MicroSquirt.com read only forum (Jan.15,2018)

Thanks for the replies guys!
I've got a new problem. With the MAP sensor disconnected from the manifold, the engine idles without problems. When I connect the MAP sensor again, the engine dies. When I attempt a restart, the engine fires and dies right away.
Any idea what the problem might be?

What are your MAP readings, maybe you have wired up the 5V Vref or MAP sensor wrong way?

I would imagine it fires, because it is "cranking", then it goes "poop" when it reads the MAP signal.

What does the MAP sensor read when it is connected and when it is disconnected, with no rpm and at starting rpm. If it reads say 50 connected and and 100 disconnected, then your fuel would be cut in half - so engine won't run. But that just means raise your cranking rpm. If your map works, reads around 100 or so (less at high altitude) with no rpm and then drops to 60-30 with rpm or just by sucking on the hose end, then just plug in the map and try to figure out why it won't start.

MAP shows 115 with the engine out and drops to about 30 whilst cranking. I think it dies because of lack of fuel after start. I played around with the after start enrichment settings which showed some improvement, but it still dies after a second or so. It almost looks like it's not picking up the fuel map after the initial start. Anybody suggestions?

It is important to be sure that the engine dies after cranking, by that I mean look at your cranking rpm input and verify rpm is higher than this number when it dies.

If that is true, then you can increase either the VE at a map of 30, rpm around idle. Or you can increase your afterstart enrichment. It doesn't really matter which, because as soon as you can get it to idle on its own and the engine is completely warm, so there is no temperature enrichment, you are going to tune idle fuel(VE) and spark, tuning each until you get the lowest map value you can get while the engine still runs smooth with no surge. Then you never change that again unless there is a really good reason and you understand why you need to change it. Then you wait until the next day and you may not be able to keep it running. Then you need to adjust your after start enrichment - you now know your idle fuel is ok, so you only have to play with ASE. Of course you have to keep repeating this to cover summer and winter conditions, but eventually it will be completely tuned.

Björn the Bear wrote:MAP shows 115 with the engine out and drops to about 30 whilst cranking.

OK, 115 is slightly high unless you are underwater ;-) (have you calibrated your MAP sensor) but what is your VE set at? Do you have a .msq you can post? I too would just increase the fuel until you can get idle to catch and retune after. It sounds like you definitely do not have enough fuel. ASE or AfterStart makes a difference, but you can cheat just by ramping up fuel, and all that happens it will have too much as the engine warms, but by then you'll hear this and be reducing the VE values to compensate.

Give us some info and we will be able to help better.

Thanks again for the replies guys!
I'm still using the base fuel map that came with the ECU. I'm running a wide band lambda sensor which (I think) is set for a target AFR. I've still got issues with the MAP sensor because it's shows 115 kpa which, as stated before is slightly high. I'll need to fix this first.
Another issue I've got is with the idle control. I'm kind of a newbe and I'm not really sure if I've got the right settings.

I'm using the standard Ford Zetec inlet and injectors (175cc) and standard idle control/warm up, but I don't know which setting to use.
As I was playing around with the ASE, I've got it running again although it wasn't running very well. But I did manage to get it to run for a couple of minutes. So it must be one of the idle setting with a cold engine. One thing that did caught my eye was that the AFR "yo-yo's" around. It goes from about 13 to 17 like a on/off switch.

I've posted my MSQ file. Could somebody have a look and tell me were I go wrong? I could really use your help as I can't seem to be friends with the MS manual.