Fuel pump running with engine off

My fuel pump seems to be stuck in the "on" position. Went to start the truck this morning and battery was nearly dead---not even a click when attempting to start. As soon as I attached my jump pack I heard the fuel pump kick on. Drove the vehicle for about 20 minutes, came home, turned engine off and immediately heard the fuel pump kick on. When I turn the key to the "ready to start(?)" position the fuel pump sound turns off. Pulling the Fuel pump relay in the engine bay turns off the pump and sometimes after the relay being unplugged for a few minutes I can replace the relay and the pump does not turn on. But if I then start the engine and turn it off the fuel pump immediately starts up again. Any suggestions as to tracking down the cause would be appreciated. No other symptoms are present that would make me think the fuel pump was going bad.

We just had a lot of rain and I suspect it may be a factor in this problem. Moisture was triggering the piezo and unplugging it fixed it, so to speak.

 

Swapping relays keep it from kicking on? Maybe blow dry it with compressed air?

 

Not swapping relays. I mean just removing the one relay for a few minutes and then putting it back in. Is there a way to test the relay? I'm not familiar with this style of relay as I've only encountered the Bosch style until now.

 

Generally speaking a generic relay is just a two-way circuit where, when one pin (voltage input) is hot, the circuit is tripped to the ON position, feeding power. Take power off that one wire, the circuit is tripped to the OFF position.

That in mind, sounds like one of two things is happening:

1. Whatever is responsible to send the voltage input which triggers the relay doesn't stop sending voltage after shutoff (i.e. bad input) or
2. The relay isn't tripping back to its "off" position after the input trigger stops feeding power (i.e. bad relay)

To get around testing the relay, you just need to figure out which of the 5 pins on the FP relay is the input voltage/signal - this pin would be OFF (0v) when the truck is ON but not running, but it'd have some level of voltage while the truck is running. If you find that pin, you could wrap a copper wire around that pin of the relay and hang it off to the side so you have a lead to test while the relay is plugged in. Start by pulling the relay to 'reset' it. Test that feeder line you installed for voltage. Kick the key to the ON position, test feeder for voltage. Start the vehicle, test the feeder for voltage. Turn the key to OFF, then test the feeder for voltage.

Yes, this is straight-up caveman type shit, but it's going to tell you whether the issue is your relay, or whatever is feeding the relay its signal voltage. If it's the latter, we can look back through the EWD and/or fuel pump circuit breakdown to see what is responsible to push the signal over. It could be the fuel resistor is going bad and sticking, or the crank position sensor, or who knows. If you did the timing belt recently, may be worth checking the crank position sensor harness to make sure the pulley isn't rubbing through it and sending whack ass signals to the ECU, telling it the engine is running!

 

Haven't done the timing belt recently. I did just notice that the purple relay, labeled "SL Relay" on the fuse box lid, has burn marks around the spade connectors. What does that relay control? Certainly seems suspect anyway.

 

What year?

my '02 purple relay is labeled starter.

 

I can't read minds, and you haven't updated the "Vehicle One-Line Description" inside your profile (here) to say what year/cab type/engine/drivetrain your truck is, so I don't want to provide more info until you update your profile, or tell us. But prefer you to update your profile for future help cases.

 

Sorry about that. 2003 Access Cab 4.7v8 4x4 TRD with 259k. And yeah I think it is labeled ST not SL.

 

Tthere are burn marks around all 4 connectors on the purple relay so at the very least I assume it ought to be replaced.

 

For the '02, which should ballpark match your '03, this is what I can tell you about the fuel pump relay, per a video on YouTube:

Basically the two pins indicated here, when fed power, will pass power to the fuel pump. So maybe it's a 3-way relay? Basically, if you feed battery power to the right-hand pin, it sends voltage straight to the pump at full flow. If you feed battery power to the left-hand pin, it sends voltage to the fuel resistor, which nerfs the voltage, causing the fuel pump to pump at lower speed. What does that mean? The top and bottom pins should be power and signal wire, I guess?

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LMK if you need the OEM part number, I can grab it. Sounds like you might've had something arc in the vicinity...

 

Sure a part number would help. Are these relays not readily available at most parts stores?

 

should be at any ****zone or oriellys. Just match up the marks on top and pin layout.

 

Of course. I got it and thanks. Gotta' get back to work as this has eaten up enough of my day so far.

 

Hmm. You're fixing a symptom, but might not be fixing the problem. If the new one pops, maybe a short somewhere.

