unsolvable cold start issue...

[acarr6]

So, I’ve been chasing a cold start issue for 2 years now. Basically the car just cranks got like 6 seconds after sitting for 24+ hours. Then I press the start button a second time and it cranks right up. Only first cold start of the day, rest of the starts are fine no issues

Things I’ve replaced:

Fuel sender unit (regulator and filter)
All 8 injectors
Fuel pressure sensor

Any ideas? No codes.

[Redd]

You didn't try a new starter? Also check your grounding and the main starter cable.

[acarr6]

Originally Posted by Redd

You didn't try a new starter? Also check your grounding and the main starter cable.

Not yet - cranks very strong.. can I see the ground in the engine bay?

[amrazM]

you checked the EKP? what kinda voltage is the pump getting on crank? you should also mechanically check the fuel pressure at the rail when the engine is experiencing this delayed crank.

[acarr6]

Originally Posted by amrazM

you checked the EKP? what kinda voltage is the pump getting on crank? you should also mechanically check the fuel pressure at the rail when the engine is experiencing this delayed crank.

I have not checked the EKP yet, but I was going to swap with a spare just to see.

I have mechanically checked the fuel pressure at the rail, upon prime it’s immediately full pressure, and when I crank it doesn’t drop.

[RocketyMan]

Originally Posted by amrazM

you checked the EKP? what kinda voltage is the pump getting on crank? you should also mechanically check the fuel pressure at the rail when the engine is experiencing this delayed crank.

I second checking the fuel pressure on crank. On the forum somewhere there was a "mod" that had an inline fuel pressure gauge right off the rail or near the fuel pressure sensor somewhere.

Lemme see if I can find it...

[RocketyMan]

I can't find it!...ergh. Anyway, if you can easily reproduce the problem I would check the fuel pressure BEFORE priming the pump. See what pressure it sits at "overnight" when the problem happens.

Someone on the forum shared this before, but look at your fuel pressure readings using INPA without priming the fuel pump.

[acarr6]

Originally Posted by RocketyMan

I can't find it!...ergh. Anyway, if you can easily reproduce the problem I would check the fuel pressure BEFORE priming the pump. See what pressure it sits at "overnight" when the problem happens.

Someone on the forum shared this before, but look at your fuel pressure readings using INPA without priming the fuel pump.

https://youtu.be/yyzrHMstvvs?si=qLGLu5RQUp9uLgRI&t=226

Yeah I’ve checked all that. The thing is, even if I prime the system to fill pressure the initial crank is still long.

[RocketyMan]

Okay. What was your pressure reading?

[acarr6]

I believe around 50-55 psi. Should be plenty to fire right up. When I prime, it just immediately to 75 psi. It actually DOES sound like it’s starving for fuel - but with every component being new, and the pressure being fine..: it’s quite odd (and frustrating lol!)

[RocketyMan]

Well then yeah...that should def be enough "residual pressure" from a cold start. That's good to know!

[acarr6]

So, to update this thread.

I pulled the rear seats back out, and primed the fuel pump. I then clamped the fuel line right after the fuel pump (right side) and the pressure did NOT drop significantly on the gauge. It was about 4 psi over 30 minutes, which is well within spec. Given the sender (left side) is brand new, this tells me the fuel pump is bad.. or the check valve in the fuel pump is. Finally may have figured out the issue. After removing the clamp, the pressure started falling off instantly.