SOLVED: Extended cranking hot starts 3.4L

Yep, 3 different outfits "cleaned, checked for flow, pattern and leakage", all said "they are fine" including the last bunch that finally used the scope and found the drip.

 

Well I guess I will wait and see what they say tomorrow. If they tell me it's the fuel pump again I'll probably just put it off until I get the time to change the injectors myself.

 

Here are a few items that may help or at least add some ducks to the line.

The fuel system should hold pressure for a while, the FSM has a spec for it in PSI over a given time. That said, a good pump will fully pressurize the system from 0 PSI nearly instantly.

It's sort of a pain to monitor fuel pressure on the 3.4, hence you see many cases of guesswork. On your own, without installing the needed fitting at the fuel rail for pressure testing there is kind of a "poor mans leakage test". The idea is to go about your normal drive cycles but at shut down, crack open the gas cap and shut the fuel pump off instead of turning the key off. This will bleed off most of the fuel pressure. In theory there will be significantly less pressure and less leakage at the injectors. If this process noticeably improves the hot starts it's another point in favor of leaking injectors.

To make this simple just put in a fuel pump cut off switch (somewhat hidden). This can also be considered a layer of security to justify the $5 switch and 15-20 minutes time. Full load amps of the pump is under 10 amps DC so choose a switch accordingly.

You will be looking for a blue wire that runs from the "circuit opening relay" to the fuel pump. This is the "power" wire to the pump. Different years have different locations for the COR but this wire can easily be found in the bundle under the driver side door sill, the bundle branching off the door sill under the seat to a grommet in the floor and/or behind the driver side kick panel.
When the switch is opened it will affect the engine quickly. It will stumble and die. Listen carefully for a few seconds afterward and you can hear the COR click off. The ECU has noticed a lack of signal from the crank position sensor and shuts the pump power off, but you have already done that with the switch. Leave ign on and pump sw off till you hear this or at least 5-10 seconds after engine stops.

FWIW, I can shut my truck down normally and let it sit over night. Then in the morning, kill power to the pump and try to start her up. It will try to start and sometimes actually run for a second or two indicating at least some residual pressure. A switch like this comes in handy for lots of troubleshooting scenarios. It's not going to fully take the place of a good fuel pressure tester with isolation valves but with a bit of logic it can really help and the price is right.

 

hmm well the shop I took it to are supposed to be Toyota/Lex specialists so I would have assumed they are using the correct tool to check pressure on the fuel rail.. but who knows. I don't have the truck since it's still in the shop but if they say it's the fuel pump again (even tho the issue didn't start until after they did the injector cleaning service) then I may have to go that route and hook up a switch. I must say though that the idea of digging through a wire bundle by the door doesn't sound fun. Do you happen to know which fitting they need to be using the do pressure tests?

 

No guarantees, just ideas.

It's a pretty small bundle and even smaller under the seat. Below is a shot of the COR location on a 99. The fitting is a an adapter for one of the banjo fittings at the end of the rail. It has a 1/8" female pipe thread port in the end where pressure gauge plumbing can attach. Access to that point is the pain.
https://www.autozone.com/fittings-a...1110-and-641120/773861?CJPID=2206300&cmpid=cj

You could find the wire at the relay but I think your year has the relay in the in dash fuse panel.

 

This is their reply:

Good afternoon Mitchell, I pulled the spark plug hot after the engine sat for an hour. Spark plugs were dry, no fuel vapors.Inspected cylinders with a Boroscope, no fuel present in cylinders or dripping off of the intake valves. Disabled injectors with spark plugs out and cranked engine, no fuel or fuel vapors where present. I am very confident that the injectors are not leaking. That being said, it is an older truck, the fuel pump is the logical place to start for the fuel pressure drop that can not be attributed to anything outside of the fuel tank. This will likely be the end of the extended crank issue, but if not, it creates a solid foundation to move forward on any additional diagnostic steps that would be needed.

What gets me is this:
the fuel pump is the logical place to start for the fuel pressure drop that can not be attributed to anything outside of the fuel tank.


But everyone agrees this behavior is normal? Or is the "fuel tank" supposed to hold pressure?

 

I would have assumed that they would definitely have seen injector leakage at that point in the test much like the videos from this post... so I'm beginning to believe them:
https://www.tacomaworld.com/threads...e-swap-3-4l-5vz.354399/page-143#post-10201558

 

I guess I'll bite the bullet and have them replace the pump and pray that it fixes it. I'm sure they are going to piddle around with it to make sure it acts normal before giving it back.

