Fuel Pump Drains Battery HELP!

Hi all, long time lurker and first time poster here. Hoping somebody has had this happen before, all the research I have done on this platform and other tundra platforms has been fruitless. So here it goes-
03 Tundra AC 4x4 SR5, upon shutoff I can hear a hum coming from the engine bay (fuel pump?) that will drain the battery. When I pull the fuel pump relay the hum stops but there is still a high pitched, barely audible tone that does not stop until I pull the EFI relay. I have replaced the three fuel relays a few times previously and that has helped up until yesterday. Went out to a completely dead battery and when I connected jumper cables, the fuel pump hum started right up again. So this morning I went down to the parts store to get three new relays and a new battery. But that didnt work this time. The fuel pump still runs with the keys off but will stop once I turn the key on. When i try to turn it over she runs rough for a second or two and then sputters and quits.
So far i have done:
New relays and battery, checked all fuses in the engine bay and dash, opened up the ECM and checked for water damage, disconnected the battery for a prolonged period of time and reconnected. Kinda limited on resources, my multimeter is far away and Im 12 miles from the closest town and 30 from the nearest parts store.

Thanks in advance

 

First of all, per Toyota's fuel circuit documents, the fuel pump should only be on in two main cases:

• Key is turned all the way to the START position (i.e. engine is turning over)
• Crank Position Sensor notified the ECU the engine is running while key is also in ON position.

If you're saying your fuel pump is ON outside of the two cases above, I personally think you have a problem. Like ... Maybe the relay you bought at the store is the wrong fuel pump relay, and it's completing the circuit when it shouldn't be. Relays aren't universal. One member already found out the hard way recently not to trust 'universal' relays from the local auto parts stores for starter/fuel. Another found out the hard way with a generic relay for their heated seats, after their seats would never turn off. In general it's a mistake to buy non-OEM parts on these trucks, especially lower ball joints and anything electical.

Hum in the engine bay shouldn't be the fuel pump. It's in the gas tank.

High pitch whine in the engine bay is often the security piezo, which is usually hanging off the harness that comes out next to the brake booster.

I'm not saying your fuel pump relay isn't bad. But I'd revert back to the original OEM relay to get back to square 1.

Do you have any way to measure fuel pressure before the fuel rail?

Are you familiar with the fuel system, and how it works? This video may help, but just know, it has misinformation in it, the fuel pump is NOT normally on when the key is in the ON position.

Here's the fuel pump circuitry if you want to understand how the fuel system works.

Here's a link to some diagnostic videos that may help you diagnose starting issues:
https://www.tundras.com/threads/2005-ac-wont-start-fuel-system-problem.113385/#post-2921783

 

Thank you very much for the info! I am going to read up on your links and go back to an OEM relay. Unfortunately I dont have a way to measure fuel pressure where I am. Would it change things if I hear the pump running in the tank as well as something running on the engine? Ive got a video but it sounds like two different pumps are running. Its been hard to pinpoint exactly where in the engine bay but its around the intake manifold/fuel rail/injectors area and stops when the relay is pulled.

 

If you're 100% positive the fuel pump is running, while the key is out/off, that's a problem.

You'd need a DMM to pop out the relay and see if any of the pins are always-hot. I can't remember, and those startup videos are for a model a couple years older than yours (same generation, though) but the general overview should be right.

Big thing is understanding the relay is supposed to take the hot input lead, and push it either (A) direct to the pump at full voltage for "hi speed" mode, or (B) through the fuel resistor (opn/c?) which dumbs down the voltage making the pump run in "low speed" mode.

If your pump is running at all times, except when the fuel pump relay is out, that to me is a great symptom to run with diagnostically.

As far as what else is buzzing, I ... dunno. I'd need to hear it. But you should be able to put a steth or rod or something on the fuel rail to see if that's where it's coming from.

 

https://imgur.com/Hv56nHq
https://imgur.com/slSvTKI

The keys are in my pocket

 

I see you have a hot air intake there. Stock airbox is arguably better though of course not causing your issue.

Any chance there is an air compressor or air pump on the truck? Have you owned the truck a while?

 

Not gonna deny, it sounds like the fuel pump is running to me. And if you pull the relay, which is the primary conduit that connects power to the pump if I'm reading the diagrams correctly, the pump stops running? But you still hear noise in the engine bay?

If yes, does the engine bay noise stop after 15, 30, 45 minutes with the fuel pump relay out?

 

When I pull the relay all noises stop except a slight, barely audible hum that is sometimes a touch louder than others. Maybe surplus power drain?
I do run a compressor for rear bags and I cannot recall if i had this problem before or after I installed it. I just wired up my light bar again, with its wiring on the same side as the fuse box, maybe interference from that? Ive had the truck 10+ years now.
New oem relays are awaiting me tomorrow morning, with what shify said about parts house ones they could be the culprit.
I appreciate everybody's help on this
Stock box worked just fine until it packed with snow and suffocated the engine...

