Fuel pump failure - any advance warning/symptoms?

[mckennar]

I was under the impression that fuel pumps, before they failed, would give some kind of warning, like hesitation, loud whining, or long crank times or whatever? Because I'm thinking mine just failed, and didn't give any warning.

I'm out of town for 3 days, can't troubleshoot in depth but long story short the vehicle died on the highway yesterday without warning and I had to have it towed back to my house. It'll start and stumble around for 1-2 sec but it dies immediately thereafter, giving it gas while cranking or while it's stumbling doesn't impact the situation at all. Fuel tank is 2/3 full (<100 miles on this tank). No raw fuel smell from tailpipe during no-fire cranking makes me think no or very little fuel. Fuel filter is new 2 months ago.

I did a fairly detailed troubleshooting on the roadside waiting for AAA but explaining it here would make this 10 pages. TL;DR I checked all of the usual suspect connectors and everything was tight and there are no codes active or stored. CEL illuminates when key is in "on" position but disappears when it's stumbling/misfiring. Nothing screwy going on with timing/belt as far as I can tell. Belt is intact and cranking sounds normal like all of my other 3rd gens. No raw fuel smell, intake not clogged, probably have spark due to it firing up sporadically.

Any thoughts or things I may have missed? Probably going to order a replacement pump so I can replace it this weekend but wanted to know if I should order any more things (crank/cam sensor, etc).

Thanks.

 

[JayRolla]

Smack the tank above the skid plate from the driver side rear tire. Have someone crank when you are hitting the tank. You may need some type of rod and hammer to get a good hit. Usually this will get the pump to fire if its failing.

 

[mckennar]

Smack the tank above the skid plate from the driver side rear tire. Have someone crank when you are hitting the tank. You may need some type of rod and hammer to get a good hit. Usually this will get the pump to fire if its failing.

While the AAA guy was cranking I was underneath kicking the tank with my heel on the driveshaft side towards the front near where the pump assembly is located. Nothing gained except for wrecking my work shirt, pants and shoes. I also held my ear to the skid while cranking and heard nothing, so I pulled the rear seat up and put my ear as close to the tank as I could on the inside and couldn't hear anything either.

The thing was idling poorly around 400rpm (tach registered) when I first pulled over but turning the throttle by hand with the hood up caused it to stall and it hasn't restarted completely since.

 

[mckennar]

For any future people viewing this for whatever reason, it was the fuel pump.

Turns out previous owner had been in there and replaced everything with used parts and put it all together poorly.

Something interesting to note:

The blown fuel pump's resistance measured 3.5 Ohms, well above the spec outlined in the FSM. I ordered a brand new Denso pump, but it measured ~29 Ohms at the connector. I thought it was faulty, so I sent it back to Rock Auto and bit the bullet and ordered the part from Toyota... and it too read ~29 Ohms. Checked my meter against a known resistance (... a resistor) and it was spot on, even brought my Fluke meter from work in case my Crapsman had taken to its namesake. But both read nearly identical, and either way the Toyota unit worked fine.

Temperature here today was 62f in the garage and yes I was using the correct setting on the multimeter...

 

[LittleCaesar]

Good to hear you fixed the problem. The only two possible signs of future pump failure from other members have been a long crank time and when going up an incline on a freeway, etc, the 4runner dies or throws a misfire code due to a lack of fuel. Others begin to whine louder and louder as they approach death but I haven't heard the whine on any Toyota pump.

Sorry to hear about the shock mount. Probably the previous owner liked his impact too much and went at tightening the bolt without checking to see if the bolt threaded correctly into the axle. Don't know the thread pitch off hand.

 

[nissanh]

Thanks for sharing the specs of a bad pump and a new one.

Here in west TX roads are lonely and deserted, hence I carry lightweight parts such as the fuel pump, belts, Alternator brush kit, cam and crank sensors, starter brush kit with the plunger, 2 ignition coil packs, spark plugs etc inside the jack compartment. Oh.. I even have an extra brake master pump. I have the same setup in my car too!

 

[mckennar]

Thanks for sharing the specs of a bad pump and a new one.

