Ut oh..what did I break?

[xminos]

Standard info:
MS-II V3 board
Ford 5.0 engine
I made the engine wiring harness
MSD 6A with a 94/95 external TFI ignition
GM IAT & temp sensor
Current running configuration:
http://performanceclassifieds.net/megas ... 291715.msq


This was a perfectly working MS setup. Engine ran fine for the last two months.. Sadly in an attempt to do some engine bay clean up I degreased the engine bay and washed it off. After letting it sit for a week I went to start it up and now I'm having issues.

The first time I tried to start it (not logged) it fired a bit drunken sounding but did start. Then the engine surged into 2-3k on it's own and I shut it off. After a couple of more runs like that I got my friends laptop to do a quick datalog.

The log below is of the engine trying to start (it won't start now). I have confirmed that I have spark(at least in some form as it does fire every once in a while) and fuel (I can hear pumps going, as well as smell unburnt fuel).

http://performanceclassifieds.net/datal ... 221740.msl

I can't believe I jacked something up after it took me so long to get this thing running. What did I do? Is my MSD toast? (How should I test for that?)

http://performanceclassifieds.net/datal ... 221740.msl

Thanks guys..
-Tim

[Matt Cramer]

Usually the MAP reading drops when the engine cranks. I see yours isn't. Check to be sure it didn't come unplugged when cleaning the engine compartment. If it is plugged in, check it with a vacuum pump. If the MAP sensor is unplugged or nonfunctional, it is likely to add enough fuel to flood the engine.

[xminos]

Lance/Matt, thank you both very much for your input and suggestions.

Lance- I've checked all the fuses and tried to go over much of the wiring to confirm nothing is out of order. So far everything looks good.


I snagged the laptop and went and sat in the mustang for another 10 minutes or so today trying to get it started after I confirmed the vacuum system is still in order. The line was plugged in as it should have been but I went ahead and reseeded it and ensured there were no kinks or bends any where in the rubber line. Then I tried to start it up a few more times.

http://performanceclassifieds.net/megas ... 231243.msq
http://performanceclassifieds.net/datal ... 231244.msl


It tries to start and fires a few times but will never get beyond that. It doesn't sound like a drunkin firing but like a normal start up. It just seems like perhaps one side of the engine isn't firing or my MSD box is perhaps toast?

I really wish I knew what to look at in these logs to troubleshoot this thing better. Sorry to keep relaying on you guys. I am learning however.

Usually the MAP reading drops when the engine cranks. I see yours isn't. Check to be sure it didn't come unplugged when cleaning the engine compartment. If it is plugged in, check it with a vacuum pump. If the MAP sensor is unplugged or nonfunctional, it is likely to add enough fuel to flood the engine.

I took a quick look at the MAP values of this latest datalog and it does drop when the engine cranks now.

Thanks again guys. I truly appreciate the help. I'm still pretty frustrated at myself that I screwed up my system some how after it took me so long to get it running.

[xminos]

I went through all of my ignition wiring, everything is nicely soldered together still.

So I went down to the parts store and replaced the TFI module. Sadly no change..

Next on my list is to swap out the MSD box... see if that is the issue.

[xminos]

I went through all of my ignition wiring, everything is nicely soldered together still.

So I went down to the parts store and replaced the TFI module. Sadly no change..

Next on my list is to swap out the MSD box... see if that is the issue.

I tested my MSD box via this method: http://www.msdignition.com/forum/showthread.php?t=74

It sparked fine. I know that doesn't mean there's not another problem with it but that at least rules out a portion of the unit.



Any further suggestions Matt/Lance?

[xminos]

Well I guess I need to find out if the problem is with my MS unit or my wiring.

I went ahead and ordered a MegaSquirt Stimulator from DIYAutoTune. We'll see what that has to say/show.

[xminos]

So one thing I have noticed when comparing my datalogs to that of other running mustangs with MS.

My dwell is flat. When it does move (drop) that is when the engine will fire. I researched what dwell is (again I'm a complete EFI dumbass):

Dwell angle is a measure of the duration of time that the primary circuit of the ignition system is closed to energize the primary windings of the coil. It expressed (and measured) in degrees of rotation of the distributor rotor, hence the use of the term "angle".

Ok, that helps. It's ignition. My question is how do I go about testing and try to narrow down the issue? What wire/device sends dwell to the MS is it the MSD or the dizzy?

I'm going to try to take the dizzy out and spin it by hand. I have another dizzy I can swap to see if that resolves my issue. Sadly I have a feeling that it will infact be the MSD box for some reason still.

