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Jeep Wrangler YJ
YJ General Discussion
Just bought 95 YJ and it died immediately
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<blockquote data-quote="DOWNS" data-source="post: 438452" data-attributes="member: 21038"><p>Could be a host of problems but don't forget you're dealing with a 28 year old vehicle that has an unknown maintenance history. On Jeeps this old it's always good to replace all of your battery cables both positive and negative, dont' rely on exterior appearance of the cable sheathing or what the lugs look like. I've cut apart old battery cables that looked ok externally but under the insulation it was a tube of corroded copper strands. All of the sensors operate on a 5 volt reference signal so if you have poor grounds it will show in various hard to track down electrical gremlins and it will make your ECU see bad data from the various sensors. IMO far too many sensors have been replaced </p><p></p><p>The way you described the Jeep shutting down is a classic sign of a bad Crank or cam position sensor. Crank sensors seem to fail more often than the camshaft sensors. And testing may or maynot show a bad sensor. Many times a bad sensor will work fine when cool but when the engine gets hot the sensor fails suddenly and then when it cools again the vehicle will start again and will test fine when cool as well. </p><p></p><p>Here is the testing procedure for a CPS from the 95 service manual. </p><p></p><p></p><p>As for fuel pressure. Just because fuel is coming out of the rail doesn't mean it's at the proper pressure. You need to get a proper fuel pressure gauge which is very cheap and something every Jeep owner should have on their shelf and test it properly. When running, you should have around 31 psi at idle with the vacuum line hooked to the Fuel pressure regulator and about 10 psi more without it hooked up. Too high and you're running rich, too low and you're starving for fuel. The pressure has to be a specific pressure because all the computer does is open the injectors for a certain amount of time based on various factors and it has no control or reading over what fuel pressure is in the line so all the fueling data in the computer is based on that 31 to 41 psi of fuel pressure.</p></blockquote><p></p>
[QUOTE="DOWNS, post: 438452, member: 21038"] Could be a host of problems but don't forget you're dealing with a 28 year old vehicle that has an unknown maintenance history. On Jeeps this old it's always good to replace all of your battery cables both positive and negative, dont' rely on exterior appearance of the cable sheathing or what the lugs look like. I've cut apart old battery cables that looked ok externally but under the insulation it was a tube of corroded copper strands. All of the sensors operate on a 5 volt reference signal so if you have poor grounds it will show in various hard to track down electrical gremlins and it will make your ECU see bad data from the various sensors. IMO far too many sensors have been replaced The way you described the Jeep shutting down is a classic sign of a bad Crank or cam position sensor. Crank sensors seem to fail more often than the camshaft sensors. And testing may or maynot show a bad sensor. Many times a bad sensor will work fine when cool but when the engine gets hot the sensor fails suddenly and then when it cools again the vehicle will start again and will test fine when cool as well. Here is the testing procedure for a CPS from the 95 service manual. As for fuel pressure. Just because fuel is coming out of the rail doesn't mean it's at the proper pressure. You need to get a proper fuel pressure gauge which is very cheap and something every Jeep owner should have on their shelf and test it properly. When running, you should have around 31 psi at idle with the vacuum line hooked to the Fuel pressure regulator and about 10 psi more without it hooked up. Too high and you're running rich, too low and you're starving for fuel. The pressure has to be a specific pressure because all the computer does is open the injectors for a certain amount of time based on various factors and it has no control or reading over what fuel pressure is in the line so all the fueling data in the computer is based on that 31 to 41 psi of fuel pressure. [/QUOTE]
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Jeep Wrangler YJ
YJ General Discussion
Just bought 95 YJ and it died immediately
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