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NA (1989-1997) NA Miata discussion within. The MX5's first generation, the NA, sold over 400,000 units from 1989 to 1997.

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Old 02-13-2012, 01:39 PM   #21
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Not recently checked, but there was good fuel delivery as the plugs were wet as well as the cylinders after trying to start it with new ecu and afm yesterday. I didnt jump fp to gnd yesterdy but in the past weeks that worked. Fuel does not seem to be the problem. Wht wiring issues might keeo it from starting if there is fuel and spark?

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Old 02-13-2012, 02:44 PM   #22
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try the fuel pressure regulator, the only other thing i can think of would be the idle control valve went bad.
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Old 02-14-2012, 08:15 AM   #23
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fuel spark and timing. If you have fuel and spark, then timing is either off because of the timing belt, or because something like a CAS/CPS is gone.
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Old 02-14-2012, 04:33 PM   #24
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fuel spark and timing. If you have fuel and spark, then timing is either off because of the timing belt, or because something like a CAS/CPS is gone.
Timing belt was rechecked, all the marks line up. 2 weeks ago I took the covers off to be sure. The CAS was swapped to a known good one, no start. I swapped ECU and AFM too, no go. The only thing that I know is a little off is that the vacuum holds at 15, while some have suggested it should be more. There's good compression, the plugs spark, and the fuel pumps. Actually if anything it would seem to be a spark problem as the plugs appear to spark, but the plugs are quite wet with fuel after trying (and failing) to start it. Can the plugs spark on the valve cover, but not spark when in the chamber and the car is cranking? If they spark, and fuel pumps, what can make it not run? I had a guy who is good with this stuff and not long ago rebuilt a Miata engine come over sunday last and he had no idea either.

Unfortunately I am not sure where the ignition timing is right now as when I took out the CAS and replaced it, I didn't mark it to have it line up again. But being roughly in the right place it shouldn't matter much.

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Old 02-14-2012, 05:18 PM   #25
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Yeah, my plugs were wet when my fuel pump wasn't working right, too. It turns out that low fuel pressure gives you a stream of fuel out of the injector instead of a mist. The plugs were dripping. Good luck with that.
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Old 02-16-2012, 09:37 PM   #26
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I think I found it. The ground behind the throttle body was loose. It started once but now isn't again, but I must be on the right track. Sheesh I sweated that. Thanks all! Will post back if this isn't the final solution.
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Old 02-16-2012, 10:18 PM   #27
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There's one on the back of the intake manifold also.
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Old 02-19-2012, 10:08 PM   #28
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Well, it failed to get going. But I am still thinking it must be a ground problem. In a thread on miata.net http://forum.miata.net/vb/showthread...ghlight=ground prb showed pictures of grounds. The bolt under the throttle body in my car has nothing on it unlike what is seen in his 4th picture. Instead of braided wire, I only have a wimpy little wire going to the ground spot in the first couple pictures, but I haven't traced it yet. What I was concerned about in post 26 vabove was back by the CAS, and was not firmly attached. I thought it seemed closer to starting after bolting it down, but it has progressed to actually starting.

I was messing around this afternoon and saw that the input to the coil was 12.3 V or so, but when cranking it dropped to 10.4. Is that enough? Could that be a symptom of a ground issue?

I need to find what is supposed to ground above the alternator there by the intake. Not good that no wires are bolted on there.

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Old 02-19-2012, 10:44 PM   #29
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alright i dont know what voltages are supposed to be but a drop like that would lead me to believe yes you have a wiring issue.
now i happen to have pictures of my car with the intake manifold off so hopefully these will help.
heres the intake manifold fully assembled
http://s1191.photobucket.com/albums/...t=ba773fd0.jpg
side of the motor
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Old 02-20-2012, 05:22 PM   #30
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Yeah, my plugs were wet when my fuel pump wasn't working right, too. It turns out that low fuel pressure gives you a stream of fuel out of the injector instead of a mist. The plugs were dripping. Good luck with that.
Fuel pressure was about 45 in Hg per the gauge, which is slightly better than spec, maybe the gauge reads high. (Which if so means my vacuum is weaker than expected, which tested at only 15.)
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