Hopefully someone can enlighten me on what wire/device sends the dwell data to the megasquirt unit as well as take a look at my original data logs to confirm what I believe to be the issue (at a high level).

Thanks all,
-Tim

[Matt Cramer]

Hi Tim,

How exactly is your MS wired up? Is the MS wired to control spark through the TFI module, or wired directly to the MSD box? Sounds like a problem with the

MSD boxes do not have dwell in the usual sense, and the TFI module if being used will expect a square wave with a 50% duty cycle. I'd also be interested in seeing the data log with the odd dwell behavior, along with the MSQ from the unit at the time you made the log.

[xminos]

How exactly is your MS wired up? Is the MS wired to control spark through the TFI module, or wired directly to the MSD box? Sounds like a problem with the

MSD boxes do not have dwell in the usual sense, and the TFI module if being used will expect a square wave with a 50% duty cycle. I'd also be interested in seeing the data log with the odd dwell behavior, along with the MSQ from the unit at the time you made the log.

My configuration and data logs are in my posts above. Let me know if you don't see them or if the links are down. What I'm refering to is

As for wiring..
Here is how I'm wired up for the most part.



Here is a picture of it normally running:


Here is a picture of what I'm referring to. Notice how the dwell is completely flat until it fires. Then remains flat well after that.

[Matt Cramer]

Ah, sounds like the coil driver output may be damaged. What do you have in the Q16 slot?

[xminos]

Ah, sounds like the coil driver output may be damaged. What do you have in the Q16 slot?

I have no clue. I bought this pre-built and had Peter Florance mod it for me to work on a mustang. How shall I test for this Matt?

[Matt Cramer]

I'd check it on a Stim first, see if the IG LED blinks on and off. Also take off the cover and check the markings on the transistor there.

[xminos]

I'd check it on a Stim first, see if the IG LED blinks on and off. Also take off the cover and check the markings on the transistor there.

Alright, thanks Matt.

My stim hasn't arrived yet so I'll put this on hold until it does. I was *really* hoping it was wiring/dizzy/msd as all those are relatively cheap fixes. A fried MS box is not going to be kind to my budget.

[Matt Cramer]

If you're handy with a soldering iron yourself, fixing a fried MS box in this case would probably be less than $20 if the problem is what I think it is. I would not be surprised if it is just a single damaged transistor. The Stim will be the easiest way to find out unless you happen to have an oscilloscope.

[xminos]

I'd check it on a Stim first, see if the IG LED blinks on and off. Also take off the cover and check the markings on the transistor there.

My stim arrived today (thanks again DIYAutoTune).

Dwell looks perfectly fine on the stim. The IG LED stays on constantly. I took a quick data log (I dunno if it helps at all) http://performanceclassifieds.net/stim.xls

What does that tell me? Back to my MSD/Dizzy/Wiring?

[Matt Cramer]

The IG LED should not stay on constantly - it should pulse on and off. Sounds like a problem with Q16.

[xminos]

The IG LED should not stay on constantly - it should pulse on and off. Sounds like a problem with Q16.

Hrmm.. I'll double check. But I did see the dwell gauge move as if it was normal in Megatune when hooked up to the stim. The log shows it moving (flat lines because I was playing with maxing it out).

I'll double check it again and make sure the IG LED stays on constantly. If that is the case what is the replacement part for Q16. More importantly does DIYAutoTune sell it separate?

Thanks again for your help Matt,

-Tim

[Matt Cramer]

The gauge shows what the MS "thinks" it's doing, but the Stim shows what it really is doing. The LED turns on when the spark output is grounded, but if it's grounded full time the MSD won't fire.

And yes, we sell replacement parts in the MS Service Parts section of our website.

[xminos]

The gauge shows what the MS "thinks" it's doing, but the Stim shows what it really is doing. The LED turns on when the spark output is grounded, but if it's grounded full time the MSD won't fire.

And yes, we sell replacement parts in the MS Service Parts section of our website.

Ahhhh.. Makes perfect sense. Hence the it'll fire once (maybe twice) upon initial key on but not after that...

Sheesh. Well done Matt. If you lived any where near the midwest I would buy you several beers. Since I don't I'll continue to sing your praise anytime I order from DIYAutoTune. I don't know what they pay you but you obviously need a raise.

I found the part I think I need on your website. I'll make a go at it and see if I can do it. Thanks again!
-Tim

[xminos]

Small update-

I got infront of the stim again to see if the IG light on the stim flashes or not.

The IG light on the stim does flash but goes solid above ~350 rpm.

Not sure if this changes things at all.I doubt it would but I wanted to be sure to state it.