1990 Miata run issues. Need help please.
 

I have a 1990 Miata that was running fine. Parked it for about a year and now no start on it's own. I drained the fuel tank, purged the lines, checked fuel pump (replaced), filter, dis-connected the MAF, ETC...

I know it is fuel related because I can take the elbow loose from the MAF and pour gas in and it runs as long as I feed it. I took the fuel line off at the fuel rail and made sure the line was clear and had steady flow. I am absolutely lost on these cars so any help would be very much appreciated.

Thanks in advance.

Well if you are sure it's a fuel issue, and you have fuel allllll the way to the rail, there is really only one other thing in the way of the fuel getting to the cylinders.

Do the injectors cycle? Might be clogged/seized after sitting that long? Just a guess...

That would be my guess also. That or bad fuel, but I'm assuming he filled it up with more/new fuel after he drained it all.

Flushed the tank and added 4 gallons fresh fuel. The injectors seem to be cycling but not 100% positive. What are the odds of all 4 seizing at the same time? Is this a common issue? I am not familiar with Miata's so I am just looking for common things I can check. I eliminated several just by common mechanical sense.

Thanks for your input about this, I would love to take it for a spin tomorrow. :laugh:

Pretty much all fuel injectors are made of regular mild steel. If they are left exposed to any moisture they will rust internally as well as externally.

Also, any fuel left sitting in them that is not properly treated will basically turn into like a varnish/wax that can also clog and seize them. That is one of many reasons that a car that will sit for a long period must be prepped properly.

That could very well be the issue here. If I take the fuel line off from the fuel rail how steady should the stream of fuel be while turning the car over? It is flowing but I am not use to these lil cars and it seems very little but steady enough to at least idle.

What is the "FP" I have read about people jumping to the Ground? Is this something I may need to try just to make sure the pump is doing it's job?

They sell little lights you can plug into your injector sockets to see if the PCM is triggering them. If it is and you have fuel pressure, then it might be time to have the injectors rebuilt. Does this forum have an injector rebuild sponsor or can I recommend my personal favorite (don't want to step on anyone proverbial toes)?

FP & GND jumped and same results. It sounds like it wants to start but won't. It will start for 1/2 second or so but die immediately as it has done the entire time. Man this is aggravating but what I get for messing with crap I know nothing about.

You can do wtfever you want. This isn't a gay forum that doesn't allow you to say other non sponsor companies (at least that I've ever seen and I've been here a while). We are and have always been about getting the best deals.

The FP you are talking about is one of the terminals in the DIAG box on the driver side under the hood. Near the Exhaust manifold. As for varnish, they make products that you can put in your tank and just circulate it by jumping the fuel pump using the FP terminal you are talking about. It will clean it all up, and then you dump your tank using the drain bolt. Should work well for the system up to the injectors since you have an NA with a return system.

As for the injectors, the best thing to do would be to send them away for cleaning. They WILL be varnished, even if not enough to clog them. It takes roughly like 6-8mo and fuel will varnish. A year and it just gets thicker. Best to just get them cleaned anyway and its relatively cheap, like $15-20 each. Assuming there is no rust in them they will flow and look almost like new when you get them back.

Its likely your injectors are at fault like we've said. It could also be semi clogged fuel lines, but even a half clogged line would flow enough fuel to run a na miata.

John at FIC injectors is who I send all mine to. He usually gets them out same day.

When running the varnash cleaner- flush it all out before you pull your injectors, but I'm not sure I'm seeing the injectors being the whole issue. Typically if 2-3 halfway work, the car will start.

As I said, go pick up the injector harness test lights and see if the PCM is firing the injectors. If it is, check your fuel pressure. If fuel pressure is within spec and the PCM is lighting up your test units, then take a look at the injectors.

You didn't happen to mess with the timing did you?

No timing issues, runs perfect when force feeding it with fuel in the intake elbow.

If you want to try some different injectors, I have some I can bring up to you early next week.

It should be very steady and if you put your finger over it like a garden hose there should be a good pressure build up that will spray out.

Hey man long time no see. I see your car from time to time when I am running route... Still looks killer IMO.

I would really appreciate it if I don't have it figured out by then. Good to know your on here. I know your thinking I should just stuck with the Mustangs right? lol

It will build a little pressure so should be enough at least for idle. I am just not use to these lil engines so not sure how much pressure it should build.

I am thinking maybe a injector relay in the fuse box under the hood possibly? How often do these go out?