Here in west TX roads are lonely and deserted, hence I carry lightweight parts such as the fuel pump, belts, Alternator brush kit, cam and crank sensors, starter brush kit with the plunger, 2 ignition coil packs, spark plugs etc inside the jack compartment. Oh.. I even have an extra brake master pump. I have the same setup in my car too!

Ref: the Ohms... the FSM indicates 0.2-0.3 Ohms as being within spec for a fuel pump. My bad pump was 3.5 Ohms, which is too much resistance according to the FSM. When the replacement unit arrived, I was going off of the FSM's advertised 0.2-0.3 Ohm range when I sent the first one back. The second one showed the same 29 Ohms across the 4-5 terminals of the fuel pump connector. Is the FSM wrong, or did I get 2 bad pumps that just so happen to work despite the high resistance?

Also - If I was faced with the prospect of having to replace the pump in a remote area, I'd bring along an angle grinder to cut a hole in the floor vs. dropping the damn tank. I siphoned as much as I could (by pulling the filler neck where it connected to the tank) and there was still some fuel in there that made it annoying and messy. In a bit of poor planning, I only had a 2 gal jerry can available, and the tank was 3/4 full. So ~13 gallons, 2 gallons at a time. But I did fill up all of the gas tanks of all of the cars in my driveway.

But that is a good idea - carry along all of the "deal breaker" parts that you can to insure against getting stranded. Mercifully, mine failed about 3 miles from home, and I had AAA and a yard full of "lifeboat" cars. I even made it to work on time and caught my flight that day, albeit with a pretty dirty shirt/pants from rolling around on the side of the road kicking the fuel tank and whatnot.

 

[mckennar]

Good to hear you fixed the problem. The only two possible signs of future pump failure from other members have been a long crank time and when going up an incline on a freeway, etc, the 4runner dies or throws a misfire code due to a lack of fuel. Others begin to whine louder and louder as they approach death but I haven't heard the whine on any Toyota pump.

Sorry to hear about the shock mount. Probably the previous owner liked his impact too much and went at tightening the bolt without checking to see if the bolt threaded correctly into the axle. Don't know the thread pitch off hand.

I had neither long crank times, nor noise or trouble climbing inclines... I had no misfires, my STFT/LTFTs were good.

Ref: the previous owner: I should have known I was getting into trouble... the guy lived in an apartment, and the only tools he had was an electric impact and a set of impact sockets, extensions and u-joints.

So far, pretty much every bolt I've worked with on this thing has been some manner of cross threaded or stripped. Someone needs to take that guys impact before he kills someone with it. He used it to connect the coil packs on the p-side valve cover. Yep, all of those holes are stripped clean. JB-weld to the rescue.

 

[LittleCaesar]

IMHO the FSM doesn't always need to be followed word for word. Whomever wrote it with the incorrect values needs to be out of employment. As long as the fuel pump works, so be it.

Nothing scarier than people who become falsely empowered with the use of tools, especially an impact. It usually leads to big trouble down the road. Sounds as he would have been better just hand tightening the coil pack bolts.

 

[JayRolla]

To test the pump directly wire to 12v battery. If it spins. It works.

 

[mckennar]

To test the pump directly wire to 12v battery. If it spins. It works.

My failed pump spun once I got it out of the tank and kicked it around a bit. But it didn't move enough fuel to keep the engine running.

 

[mckennar]

Hate to keep bumping my own thread here but I've noticed that since replacing the pump my fuel mileage has tanked. I went from ~17-18 MPG to ~9-10MPG.

Now that the pump is providing the correct pressure, I think its exposing the fact that my injectors and FPR are 345k miles and 19 years old and probably have a spray pattern that looks more like a super-soaker than a spray bottle set to mist.

 

[LittleCaesar]

Any noticeable difference in start-up, engine performance, etc? I will say that after my brother replaced a fuel pump and filter on his truck last year two injectors bit the dust.

 

[mckennar]

Any noticeable difference in start-up, engine performance, etc? I will say that after my brother replaced a fuel pump and filter on his truck last year two injectors bit the dust.

Yeah, cold start is normal, hot start takes less than 1 crank and 2 or 3 cylinders start firing before the rest catch up. Leads me to believe leaky injectors.

