at the high pressure side of the fuel system by the check valve inside the fuel pump.

When you turn the IG key into P3 to crank/start the engine, the ECU will activate (or keep activating, if you went into P3 within 2sec from P2) the fuel pump relay to make the pump operate at max speed until the ECU detects around 400 – 500rpm.
Cranking speed is much lower than this so in other words, the fuel pump relay is activated (pump operates in max speed mode) until the engine starts.

For your reference, as long as you can prime the fuel system through the resistor side of the fuel pump circuit (pump operates in lower speed mode), you can still start the engine even with the faulty fuel pump relay.
In fact, you can even completely disconnect the fuel pump relay and still be able to start the engine but you will notice significant dip in rpm for a fraction of a second at the very beginning of the engine start due to lack of voltage applied to the fuel pump through the resistor while the starter is eating up majority of the battery power.

Kaz

 

[michaelbrat]

Because in many conditions, the fuel-pump relay bypasses the fuel-pump resistor at 4k rpm, having a change in misbehavior of your car at that rpm can indicate a problem with the resistor. The easy way to test is to bypass the resistor, either at the connector to the resistor itself (in the engine compartment against the firewall) or at the relay (on the passenger-compartment side of the firewall, slightly driver's side of center). With my non-OE fuel pump and pressure regulator, I replaced the fuel-pump relay with a jumper.

I installed a fuel pressure sensor and saw that the pump would run at 290kpa at WOT below 4k rpm, and jump to 370kpa above 4k. I could feel the hesitation, then the jump in pressure. Replacing the resistor fixed it. It will now run 320-370kpa at WOT below 4k rpm.

Is there any downside to bypassing the resistor? Did you just connect a wire between the pins? I've been told the only downside is noise.

Thanks for this advice!

Mike B

 

[jwmelvin]

I installed a fuel pressure sensor and saw that the pump would run at 290kpa at WOT below 4k rpm, and jump to 370kpa above 4k. I could feel the hesitation, then the jump in pressure. Replacing the resistor fixed it. It will now run 320-370kpa at WOT below 4k rpm.

Is there any downside to bypassing the resistor? Did you just connect a wire between the pins? I've been told the only downside is noise.

If replacing the resistor did the trick, that's great.

It wasn't clear to me that the reduced voltages were good for all fuel pumps, so when I replaced my fuel pump I bypassed the resistor. I did so by putting spades on a 1" piece of solid copper (romex) and plugging it into the connector instead of the relay. Had I kept the resistor in the circuit, it may have allowed me to keep the OE fuel-pressure regulator. With my pump (Deatschwerks DW200) and a bypassed resistor, the regulator could not pass enough flow to get down to the desired 42 psi (290 kpa) at idle. Instead, I replaced the pressure regulator with one from AEM.

I'm not sure about downsides to bypassing the resistor. Certainly, the fuel pump makes a bit of noise but it's inaudible when the engine is running. If in fact using the resistor would have allowed me to use the OE pressure regulator, then having to change to an aftermarket regulator is an additional downside; that necessity depends on the fuel pump one uses.