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Old 08-08-2013, 10:34 PM   #1  
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Default weird/intermitent problem

i have a weird/intermitent problem wich i think is related to a MS,i would just like to confirm my fears.

i have a 1990 miata with a built 1.6 running a custom gt2560rs/MSPNP ms1v3.

i recently sold the car to one of my good friend and he forgot the key on ``on``position for a long time(couple of hours)and the next morning, the fuel pump wasent priming when the key was on the ``on`` position.

since that day a couple of problem happened,wich are probably all related i guess.

the fuelpump is normally activated by the MS to prime for 3 second. now it`s not turning on at all. we installed a new relay,so the the pump is ``on`` in all time when the car is on the on position. it `solved` the problem and now it`s working great again.

on the first road test, the oilpressure and water temperature needles start freaking and bouncing(a lot, not like a little milimeter) and when the needles freak like this, the alternator stop charging.when the car runs, my multimeter indicate 12.2 volt, while the car runs.

details-alternator is new, not rebuilt, battery is new, and no parasitic lost anywhere,,.

it`s really, really weird, and if i`m not mistaken, the 1990 alternator is regulated via the compurer, right?

so i fear something happened to my mspnp, because not the fans wont come on, the alternator wont charge,and the pump wont prime as it should.

i know it`s a long message, but i tried my best with my broken french accent to explain what`s happening.

if you have some spare time, i would greatly appreciate,since i dont want to let him drive the car as is

thanks a ton for youre time.

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Old 08-09-2013, 12:06 AM   #2  
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The regulator in a 90' alternator is part of the alternator... it's not charging if you only have 12.2 when it's running. Leaving the key "on" shouldn't do anything other than drain your battery.
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Old 09-16-2013, 01:06 PM   #3  
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I am having similar problems on my 91 with 96 engine and alternator using MS. I have had several instances where the engine stalls when I come to a stop with the AC running. It then refuses to start for 5-10 minutes and then magically starts. During this time there is no fuel relay clicking or pump priming sounds. It happened to me this past Friday while logging and I noticed that tunerstudio was showing the fuel pump being on during the priming pulse, so the MS is sending the signal, but the relay is not getting energized.

I have also noted the coolant temp and oil pressure needles moving, especially at higher rpm. I also had to replace my second alternator in 2 years this past weekend (I know rebuilt alternators arn't the best).

I tried installing a new Bosh 40A relay directly controlled by the MS to bypass the circuit opening relay (fuel pump relay in the 91) and ran a seperate circuit for the relay control both while using the Bosh relay and the OEM relay. Still had the random cutouts.

It only does it when warm. I know the battery voltage is OK because I am always able to turn the engine over just fine, just no fuel pump.

I now have a jumper permanently located in my diagnostic box so that I can at least install a jumper between TEN and F/P to force the fuel pump to run. This will usually get me going. Once I get it started with the jumper I can remove it and the normal fuel pump control will work fine. I can even restart it without issue.

I even thought it was a bad MS, but I had just swapped to my old MS1 box 30 min before it stalled on me this past Friday. I don't think it is MS related, thats why I cose to post it here.
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Old 09-18-2013, 03:18 AM   #4  
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Have you tried changing main relay?
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Old 09-18-2013, 03:18 AM   #5  
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Have you tried changing main relay?
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