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What kind of fuel pump are you using ? Airtex or Carter or Duralast by chance? I would recommend a Delphi or Bosch or Denso on fuel pumps, The system is set to work where the fuel pump only gets power when you first turn the key ON, (a 2-3 second prime) then when cranking you should get battery voltage, then when running, you should get a constant system voltage of around 14 volts.The pump does NOT run the entire time the key is ON. So if you turn the key ON, the pump will not continuously run. Only when the engine computer see's a signal from the crank sensor does it ground the fuel pump relay to allow power to the fuel pump.
You will have to check for that prime power with a test light, as a digital volt meter isn't quick enough to show it really. You should get a bit of a prime though with key on. I do not trust cheap fuel pumps. I have had my fill of Airtex and Duralast pumps. I'm not familiar with HighFlow, but I'm skeptical if it's not a name brand like Bosch, Denso, or Delphi, even Carter is ok. It's possible you are losing fuel pressure when you turn the engine off. Try cycling the key a couple of times then starting the engine.
Put a good quality fuel pump in it. Denso, Delphi, or Bosch, You won't have these fuel pump problems in my opinion. make sure your getting a good solid 14 volts to the pump when it's running.
It just spins and spins for a while correct? then eventually fires up?
I believe your losing fuel pressure with these cheap pumps honestly. The pump has a check valve in it. it is supposed to HOLD pressure when you turn the key OFF, when pressure bleeds back off after it sits a while, (usually either through dirty fuel injectors or a leaky check valve in the pump) you have to spin the pump for a while to build pressure back up, if when it fired up it smoked black a bit, and ran rich, I would say the injectors were leaking down and bleeding off some gas into the engine, but if it didn't fire up and run rich for a few seconds, I would say fuel pressure is leaking down, try this, cycle the key a few times before starting, this builds up fuel pressure before you turn the key to the START position. I'm thinking a good quality pump will help that problem too. Run some techron through the injectors, a good fuel injector cleaner in case they are leaking down.
the pump does not get power the whole time the key is on. The system was not designed so the fuel pump would run constantly when the key is on.
Now it does run constantly when the engine is running of course. It will only get a very short prime of voltage when you first cut the key on. If you probe that wire with a test light, you'll see the light come on just for a very short time, (sometimes just 1 to 2 seconds) before the light goes off with the key on.
I follow you, they generally take longer to measure than duration of power your getting in my opinion. I've always checked that with a 12 volt test light, Now cranking what do you get on your volt meter? should be battery voltage, but battery voltage goes down some with the starter motor drawing a good bit of voltage,
Alright, that is interesting. it shouldn't pulse like that, should light up for 2 seconds or so on initial prime with key ON. Here is the diagram.
There is an EFI relay, and there is an circuit opening relay in the wiring diagram. I suspect something is causing an issue there. the Engine computer grounds the circuit opening relay so it's possible it may be something there pulsing. Turn the key to the ON position and check a fuel injector wire BLACK and WHITE wire with key ON, tell me if that pulses too.
The engine computer does. or is supposed to. The engine computer grounds the circuit opening relay which puts power to the pump.
Do you have an OBD II type scan tool you could check to see if any codes were stored in the ECM with?
let me opt out and let another expert assist, I m not showing it's exact location in my references. Thank you