Do you have a keypad or datalogger? If so, do all of the sensor readings look normal at key-on before cranking? Do RPM and MAP values change as expected and do the injector pulse width & ign advance look normal during the brief run that you do get? Do you have gnd and +12v power at the MAP box when the key is on?
Since the engine fires briefly but doesn’t continue to run even with the fuel pump jumpered to stay on, I’d guess that the plugs are firing, and the initial start is fueled by prime fuel but the ECU thinks that there is high manifold vacuum or high coolant temp and isn’t supplying enough fuel to continue running ... or maybe the fuel map in the ECU got hosed somehow. The FP shutting off when the starter isn’t running says that something is wrong with the MAP box or connections to it. Normally the ECU turns that transistor on in the map box to keep the FP relay energized as soon as it senses RPM > 60. From: Eric McCord Sent: Friday, July 13, 2012 11:39 AM To: [email protected] Cc: [email protected] Subject: Re: '91 fires, won't stay on... Swapped out both the ignition switch and CAS. No change. I have only used the Link. I also swapped out the fuel pump before purchasing a fuel pressure guage. I am getting 40 psi at the rail at all times with the key on. It is not looking like it is fuel related. Eric On Fri, Jul 13, 2012 at 2:35 PM, [email protected] <[email protected]> wrote: A long shot here, but it may be that the ignition switch is faulty, allowing to to start the car and then losing electrical contact, or perhaps the current from the ignition to the CAS has been interrupted. WAIT! You are using the Link now, but did you EVER use another method of engine management? Did you use an MSD? I recall long ago having a problem develop after I upgraded from the Bell Sys II to full FM II spec with link, and it turned out that old wiring for the MSD unit had developed a short (or some problem... was years ago!) LGO -----Original Message----- From: Eric McCord <[email protected]> To: Mark Phillips <[email protected]> Cc: miatapower <[email protected]> Sent: Fri, Jul 13, 2012 11:54 am Subject: Re: '91 fires, won't stay on... No luck. I just replaced that transistor and it is still doing the same thing. Eric On Fri, Jul 13, 2012 at 10:41 AM, Eric McCord <[email protected]> wrote: I am off to the Shack. Eric On Fri, Jul 13, 2012 at 10:39 AM, Mark Phillips <[email protected]> wrote: Yes. On 07/13/2012 10:28 AM, Eric McCord wrote: on yours it was T2? Did you just replace the transistor to get it back up and running? Eric On Fri, Jul 13, 2012 at 10:25 AM, Mark Phillips <[email protected]> wrote: The relay has 12 volts applied to one side of the coil with the ignition on. When you jump F/P to GND you are taking the other side of the relay coil straight to ground bypassing the transistor. Normally the transistor performs this grounding function (sinking current). T2 also interacts with other circuity in the MAF box. This happened to me about 4-5 years ago on my '92. Mark On 07/13/2012 10:00 AM, Eric McCord wrote: When I jump out the F/P to GND the pump stays on but I still have the same symptoms. If that transistor drives the relay but I jump it out should that not run? Eric On Fri, Jul 13, 2012 at 9:54 AM, Mark Phillips <[email protected]> wrote: Hi Eric, I sent this out earlier but didn't see it repost. I apologize if its a repeat. There is a transistor in the Link box that replaces the AFM; it drives the fuel pump relay. It is an NPN transistor, is marked "T2" and may have failed. About $1.50 and a soldering iron to replace. Mark Phillips On 07/13/2012 09:40 AM, Eric McCord wrote: I just swapped out the CAS and same symptoms. If it's a bad MAF box where can I get one of those? Since my Baja went down the Miata has been my only transportation and Kaitlyn and I are leaving in a week and a half for the dragon and our road trip. Eric On Fri, Jul 13, 2012 at 9:18 AM, Ray <[email protected]> wrote: Can also be that one of the two signals from the CAS is not there. From: Eric McCord Sent: Thursday, July 12, 2012 6:21 PM To: [email protected] Cc: [email protected] Subject: Re: '91 fires, won't stay on... Just checked that connector. It looked fine, I reseated it and still have the same symptoms. Eric On Thu, Jul 12, 2012 at 9:07 PM, [email protected] <[email protected]> wrote: Have you checked the manifold pressure connection (heck! I think that's what its called - I can't remember!) ? If it comes loose, it may begin to fire and then die. On mine its the small box with the AFM-like connector (multi-pin) on the driver's side. LGO _______________________________________________ Miatapower mailing list [email protected] http://list.miatapower.net/cgi-bin/mailman/listinfo/miatapower -------------------------------------------------------------- _______________________________________________ Miatapower mailing list [email protected] http://list.miatapower.net/cgi-bin/mailman/listinfo/miatapower _______________________________________________ Miatapower mailing list [email protected] http://list.miatapower.net/cgi-bin/mailman/listinfo/miatapower _______________________________________________ Miatapower mailing list [email protected] http://list.miatapower.net/cgi-bin/mailman/listinfo/miatapower _______________________________________________ Miatapower mailing list [email protected] http://list.miatapower.net/cgi-bin/mailman/listinfo/miatapower -------------------------------------------------------------------------------- _______________________________________________ Miatapower mailing list [email protected] http://list.miatapower.net/cgi-bin/mailman/listinfo/miatapower
_______________________________________________ Miatapower mailing list [email protected] http://list.miatapower.net/cgi-bin/mailman/listinfo/miatapower