@shifty` can you post the related wiring diagram? Maybe something chewed on wires somewhere.

 

I wouldn't recommend buying non-OEM relays, but that's just me. Especially after what another member went through with the 'universal starter' relay they bought.

Anyway, EWD are here: https://www.tundras.com/threads/ultimate-tundra-wiring-diagrams-collection.81448/

And for the FPR, assuming there's enough similarity between the years, check these: https://www.tundras.com/threads/2006-double-cab-fuel-pump-no-power.36822/#post-933129

 

I agree that OEM tends to be a better choice. What went so wrong with another member's "universal starter" relay? I did try swapping my relay with a known working relay and the problem went away so I would say this is solved unless a deeper problem still exists.

I'm not sure if this would have fried the starter relay but in the last month I've had to jump my Tundra 4 or 5 times as the cold killed off my old battery and then the new battery getting drained due to a faulty ST relay. My jump pack is supposed to be a good one, even for large diesel engines, and hopefully is not responsible for damaging the relay.

https://www.jbtools.com/goodall-jp-...pack/?refSrc=152142&nosto=productpage-nosto-1

I paid much less than the listed price in that link and it has paid for itself already just by not having to rely on another vehicle or AAA.

 

If I look at this page, it looks like the p/n for the relay used for fuel pump is the 1st item in the list. Note: There are two part numbers in the description, 90084-98032 and 90987-04004, so I recommend looking at the side of your current relay to see which it is.

When I ran went to add-to-cart for local pickup at one dealership near me, it's $42. Another has it for full MSRP at $67. A 3rd has it for $54. Every dealership has different price breaks when you buy thru Parts.Toyota.Com website, if you order direct over the phone or at the parts counter, you almost always pay the full MSRP price.

 

Oh - and here's what happened with the 'universal relay' recently from O'Reilly's: https://www.tundras.com/threads/help-2000-tundra-no-crank-no-start.116623/

 

Well crap. I guess the problem is deeper. After about 10 minutes of sitting there quietly the fuel pump turned on and I'm back to the beginning.

 

I know this may be a stupid question, but what do you have for aftermarket electronics? Aftermarket alarm, brake controllers, remote start, anything?

 

I've installed nothing but the PO installed an aftermarket stereo and there's old wiring for a mic going to the driver side visor.

 

While the fuel pump is running and engine off if I remove the S.T relay then the FP, open circuit, and EFI relay all start clicking. I may have to pay a visit to the Toyota mechanic I know as electrical troubleshooting is not something I've done much. Mechanical all day no problem but electrical is often more fun than I need.

 

Check for water leaks onto the ECU?

Or follow pin outs to find out what is causing a signal to engage the relay (short, bad part, etc).

 

I'll check the ECU once I figure out where it is. My best estimate as to when this problem started is that I drove the truck Saturday morning in heavy rain and through some deep puddles along the road, didn't notice anything Sunday but I didn't drive the truck either, and then this morning(Monday) is when I noticed the issue. So with any luck it may be simple water intrusion that hopefully didn't permanently damage anything.

 

Or potentially water leaks into the fuse/junction box in the dash. We've seen both cases happen.

Here's a junction box example, another recently popped up last month: https://www.tundras.com/threads/02-tundra-electrical-problems.45605/#post-1174202

Here an ECU example, at least one or two others have come up: https://www.tundras.com/threads/time-to-ask-for-help-truck-wont-fire.108227/#post-2791821

I consider @BubbaW to be the resident electrical/circuit guru, maybe he can tell you trace back and find what's signaling the relay to fire.

 

ECU is behind the glovebox. Remove the glovebox and you'll see all the bundles of wire connectors going into it.

See threads I linked for pics of what to look for. Also, if you've never fixed the dreaded cowl fastener leak, or you're in a salty area, water intrusion at the windshield edges could be the source of the intrustion.

 

With this last rain I found out just how many leaks I have. At least 2 and likely 3 leaks are allowing water in the cab. Pretty sure one is the 3rd brake light and one is under the cowl, but I also noticed a lot of moisture on driver side floorboard.

 

Gonna' give it my best until I run out of daylight, headlamps, and patience. Thanks to all.

 

That screams poor windshield seal on the driver's side issue. And concerns me, you may find the fusebox with green traces on the outside.

This leak thread may help: https://www.tundras.com/threads/definitive-2000-2006-cab-area-rain-water-leak-thread.70464/