nitroxsteve Posted July 18, 2011 Share Posted July 18, 2011 How long does your 4.0 crank before starting. My truck is an "88" with a rebuilt engine, new crank sensor, Cap, Rotor button, plugs, wires, and knock sensor. It seens to turn over a few times before it fires and I'm wondering if thats normal. Thanks, Link to comment Share on other sites More sharing options...
JeffN Posted July 18, 2011 Share Posted July 18, 2011 anywhere from 3 to 10 seconds Link to comment Share on other sites More sharing options...
nitroxsteve Posted July 18, 2011 Author Share Posted July 18, 2011 anywhere from 3 to 10 seconds Thanks Thats what I was thinkin. Link to comment Share on other sites More sharing options...
Jerry Posted July 18, 2011 Share Posted July 18, 2011 anywhere from 3 to 10 seconds x2 Probably why the motors last so long. Gives the oil time to pressure up & circulate. Link to comment Share on other sites More sharing options...
dakal Posted July 19, 2011 Share Posted July 19, 2011 x4 Link to comment Share on other sites More sharing options...
jpnjim Posted July 19, 2011 Share Posted July 19, 2011 How long does your 4.0 crank before starting. For- Effffing- Ever. :doh: 1989 with new CPS Link to comment Share on other sites More sharing options...
Boots Posted July 19, 2011 Share Posted July 19, 2011 x6 Link to comment Share on other sites More sharing options...
dakal Posted July 19, 2011 Share Posted July 19, 2011 my renix fires on the third or fourth crank. Link to comment Share on other sites More sharing options...
87Warrior Posted July 19, 2011 Share Posted July 19, 2011 Must be a Renix thing or something. My 03 TJ fires right up, almost immediately after touching the key. My '92 MJ would crank for about 1/2 a second before firing up. Link to comment Share on other sites More sharing options...
Sir Sam Posted July 19, 2011 Share Posted July 19, 2011 about .5-1 second for cranking time. Hell sometimes I just think "start" and it fires up before I know it. Course, thats on my 00 XJ. Link to comment Share on other sites More sharing options...
Incommando Posted July 19, 2011 Share Posted July 19, 2011 My '88 Renix cranked for ever, too. The '91 HO also cranks for a second or maybe two, but not as long as the Renix did. Link to comment Share on other sites More sharing options...
ratrapp Posted July 19, 2011 Share Posted July 19, 2011 it is a renix thing.in the morning my mj cranks for maybe a second,second and a half and it fires up.now in the afternooon about 9 hours later when i leave work it cranks 3 to 10 seconds before it fires.it's been doing this for years and i have replaced the dist. and a new updated straight wired mopar crank sensor to no improvement.my gf's 95 zj and my grandmothers 96 zj fire on the first crank even after sitting several days.the renix stuff is different than chrysler electronics.i've just learned to deal with it. Link to comment Share on other sites More sharing options...
comanche12 Posted July 19, 2011 Share Posted July 19, 2011 x7 mine cranking for like 3 sec. i checked fuel pressure, its still fine and spark fine. so i agree with you guys. its might be renix thingy :roll: I'm still gotta to get used with it compare with my subaru. started fast Link to comment Share on other sites More sharing options...
Car RamRod Posted July 19, 2011 Share Posted July 19, 2011 It's a renix thing. Something like it has to recalibrate it's fuel signal every time you turn it off. Look it up. Mine cranks for 2-3 seconds. Link to comment Share on other sites More sharing options...
Boots Posted July 19, 2011 Share Posted July 19, 2011 My dad has a cj5 with the 4.2 liter and Mopar fuel injection, It sits for months at a time and fires on the first crank every time. Link to comment Share on other sites More sharing options...
jpnjim Posted July 20, 2011 Share Posted July 20, 2011 Renix engines have to turn a couple revolutions to compute the CPS sensor location. That alone shouldn't cause the long crank time, but Multiport Fuel Injection was new technology when the 4.0L was introduced, look around for other 1987 MPI engines, it's a pretty short list. Long crank time was just one of the bugs that didn't get worked out till they redesigned the engine controller in 91. Link to comment Share on other sites More sharing options...
Sir Sam Posted July 21, 2011 Share Posted July 21, 2011 That alone shouldn't cause the long crank time, but Multiport Fuel Injection was new technology when the 4.0L was introduced, Wasn't for the Japanese, they had been using it for over ten years. Link to comment Share on other sites More sharing options...
jpnjim Posted July 22, 2011 Share Posted July 22, 2011 That alone shouldn't cause the long crank time, but Multiport Fuel Injection was new technology when the 4.0L was introduced, Wasn't for the Japanese, they had been using it for over ten years. MPI in 1977? Bosch, Bendix & Rochester injected cars go back to the 1950's, but multiport, as in a separate fuel injector for each cylinder was still new in 1987. The first Multiport Injection I can remember was the TPI Chevy's in 1985, for Corvettes, Camaro's & Firechickens, then the Mustangs got Sequential Fuel Injection in 1986. I can remember Bosch injected VW's in the early 1980's, but I don't think they used separate fuel injectors like the Jeeps, Chevy's & Mustangs were using by the mid 1980's. Link to comment Share on other sites More sharing options...
Dirteatr717 Posted July 23, 2011 Share Posted July 23, 2011 shortest it ever takes mine is like 8 seconds.... :nuts: Link to comment Share on other sites More sharing options...
Sir Sam Posted July 23, 2011 Share Posted July 23, 2011 That alone shouldn't cause the long crank time, but Multiport Fuel Injection was new technology when the 4.0L was introduced, Wasn't for the Japanese, they had been using it for over ten years. MPI in 1977? Bosch, Bendix & Rochester injected cars go back to the 1950's, but multiport, as in a separate fuel injector for each cylinder was still new in 1987. The first Multiport Injection I can remember was the TPI Chevy's in 1985, for Corvettes, Camaro's & Firechickens, then the Mustangs got Sequential Fuel Injection in 1986. I can remember Bosch injected VW's in the early 1980's, but I don't think they used separate fuel injectors like the Jeeps, Chevy's & Mustangs were using by the mid 1980's. My 84 Nissan had Multipoint fuel injection, a 75 280z had multipoint fuel injection, 1980 VW+ Vanagons all were MP fuel injected(hell they were fuel injected before they were water cooled). Link to comment Share on other sites More sharing options...
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