Just another 91 Miata VVT swap no-start
 

Hey guys,

So here's the background:

-91 Miata w/ 2003 1.8L VVT with 39,000 miles.
-MS3X
-Currently has oldish E85 in the tank
-FF640cc injectors converted to sequential injection.
-Using 99-05 Miata OEM trigger wheel (FM 36-2 in the mail)
-RB Headers
-Using 91 Coils and wires
-Followed the VVT swap guide

As for the problems, the car will crank but won't start. I have attached both regular and composite logs as well as my tune. Basically the car will crank, kind of fire, and not catch. After a while it smells like fuel. I feel absolutely defeated. This thing is kicking my ass. Any ideas?
https://cimg4.ibsrv.net/gimg/www.mia...e8e505bf33.png

losing sync, Reason 31

31 = Miata 99-00 - 2 cams not seen

Yeah i saw that. I don't know why though. I redid the wiring and doubled checked it today. It has power, ground and signal coming out. Unless there is another setting that I have to change in Megasquirt for it to work. Or the sensor could be bad I suppose.

settings didnt have anything that jumped out at me. suspect sensor and or any modified wiring associated. report back

When I got stuck where you are, it was because I had the fuel lines backwards.

flip your polarity to falling edge on your tune. you have a perfect signal, but your tune is still set for raising edge.

happy Thanksgiving. you're welcome.

Thanks guys. Hope everyone had a great Thanksgiving.

So here's what I did:

-Set tune to falling edge.
-Tune still set to going high instead of going low.

I'll post a picture of the fuel lines but I'm 90% sure it's right. When I swap them, the fuel pump makes a different (weirdish) noise. Below is a picture. Red is connected to red, blue is connected to blue.

To do today:

-Test all grounds
-Now that I have another helper, I'll go through the ECU and test all my wiring.
-Install 36-2 wheel
-Potentially empty E85 and put in new 93 octane and adjust tune.

Will keep you guys updated. If that doesn't do it, could it be a cranking pulsewidth issue? Keep in mind the car is cold. Colder than it's ever been ~35 degrees F.

https://cimg3.ibsrv.net/gimg/www.mia...453961ccd4.jpg

and post another composite log.

Not to be rude here, but when I step into a job to take over and all the wires are the same color....First thing I do is re-wire with colors. I just assume the wiring is fucked up if they couldn't use different wires per circuit.

You can ebay high quality wire in a color assortment for really cheap.

Will do. omw outside to try it now

You're good dude. No hard feelings here. I have it labeled with a label maker before, this is it the second wiring redo so that's why it looks like a shit-show. If everything works, then I'll clean things up a bit.

New log, new tune.

https://cimg8.ibsrv.net/gimg/www.mia...85035d3c76.png

I had a similar problem on my engine where it would crank but not start. I reloaded the basemap from DIYautotune and scaled the VE table by 1.5 and was able to get the car to start. Long story short, it ran like crap and the cause was the car's timing belt being way off. The belt wasn't aligned at TDC on the crank and the intake cam was 1 tooth off.

Okay, testing spark plugs. All 4 plugs are getting spark.

-Pulled a plug after crank and it's pretty dry. I suspect it's a fueling issue. Can anyone smarter than me confirm the fuel line orientation as seen above? Is the fuel regulator upside-down?


I suspect the timing could very well be off in addition to fueling issues.

Anddddddddd we're good!

A combination of checking grounds and flipping the polarity fixed it. Car fires right up and idles great. (A bit rich).

I owe you guys a beer if I ever see you in person.