Laur3ns

Hello all,

Something needs solving: I shut my MSPNP 94 car off when hot and come back hours later, turn the ignition on (not cranking) and I hear a POP and smell burnt fuel in the interior. If I start after that, the car cranks very hard, as if it is not getting fuel and will run rough for a while.

I've datalogged the POP, not the cranking yet.

I looks like some fuel is left somewhere and ignited when I turn the ignition on. Does MSPNP fire all spark plugs when powering on?

Thanks for you input!

Joe Perez

iTrader: (8)

Yes. Yes it does.

It's not really intentional, just a side-effect of the fact that MSPnP (along with pretty much all the rest of us using regular MS) has the ignition output drivers configured in such a way that they float high for a moment at initial powerup, before the CPU has booted up and pulled down the outputs. Same reason that the ignitors fry when you do a firmware update w/o disconnectiong them.

It has been rumored that if you go into the Cranking Settings menu and change "Fire Priming Pulse" from "Power Up" to "After 2 Secs" that it may fix this. I don't see how, since the ignition glitch happens before the CPU would even have a chance to fire the pulse, but ymmv.

paul

iTrader: (21)

the "After 2 secs" doesn't eliminate it for me.

WestfieldMX5

might be a leaking injector

paul

iTrader: (21)

That's what I've been leaning toward because the problem followed from one car to the next when I transferred my 460s. I'm pretty sure the car with 550s doesn't do it anymore.

Laur3ns

@paul: so, you have a pop + exhaust smell on ignition?
I have brand new flow tested RC 550s from BEGI. I am not looking forward to RMA-ing these. How do I check which one?

Joe Perez

iTrader: (8)

That is very possibly the most logical explanation I've heard for this phenomenon, and explains why quite a large number of us have never experienced it.

paul

iTrader: (21)

hell if i know how to without making a mess.

get an extra fuel rail. stick the injectors in it and find a way to secure them. then pressurize the rail i guess.

kotomile

iTrader: (24)

after two seconds works for me and Ben

Laur3ns

Tried the 'After two seconds', but that doesnt change the behaviour. Only takes longer to crank the car.

From what I observed, it only happend when I leave the car for 2-4 hours. Not when I shut down and start directly. Not when I leave the car overnight.

I find it hard to think it's a leaking injector because they are new, flow tested from BEGI, installed by a professional shop and the car idles like a charm.

I am running Megasquirt. Could the charcoal cannister (that stores fuel fumes) be related in any way? Say it has stored fumes, Megasquirt boots and releases the cannister (does it control it in any way? or is the valve always open?) and fire a spark at the same time?

chucker

iTrader: (4)

My experience exactly.

Mine only does it after sitting overnight.

I've had two sets of professionally flow-tested/cleaned injectors (injector rehab) installed in two different 1.8 engines and I still have this condition at nearly every cold start.

I run standalone MSI so the charcoal canister is not affected.

I've resolved to living with it.

EDIT: I've also tried lowres firmware versions as well as my current 10g. I observed zero difference between them in this regard. And I've tried fresh .msq's (figuring corruption as a possible culprit) but that made no difference.

wes65

iTrader: (7)

Anyway, i had this problem nearly every time i went to start my car. I changed "Prime Pump when" to "Prime Pulse>0*^"

"Fire priming pulse" to "after 2 secs"

"Priming PW source" to "standard prime"

"Standard Priming PW: (mS)" to "0.0"

That almost completely solved it. I still get the pop maybe 1 in 10 times. One thing i have learned to do is hold the throttle to WOT while turning the key on and then letting out before i crank. This will help keep from blowing an intake gasket or blowing vacuum lines off the intake manifold.

Braineack

iTrader: (62)

your not going to be able to start the car tomorrow.


tune your cranking pulse table correctly for your 550s.

wes65

iTrader: (7)

I assume you are talking to the OP. However, i dont understand, did i miss something in the thread? I have been running with these settings for a month or more now and my car starts perfectly every day. It's been down in the low 50's and high 40's and it starts just as well as when it is 90 outside. I would go as far as to say that it starts better on the 550's than it did on the 460's. I get no backfires while cranking only before cranking. Just like the OP.

Laur3ns

Good to hear I'm not alone. Has anyone pinpointed down the exact cause of this behaviour? Is MS floating all outputs high at startup, including injectors and spark and therefore it backfires where the intake valves are open? Is the cannister involved in any way, like I suggested? Something else?

