Fuel pump confusion

Hi all, new member here. Having a no start issue and looking for advice on where to start.

Just bought a cherry 2001 Taco Limited 3.4L V6 2WD for $700. It had been sitting for ~1 year needing a fuel pump (hence the screaming deal). 250k miles, everything works.

Dropped the tank, put a new fuel pump and fuel line filter in, fresh oil, hooked up my 4Runner’s brand new battery and she instantly fired right up! Let it run for about 10 mins. Cranked and ran it a few times after that, started and ran perfect.

Drove it about 12 miles, shut it down and now it cranks and sputters trying to start. It DID start twice after this, and runs and revs fine once it’s running, so I don’t think it’s the fuel pump I just replaced.

I was extremely careful not to get any contaminants in the tank when I had it open. I’m 100% sure all the fuel lines are hooked up properly.

It does have an aftermarket alarm system (key fob doesn’t work to disarm) that causes the lights and dash lights to blink (no horn) for about 1 minute once you put the key in. Right now this is my only thought, that it could be interfering with the ignition system, but I would assume it wouldn’t crank or have started at all if this was the issue (dealt with this on my 93 4Runner after a dead battery).

I’d love to hook up a fuel pressure gauge, but these don’t have a schrader valve on the fuel rail. Again, I don’t think it would run as smooth as it does once it does start if this was the problem.

What are your thoughts? Bad fuel? Air in the lines? Spark plugs? Security system? Any advice is greatly appreciated…I was ecstatic I was able to get this truck running, but my excitement was short lived…

 

Have you pulled any Codes?

Best Guess!

First thing that comes to mind is leaking injectors fouling the plugs once they burn off it runs fine.

Your Cold starts will be fine it is those 15 minute shut downs or so that cause long cranking times

Injector damage from sitting with bad gas??

 

Hi and thanks for the quick reply!

I forgot to mention no CEL’s during any of this, although I have not hooked up a scanner.

That is a good guess! Wouldn’t bad injectors throw a CEL?

I tried starting it this morning after it sat overnight. It ALMOST started the first attempt, but chokes up then just cranks without sounding like it’s going to start on following attempts. Last night when it wouldn’t start, I gave it a little gas while cranking and it did fire up (twice). But this hasn’t worked since.

 

Most fuel related issues do not trip a code.

Remember EFI throttle only gives it more air.

When the tank was out you did drain the tank??

Did you clean it out at all?? Moving the tank may have knocked dirt loose which coated the fuel pump sock.

Have you pulled the plugs How do they Look??

How is the Air Filter ?

No short cuts start and work through every thing.

 

Good to know it could still be the injectors without throwing a code, I didn't know that!

There was about 1/8th tank of gas in the tank when I pulled it. I feel like a moron now for not draining it when I had the chance (I've brought other Yoda's back to life with much older gas so I didn't think much of it). I was planning on fueling up right away with fresh gas.

I inspected the inside of the tank, which looked immaculate (no dirt or debris), so I did not clean it out. I did replace the sock with a new one. Everything on the pump assembly was connected perfectly and snug before I put it back in the tank.

Air filter looks great.

I'm going to look at the plugs as soon as I'm off work in a couple of hours and will update with what I find. Thank you so much for your help! It is MUCH appreciated

 

Pulled out the first 2 plugs on the drivers side (pic of plug 1 attached). They aren’t new for sure but they don’t look fouled to me. Lined up a screwdriver on the intake plenum to check spark/arc. They are both sparking good. I’ll inspect the rest of the plugs. Starting to suspect the old gas is the issue…just seems strange it starts intermittently and idles smooth and strong once it’s started if that is the case.

I want to punch myself in the face for not draining the gas when I had the chance…

Edit: It started when I had plug 1 out while checking for spark. Could have been a fluke since it does start about 1/20 cranks

 

That plug looks relatively normal, depending on mileage.

Stale gas is the most likely suspect in everything you have described so far. Best approach now, especially if you haven't filled it up yet, is to drain the tank, add a couple of gallons of fresh gas, agitate and drain it again, then add another couple of gallons of gas and run the fuel pump from a 12V source and collect the pumped fuel into a container just before it goes into the fuel rail(s). Once you have flushed that stale gas from the lines, try to start it again. If you can get it to fire, you will be good to go. Nowadays, with the ethanol they mix into the gas, any fuel over three months old starts to be suspect.

 

Thanks for reading, 1schoir!

I think you’re on the right track with the stale fuel. I could siphon out the old gas, but I want to make sure I get it all. I will probably pull the tank back out, get all the old gas out, rinse a few times with new gas and drain, then pump the remaining gas out of lines as you suggested.

Might take me a day or 2 to make time for that fun project again. I will update with what happens. Thank you and Bivouac for the advice! This forum is awesome!

 

Update - I also located and disconnected the Automate keyless entry/alarm system behind the dash kick panel. At least now the door locks aren’t engaging and lights flashing every time I put the key in. The truck also now starts every time but sputters out after 2-3 seconds. This happened right after I disconnected the alarm box. Seems strangely related, but I’m still leaning towards old gas being the culprit, as I think an anti-theft feature would cut the relay to the starter, and this isn’t the problem

 

Are you still running the existing 1/8" a tank? I don't know that'd I'd go as far as a previous poster said with draining, mixing, draining, I'd just fill er up and "dilute" (for a lack of a better term) the existing gas as much as possible and send it.

 

I picked up a cheap siphon kit from Lowe’s and pumped the old gas out before going to the trouble of dropping the tank again. Fairly certain I got it all out (fuel gauge says empty). Tomorrow going to try pumping what’s left in the lines out with the siphon pump, slapping a new fuel line filter on for the heck of it and filling it up with fresh gas.

