General Supercharger Thread

DW650cc injectors, and I hear the fuel pump when it’s on the ON position. It makes it a bit better when I leave it for a few seconds but definitely not like stock. Still sounds like it doesn’t wanna start

 

Your new fuel pump relay is triggering from the stock fuel pump power wire, so it doesn't prime, it only starts pumping when the engine is cranking. You are likely hearing your intercooler pump running at key on, not the fuel pump. Did your mechanic install the check valve? That should help a bit.

 

I ordered the check valve but haven’t installed it yet. I hear a hissing noise when i turn my key near my fuel tank.. thought it was the fuel pump

 

Yeah, that would definitely help low speed/idle but probably won’t make any difference at 20-30+mph without an additional coil/heat exchanger to increase the actual capacity.

 

When your pump is running you should hear a low humming sound, not hissing from the tank. The fuel pump relay is triggering from the stock pump power, so the pump doesn't turn on until the stock pump would normally turn on, which is during cranking and not Key-On (Ignition).

 

I have my pump wired to battery and ignition. The pump comes on immediately. If I wait more than 3 seconds I'll occasionally get an extended start. I'm on denso 750's with a check valve.

 

No more extended start issues here

 

Do tell what you suspect cured this horrible affliction!

 

There's been a number of people I've tuned where there was an extended start issue and it somehow got resolved. It seems to be in relation to the injector constant value in the tune, and there's a window where it makes the truck happy during start up. There's also an additional value called cranking pulsewidth that only some ECMs have and that can also be used to help start up. My understanding is the startup sequence is kind of dumb, in that the truck isn't gathering much information from the sensors, so presumably if the base values for the tune are off then it won't start nicely. Once it's running the truck can compensate and dial itself in.

With that said, more often than not there's no issues with startup. On my personal truck I can run an injector constant of .06 to .16 and the truck will run 100% fine and start every time. @armyoffoo had bad startup issues, and his setup seemed to be specifically happy at ~.09 for injector constant, and by .10 it was having issues. @Fastlane47 was an absolute pain and the injector constant alone seemed to make no difference and we moved it all over the place, and would move cranking pulsewidth and that would sometimes be a temporary solution and sometimes not work at all, and then one day with a specific injector constant AND cranking pulsewidth and it (knock on wood) was fixed all of a sudden---but that was only needed with 1000cc injectors, his 750s there was never an issue.

In conclusion, there doesn't seem to be a one size fits all. But from my experience, it seems to primarily trace itself to injector constant on some trucks with some injectors. That brings in another hurdle to work around, but I would start there of increasing/decreasing injector constant by 10% and work it around and see what happens. And if you have cranking pulsewidth control, then try dropping it by half too and see if that helps.

 

Ok, Rey i just realized after the new tune I haven't experienced any...knock on wood. Oh wow! Crazy I tell ya...
Injector constants being raised?

 

Yeah we tried doing all those things and no change in the warm starting issue. Then reached out to Mat at VF to verify we are hitting the tables correctly and no work needed done on the definition. Mat didn't identify any other tables.

When the engine is cold I can start it and turn it off 10 times in a row and it's fine. That being said I have been meaning to reach out to you. If I decide to take the plunge of the 77.5mm I would likely make an appt with you to do it all and retune if you would be interested. I think you already suggested I fix the starting issue before further modding so here I am.

 

The cranking pulsewidth has tables based on temperature too I think, and there's also the MAF air temp correction. Maybe try setting those so they all read the same as the cold start values and see if that helps? I'm not sure. Rey was having starting issues on his truck and then I tuned it and it went away and I have no idea why. It's pretty hit or miss.

I'm certainly down to give it a try tuning it, but no guarantee it'll be any better. I also haven't messed with VFT to any useful extent. I was hoping to start experimenting with VFT on my wife's GX460 but I'd have to send the ECM in so Mat can decode it which I'm on the fence if I want to do that.

 

@snivilous I used to have occasional extended starts when warm. Any difference in my or reys tune?
Probably quite a few changes but...

 

Used to? Did it stop after the airload changes for the throttle body?

 

Who knows lol this one’s a weird one.

 

Yeah. Usually when warm but only a few times. When you wrote the new tune I didn't even realize it but I didn't experience any. Only when @reywcms posted he used to. I was like oh yeah I haven't had any.
I know the injector constants were changed quite bit. But...

 

Quite a few pages back not sure if it was @Silver17 or @Saltyhero13 who mentioned changing up the injector setup to stop them from being rich at startup? Not 100% or me being an old man rambling...

 

Yea injector constant changed a lot, plus the airload. Could be either of them, though I haven't messed with airload enough to know if that makes a difference to starting.

 

Before you start your truck, adjust the passenger side view mirror so that you can see what comes out your tailpipe. When I had long crank issues, there was an over abundance of fuel and it would belch sooty exhaust, so I was convinced that it wasn't a lack of fuel. While I had the FiveO 750s in, this soot is what was happening. I tried everything I could think of in the tune to try to figure it out. I even exchanged the injectors for another set of the same brand and flow, the second set gave me the same trouble. I even drove my truck to sea level (I live at 8k ft) to see if that made a difference.

Nope.

The only resolution for me were different injectors, as a matter of fact, any other injector was fine. There was never an issue when the truck was N/A with the stock injectors, not the TRD 535s, nor the ProSpeed 750s that @snivilous sent to me, which I'm currently using. Just the FiveOs; two sets. I sent the last set to @Mdl to try out, as he doesn't seem to have issues with his set.

As to the exact cause of the issue, it remains a mystery. We've just kind of fumbled about until it stopped, or just kind of faded away.

 

In my case, the same injectors started fine.. but it started have extended cranking after I installed the Prospeed fuel rails and lines along with hardwiring my fuel pump. I do think what I’m hearing is my fuel pump since it’s pretty noticeable near my fuel tank but not sure why it’s not priming.. it’s really random. I could have an extended crank at the start of the morning, get to my buddies house and turn the truck off for 2-3 minutes then try to turn it back on and it’ll do it again.. but sometimes I leave it for an hour and it starts right up

 

Interesting. I'm sure the last thing that you're interested in doing is changing back to the stock configuration and stock fuel rails to see the that resolves the extended cranking. I'm not familiar with what's involved with the changes that were made, but would you be able to change back to say, the stock fuel rails retaining the wiring? Or the inverse? Which ever is easier. It's a pretty standard troubleshooting technique, make one change at a time and test. The last change that was made before the issue would be the most suspect.

 

With after market fuel pressure regulators your system will be at 0 pressure. Usually bleeds down after 30 minutes to an hour. I hard wired it to the ignition so it would come on before cranking. For you you're cranking without it being primed so it will take a bit until pressure builds.

 

I haven't experienced that since I installed mine...

Edit: Sorry, allow me to clarify. My pressure drops after a while, but I didn't experience any changes in starting behavior.

 

That is what I was curious about with the dw fpr mounted at the fuel rail. If it would lose pressure. @reywcms same?
Good to know! When I can I can pick up a few adapters and mount it at the rail. Just need to redo my return system. Maybe later...haha

 

Sorry, I went back to clarify what I meant.

Another edit: My truck hasn't been started in about two weeks, the FPR reads 13psi.

 

I added this pressure gauge a while back and mine also bleeds down after an hour. Stock rails and lines, just dw300 fuel pump and dw650cc injectors with the supplied Harrop FPR.

 

My Haynes manual says that after five minutes of being shut off, the fuel pressure can drop down as low as 21psi. I know that they're not the gold standard reference, but the book was within reach...

 

Same here

 

Interesting about the soot. I just noticed some the other day.

 

I thought mine was from running rich...