 

I looked up at the intake valves directly below the injectors, some valve where, some not, but regardless fuel would likely drip past the closed valves, and further i cranked the engine with the spark plugs out and injectors electrically disabled, any trapped fuel would presumably sprayed out with the spark plug hole.
Dripping injectors have three characteristics; 1- Extended crank, 2- rough start that clears out as the excessive fuel in some cylinders burns off, 3 - fuel smell under hood or out tail pipe on startup as well as fuel smell in crankcase. You have extended crank with no evidence of excessive fuel, and appears it is the opposite in that it is waiting to get fuel causing the extended crank.
If you still like, I will pull the upper and lower intake plenums to actually see the image you are looking at on you tube. I don't know if this helps but if it where my truck and i was putting injectors in, I would probably go ahead and change out the pump to get another 10 years plus and not worry about.

This is their add'tl response after I said they could do the fuel pump. Thoughts?

 

Man Im perplexed at this issue as I have a long start issue since I bought my truck 10 yrs ago, it will always start w/a key but only half the time it will remote start correctly, it’s bugged the shit out of me forever. I have replaced the fuel pump & pump gasket 2 times, injectors were cleaned and tested had two dripping but fixed, fuel pressure regulator, all new vac hoses, new complete charcoal canister with brand new vsv valves, new wires, plugs, cleaned tb then put on new tps sensor and iac valve, all new timing shit, new maf sensor, new radiator and hoses, new o2 sensor and loads more im forgetting. I need to dyno it and get the definition for the ecu so I can read more than a scanner whilst running and stopping the engine and restarting thats gonna be the only way around throwing more factory parts at it.

 

There is another thing you could have tried. When you expect to have the long crank, open the throttle all the way and hold it there while starting. This does two things. It adds more air and airflow, both leaning the potentially rich condition and clearing it faster. Just another clue in the puzzle.

The Fuel tank per se does not hold fuel system pressure. The pressure we are dealing with is between the pump and the fuel pressure regulator. The injectors are between these two. So leak down can come from any of those 3 parts. The pump has a one way or anti drain back valve (check valve), the injectors are theoretically closed and the FPR is essentially a closed valve when pressure is below a threshold. Thus a good pressure test with isolation valving can point to where the fuel pressure is bleeding off.

Anyway they seem to have made a pretty good case that the injectors are not leaking but they could still be wrong. The leaking fuel could be vaporizing leaving a super rich condition and no apparent "wetness". From here that is going to have to be their call.

One would think that they have read intake air temp, coolant temp and throttle plate angle values compared to actual and checked that the "throttle opener" (a starting aid) is working. Pumps have cured similar cases so it's not out of the question and OE pumps start to fail around the 175K mark while many go far past that. I consider a new Denso pump at 175-200K as just plain PM regardless of any symptoms.

After the fact addendum.
One would think any drain back issue would be worse the longer it sat and not somehow fill on it's own when cold.

 

Well I'm right at 185k so I guess it might be time to replace. I will just hope that this fixes it. I will report back if it does or not.

 

Got my truck back, $900 later. Drove to work, shut it off, 2 hours later started right up, no long crank.

But now I smell gas around the engine bay. I don't think they did anything with the injectors so not sure what the hell it could be now. Hope the smell goes away.

 

Well the fuel smell was coming from the fuel filter outlet. Which is annoying because I just changed my fuel filter two years ago and told them not to change it.

I remember I had to tighten the shit out of it so it wouldn't leak. That poor flare nut is not happy being torqued so much. And yes I'm using a flare nut wrench

 

I read this whole thread and have the same issues sometimes not as much as usual though. I use Bg products like the 44k and CF5 and never had an issue. My issue does the same thing on hot days it may have a longer start and stumble. And sometimes on a graded hill it does it as well. This has been going on for 14 years and mine is 2002. I think its improved since using the CF5 as it removes water from the lines from ethanol fuels. We have a lot of that in Colorado.

 

depends on your mileage but changing the fuel pump *seems* to have fixed my issue. Seems to start up nice and quick, and smooth too. I noticed my engine would shake a little when it fired up before. Now it seems smoother. Could be placebo.

 

fuel pump? Damn,

 

Definitely seems to have fixed the issue. Did a couple of heat soaked starts and had no issues.

 

sigh...so after multiple road trips I developed a stutter while going 70mph, after a couple of secs it would go away. I just replaced the 3 ignition coils with denso's. I think I'll do the fuel pump for safety measure.

 

Curious if the fuel pump fixed your issue long term? Sadly I've been dealing with the same issue for years. My pickup is at the mechanic's now and they said they can't recreate the issue and they don't want to charge me for something that *might* fix the problem. I might have them go ahead and just replace the fuel pump anyways, but that's a $450 shot in the dark.