 

If yes, does the engine bay noise stop after 15, 30, 45 minutes with the fuel pump relay out?[/QUOTE]

Im not sure, after watching my voltage to from 12.6 to 12.1 on a brand new battery I didnt want to keep draining it. It is ever so slight sounding

 

I was just wondering if theres any chance that's what's running but weird if it stops after you pull the fuel pump relay. Shouldn't be on the same circuit so that wouldn't make much sense.

Was that with or without wheel well liners?

 

"Shouldn't be" doesn't mean "doesn't", though, and could be worth checking. It's a good observation.

If the fuel pump and compressor circuit are both hot with key OFF, and both go cold with FP relay out, it would tell another story, one that's worth investigating.

The main reason I ask this question is, and I can't imagine it being the case, but ... if the fuel pump is running constantly, I was wondering if what you're hearing in the bay is the fuel pressure built up, and sending fuel back to the pump on the return line. But that should clear within a minute or two.

Just for shits n giggles, have you tried pulling the EFI1 fuse with the FP relay IN, and with the FP relay OUT, just to see what happens? Pretty sure your earlier model will have the EFI1 fuse. I just ask because I remember a bizarre case from summertime where someone was seeing really weird results with the FP & starter relays and pumps running when EFI1 and either of the relays are out, but don't remember the order. Let me try to dig up that post. It was such a bizarre set of symptoms to me.

 

Here it is: https://www.tundras.com/threads/bizarre-electrical-gremlin.109383/

 

And from that post I linked, a good point is made. The ECU is responsible for sending the voltage trigger to the starter relay receptacle to trigger the relay pole to throw, opening voltage down to the pump.

It's possible the ECU is just constantly sending that signal, and this is an ECU issue. Or it's possible something is giving the ECU an input that's telling it it's OK to trigger? Dunno, not a fan of diagnosing electrical circuits.

In that guy's case, it looks like it was corrosion on one of the connections? If you're in the rust belt or a salt-prone area, that wouldn't surprise me.

 

The two of my three relay replacement trifecta finally showed up today and lo and behold that was the problem. As soon as I installed the new, OEM ones the buzzing when off stopped and the vehicle fired right up on the first try. Kudos to everyone for their input and a big thank you to shifty for taking the time to send diagrams,past forums, detailed descriptions, videos, etc. These trucks are great and this almost makes me want to keep it, maybe almost haha.

I did pull the fuse with the relay in as well as out and the pump stopped running for both.(before OEM relays)

As far as the intake goes- I cant remember about the wheel well liners but with E rated duratracs, medium lift and ARB Saraha bar Im getting about 415 miles to a tank as long as i keep my foot out of it. Works for me for now

 

Damn. I'm lucky to pull 300 miles per tank!

Glad to hear the issue is solved. Nobody ever wants to believe OEM parts make a difference. The auto parts store stuff, especially 'universal' are a crapshoot (at best).

 

Well its back to the drawing board. I went out to my truck yesterday afternoon and the pumps were running again even after its been sitting for over 24 hours. Tested the relays and one of the new OEM ones had failed. $120 relay and it didnt last a month.

 

The only thing I know that can cause a relay to fail so abruptly is voltage spikes/overload.

You may have a more serious electrical problem at play. I can't help but wonder if the corrosion problems back near the fuel pump someone else posted about could be the root cause.

I'd probably cry "defect" on that part with whoever you bought it from though, just to try and recoup some $$

 

Luckily i have a my multi meter this time and was able to do some more digging. Both the EFI and Circuit Open ports on the fuse box are hot with the key off and relays removed, they test the full 12.30v coming off the battery. When you add both those relays it charges the Fuel Pump port as well. When I referenced the fuel management schematic it looks like upstream from the fuse/relay box and before the battery there is a switch(?) called EFI No.1. Do you know what EFI No.1 is?

 

There's an EFI No.1 fuse in the engine compartment fuse/relay box, is that what you're seeing in the schematic? There are two fuel relays also, is the other one called EFI No.1? I don't have the diagrams in front of me.

 

Awesome thank you. I think thats what they are referencing to on the schematic. Unless there is something else with that same name. I havent found any additional fuel related relays, just the EFI, Circuit Open and Fuel pump ones. I am so lost at this point, nothing is making sense

 

There are 2 EFI fuses....EFI NO. 1(10A), EFI NO.2(10A)....there is 1 EFI relay, 1 C/OPN relay and a Fuel Pump Relay, not 2, as far as Engine Control, in particular fuel delivery.

What are you meaning by this @colo4x4xj ....

Are you calling ports the empty sockets with the relays pulled ?
The below pic should be your ENG Bay fuse panel according to 03 EWD. Where is this Hot(voltage I'm assuming) with key off you're seeing....pin 1, 2, 3, or 5, ?
You may already know how but but explain just in case....negative lead of meter to neg of battery. When things are "hot" as you described with key removed, what is voltage at pins 1-5 of each relay using pos lead of meter

 

Thank you for your reply. Yes the "ports" I was talking about are the empty sockets. Just put a meter to the EFI and Circuit Open relays- on the EFI relay I got 12.27v in pin 3 and on the C/OPN I got 12.27 in pin 1. No voltage was detected at any other pin locations

 

- EFI pin 3 will always have 12vdc with Battery hooked up and it's associated fuse EFI NO. 1 is good....EFI pin 1 is GND
- C/OPN pin 1 should only have 12vdc with key in IGN ON position.

