So, though I do not wish to further confuse people trying to track down a 'lazy' starting issue, I do have a fix for it in my case. My main symptom was that my starter/battery just sounded weak when starting my pig. Never failed to start though occasionally I did have to turn the key twice to get it to start. My first thought was the same as many, replace the battery. So I replaced the battery, and unfortunately it had no change in the way it sounded when starting. No fix.

So next I assumed it might be the starter itself since previous owner had metal coolant pipe installed, I thought maybe it had leaked coolant into it when they had the plastic pipe issue and maybe the starter was just dying. While wrestling with the idea of replacing the starter, I also started researching other little things that were bugging me. Mainly the fact that sometimes sitting at idle at red lights, my idle would occasionally dip down a bit for a second and recover but I always felt it. I tried cleaning throttle body and resetting it, same thing would happen every now and then. No fix.

Started reading more and more about fuel pumps. Found a thread that explained how to test pumps by pulling fuses and starting the car. Guys with 955 cayennes discovered that when the left fuel pump (primary) would die and thus their truck would stop running, they could turn it off and pull under hood fuse number 14 to force the ecu to use the right fuel pump (secondary) and get home fine. So I decided what the heck, I'll pull some fuses and do a quick fuel pump test. Here is what I did:
Step one...
Truck off, key out, pull fuse 14 (primary pump), key in and start, let run for a few minutes to make sure pump is good. Turn off and replace fuse 14.

Step two....
Truck off, key out, pull fuse 13 (secondary pump), key in and start, let run for a few minutes to make sure pump is good. Turn off and replace fuse 13.

If your truck passes both, you can assume both fuel pumps are fine.

Here is where mine got interesting, step one and truck started like always and ran as it always did. Replaced fuse 14 and went to step two. When I went to start truck I noticed the starter spun faster and fired up stronger, however it died after running for about 10-15 seconds. Tried again and same results. So I concluded that my left (primary) fuel pump was toast. So I ordered a new one and replaced it. I know, I know, everyone says you should replace both but I really wanted to test out and see if that was my starting problem the whole time after being surprised by the way it sounded during test. Left fuel pump installed..finally a fix.

Long story short, if having idle dip issues and/or a weak or slow sounding starter, you might want to go ahead and run the fuel pump test by pulling the fuses. Only takes a few minutes and could either find the problem or mark another possibility off the list.

 

That sounds like my issue.. I'm going to test this when I get home today. Its never not started but it just sounds weak when starting and I have an occasional rough low idle.

 

I have the same sluggish sounding starter issue so I will be testing this out.

 

Post your results guys if you don't mind. I've noticed there aren't that many threads with actual fixes which can make it hard when trying to diagnose things. Thanks!

 

Mine started with each fuse pulled. With 13 pulled it didn't turn over on the first try though.

 

Did you drive it any on one pump? Funny, mine didn't even try it start the first twist of the key with fuse 13 pulled either. Guessing the ecu had learned to just run off the other pump and it needed a 'nudge' to try the other pump again.

 

I didn't, I actually didn't even try to drive or let it idle for any period of time, just a couple of seconds. Basically as soon as it started I turned it back off. I'll re-test it with giving more time for it to run on a single pump sometime this week or weekend.

 

Interesting post.. subscribed. Would like to see more feedback from other DFI owners.

 

I would at least let it sit and idle on each pump for a minute or so. Mine started and ran great on the primary pump but would die after about 15-20 seconds every time. That is why I replaced that pump. Just a thought.

 

I did that over the weekend, it ran just fine with either fuse pulled. Im guessing my laggy start is something else.

 

Tried this out as well, but started and ran fine. My sluggish starting sounds like a low battery, and one piece of evidence that it might be battery related is that the colder it gets overnight, the more sluggish the start. But I just changed the battery a year ago, so still scratching my head on this one. In any case, thanks OP for letting us know about this useful diagnostic trick!

 

No problem guys. Sorry it didn't help out your issues. I've read about grounding wire issues that cause the symptoms as well. Might also want make sure the alternator is putting out correct voltage to keep battery charged. Good luck guys

 

No apologies necessary, thank you for making this post!

 

Thanks for the write up, rep given. I had similar issues and after step 2 figured out it was my secondary pump.

 

i'm getting very sluggish start and sometimes have to crank it 5+ times. It eventual starts but takes very long especially after sitting more than a full day.
Pulled each fuse....runs fine. Besides the secondary pump was replaced 15k miles ago...
I'm thinking clogged fuel filter or fpr...