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Jeep Wrangler YJ
YJ General Discussion
95 YJ crank, no start
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<blockquote data-quote="deadpool1" data-source="post: 440931" data-attributes="member: 21229"><p>This is the FSM page on your PCM 2.5:</p><p>F1 blown kills dead PCM memory storage so that only live errors are seen keyon. see why?</p><p> be a huge shame running any jeep with F1 blown. and will not store live DTC found.</p><p>F1 also kills dead FP relay and ASD both</p><p>if you have spark past 3 seconds, F1 is working</p><p>page 14-31, FSM page states (free and now you have it)</p><p></p><p></p><p>this is the <strong>3 second rule</strong> I mentioned</p><p>knowing this 1 rule we must test fuel pressure and spark both for at leas<strong>t over </strong>3 seconds, 10 is a good choice.</p><p>to see if spark or fuel fails. or both.</p><p></p><p>in effect the PCM monitors A142 and lets it overload (may) for 3 seconds and if does it drops the ASD killing both spark and fuel.(on purpose)</p><p></p><p>this 3second rule is for key on pump test, heard to spin for 3 seconds, this is called the PRIME mode, before the crank.</p><p>the pump is active cranking and running both, full time. done.</p><p></p><p>the pump has many tests not just 1.</p><p>even 75psi <strong>shunt</strong> test</p><p>if shunt fails and only 6volts makes it to the pump, the shunt test fails. (or cranking)</p><p> 41psi keyon,3 times it must be , (assumes pump check ball leaks a tad as mine does)</p><p>the highest pressure (normal) as at cranking, 41psi. then drops</p><p>then running idle pressure is 31. psi. FPR does that.drop.</p><p></p><p>the cranking voltage is about 11vdc. at the battery and near that at the pump, may be 10v. there at pump pins actual, IDK. the wiring is small gauge (AWG)</p><p>key off voltages is 12.6vdc rested , this is SOC state of charge spec.</p><p></p><p>if spark ends a<strong>t 4 seconds </strong>1,good, 2good, 3good 4 fails spark.</p><p>we know the ASD dropped off line!!!! killing spark dead and so is fuel.</p><p></p><p>for 2 reasons. voltage at the battery is way way to low.</p><p>or A142 voltage tests failed. (o2 shorted is like slam dunk guess but is easy to prove unplugged O2)</p><p>i guess A142 fails at 8v or 6v IDK, but means overload. on the bus.(or car battery is a wreck) my battery fail at 5year marks,</p><p>for the reasons in the manual stated.</p><p></p><p>this post is to understand PCM timing, rules. 3 second rule is super important to know and PSI cranked and more.</p><p>most tests are 2 man tests .</p><p>man1 cranks</p><p>man2 measures</p><p>lacking long test leads or even long hose fuel pressure gauge.</p><p></p><p>my last 95 car (not this one yet) I had a dash mounted electronic fuel pressure meter. (my work)</p><p>The PCM can't tell me this but the meter sure can.</p><p>and a real scan tool.</p><p></p><p>[ATTACH=full]122429[/ATTACH]</p></blockquote><p></p>
[QUOTE="deadpool1, post: 440931, member: 21229"] This is the FSM page on your PCM 2.5: F1 blown kills dead PCM memory storage so that only live errors are seen keyon. see why? be a huge shame running any jeep with F1 blown. and will not store live DTC found. F1 also kills dead FP relay and ASD both if you have spark past 3 seconds, F1 is working page 14-31, FSM page states (free and now you have it) this is the [B]3 second rule[/B] I mentioned knowing this 1 rule we must test fuel pressure and spark both for at leas[B]t over [/B]3 seconds, 10 is a good choice. to see if spark or fuel fails. or both. in effect the PCM monitors A142 and lets it overload (may) for 3 seconds and if does it drops the ASD killing both spark and fuel.(on purpose) this 3second rule is for key on pump test, heard to spin for 3 seconds, this is called the PRIME mode, before the crank. the pump is active cranking and running both, full time. done. the pump has many tests not just 1. even 75psi [B]shunt[/B] test if shunt fails and only 6volts makes it to the pump, the shunt test fails. (or cranking) 41psi keyon,3 times it must be , (assumes pump check ball leaks a tad as mine does) the highest pressure (normal) as at cranking, 41psi. then drops then running idle pressure is 31. psi. FPR does that.drop. the cranking voltage is about 11vdc. at the battery and near that at the pump, may be 10v. there at pump pins actual, IDK. the wiring is small gauge (AWG) key off voltages is 12.6vdc rested , this is SOC state of charge spec. if spark ends a[B]t 4 seconds [/B]1,good, 2good, 3good 4 fails spark. we know the ASD dropped off line!!!! killing spark dead and so is fuel. for 2 reasons. voltage at the battery is way way to low. or A142 voltage tests failed. (o2 shorted is like slam dunk guess but is easy to prove unplugged O2) i guess A142 fails at 8v or 6v IDK, but means overload. on the bus.(or car battery is a wreck) my battery fail at 5year marks, for the reasons in the manual stated. this post is to understand PCM timing, rules. 3 second rule is super important to know and PSI cranked and more. most tests are 2 man tests . man1 cranks man2 measures lacking long test leads or even long hose fuel pressure gauge. my last 95 car (not this one yet) I had a dash mounted electronic fuel pressure meter. (my work) The PCM can't tell me this but the meter sure can. and a real scan tool. [ATTACH=full]122429[/ATTACH] [/QUOTE]
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Jeep Wrangler YJ
YJ General Discussion
95 YJ crank, no start
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