5.7 hard start after sitting for 1+ hours

I've got a 2011 tundra with the 5.7, 148k miles and I'm thinking I've got some leaky injectors, but I'm not sure how it's happening. Cold starts are fine and it fires right up. I have problems when it sits for 1+ hours it stumbles a bit on start, and takes longer to start. If I let it sit overnight it fires right up everytime. Definitely symptoms of flooding, with fuel smell out the exhaust when it stumbles when starting accompanied by a little bit of black smoke out the tail pipe. Thought it might be a leaky injectors so I replaced with a junkyard set to make sure it really was that. Installed the injectors from the junkyard and the problem went away for maybe 750+ miles then the problem came back with the exact same symptoms.

My question is, is there some sort of check valve, regulator, sensor or something else that can cause GOOD injectors to leak eventually or do you think I got unlucky with the junkyard injectors? Checked the fuel pump and is working fine. I'm positive that fuel is leaking into the cylinder and flooding it, but with time it evaporates out or leaks down which is why I think it starts fine after sitting for several hours is my conclusion. I dont want to buy brand new injectors and the same issue happen 750+ miles down the road, because I'm not looking at the right part. What are the chances that two sets of injectors are leaking? Anything else would cause fuel to get in the cylinders? Any ideas would be greatly appreciated. Been fighting this issue since buying it used.

 

Get a junkyard fuel pump control module and give that a shot. They are common to a ton of different Toyotas and are a lot easier to try than the injectors. If junkyard parts swapping isn't bothersome, this is what I would try next.

Otherwise these are not the easiest engines to hook a fuel pressure gauge to, and that would also be of interest.

Really leaky injectors would pollute your oil with gasoline. How does your oil smell?

 

You could try the fuel pressure regulator. Someone had a similar issue recently and it was his regulator I think.

 

Since you have the old injectors out you could send them to Injector Rehab in New Jersey and let them do some tests on them to verify if they are the problem.
Injector-Rehab - Fuel Injector Cleaning and Components - Injector-Rehab

 

Gotcha, I'm pretty sure I replaced the fuel pump control module. Isnt it mounted near the frame by the fuel tank? Ill need to confirm on that. Checked the oil dipstick and there is a smell of gas. I'm just perplexed why different injectors fixed it for a little while and now back to doing it again. I wish I knew the process of how the injectors work after you turn the vehicle off. Like something isnt doing its job and pressure allows gas to leak through the injectors or are the injectors never suppose to leak after shut off regardless of pressure if they are working properly. Like injectors are simply on or off?

I saw that thread, it seemed his symptoms were a little bit different. The truck starts fine warm or cold just fine, only when it's been sitting for an hour or more does it stumble to start. I can run it for hours, fill up gas or get a bit to eat and it will start up fine. I'll take a look at that thread again though. Thanks for the input.

Thanks for the link, I'll give them a look.

 

The suggestion to have the injectors you pulled out tested is a good one. I know there's a shop down the road from me that's just a fuel injector shop, and they will put your injectors in their machine right in front of you to show you what's up.

Knowing that the injectors are leaky would have me wondering if something is up with the fuel filter in the tank among other things, or possibly fuel pressure is just too high. How are your short term/long term trims?

 

Havent checked fuel trims, I suppose I can check the trims with a scangauge, torque app? On my 3rd gen 4runner Ive checked my trims through my scangauge. Havent looked at the tundra trims. When I first tried messing with this, I'm pretty sure I tested the fuel pressure and it was within spec. I appreciate the ideas for sure. Would a gummed up injector from say sediment in the gas tank cause it to leak? What's weird is I'm not getting any lag, cutout, loss of power under driving conditions. I think I'm going to see if I can find someone locally to test out the injectors.

 

If the ECU is trimming fuel way, way back, that could suggest leaky injectors. An injector shop would be able to confirm this and if the guy working there is older than dirt, he might look at what's in the bottom of the little tubes they have the injectors spraying into and make some suggestions about what's going on.

 

I wanted to update this thread. I replaced the set of injectors with some new ones. They were supposedly new denso injectors, but you never really know when you buy online and if they are just refurbished or knockoffs. So far the new ones seem to be working and my symptoms are gone for now. I ran the truck then let the truck sit for 2 hours and then 3 hours and each time the truck started right up without hesitation. Before it would always have a hard time when 2 or 3 hours passed. I'll make an update when more time has passed. Perhaps I just got unlucky with the junkyard injectors and had some leaky injectors twice. Thanks for all your help.

 

I would not trust junkyard injectors. You don't know how long they have been sitting and may have dried out and caused corrosion in the injector which would lead to bad things happening. Just chalk that up to a new experience. Hope the new injectors give you good service!

 

I definitely think you are right on the money. Lesson learned for sure. So far so good, no issues.

 

Just want to give an update. Everything continues to work fine after 5 months. It's safe to say the junkyard injectors were the culprit.

 

Good deal!

 

I have the exact same hard start/stumble start issue that is described here, so I am going to replace all injectors with brand new ones. Where is the best place to get REAL Denso (OEM) injectors for the best price?

 

Is yours a flex fuel motor? 3UR-FBE?

 

I'd go with rockauto.com
Picked up a few things from them over the last couple years.

 

It is not a Flex Fuel. It is a 3URFE engine

 

I looked on Rock Auto, but they only have other after market brands, and I was wanting to stick with the original OEM part, which is Denso. The Denso injectors in there now have part # 23250-0S020 on them. As far as I know, these are the original stock injectors, at least that's my assumption.

 

Also, what fuel filter brand do you like for the Tundra? I'm going to replace the fuel filter at the same time.