Starting Issues after Fuel Pump Upgrade

Hello everyone, I am having a really hard time figuring this one out. I recently upgraded my 2002 Tacoma Supercharged (113K) to have a new fuel pump and upgraded injectors. I did this to eliminate the need for a 7th injector kit (I live in Denver.) I installed an
AEM 50-1000 320 LPH High Flow In-Tank Fuel Pump and Bosche 295cc 28lb Upgraded Fuel Injectors into the truck, and for some reason, I'm dealing with startup issues. Before the upgrade, I dealt with the dreaded P0171 code, and after battling for many months, decided this was the only way to go. Now, after the upgrade, when I turn my key, no priming occurs. As you may or may not know, the Tacomas do not prime the fuel injectors before startup, they do so on crank. Currently, when I go to crank, the first time the truck refuses to start. After I try again to start the truck, the engine fires right up and runs great. My guess is that the injectors are not being fully primed before startup, but I don't know if that is the issue, or if it could be something else. I posted the links to the injectors and fuel pump below. Does anyone have any ideas or solutions?

https://urdusa.com/aem-50-1000-320-lph-high-flow-in-tank-fuel-pump/and

 

I would verify that your ECT engine coolant temperature sensor's connection ha not been damaged. This happens frequent enough to mention it here.

 

I do not think that that pump has a drain back check valve in it. A pressure test to see if the system holds pressure after it is shut off would confirm this. The AEM web site tells you that this is a "race only" pump, that might be code for no check valve.

On a side note... working on my buddies '05 F150 with a similar issue. On this truck, Ford primes the pump when you unlock the doors with the remote. His problem was 3 fold, the module wasn't sending the prime signal, the pump was whining and the fuel rail pressure sensor was reading wrong. Was he pissed, yes, but as I showed him every test and how each test failed and went on to the next test he understood. Have not heard from him in a month so I guess it is fixed.

 

You could be right, I guess I just didn’t think about the pump being a race pump. I’m going to try installing an in-line check valve before replacing the pump, and hopefully that helps.

 

Sounds like Glamisman nailed it !!

Pump drains back First Crank only does so much second time is the winner.

It does run and drive just fine .

 

Looks like the check valve solved some of the issues, but now i’m running into others. Now, on warm/hot starts, the truck misses pretty badly, and refuses to take gas when the accelerator is pressed. If I drive it or let it sit for 5-10 minutes, issue seems to resolve itself, but it’s pretty much on every single hot start.

 

UPDATE: I tried wrapping the fuel lines in heat shielding, and i replaced the check valve with a much larger one. It seemed to help with full throttle, but I am still experiencing issues with misfiring on hot starts. Anyone have any guesses?

 

Hot Starts I know your injectors are new but Quality has gone down hill .

Leaky injectors?

Once it runs burns off the fouled plugs it runs what passes for normal?

Sits long enough plugs dry fires right up.

 

Bro i had no idea the pumps don't prime on startup, Ive been having startup issues aswell and I've been "priming" the pump before start by putting the truck in the ON position for 5-10s

 

Right? I don’t think many people actually know that, but it’s true with many Toyota vehicles. I’m going in and doing a bunch of work to the truck this week, including spark plugs, spark plug wires, 295cc injectors, check valve in fuel tank, oil and oil filter, air filter, and a 170 degree thermostat. Anything else I should take care of? I’m trying to figure out if I should go in and replace the fuel pressure regulator as well

 

I realize you didn't mention fuel filter check that unless you have already and oil as you said. How is your starter, battery alternator or even your ignition switch could be faulty?

 

Fuel filter was just replaced before have this issue, not even 1K on it yet. I assume my starter and alternator are fine, although I do draw a fair amount off power. What would be the signs of a faulty ignition switch on the 5VZ?

 

(Got this from a quick google search):

• Car Won't Start. If you turn your key and the car attempts to start, but fails, then you might have a broken ignition switch. ...
• Key Won't Turn. ...
• Car Stalls. ...
• No Noise From The Starter. ...
• Dashboard Lights Flicker.

 

Ok then no issues there, as of right now the only symptoms I don’t think I have figured out are no acceleration after about 80% throttle, the truck slugs down and almost feels like it’s starving for fuel.

 

Yeah, that really weird, fuel injectors, fuel pumps are my best guess. Who knows maybe the lines could be clogged but their stick behind the filter which is why your filter has no issues. Just a thought.

 

When I go in to do all the work, i’ll go through with my air compressor and blow the lines out just to make sure!