Engine performance is improved. I have 2 up hill grades on my commute that used to require a downshift to maintain 75mph, now I can keep it in OD and maintain speed, and even accelerate w/o downshifting if I keep my foot steady.

 

[LittleCaesar]

My brother could smell the gas in two cylinders after a cold start after pulling the plugs and with live data could see the O2 sensors for the left bank trying to compensate for the richness. At 345k miles with prior shady ownership....

Good luck, I know a few guys who have used this company with good success:
WitchHunter Performance - Injector Cleaning & Flow Testing Services

I'd avoid OEM injectors off Flebay like the plague. Fellow members can tell you they have learned the hard way.

 

[gamefreakgc]

Yeah, cold start is normal, hot start takes less than 1 crank and 2 or 3 cylinders start firing before the rest catch up. Leads me to believe leaky injectors.

Engine performance is improved. I have 2 up hill grades on my commute that used to require a downshift to maintain 75mph, now I can keep it in OD and maintain speed, and even accelerate w/o downshifting if I keep my foot steady.

I sure hope you can with all that fuel being injected lol!

A note about the resistance readings... I'm not aware of any multimeter that can read a fraction of an ohm. Are you sure it didn't say 0.2 - 0.3 kOhms? That would mean 200-300 ohms.

 

[mckennar]

My brother could smell the gas in two cylinders after a cold start after pulling the plugs and with live data could see the O2 sensors for the left bank trying to compensate for the richness. At 345k miles with prior shady ownership....

Good luck, I know a few guys who have used this company with good success:
WitchHunter Performance - Injector Cleaning & Flow Testing Services

I'd avoid OEM injectors off Flebay like the plague. Fellow members can tell you they have learned the hard way.

Solid copy on all of the above. I've used witchhunter and RC Engineering before on previous vehicles. Looks like witchhunter has a slight edge on price and turnaround time. I have a parts car I'll be pulling injectors from and sending them off to be redone while I daily this thing.

Good call on checking the live data on the O2... I'd been paying attention to overall fuel trim PIDs vs. O2 live data.

Cold starts are very slightly long-ish. On my parts truck (and other 3rd gen V6s I've owned & driven) it would crank over 4 times and then fire on all 6 whether cold or hot. On this thing, it's closer to 6-7 cranks before it fires when cold, and when hot it's 1-2 before it stumbles to life on 3 or 4 cyl before the other cylinders join the party. I had previously thought I licked this problem when I replaced my throttle position sensor with a new unit, but I was incorrect. It came back within a few days.

Oh the joys of caring for a previously-unloved beater truck. I'd still rather this than my wife's 5th Gen.

 

[SaulG]

factory manual

 

[mckennar]

I sure hope you can with all that fuel being injected lol!

A note about the resistance readings... I'm not aware of any multimeter that can read a fraction of an ohm. Are you sure it didn't say 0.2 - 0.3 kOhms? That would mean 200-300 ohms.

I'm aware of the difference between Ohms and kOhms, but I appreciate the insight. It's always good to double check, thanks.

One thing I did notice just now is that what I had been using as a point of reference was page 938 in the FSM which states "RESISTANCE: 0.2 - 0.3 ohms at 20 c (68 f)"

However service data on page 140 shows resistance between 0.2 and 3.0 ohms. So there's a discrepancy / typo.

So if page 140 is to be believed, my old, failed pump was very close to being within spec, and two brand new and 100% functioning pumps had 10x more resistance than they should have.

I did a few tests of other components based upon page 140 and everything else (MAF, TPS, O2, Cam & Crank sensors etc) all came out within spec per the FSM... except for the fuel pump. Oh well.

Not really sure what to say except that 2x brand new fuel pumps - one Denso branded the other that came in a Toyota box that I assume was also Denso (but didn't check the p/n) both registered 29 Ohms and nowhere in the FSM does it mention that as being even remotely close to in spec, whereas the pump that was actually close to spec (per page 140 of the FSM) did not.

 

[mckennar]

factory manual

The FSM I am referencing (RM887U) has both values listed - 0.2 - 0.3 Ohms AND 0.2 - 3.0 Ohms.

Neither of which are remotely close to the two brand new pumps I received, FWIW. Thanks though.