I want to totally understand what is happening so we can solve the issue by attacking the root cause.

wes65

iTrader: (7)

Well, i have no charcoal canister so that cant be it. We know that the spark is pretty much unavoidable so we need to figure out where the fuel is coming from. A leaking injector is what i always attributed mine to but i've always had used ones. Since yours are new we can rule that out.

wes65

iTrader: (7)

I dug up my old emails with Matt at DIYautotune. This is what he had to say. I told him i fixed it but a couple of days later i noticed the problem again. As i said this made it MUCH less frequent but it still does it occasionally. I tried to make these legible.



Wes Wingham <wes.wingham@gmail.com> Wed, Aug 13, 2008 at 1:48 PM
To: "DIYAutoTune.com Sales (Matt)" <websales@diyautotune.com>
I have the mspnp9495 and whenever i turn the key to the on position
before a cold or warm (not hot) start, there is an intake backfire. It
seems to be exactly 2 seconds after the key is turned to the on
position and will occur before cranking. If i don't allow 2 seconds
between key on and cranking, it will usually backfire while cranking.
I have recently changed from 460cc injectors to 550cc injectors and
the problem occurred with both sets of injectors. Any idea what may be
causing this?

Thanks in advance,
Wes Wingham

DIYAutoTune.com Sales (Matt) <websales@diyautotune.com>
Try turning off the priming pule and see if this has an effect.

Thanks,

Matt Cramer
DIYAutotune.com Technical Support


Wes Wingham <wes.wingham@gmail.com> Wed, Aug 13, 2008 at 2:55 PM
To: "DIYAutoTune.com Sales (Matt)" <websales@diyautotune.com>
Okay, i see 2 options. One that says prime pump when: and i have that
set to always. The other says fire priming pulse: and that is set to
after 2 seconds. Should i change it to prime pump when prime pulse>0 ?



DIYAutoTune.com Sales (Matt) <websales@diyautotune.com> Wed, Aug 13, 2008 at 3:03 PM
To: Wes Wingham <wes.wingham@gmail.com>
Set it to when prime pulse >0, turn off the priming table, and set the priming pulse to zero.


Wes Wingham <wes.wingham@gmail.com> Wed, Aug 13, 2008 at 3:03 PM
To: "DIYAutoTune.com Sales (Matt)" <websales@diyautotune.com>
Oh, change it to standard table from priming table and set it to 0 ms.
I see now. Thanks!


Wes Wingham <wes.wingham@gmail.com> Thu, Aug 14, 2008 at 10:07 AM
To: "DIYAutoTune.com Sales (Matt)" <websales@diyautotune.com>
That fixed it. Thanks for your help!


DIYAutoTune.com Sales (Matt) <websales@diyautotune.com> Thu, Aug 14, 2008 at 10:10 AM
To: Wes Wingham <wes.wingham@gmail.com>
Glad to hear that fixed it. You may need to adjust the cranking pulse width a bit with this change.

Braineack

iTrader: (62)

The root? Incorrect cranking setting. Specifically I'm convinced it's too much fuel in your cranking table. I've found no matter what the settings are, if the pulse table is poorly tuned, then you'll pop and backfire.

If you cranking table doesn't look close to these:

then you'll probably run into these popping/backfiring issues.



I'm surprised your car will start with standard prime set to 0.0ms. Scratch that, it makes sense and it supports my theory. Setting Stand Prime to 0.0ms prevents the priming pulse to happen, otherwise the prime injects based off your cranking table. Too much fuel during the prime and you'll ignite a lot of excess fuel.

wes65

iTrader: (7)

Okay, correct me if i'm wrong but too much fuel in your cranking table would cause a backfire while cranking. The MS doesnt even look at the cranking table until you start to crank. Therefore the cranking table should have nothing to do with a backfire that happens BEFORE cranking.

Braineack

iTrader: (62)

Standard Prime which will inject a fixed amount of fuel as specified in the Standard Priming PW box, or you can select Priming PW Table which will have your priming PW be based off the Cranking/Priming PW Table.


I went through all this last Decemeber...I haven't had these problems since. Failure to start the car and having to dry your cylinders out for upwards of 30 minutes before going to work because your cranking table was incorrect, when it's 30 degrees out, was all I needed to wise up and get the cranking setting tuned properly.