Anybody help with shotgun blasts coming out of exhaust!

[Sharino]

Car has a real hard time starting, was running decent but always needed work on the cold start issue. right now if I try to start it, it will crank for 20 seconds and they fire what sounds like a shotgun and wake up entire neighbourhood! It is a little colder here than what I normally drive the car in, about 5-10 celcius. I tried a few days later was able to get it started and it drives fine. Then tried again a few days later and same shotgun blast and cant seem to get it to start! Not sure if its beneficial to take a log of it not starting.

Car is a VW VR6 turbo with MS3X running full sequential.

[jsmcortina]

[Sharino]

sorry

Thanks for any help!

[billr]

What is your injector flow rate? The MSQ shows "0". Battery voltage is high (up to 15V) and MAP is higher than possible, 115+ ambient (no running/cranking). Any clue what is going on with those two?

[Sharino]

Injectors are 630cc, the calculator was not filled out but final required fuel value is correct, 5.3.

Battery was on a charger while trying to get it running when i took the log, didnt think that would effect anyting.

What do you mean by MAP is higher than possible? Sorry dont understand. Its about 70 when it was idling, is that not correct?

Problem is now, I cannot even get it started, just get a shotgun blast!!

[billr]

Look at the beginning of the log, before the engine is started. MAP is the barometric pressure, and reading 115.5 That is impossible, as the highest baro ever recorded on Earth is just a bit above 108 kPa. That is a big hint that your MAP readings aren't going to be correct. When I plug 630 cc/min into the calculator, I get 3.6 msec for req_fuel. Is the stoic you are using not 14.7? That 15V supply shouldn't be a problem, I was just pointing out that it was unusual, and might be another hint. I am kind of surprised the charger "swamps" the battery that much though; I didn't think most common chargers will take the battery voltage up that high.

Getting back to your posted problem: Have you verified spark timing, with a simple light and on all cylinders?

[Sharino]

The feeling i believe is correct. Its a 3 liter 6cyl with 630 injectors which i get 5.3.

I think you are onto something with the MAP. When I just have accessory on and no running the car (it wont start anyways!) I turn on the Fuel Load gauge and it sits at 115kPA and the barometer Gauge sits at 100kpa which I understand it correct.

Problem is I don't really understand what the fuel load gauge is compared to the barometer. Why would it be that high? Faulty MAP sensor?

Any other tips or what i can check greatly appreciated!

thanks!

[billr]

Do you have the stock MAP sensor on the MS mainboard? If so, I think you are using the wrong MAP calibration for that. Look at an "example project" for the correct (default) calibration. So, this is a 3-liter engine, not 2-liter as shown in the MSQ? Providing erroneous data adds to the effort and confusion!

[Sharino]

I apologize for the confusion, I set the specs up for fueling years ago and never really looked again, not sure when that changed.

I believe I have the 4 bar Map built into the MS3X unit. I remember paying to get it upgraded when it was built.

I will try and research what i need for calibration unless you know.

Really appreciate your help/guidance!

[Sharino]

I cannot for the life of me get it to start again. I pulled out the plugs, they are all flooded. I let everything dry overnight. and reinstalled. I took a log this time of it not starting if that gives any clues. It gave the shotgun blast part way through trying to start it. Fuel pressure is good at 40ish PSI. Not sure what is causing this problem,

[CRSTune]

Other than what's already been said, I noticed in your logs that you're not pumping the gas (granted, you shouldn't have to). Is it any easier to start while you try and give it a bit of gas while cranking? If giving it gas helps, it might be too rich for that temperature or it isn't getting enough air.

One thing I noticed is that while cranking, the idle PW is around 60% which correlates with your cranking settings. However, immediately when the RPM rises above the cranking RPM, the idle PW drops to 23%. That's the maximum allowed duty cycle you have set in the idle settings. That may not be enough PW to keep the engine alive when it's cold. You normally want it to gradually settle from the cranking duty cycle to the run duty cycle.

[Sharino]

Thanks, i will look into what you recommended.

I can't even get it started with giving it that gas pedal/

Weird thing is, the car use to start, it was never good at starting but could always get it started. I am wondering if its more of a mechanical failure somewhere. I did a smoke test to make sure I don't have a vacuum leak. Really stumped!

[Six_Shooter]

If your plugs are fouled as you say, throw them away and install a new set. Even after drying out, cleaning etc, they will never be the same.

I've learned the hard way to just throw away fouled plugs. New plugs are needed to ensure proper spark in the cylinder.

[CRSTune]

Try adding 20% to your cranking pulse curve around the 13C and -1C marks and see if that helps (make a backup file before you do though). If not, go the other direction. The fact that giving it throttle makes no difference may be an indication that it's just too lean to start (which may sound odd since you've got backfire). I was looking at the time scale and realized this was you cranking for a good 5s to 10s at a time. The backfire might be because you have it set to wastespark and just so happen to get it to catch at the wrong time. Of course, I'm making an assumption that it's a calibration issue and not a mechanical one.