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2003 ford 6.8 liter cranks good starts right away then stumbles and even stalls.

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12 Sep 2019 21:09 #33581 by gearwrench73
So when i start this truck and its cold it starts right up then stumbles and stalls. The idle air control solenoid is working verified that, the the full pump is at 35 psi when key on ,drops off to low pressure when cranking, comes right bact to 35 to 40 when idling. Havnt figured out why it drops off at crank when cold warm starts are good no issue. Any thoughts?

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13 Sep 2019 09:42 - 13 Sep 2019 09:47 #33582 by John Curtis
What kind of ford? I’m guessing F250 since it’s the 6.8 but I’m not going to assume that.

What is live data looking like?

ECT
IAT
MAP
MAF



You can give It some bursts of fuel in the intake and see if it keeps running.

Thinking out loud always helps me in the process.
Last edit: 13 Sep 2019 09:47 by John Curtis.

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14 Sep 2019 09:27 #33595 by gearwrench73
Its a f350 . Havnt had a chance to get the truck back in for some snap shots. Have changed the injectors cause a few were leaking fuel so it would cause a rich condition when hot and a long crank on a hot start. Now its good for a hot start it just stumbles after starting when cold.

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15 Sep 2019 16:55 #33614 by Crombie
I have a similar issue with my car, I think its the ignition timing on mine, as it stays advanced instead of retarding it, but then after it warms up a bit it idles fine and at the base timing

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15 Sep 2019 17:13 #33615 by gearwrench73
Thks for the info bud. Ill keep looking but good to know that.

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16 Sep 2019 14:42 #33620 by John Curtis
Since it is happening only on cold starts load test battery as silly as it may sound. A parts store can load test it for you. Does the vehicle ever actually fully start when its cold?
I would check PCV and EGR however, that doesn't seem like the likely cause of your stalling problem since you're loosing fuel pressure. A drop in fuel pressure IS a problem.

When it is giving you problems, I would verify spark and injector pulse. Just to make sure the cold isn't causing a driver or an input problem.

Thinking out loud always helps me in the process.

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18 Sep 2019 16:58 #33673 by Crombie
With fuel pressure though, when I did mine it raises to 38 then lowers to 32 or so, maybe this lowering of the fuel pressure is just rest pressure?

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18 Sep 2019 17:01 #33674 by Crombie
With fuel pressure though, when I did mine it raises to 38 then lowers to 32 or so, maybe this lowering of the fuel pressure is just rest pressure?

His engine fuel pressure is dropping during cranking, I would of thought that was normal?

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