1990 1.6 turbo no fuel no start
 

Hi, first post since I normally just lurk the forums but couldn't find anyone with a similar issue to mine. I have a 1990 turbo 1.6 running an AEM ecu 680cc injectors. I have a no start condition that at first was intermittent it is now sticking around. I've replaced the plugs and they're all getting spark, but they're coming up dry so no fuel. The fuel pump is good, pulled the panel off behind the seats and I can clearly hear and feel it running as well as feel fuel running through the lines. Up at the engine I can hear fuel flowing through the lines all the way up to where they link up with the rail, however there is still no fuel getting through to the cylinders so no start. I have made it start using starting fluid, but it of course dies immediately. I'm relatively new to the Miata life, so hopefully it's something simple I'm just not seeing or thinking of. Any guidance in the right direction would be awesome so I can get back to the other Miata projects I have planned for the winter!

Update! So she started yesterday. Turned right over nice and strong like nothing was wrong, drove around just fine for approximately 15 minutes and shut it off. Today, back to no start again. Some kind of loose or corroded connection that gives the injectors power during startup?

Got a couple ideas from another forum, so I'm putting in a new adjustable fuel pressure regulator, and a new throttle body with TPS/IAC, just to cover a few bases. We'll see what happens 😑

Put in new throttle body/ TPS/ IAC. No change, except now my ecu is only reading 0 and 100% throttle instead of the whole spectrum like it was before , so I'm probably going to just really clean out the old throttle body assembly and swap it back in. I also noticed when I crank the engine, the tach doesn't move at all. Ordered a new CAS in case that's the issue, may also pull an injector and wrap the orifice in a cloth and run the fuel pump to find out once and for all of this is a no fuel situation. Hopefully I'm just slow at learning this stuff and the CAS will be the magic piece.

ps. Also going to get a signature and post a meet and greet thread with pictures once I get a few minutes to craft one. Sorry if I circumvented the proper customs and courtesies ��

While I don't have a good answer, I feel bad that no one has any helpful information to give you so far. Just as a side note, intermittent troubles are maddening!!!! It seems to me (as I'm sure it does you) that it's an electrical issue. For some reason the signal to the injectors is being cut. The why or what to check though, that's a tougher issue to solve. The only "thought" I do have is to pull an injector wire after a no start situation and then turn on the key and pull off an injector connector (taking the upper off I realize) and see if there is indeed voltage there. If there isn't any voltage there, then I would look into the wiring schematic of the car to try and track down the culprit. Good luck to you.

Hoping thats not the issue, i dont understand why that would be the case because when I bought the car around 4 months ago it was running great. then all of a sudden every once in awhile it would crank but not start, I'd come back later and the car would either still not start or crank up just fine and run like nothing was wrong. over about a month's time, it has now decided to never start. during the time I've owned the car I have yet to touch the tuning as I know nothing about the process. If it does turn out to be something tuning related, this is going to be a long road for me since I wot be able to move the car anywhere once winter really sets in here in ND, and short of paying a tuner to travel from Minneapolis, I'm SOL until I can learn the ways of the tuning jedi myself haha.

temperature related?

Don't believe so, my garage is heated and there were days at the beginning of this issue where it would no start at 75+ degrees out. on another temp related note, the temp gauge reads all the way at hot instantly when you turn the key on, but its been doing that since i bought the car. recently purchased a new coolant temp sensor and its going in when i do the CAS since the coil pack will be out of the way. I'll also run along the wires and see if there's just a loose wire or bad ground somewhere causing the gauge to do that, but ill feel alot better overall once I discover the culprit of the no-start and get that out of the way. Still in the beginning stages of this project so can't let anything get me down this early, I've got a long way to go!

So got out a test light and started probing the connectors on the injectors. They are all getting their 12v power. When I check the pulse side with the test light hooked up to 12v constant, I'm getting a dim lit up ground when the vehicle is off. As soon as I turn the key to on, the test light goes off. I'm getting no light pulses when I try to crank the engine, so I'm guessing no fuel injector pulse for some reason. Any ideas on wires to check for wear or breaks? I'm thinking maybe a bad signal wire somewhere that's getting a good deal of heat and or vibration that caused this over time. May or may not be the case, just looking for input. Maybe I did something wrong during my test?

Had another random day yesterday where it started up no problem and ran great. Even shut it off and restarted it a bunch of times and drove it all around town. Today we're back to not starting again. Far as I can tell I changed nothing. Still haven't tried the new CAS but I'm losing faith in myself. Used contact cleaner on every harness connection I could get my hands on, still no joy

Well the new CAS and fuel pressure regulator are in. Still not starting. I can hear the fuel pump running nice and strong and feel fuel flowing through the lines through the fuel pressure regulator, and the rail. However, I pull the plugs and they're all bone dry. Does anyone know of a setting I can change in AEM Pro that may be interfering with the injectors priming? What gets me is that it starts once a week or so and runs like a top. Maybe there's a ground somewhere in the engine bay that's loose and could be someway affiliated with the fuel system? If anyone can point me toward anything that sounds related lol I'm running out of ideas

log when it doesn't start, see if the AEM even injecting fuel. I -- still -- suspecting not.

Maybe I missed the part where you posted logs?

I bet the coolant temp sensor is the culprit, but we'll never know until you post a log.

Sorry, like I said new to the whole tuning concept. I'm not sure how to use the AEM Log program that's on the computer I got with the car, but I'll do some research and get back to you guys when I learn how to do it. I appreciate the suggestions and helping point me in some direction even though I'm not giving you guys much to go on. I do have a new coolant temp sensor so I'll put that in tonight and see what happens.

Hopefully this is the log file you were asking for, just logged while I was cranking.
Also replaced the coolant temp sensor, no change in the gauge, but Im thinking itll be a loose connection or bad ground in one of the harnesses behind the gauge cluster, because the oil pressure gauge acts finicky from time to time too.

Attached are a couple of pictures from when it was actually running haha :) (not sure how I feel about the wheels yet, but obviously that's a problem for when It's running reliably.)

The gauge and the ECU use two different coolant temp sensors.

This is the EMS I'm running in case it's some sort of red flag to anyone. The connections seem ok and when I'm cranking it with the laptop connected I'm getting varying readings for fuel injector pulse on 4 injectors. So I'm assuming the AEM is doing what it's supposed to and something else is interfering with that ground signal getting to the injectors. All four plugs are coming up dry so whatever is stopping them from firing is stopping all of them. Furthermore like I had mentioned, once in a blue moon it will just fire right up and run like nothing's wrong so I'd like to believe it's just a loose or janky ground somewhere and I can fix it and be on my way to better things. Just don't know where to look and the diagrams I'm finding aren't leading me anywhere.https://cimg5.ibsrv.net/gimg/www.mia...e095bed6b3.jpg

Also, thanks I'm assuming the sensor on the top of the water pump in front of the valve cover is the one that sends the signal to the temp gauge? I'll replace it and the wire going to it either way and see if that solves my gauge acting weird

not a lot of us are familiar with AEM to review the logs. @Savington might be able to help. But I'm pretty certain your issue is stemming from the tune.