Ωhm Posted May 5, 2020 Share Posted May 5, 2020 Since I've got a 87/88 schematics and we're dealing with a 86, things are sketchy. Disconnect both TPS and MAP connectors. Connect DVOM to B- and on each connector one pin should have 5vdc on it. KEY ON. If true, note which pin_letter it on (A, B or C). One of the pins may show a lower voltage then that. Note which pin that is too. Link to comment Share on other sites More sharing options...
eaglescout526 Posted May 5, 2020 Share Posted May 5, 2020 I have an 86 schematic book and I did post pics of that on like page 6 or 7 of the engine management section. Link to comment Share on other sites More sharing options...
Ωhm Posted May 5, 2020 Share Posted May 5, 2020 I'll check it out. Link to comment Share on other sites More sharing options...
Ωhm Posted May 5, 2020 Share Posted May 5, 2020 Between the three (3) schematic (86, 87 and 88), TPS is a mess for INPUT and GND circuits. Link to comment Share on other sites More sharing options...
eaglescout526 Posted May 5, 2020 Share Posted May 5, 2020 TPS seems like a bigger mess in 88(C101) than the 86 being a direct line to the ECU. Link to comment Share on other sites More sharing options...
Ωhm Posted May 5, 2020 Share Posted May 5, 2020 Both 86 & 87 show TPS wiper circuit as going to GND, but 88 has it as INPUT. 88 is correct physically. Link to comment Share on other sites More sharing options...
SoCalManche Posted May 5, 2020 Author Share Posted May 5, 2020 33 minutes ago, Ωhm said: Since I've got a 87/88 schematics and we're dealing with a 86, things are sketchy. Disconnect both TPS and MAP connectors. Connect DVOM to B- and on each connector one pin should have 5vdc on it. KEY ON. If true, note which pin_letter it on (A, B or C). One of the pins may show a lower voltage then that. Note which pin that is too. 26 minutes ago, eaglescout526 said: I have an 86 schematic book and I did post pics of that on like page 6 or 7 of the engine management section. These are what I got: MAP: A = 4.02V / B = 3.99V / C = 9.06V TPS: A = 3.98V / B = 4.02V / C = 9.06V Link to comment Share on other sites More sharing options...
Ωhm Posted May 5, 2020 Share Posted May 5, 2020 That ain't right. I need to chew on this for awhile. Link to comment Share on other sites More sharing options...
SoCalManche Posted May 5, 2020 Author Share Posted May 5, 2020 1 minute ago, Ωhm said: That ain't right. I need to chew on this for awhile. Please do, this is why EagleScout and I have been going at these two connectors for some time now. Hopefully this will pick your mind more. Link to comment Share on other sites More sharing options...
eaglescout526 Posted May 5, 2020 Share Posted May 5, 2020 14 minutes ago, Ωhm said: That ain't right. I need to chew on this for awhile. Can't tell ya how many times ive come close to beating my head on the wall with this one. Lol. Real brain teaser. 12 minutes ago, SoCalManche said: Please do, this is why EagleScout and I have been going at these two connectors for some time now. Hopefully this will pick your mind more. The only absolute thing I can think of if the ECU has gone bad is something in the 5V rail has gone bad and is sending more voltage than it should down the line. But even with negative lead in B and checking for 5V at C we still don't get anything close, seems like it is high or it is low, never at 5V. Link to comment Share on other sites More sharing options...
SoCalManche Posted May 5, 2020 Author Share Posted May 5, 2020 35 minutes ago, eaglescout526 said: Can't tell ya how many times ive come close to beating my head on the wall with this one. Lol. Real brain teaser. The only absolute thing I can think of if the ECU has gone bad is something in the 5V rail has gone bad and is sending more voltage than it should down the line. But even with negative lead in B and checking for 5V at C we still don't get anything close, seems like it is high or it is low, never at 5V. Does this help? I went back out to try the (B) and (C) again. Before doing so, I checked each pin of both connectors with ground probe at Batt Neg post and power probe at each pin. The readings basically stayed the same; actually went up about 0.1V. Anyways, after that, I tried the (B) & (C) for both connectors (unplugged) and got 5V. Ground probe on (B) and power on (C). Link to comment Share on other sites More sharing options...
eaglescout526 Posted May 5, 2020 Share Posted May 5, 2020 So we have 5V now? Hey MJ! Make up your mind! Perhaps we jostled a connection in the harness back to life? Link to comment Share on other sites More sharing options...
