7.3L runs rough at start up

[paulfrantz]

I've got a 2002 F-550 with a 7.3L with 120,000 miles. On cold starts (and I'm not talking freezing temps, even at 70F) it runs for the first few minutes like it's only firing on 5 cyl. I've checked the GP relay it comes on and stays on for about a minute at around 70F. All the glow plugs test good at the harness conection at the uvc. When I plug up the block heater it cranks up and runs great. Any suggestions, other than plug it up every night?

[85_305]

Scanned for any codes? Replaced fuel filter recently? Do you run fuel additive? Have you checked the FPR screen for gunk/buildup? Does the truck smoke at all on startup/warm-idle/driving?

[paulfrantz]

no codes, just replaced fuel filter, I have never run additive in any of my trucks, haven't checked the FPR, truck doesn't smoke at any time

[85_305]

I'd try running additive for starters.. these trucks dont like ULSD. But i'm wondering if injectors or hpop are bad... maybe cps?

[paulfrantz]

I doubt cps, and hpop shows good #'s. The injectors are what worry me, but my scanner can't run any tests on them, so I have no way to check them.

[paulfrantz]

What additive do you use, and what is it for. I originally assumed you meant it was for cold weather.

[85_305]

Originally Posted by paulfrantz

I doubt cps, and hpop shows good #'s. The injectors are what worry me, but my scanner can't run any tests on them, so I have no way to check them.

AE can run contribution tests for the injectors

Originally Posted by paulfrantz

What additive do you use, and what is it for. I originally assumed you meant it was for cold weather.

I use silver bottle diesel kleen in every tank to help with the lubricity that the ULSD doesn't have. In the winter I use white-bottle diesel kleen to prevent gelling.

[mobileman]

Any luck? I have the same problem on my 01 f550 220000 miles