Cold start capability vs overfueling with FDC bypassed

[JasonS]

I have been operating with the FDC bypassed for a couple of years and decided to turn the fuel down so that I didn't have to keep an eye on the pyro all the time. I turned it down 12 flat as listed here to put the fuel back at a stock setting. Would not start. Turned the fuel up until I the egt wouldn't exceed 1000/ 1100F at full throttle. I could still get 13 psi boost and was happy with the performance. However, it clearly has a harder time starting when cold. Stumbles for a bit at ~50F. Starts fine once warmed up. I backed off the droop screw 90 degrees but it still starts nowhere as good as before. The truck didn't seem to be like this before the FDC was bypassed and the fuel was at a lower setpoint (based on a lower maximum EGT). Does the FDC have any impact on cold start capability (allow a higher full position when initially started)? Do I need to back off the droop screw some more? Suggestions?

 

[Wildchild467]

I have a similar thing with my truck. I never knew what it was like before the FDC was bypassed, but it does start better when the fuel is turned up. I adjust my fuel by how much boost it puts out and how easily it gets to my max EGT. I recently pop tested my injectors and that did help it start better. I am also running about 90% WMO also. It was about 50 degrees this morning and it did start but still struggled somewhat. If I turn my fuel up a lot, it does make it start better, but I have crazy amounts of boost pressure. In 5th gear about 1500 RPM and then lay down on the throttle, I will reach 15PSI of boost at about 1800RPM and peg the gauge there yet, my RPM and EGTs will climb slowly. I would guess that I might be pushing 20 PSI of boost. I just do not want to stress my engine out much but the power is decent at that fuel setting. MY EGTs are always fine, but the high boost pressures make me nervous a little bit.

Anyway, If you have a boost gauge and pyrometer that is a huge plus. Do you know how good your injectors are and if the valves are adjusted properly? If not, I would adjust your valves (because its easy and a good PM), check your timing (because its easy and free to do) and have your injectors pop tested and set at 3000-3100 PSI. You could turn up your fuel more to make it start easier, but if one of those other 3 things are not up to par, you wont get the full benefits/power of the engine. After adjusting my injectors, I don't know why I didn't do it sooner. It does help them out a lot having all of the injectors clean and popping at the correct pressure.

 

[Flyingvan911]

Mine doesn't start too easy below about 30 degrees. I just give it a little shot of starting fluid and it fires right up. It just needs a little something to fire off the diesel.

 

[Floridianson]

You could think about a block heater for water and the magnet one for the oil pan.
Watch turnning the droop too much a little goes a long way do add or decrease fuel from 1600 to 2000

 

[JasonS]

On the advice from deuceman51, backed out the droop screw about 1.5 turns. Started up this morning at about 2°F. The flame heater did work but it seems like it works best if you modulate it a little bit off/ on while cranking instead of holding it on.

 

[brianp454]

When I got my truck it did not have the FDC bypassed and it would rough start and start and want to die. If memory serves I put a video on youtube of it. I had my injectors tested and they popped at about about 3000-3200 psi if memory serves. I pusted info in here in one of the threads on injector testing.

After I bypassed the FDC it would start right up and never die. Big difference. I haven't touched the fuel settings yet and watch the pyro and boost, backing out when it drifts up.

I would suggest bypassing the FDC. It worked for me!

 

[Floridianson]

Do believe he said his was for years.
Believe no matter wether we increase droop to allow the fuel collor to go higher or increase the main fuel twin nuts we are raising the collor and closeing the spill port longer. Don't know if you ever tryed to start it before you changed the droop but some have tryed putting the fuel peddel to the floor to make shure the collor is up as far the the fuel control setting will allow. Yes when the truck is off and shut down cable is in the run pisition the fuel control should be at the 7-6 oclock pisition to start then go to idle pisition. Now this does not mean the collor will hold the spill port closed all the way till injection. Never does never will but if you increased (don't do it ) the twin nuts inner nut till the wedge stud could go no farther out that is getting close to full spill port closer but do believe we can never get the spill port to close compleaty. Will say the the longer the spill port stays closed the easer it should be to start.