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Jeep Wrangler YJ
YJ General Discussion
Non starting after new thermostat and heater core flush
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<blockquote data-quote="deadpool1" data-source="post: 441148" data-attributes="member: 21229"><p>jeep this year calls CPS a speed sensor (RPM) speed Is MPH called VSS today. CPS is call CKP now, SAE and ISO rules. for names, I am not arguing names</p><p>only to read relic manuals what they meant then, is really funny today.</p><p>the CPS (non hall) uses a ground shield cable if ground to the shield is lost, CPS tiny singles fail cranking, slow. the HALL sensors ended this pain later.</p><p>it is a design weak point, CPS 2 wire sensors. and it must work or will never start the engine.. </p><p>the 2.5 has no CMP cam sensor in the DIZZY like the 4.0L has.</p><p></p><p>my new 1988 jeep xj, 4.0 , then, the CPS failed fast, (recalled by jeep) then the alternator failed at 15k,(bad rear china bearings, used by Delco)</p><p>I had a 88 MJ jeep too, same time. (yes I love trouble)<img src="data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7" class="smilie smilie--sprite smilie--sprite3996" alt=":mad:" title="Mad :mad:" loading="lazy" data-shortname=":mad:" /></p><p>the CPS is real important here, the newer ones from SMP may be better, may have better outputs cranking for sure if the main battery is weak the crank spins slower and the CPS output is weaker. (keep th<strong>e battery fully charged</strong> at al times on any dead engine and testing it)</p><p><a href="https://www.rockauto.com/en/catalog/jeep,1989,wrangler,2.5l+150cid+l4,1184879,ignition,crankshaft+position+sensor,7196" target="_blank">or CPS NTK (high altitude)</a></p><p></p><p>I'd make sure every inch of the CPS wiring is perfect on this engine.</p><p>then P+ relay works</p><p>and S2B1 pulses. (ECM out) the pulses ICM with a pure 5Vdc square wave Chapter 8D-8 page stated.</p><p>then DC power is good to ICM</p><p>and coil is good.</p><p>and all grounds related here good.</p><p></p><p>test for spark out of the spark coil only , at first , until that works first. do not test spark plugs for spark yet , that is last.0</p><p>the HV induction spark coil must work first, goal #1 using a HV spark wire to the HV spark tower, terminal and spark plug on end grounded to the engine.</p><p>keep in mind cars this old 2 problems related can be here.</p><p></p><p>S2B1 leading edge charges the primary coil , (called dwell in the olden days) and then when the S2B1 goes to zero volts the coil drive is released (ICM does)</p><p>and HV happens, spark. happens.</p><p></p><p>that is all there is on the 2.5L, there is no CMP sensor. like the other 2 or more engines have in the same book.</p><p>page 8D -10 see how the complex teeth work on the flywheel rim tone wheel. 3 differnent teeth types, that must not be damaged.</p><p>every 90degr;. of crank angle, the last tooth is huge and allows the super WeAk cmp TOP FIRE OFF. ( YES COMPLEX THEN)</p><p>8d IS FSM CHAPTER SPARK,IGNITION 2.5: PAGE 9 TO 23. IT SAYS DO NOT CLEAN THE DIZZY ROTOR TIP. (AND WHY)</p><p>THE SCHEMATICS IN THE , ARE MIXED, INterspersed, madly. making the job harder. </p><p>8w-83 is the beginning pages for this engine.</p><p>watch out for the bad ground it mentions in the FSM about ICM ground going to the bloody, engine tipstick tube screw clamp, wow. did grounds. <img src="data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7" class="smilie smilie--sprite smilie--sprite4002" alt=":oops:" title="Oops! :oops:" loading="lazy" data-shortname=":oops:" /></p><p>ground to right rear lug of engine, must be good. page 95</p><p>the 2.5L coil page 8w-96 is missing sheet 15, and in the place is 4.2L, a huge error in 1988/98 FSM both are wrong. both books. I have.</p><p>the CPS page too is missing in the schematic but seen on the ECU pin connector pages. 2 pins CPS. Jeep must hate the 2.5L</p><p>the other engines in the book are covered fully, but not 2.5, in this regard.</p><p></p><p>make sure +5vdc is seen at TPS and MAP (ECU created 5vd this is)</p><p>if dead 5v, the PCM is offline, and or B+ relay dead or its fuses blown. fuses are always first. skip none or go way off track. fast.</p><p></p><p>ECU pin 11 and 28 is CPS 2 wires.</p><p>ECU pin 27 is fire the coil signal from ECU to ICM,. it is a 0 to 5vdc square wave, if dead the TPS/and MAP must have 5vdc or the B+ latch relay is dead</p><p>or fuses to PCM or B+ relay are blown</p><p>that is it for all tests basic spark only 2.5L diagnosis.</p><p>and cheers to you and all folks working wranglers.</p></blockquote><p></p>
