Follow the Data or Trust your Gut?<\/p>\n\n\n\n
Last week my 1988 XJ off road Jeep played a trick on me. I needed to move it out of the way so I could get my tractor out. It started with an extended crank. This Jeep normally stars quickly so this was odd.<\/p>\n\n\n\n\n\n\n\n
It was stumbling and running rough so I decided to take the long way around to it s parking spot. About half way round the driveway, the Jeep almost died but out of the corner of my eye I saw the REM indicate crazy numbers for the engine RPM. Like 9000 or so. The factory tach was showing 500 to 600 at the time.<\/p>\n\n\n\n
I finally got it around to its parking place and shut it off. After grading the driveway, I decided to take a look at the Jeep. Now it refused to start. The REM was showing zero RPM and would put an asterisk beside the number if I continued cranking.<\/p>\n\n\n\n
So I hooked up a tow rope and drug it into the shop.<\/p>\n\n\n\n
I noticed the wires to the Crank Shaft Position sensor were melted form being too close to the exhaust so I decided to check the sensor output. My scope showed a trace that matched the one int he RENIX manual exactly.<\/p>\n\n\n\n
<\/p>\n\n\n\n
I then suspected the J10 connector so I pulled the seat, laid in the floor and pulled the ECU out where I could get to the wires. I hooked up the the Crank Sensor pins and got the same proper trace.<\/p>\n\n\n\n
I figured I must have a bad ECU at this point. I have been wanting to swap to a 1990 ECU for a while so I jumped on EBAY and Got one on order. I also ordered a new CPS just in case.<\/p>\n\n\n\n
<\/p>\n\n\n\n
Once the replacement ECU arrived, I plugged in with it laying in the floor board and gave the starter a spin. I got the exact same symptoms. No start and zero RPMs on the REM display.<\/p>\n\n\n\n
The new CPS arrived the next day so I set myself to the task of changing it. This is not easy on the particular Cherokee as I have modified the cross member for extra clearance that makes it impossible to get a tool on the upper CPS bolt.<\/p>\n\n\n\n
I lowered the trans enough for access and swapped out the sensor. I plugged it in and expected the engine to start. But no go. Still the same zero RPMs on the REM.<\/p>\n\n\n\n
Next I decided to go back to basic and check spark and fuel. I put an inline spark checker on the coil wire and saw flashes as I spun the starter. That meant the CPS was actually working.<\/p>\n\n\n\n
Next I connected the fuel pressure gauge. Zero PSI! I had found the problem. I squired a blast of starter fluid in the intake pipe and spun the starter. I got a quick fire and then stall as the vapor quickly burned off.<\/p>\n\n\n\n
I could hear the fuel pump run so I then set out to find what the trouble was. Before going much further, I decided to drop in an extra gallon of gas that is normally set aside for the mini bike. The fuel pump made a different sound and this time the engine fired right up.<\/p>\n\n\n\n
It was out of gas the whole time. I guess now I need to work on the gas gauge.<\/p>\n","protected":false},"excerpt":{"rendered":"
Follow the Data or Trust your Gut? Last week my 1988 XJ off road Jeep played a trick on me. I needed to move it out of the way so I could get my tractor out. It started with an extended crank. This Jeep normally stars quickly so this was odd.<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[210,543],"tags":[],"_links":{"self":[{"href":"http:\/\/mikestrawbridge.com\/blog\/wp-json\/wp\/v2\/posts\/5433"}],"collection":[{"href":"http:\/\/mikestrawbridge.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/mikestrawbridge.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/mikestrawbridge.com\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/mikestrawbridge.com\/blog\/wp-json\/wp\/v2\/comments?post=5433"}],"version-history":[{"count":1,"href":"http:\/\/mikestrawbridge.com\/blog\/wp-json\/wp\/v2\/posts\/5433\/revisions"}],"predecessor-version":[{"id":5434,"href":"http:\/\/mikestrawbridge.com\/blog\/wp-json\/wp\/v2\/posts\/5433\/revisions\/5434"}],"wp:attachment":[{"href":"http:\/\/mikestrawbridge.com\/blog\/wp-json\/wp\/v2\/media?parent=5433"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/mikestrawbridge.com\/blog\/wp-json\/wp\/v2\/categories?post=5433"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/mikestrawbridge.com\/blog\/wp-json\/wp\/v2\/tags?post=5433"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}