Tacoma 4.0L hard to start when warm

After an hour it is down to 10 psi

Also, I'll add that I tried to use a bore scope down the throttle body, but it was a cheap one, and I couldn't see anything. When I pulled it out, I did have a drop of what appeared to be fuel on the end of the scope.

 

I know I've had lots of posts today but I've been trying to update as I go.

So I just completed the fuel pressure leak down test with the return line pinched off.

While running, when I pinched off the return line, the fuel pressure jumped from 41 to 52. This means the fuel pressure regulator is bad according to the Haynes manual...

So I shut it off and pressure was 39 with the return line pinched. After 10 minutes it's was 35, after 30 22, and after 1 hour it dropped to 10.

So it basically followed the same path as all other tests. The only difference was, on all the other tests after an hour it gave me the hard start condition, but with the return line pinched, it cranked fine after an hour.

Now I'm leaning towards a bad fpr.

 

Progress!

 

Bad FPR. Your first post had me more than convinced it was.

As for me I have the issue every once in a blue moon. So I think the diaphragm for mine leaks a super miniscule amount but sometimes enough to choke it. I need to replace mine at some point anyways.

You would have had to do the fuel pump anyways at some point. The OE ones are trash on these later model 2nd gens. The earlier ones it's a toss up. Be glad you did it now rather than later.

Replace yours and enjoy your 2015.

You too @boogie3478

 

That sounds more like a bad check valve in the pump, but it sounds more like leaky injectors.

Anyways, the regulator is easier to change than injectors. I'm pulling for it to be the issue.

 

After seeing the filter sock in the old pump I can only imagine it was about to crap out on me.

I ordered a new fpr online with a company that says I can return it as long as it is in like new condition. I'm going to be very careful installing it in case it doesn't change anything I can return it and look deeper into injectors.

 

So do you know what residual fuel pressure should be? Should it hold pressure indefinitely, it will it always eventually lose all the pressure

 

The fuel pump is brand new. If he is pinching the return line and is not seeing 82 PSI or higher that indicates the fuel pressure regulator is not doing it's job correctly.

The fact that he is dropping pressure relatively quickly on a system with a known good pump indicates that he has a leak somewhere. Seeing that the fuel pressure regulators on these trucks are not good to start and that the fuel injectors do not have a known history of failure rate tells me that's a strike two for the regulator. It is cheaper to change that piece out anyways and highly accessible so he should do it anyways. Those diaphragms on the FPR's leak and have ruptures all the time.

Keep it. The OE FPR's are not the best anyways and even if it does not resolve your issue think of this as a preventative maintenance.

One other thing you could attempt to do is pull the line which attaches to the FPR. If it smells like fuel at the vacuum line that would. Indicate it is no longer just applying vacuum to it but it is pulling fuel past a leaking regulator diaphragm.

It should not hold pressure indefinitely as it does eventually drain back. It is not uncommon to have a good amount of pressure in the system well past a day later though.

 

Just put on the new fpr, ran the truck up to operating temp. Now I'm letting it sit for an hour or so and I'll go check how it starts

 

Well, had the long start again... i guess my next course is to check and replace injectors

 

If the injectors takes care of it you will have had one of the most unique hard start issues out there on these trucks for sure. I hope this resolves it.

 

I really don't want to have to take it to a mechanic, but you are right, this has got me stumped...

 

It's not that unique. Many people have leaky injectors, but just don't know it because they don't let the truck sit for 1 hour.

 

Unique to the Tacoma. Do a search and you'll be hard pressed to find many "I have leaky injectors" threads. The fact yours may be leaking is a case I have yet to hear on these. I believe Delphi makes these injectors, but I could be wrong. Usually the stuff is pretty rock solid and reliable. Especially at the mileage you are at.

Idk about that. A lot of people let their trucks sit for an hour or less in most instances. I know I do. I am actually plagued by constantly failing MAF issues. It's pretty annoying.

 

Have you been able to test or attempt to diagnose anything on your truck? I'm close to the point of giving up on it...

 

https://www.tacomaworld.com/threads/rough-start-up-engine-sputtering-video.503441/

 

Not yet. I'll try the fuel pressure regulator first.

 

Before you replace the fpr, look around on eBay. There are entire fuel rail systems there with injectors and fpr that are used for cheap. And you can add a warranty to them for 10 bucks. You could replace the entire rail for less than I spent on my fpr. If I would've known that, I would have bought them

 

Did you pull you injectors at the same time you replaced your fuel pump?