Also, to make sure my new fuel pump was working, I disconnected the main fuel line under the hood, hooked up some rubber tubing to a gas can and turned the key for just a second. Shot gas like a fire hose. I can also hear the pump when I turn the key. I may not know the fuel pressure but at least I know my new fuel pump is doing its job . Also, I thoroughly checked the fuel lines from tank to injectors and there are no visible leaks or smell of gas when trying to start it.

I’ll update tomorrow if this does the trick. Thanks again everyone for all the helpful advice!

 

Once you have siphoned out as much gas as possible, you should repeat the procedure you used to see if your fuel pump was working. Disconnect that main fuel line under the hood again, hook it up to that rubber tubing into a gas can and turn the key. Leave the key on long enough until the tubing stops shooting out steady full spurts of gas and you will have cleared out all the bad gas from the tank and from the lines. Do not let the pump keep pumping without gas or you can burn out the pump. It overheats without gas.

Once you do that, either the truck will start right up after a couple of hiccups or, at the very least you will have absolutely eliminated bad gas as a cause.

From all the symptoms you have described, my money says the truck will start and run!

 

I just did exactly as 1schoir described above, being careful not to burn out the new pump. Took about 10 cranks, then stopped as soon as fuel stopped flowing from the rubber hose I hooked to the main line under the hood to flush out the rest of the old gas. Reconnected the lines, put a brand new fuel line filter on, filled up the tank with fresh gas. After about 8 cranks it began starting (fresh fuel getting to the motor) but shuts off after about 1-2 seconds, so same as before... I tried cranking it about 30 times. Same result every time. No leaks anywhere. I have my battery charger hooked up when not cranking it so I don’t drain my new battery.

I was confident it would fire up with fresh gas…how many cranks would it take to spit out the remainder of old gas from the fuel rails I wasn’t able to fully drain? Should I replace the fuel injectors and spark plugs while I’m in there? Is it possible the new fuel pump isn’t pushing out enough pressure? Man this is frustrating!

 

Is it possible that new fuel pump you installed is defective?

Is all the air purged out?

Did you install a new "sock fuel filter" at the base of the pump when replacing the pump?

Since there is no Schrader valve on the fuel rails, you would have to install a banjo bolt and a 1/8th NPT fuel pressure test port to be able to test fuel pressure. Here is a link to a decent quality banjo bolt for that purpose:

$16 RUSSELL/EDEL 640700 Fuel Pressure Take Off Banjo Belt

https://www.amazon.com/dp/B000CPJI8I?ie=UTF8

Be sure to verify that you have enough room to install the banjo bolt with the pressure test port on top of it and that you can still plug in the tester. IIRC, the space there may be limited so I don't know if anyone has come up with an easy way to do this.

 

One other thought...Have you looked at the vacuum hose going from the fuel pressure regulator to the throttle body? You can simply pull it off the pressure regulator and see if there is fuel in that hose. If there is fuel, then the regulator is malfunctioning and the fuel leaking past the fuel pressure regulator diaphragm will be sucked into the throttle body and into the engine.

 

Thank you all for continuing to brainstorm with me!

Today I also cleaned the MAF sensor with MAF cleaner, rechecked ALL fuses and relays with my voltmeter (all good), and tried starting it about 10 more times to make sure all the air was out of the lines, to no avail.

To answer your questions: I installed a new sock with the new pump. I am confident all the air has been purged out with the number of attempts I’ve tried after filling it up with fresh gas. I also disconnected the FPR vacuum line (which was bone dry) and tried starting with that line disconnected.

Thank you for the link! That part will be very helpful for checking fuel pressure. With the way it’s acting, the pump works, but isn’t maintaining good pressure/flow right after it starts. One thing I’ve noticed is it will just crank (no start at all) if the key is cycled between “On” and “Run.” But it will momentarily start if I take the key fully out first before cranking. Not sure what that means?

I picked up new battery terminal connectors to put on tomorrow as the ones on there are pretty rough, but I’ve seen worse. I think if it were a bad battery connection though it wouldn’t be able to keep cranking and all power would cut off, which doesn’t happen, but I’ll replace these tomorrow anyway.

Starting to think something is going on with the new fuel pump since it DID start several times and run and drive fine right after I replaced it, and now the same original symptoms are happening again. I’ll order that banjo setup you suggested to give me some more info before replacing the fuel pump again.

Just a thought, could it be the Idle Air Control valve? I read on other posts in here it could cause it do die right after starting too.

Edit: I read several poor reviews online of the Carquest fuel pump I just put in. Sounds like they often work then fail quick exactly like what I’m experiencing… Ordered a better brand pump and strainer with all good reviews, lots from people with the same truck. Even if my pump is working I don’t want it after seeing those reviews!

 

I hope you went with a Denso pump.

In case I read things wrong.

Remember the pump is only energized when cranking and when the engine is running .

Your still not having any codes trip?

Hang in there you will get this figured out.

 

Great to see that you are not getting discouraged. You have made a lot of progress in narrowing down the possibilities and eliminating possible causes.

When you go to replace the pump, take careful note of the surface of the "sock" filter at the base of the pump to see whether it's covered and clogged. Since it's a new pump and filter, that surface should be clean and clear.

 

That pump was installed into the old stale gas no telling what kind of dirt may have been knocked loose dropping and installing the tank.

 

Yes that’s the one on the way. Still no CEL’s, I don’t have a scanner but might as well pick one up. It’s one of those tools I should have got long ago