FJ62 hard to start when hot (1 Viewer)

[jonnyd42]

Ok so I'm a bit stumped on this one. My truck starts up very quickly when it's cold (about 2 seconds), or if its been sitting for > 5 hrs. If I get it up to operating temp and then let it sit for a while, it takes a really long time to crank (12s or so). If I drive it, shut it off, and then immediately try to restart it it starts up just fine. It's only when it's been sitting for upwards of 20 mins.

I have replaced the fuel pressure regulator. The fuel pulse damper at the back of the rail (firewall side) looks like it was replaced by the prev owner.

I have tried all of the following permutations:

• Starting it without letting the fuel pump build pressure
• Starting it after leaving the key on so that the pump can build pressure
• Pressing the gas pedal / not pressing the gas pedal

I have checked:

1. Condition of plugs
2. Air filter
3. Fuel filter (it's new)
4. Cap & rotor wires
5. Battery cables & ground

The truck has no loss of power or other indications that there's a fuel delivery problem due to the pump. I'm wondering if this is something sensor or computer related, since IIRC the 3FE EFI system has different behavior on cold vs. warm start.

Would love some advice on what to take a look at next...

 

[jonnyd42]

Here's a video showing how long it takes

 

[toy_tek]

I’ve had/have this same issue for about a year. Ambient temperature doesn’t seem to have an effect in my case.

The pump doesn’t actually come on until the key is in the start position, so just turning the key to accessory on isn’t pressurizing the system (I believe this is what you’re describing). Have you tested when hot and jumper the pump at the diagnostic port to build pressure? I can’t recall the pins but I think it’s B+ and Fp, then turn the key accessory… you should be able to hear the pump (it’s faint). After 10-15 seconds, turn off the key, remove the jumper then try to start.

Pressing the gas pedal won’t really make a difference- that’s old school carb stuff (accelerator pump).

Coincidentally my pump just completely failed 2 weeks ago. I’m still working through some issues so I’m not able to say definitely, but I have a hunch my fuel flow/pressure was perhaps insufficient prior to the failure which *may* have been the cause of the hot start issue.

Also suggest getting a fuel pressure indicator to help you diagnose.

 

[jonnyd42]

I’ve had/have this same issue for about a year. Ambient temperature doesn’t seem to have an effect in my case.

The pump doesn’t actually come on until the key is in the start position, so just turning the key to accessory on isn’t pressurizing the system (I believe this is what you’re describing). Have you tested when hot and jumper the pump at the diagnostic port to build pressure? I can’t recall the pins but I think it’s B+ and Fp, then turn the key accessory… you should be able to hear the pump (it’s faint). After 10-15 seconds, turn off the key, remove the jumper then try to start.

Pressing the gas pedal won’t really make a difference- that’s old school carb stuff (accelerator pump).

Coincidentally my pump just completely failed 2 weeks ago. I’m still working through some issues so I’m not able to say definitely, but I have a hunch my fuel flow/pressure was perhaps insufficient prior to the failure which *may* have been the cause of the hot start issue.

Also suggest getting a fuel pressure indicator to help you diagnose.

I’m thinking since mine is temp dependent it’s not the fuel pump

When it's cold it starts up just fine, very quickly.

Noted re gas pedal!

 

[toy_tek]

I’m thinking since mine is temp dependent it’s not the fuel pump

When it's cold it starts up just fine, very quickly.

Noted re gas pedal!

When it’s cold, the cold start injector is activated.

 

[ceylonfj40nut]

Remove fuel line to fuel rail and confirm fuel is reaching engine bay. Then check fuel pressure regulator is not blocked or inoperable. Report back.