SoCalManche Posted May 5, 2020 Author Share Posted May 5, 2020 3 minutes ago, eaglescout526 said: So we have 5V now? Hey MJ! Make up your mind! Perhaps we jostled a connection in the harness back to life? But we still have 9V on (C) when at Batt Neg. Still weird, yes? Link to comment Share on other sites More sharing options...
eaglescout526 Posted May 5, 2020 Share Posted May 5, 2020 Eh yes and no. Yes cause it should be 5V no matter which ground the reading is from but now we get 5V through the ECU ground and 5V supply, so that part of the ECU is not bad. Makes me wonder if it will fire. Link to comment Share on other sites More sharing options...
Ωhm Posted May 5, 2020 Share Posted May 5, 2020 1 hour ago, SoCalManche said: These are what I got: MAP: A = 4.02V / B = 3.99V / C = 9.06V TPS: A = 3.98V / B = 4.02V / C = 9.06V The difference between B and C on both connectors is about 5vdc. Link to comment Share on other sites More sharing options...
SoCalManche Posted May 5, 2020 Author Share Posted May 5, 2020 11 minutes ago, eaglescout526 said: Eh yes and no. Yes cause it should be 5V no matter which ground the reading is from but now we get 5V through the ECU ground and 5V supply, so that part of the ECU is not bad. Makes me wonder if it will fire. No love; it did fire, but only because I threw some fuel down the TBI. Sounds and smells like a damn lawnmower when starting up, lol. Fuel pump did not engage, per normal, with fuel relay in circuit. Link to comment Share on other sites More sharing options...
SoCalManche Posted May 5, 2020 Author Share Posted May 5, 2020 I never see the injector "mist" any fuel into TBI. Link to comment Share on other sites More sharing options...
eaglescout526 Posted May 5, 2020 Share Posted May 5, 2020 3 minutes ago, SoCalManche said: Fuel pump did not engage, per normal, with fuel relay in circuit. So no pressure was seen on the rail? Link to comment Share on other sites More sharing options...
SoCalManche Posted May 5, 2020 Author Share Posted May 5, 2020 Just now, eaglescout526 said: So no pressure was seen on the rail? Nope; no pressure. I dumped enough fuel into the TBI for her to maintain an idle briefly though. But no fuel being pushed. Link to comment Share on other sites More sharing options...
eaglescout526 Posted May 5, 2020 Share Posted May 5, 2020 @Ωhm, what would happen if he jumped 30 to 87 and 86-85 on the FP relay? Do we think the engine would actually run or is the relay regulating a safe load on 86 to 85? Cause I wonder if the ECU isn't seeing the relay so it won't fire unless there's a connection there. Link to comment Share on other sites More sharing options...
Ωhm Posted May 5, 2020 Share Posted May 5, 2020 Pin 85 is strictly the grounding side for fuel pump relay (coil) control. Jumping pin 30 to 87 just does what the relay should do when controlled by the ECU. Link to comment Share on other sites More sharing options...
eaglescout526 Posted May 5, 2020 Share Posted May 5, 2020 Then in theory the engine should still run while jumped, but it does not, but runs with relay in socket with fuel poured down the throttle body. Link to comment Share on other sites More sharing options...
Ωhm Posted May 5, 2020 Share Posted May 5, 2020 8 minutes ago, eaglescout526 said: Cause I wonder if the ECU isn't seeing the relay so it won't fire unless there's a connection there. Other inputs determine when FP relay is activated. KEY ON will prime the pump. CRANK will keep FP relay activated. CPS will demand FP relay at all times. Link to comment Share on other sites More sharing options...
Ωhm Posted May 5, 2020 Share Posted May 5, 2020 1 minute ago, eaglescout526 said: Then in theory the engine should still run while jumped, but it does not, but runs with relay in socket with fuel poured down the throttle body. That's when I first used the word "confusing". Link to comment Share on other sites More sharing options...
eaglescout526 Posted May 5, 2020 Share Posted May 5, 2020 11 minutes ago, Ωhm said: That's when I first used the word "confusing". Lol which is why this post is 10 pages long. Link to comment Share on other sites More sharing options...
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