[glaser67]

Hey all,

Warmish day with no salt on the roads, so I dusted off the 408 f150 and had some fun. Been running a little lean on the OL and WOT side, so lazily bumped up the FPR a few cranks. My 30# injectors are almost at 90% duty cycle so I figured increase pressure and scale again from there. Started up fine and WOT is down to 12.8-13.0. Cool. Go to start after a drive and it just cranked and cranked until I shut off the HP fuel pump. (I have a HP pump within a surge tank that is supplied by the stock in-tank pump). I switch of the HP surge tank pump, crank, it fires, and before it falls on its face switch on the HP pump and all is well.

I've had ZERO starting issues prior to bumping the FP (presumably a few PSI) today. I cant think of a reason for the issue, and am just curious what the cause could be? just seems odd to me...

Thanks,
-Glaser67

[cgrey8]

Most strategies don't rely on MAP or MAF on crank. The tune has a function or table that is hard-coded to fire the injectors a FIXED amount of fuel based on ECT (and possibly voltage).

Crank usually doesn't have to be that precise. It just needs to NOT be lean and not be OVERLY rich so much that you flood it. If bumping the pressure up is causing hard starts, it sounds like it might've been a bit on the rich side to start with and this pushed it over the edge.

The 1st thing you need to identify is at what engine temp conditions this is happening. Only when cold or hot? Or at all conditions? Nothing more annoying than having the engine crank fine when cold, but fail to crank hot. I learned that the hard way. My drives were mostly from home to work, then work back home that afternoon...or somewhere I'd be for an extended period of time. But I realized my tune was not right the 1st time I had to fill up at a gas station and it wouldn't crank hot. Fortunately I had my laptop with me so I could quickly diagnose the problem, make some adjustments and find some "hot start" values that would get the engine started. Unfortunately the values that got it started were AFTER the engine had gotten flooded. So those numbers still weren't right.

Point is, keep some starting fluid in the car until you get confidence in your tune at all running conditions. And if you are making these changes in the spring/summer, be prepared to revisit this the 1st time the engine has to start in freezing weather.

[JuiceSC]

Reduce Cranking PW, FN348, for the increased fuel pressure.