[QUOTE="deadpool1, post: 441148, member: 21229"] jeep this year calls CPS a speed sensor (RPM) speed Is MPH called VSS today. CPS is call CKP now, SAE and ISO rules. for names, I am not arguing names only to read relic manuals what they meant then, is really funny today. the CPS (non hall) uses a ground shield cable if ground to the shield is lost, CPS tiny singles fail cranking, slow. the HALL sensors ended this pain later. it is a design weak point, CPS 2 wire sensors. and it must work or will never start the engine.. the 2.5 has no CMP cam sensor in the DIZZY like the 4.0L has. my new 1988 jeep xj, 4.0 , then, the CPS failed fast, (recalled by jeep) then the alternator failed at 15k,(bad rear china bearings, used by Delco) I had a 88 MJ jeep too, same time. (yes I love trouble):mad: the CPS is real important here, the newer ones from SMP may be better, may have better outputs cranking for sure if the main battery is weak the crank spins slower and the CPS output is weaker. (keep th[B]e battery fully charged[/B] at al times on any dead engine and testing it) [URL='https://www.rockauto.com/en/catalog/jeep,1989,wrangler,2.5l+150cid+l4,1184879,ignition,crankshaft+position+sensor,7196']or CPS NTK (high altitude)[/URL] I'd make sure every inch of the CPS wiring is perfect on this engine. then P+ relay works and S2B1 pulses. (ECM out) the pulses ICM with a pure 5Vdc square wave Chapter 8D-8 page stated. then DC power is good to ICM and coil is good. and all grounds related here good. test for spark out of the spark coil only , at first , until that works first. do not test spark plugs for spark yet , that is last.0 the HV induction spark coil must work first, goal #1 using a HV spark wire to the HV spark tower, terminal and spark plug on end grounded to the engine. keep in mind cars this old 2 problems related can be here. S2B1 leading edge charges the primary coil , (called dwell in the olden days) and then when the S2B1 goes to zero volts the coil drive is released (ICM does) and HV happens, spark. happens. that is all there is on the 2.5L, there is no CMP sensor. like the other 2 or more engines have in the same book. page 8D -10 see how the complex teeth work on the flywheel rim tone wheel. 3 differnent teeth types, that must not be damaged. every 90degr;. of crank angle, the last tooth is huge and allows the super WeAk cmp TOP FIRE OFF. ( YES COMPLEX THEN) 8d IS FSM CHAPTER SPARK,IGNITION 2.5: PAGE 9 TO 23. IT SAYS DO NOT CLEAN THE DIZZY ROTOR TIP. (AND WHY) THE SCHEMATICS IN THE , ARE MIXED, INterspersed, madly. making the job harder. 8w-83 is the beginning pages for this engine. watch out for the bad ground it mentions in the FSM about ICM ground going to the bloody, engine tipstick tube screw clamp, wow. did grounds. :oops: ground to right rear lug of engine, must be good. page 95 the 2.5L coil page 8w-96 is missing sheet 15, and in the place is 4.2L, a huge error in 1988/98 FSM both are wrong. both books. I have. the CPS page too is missing in the schematic but seen on the ECU pin connector pages. 2 pins CPS. Jeep must hate the 2.5L the other engines in the book are covered fully, but not 2.5, in this regard. make sure +5vdc is seen at TPS and MAP (ECU created 5vd this is) if dead 5v, the PCM is offline, and or B+ relay dead or its fuses blown. fuses are always first. skip none or go way off track. fast. ECU pin 11 and 28 is CPS 2 wires. ECU pin 27 is fire the coil signal from ECU to ICM,. it is a 0 to 5vdc square wave, if dead the TPS/and MAP must have 5vdc or the B+ latch relay is dead or fuses to PCM or B+ relay are blown that is it for all tests basic spark only 2.5L diagnosis. and cheers to you and all folks working wranglers. [/QUOTE]
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Jeep Wrangler YJ
YJ General Discussion
Non starting after new thermostat and heater core flush
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