Gloyale Posted July 19, 2009 Share Posted July 19, 2009 (edited) So, in the process of doing an SPFI swap onto my wheeler, I ran into a stumbling block. I have voltage everywhere, the Fuel pump will cycle with the test connectors, and the disty passes the *pulse* test. However there is still no spark and no fuel while cranking (absent signal from disty CAS) So, I began pouring through FSM pages and flowcharts trying to find an answer. Now for the real *meat and potatoes* of the story. I used a harness from an 87 2wd SPFI. Using Matching 87 disty(round plug) Somewhere along the way I parted with the matching 87 ECU. So I am using a 91 Loyale ECU. So I decide to see if there are ANY differences in ECU wiring between the 2 years. I open the FSM for each year and layed the pages with ECU pins next to eachother and compared, one at a time. SURE ENOUGH! Pins 20 and 21, for CAS *reference* and *position* are swithced! The wire colors stayed the same at each pin #, so it isn't apparent looking at the harness. The change must have been made on the board inside the ECU, and the green wire and white wire on the Disty plug itself are switched (I knew I had seen reference to this before) Well it turns out, in 88+ EA82 fuel injection, they swapped the 2 pins (20,21) for reference and position signals on the Disty! I went back through every year FSM, and it holds true. Early SPFI models, 86-87, (round plug disty) use 20(GY) for Reference and 21(BW) for Position Later SPFI 88-94(square plug disty) use 20(GY) for Position and 21(BW) for reference. SO, in conclusion to use a late ECU with an early disty with (or vice versa) the Green and the White wire in the Disty pigtail must be swapped in the connector. Or alterantely, swap the disty and the matching ECU toghether. *note: This also is the case for the late 87 MPFI models using the CAS disty with the round plug. So anyone trying to use an 88+ ECU on there 87 Turbo will need to swap these 2 wires. (MPFI ECU pins are 8 and 17) *note: 88+ model distys with the square connectors will all interchange SPFI/MPFI and will work with any 88+ ECU. When I can get some scans of the pages and some pics of the distys I will be submiting this to the USRM, and possibly as an adedum to the SPFI swap write-up. Although, this does highlight the benefits of General Disorders recomendation of using parts from a single donor car for the swap. Edited July 19, 2009 by Gloyale Link to comment Share on other sites More sharing options...
idosubaru Posted July 19, 2009 Share Posted July 19, 2009 Wow, nice work. I've ran into problems here before as well. Did you check XT FSM's at all? Link to comment Share on other sites More sharing options...
Gloyale Posted July 19, 2009 Author Share Posted July 19, 2009 (edited) Wow, nice work. I've ran into problems here before as well. Did you check XT FSM's at all? Not intitailly, but now I have. Since Early MPFI systems were not CAS based, there is no interchange at all with 85,86, and early 87. They use an older Magnetic pick-up/vac + weights advance. And actually can run a standard EA82 Carb disty in a pinch. But I digress... So the CAS pin swap only possibly pertains to the few 87+1/2 model year XTs. And upon checking.......yes, the same scenario is true. That year XT uses a round plug for the disty, and the ECU pins are shared with the other MPFI models of the same year. Next year(88) and on after, the ECU pins switch(pins 8 and 17) switch. Also with the MPFI models the wire color appears to have changed also, though not switched. Early both wires are White, later pin 8 changed to Green for GL/RX and Black for XT, sheesh......WTF:confused: SO........anyone trying to use a later MPFI ECU in an 87+1/2 XT........OR.........a later Square plug disty in an 87+1/2 XT, Swap the White and Green wires on the pigtail of the Distributor itself. Or alterantely, swap the disty and the matching ECU toghether. Edited July 19, 2009 by Gloyale Link to comment Share on other sites More sharing options...
idosubaru Posted July 19, 2009 Share Posted July 19, 2009 Wow that's a very confusing assortment of info. I'll be revisiting this thread sometime this summer. I have a 1987.5 XT (turbo swapped to non-turbo) i've worked on for years and never got running right. The ECU was bad from the beginning and since then I've changed ECU's and Disty's a couple times, not even sure what's in there now. So the body/engine wiring doesn't matter. It just needs to have a matching set of ECU/Disty (or swap wires to match if different)? Link to comment Share on other sites More sharing options...
Gloyale Posted July 19, 2009 Author Share Posted July 19, 2009 So the body/engine wiring doesn't matter. It just needs to have a matching set of ECU/Disty (or swap wires to match if different)? The easy rule is, if it has a round plug Disty, it needs an 87(MPFI) or 86,87(SPFI) ECU. If you want to use a later ECU, the pins in the round disty pigtail connector must be swapped. When using a late disty in an early model, when you cut and splice disty pigtails, just match the wire color and you will end up correct assuming the original ECU is in place. Gary I would suggest if it runs at all, this is not you're problem.....but???? Link to comment Share on other sites More sharing options...
idosubaru Posted July 19, 2009 Share Posted July 19, 2009 Gary I would suggest if it runs at all, this is not you're problem.....but????Okay, great! I did actually get it running last summer so it *runs* (very loose definition of the word:lol:). Thanks. Explains why the later ECU's did not work when I installed them a few years ago when I first got this car. Link to comment Share on other sites More sharing options...
Gloyale Posted July 20, 2009 Author Share Posted July 20, 2009 Well sure enough....I went to the shop today to test the theory that this pin swap on the ECU was the cause of my SPFI EA81 failure.........Swapped the White and Green wires in my disty plug, and bam......I now have spark and a running fuel pump while cranking....and a bit of timing to do still with the Disty. I just picked up a radiator today from Hondasucks so thankfully I will now be able to actually be able to test drive if I do get it running. Link to comment Share on other sites More sharing options...
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