* When the ignition switch is turned to ON(IG2), the battery voltage is applied to the IGSW terminal of the ECM. The output signal from the MREL terminal of the ECM causes a current to flow to the coil of EFI relay closing the contacts of the EFI relay pins 3 to 5 sending 12vdc to pin 3 of C/OPN.
* With IGN ON, pin 2 of C/OPN should have 12vdc, when you attempt to crank, the ECM sends a gnd from ECM FC pin to pin 1 of C/OPN energizing it's relay, closing contacts 3 to 5 of C/OPN relay, sending 12vdc to Fuel Pump relay.

Long way around the barn to say C/OPN has voltage at pin 1 when it shouldn't have if I'm understanding everything you've said.

Ignition problem

This caught my attention the other day but remained in peanut gallery....

 

EXACTLY! As soon as I turn the key to the ON position, the fuel pump stops. If i turn it over, the engine will run for a few seconds and then peter out like its running out of fuel. My uncle is an old school mechanical/technical wizard and I think he summed it up best- "its like things are backasswards".

This has been an ongoing problem for the last few years but its now getting worse. Before the original January 19th post I had not had this problem since probably '18/19 ish. Now its done the same thing twice in less than a month. Worn wire? Corrosion? It doesnt explain the reversal of operations though.

 

One more post before turning into a pumpkin.
IF 12vdc is still present at pin 1 of C/OPN....do below checks please.

Checking for short to gnd.....With key not in ignition, EFI and C/OPN relays still removed, neg lead of meter to battery ground and meter switch on resistance setting(looks like horse shoe if not aware)
* Place pos lead of meter to EFI socket pin 1, 2 and 5....NOT 3
* On C/OPN socket, pos lead to pin 2, 3 and 5....NOT 1
Did any of those 6 pins show a resistance reading ?

EDIT....forgot to also ask
IF above conditions exist, does the 5 A IGN fuse, inside cab driver kick panel have voltage ?

 

Do I assume you found none ?

In all those years do you recall water penetration signs either in driver or passenger floor area under dash ?

According to what your check results were concerning ground checks I mentioned last night, we may be looking at something I always hesitate mentioning only as a last resort.

Given You and @Shifty both have mentioned corrosion, I always give thought to the below thread, which can be a perfect candidate for gremlins. Going down the corroded Integration road is not an easy task and is always a last resort to mention when assisting.

02 Tundra electrical problems | Toyota Tundra Forum (tundras.com)

 

I'm just going to re-post this link again, since I feel it describes the problem damn near exactly, and also talks about the solution, although it is for a 2nd gen. The quoted part here is important, I think. I'll also add a quote giving their solution. More text after these two quotes

Here it is: https://www.tundras.com/threads/bizarre-electrical-gremlin.109383/

Mind you, I can't say if the 1st gen has a similar control module because I don't know enough about 2nd gen trucks to know what it is or where, and don't have time to check because getting fluid changes done on the truck while I've got the free time today is higher in my list.

But it does point to corrosion (something grounding or arcing when it shouldn't) on wiring/connectors as causing the issue OP is describing. Whether it's at the integration relay or not is another story entirely, but well worth checking, even if it's a bitch to take out. Wouldn't be the first time.

 

While your 2nd para is spot on, the biggest difference in the 2nd Gen thread you linked to and this one is the fact that way before anything happens downstream, the ECM appears to receive the IGSW input when it shouldn’t be, among other tale tale signs.

 

The more time goes on and we troubleshoot this issue, the more I think it has to do with corrosion in the relay box. Went out this morning to test resistance and just for grins reinstalled the relays and guess what-IT STARTED AND RAN. No fuel pumps running when they shouldnt, no petering off after ignition.

While I was testing resistance in the box I found that the socket block where all three of those relays connect was loose within the Relay/Fuse housing. A quick bush fix tightened everything up nicely. She starts and runs, but i disconnected the battery and left it in my parents garage. I have an appointment with the toyota dealership on Thursday and I'm debating having them install a new box entirely or if I want to tackle it.

As far as resistance goes-
EFI socket had resistance in Pin 1 and 5
C/OPN had resistance in Pin 3

I did not get a chance to check the 5 A IGN fuse, will check it when I am back down there next week. There was no visible water damage or corrosion on the ECM when I checked it during the original post. BUT- I did have water leak into the cab via the rear view mirror/sunglass storage/map light fixture in the past and had it happen a for the first time in awhile about a week or so ago.

 

You wouldn't be the first person to unmount the engine bay fuse/relay box and find nasty shit under there. Look no further than here. I saw another one where the thick 8 or 10awg-ish lead that comes off the battery and heads into the fuse/relay box was shorting under the box.

But you also wouldn't be the first person to find corrosion from water intrusion in the cab fuse box, as @BubbaW shows above.

Regardless, to me, this problem REAKS a bad circuit somewhere, and corrosion is a common source.