Wont start

[robsyz426]

Just rebuilt my 4.0 and now it won't fire. Well it dose in away it will fire on #4 then#1 then nothing till it comes back around to#4. I replaced the crank sensor changed the distributor changed the computer same thing I'm stumped

 

[Bounty__Hunter]

Did you install the distributor per the FSM? Could be 180º out of time.

 

[robsyz426]

Did you install the distributor per the FSM? Could be 180º out of time.

Yea checked that first

 

[greg92jeepxj]

I'm sure that in your rebuild you would have certainly reinstalled the flex plate back on correctly since it can only be reassembled one way . That is of course important in establishing correct ignition timing with the CPS . But it still sounds like an ignition timing problem . Can you verify that the cylinder firing is in fact on TDC compression stroke ? I'm sure you feel that you did correctly plant the distributor back in correctly but please do try to check over your work since the engine isn't starting correctly . Once when I helped a friend install a timing chain and gears on a V6 Buick engine we had correctly installed the distributor correctly. Same results , no start. He disassembled the the front engine cover ( timing chain cover) without indexing the distributor and I had to rescue him. After many attempts to pull the distributor and line up oil pump,drive and finding #1 TDC did we finally get it running. Theoretically , all a distributor has to do is be pointed on #1 terminal and engine on #1 TDC to,run but I have seen many times where correct indexing to be the only way for an engine to start . The 4.0 distributor has no dwell setting for you to manually try to find the right timing mark ( retard and advance) so,it is critical that the distributor be installed correctly. Please do go,over FSM instructions and verify all in compliance . Since the engine is not running , you've got nothing to lose. As long as flex plate is right ( can only bolt up one way due to hole spacing differences on crank hub) and timing chain is to , it falls on distributor placement.

 

[robsyz426]

I'm sure that in your rebuild you would have certainly reinstalled the flex plate back on correctly since it can only be reassembled one way . That is of course important in establishing correct ignition timing with the CPS . But it still sounds like an ignition timing problem . Can you verify that the cylinder firing is in fact on TDC compression stroke ? I'm sure you feel that you did correctly plant the distributor back in correctly but please do try to check over your work since the engine isn't starting correctly . Once when I helped a friend install a timing chain and gears on a V6 Buick engine we had correctly installed the distributor correctly. Same results , no start. He disassembled the the front engine cover ( timing chain cover) without indexing the distributor and I had to rescue him. After many attempts to pull the distributor and line up oil pump,drive and finding #1 TDC did we finally get it running. Theoretically , all a distributor has to do is be pointed on #1 terminal and engine on #1 TDC to,run but I have seen many times where correct indexing to be the only way for an engine to start . The 4.0 distributor has no dwell setting for you to manually try to find the right timing mark ( retard and advance) so,it is critical that the distributor be installed correctly. Please do go,over FSM instructions and verify all in compliance . Since the engine is not running , you've got nothing to lose. As long as flex plate is right ( can only bolt up one way due to hole spacing differences on crank hub) and timing chain is to , it falls on distributor placement.

checked that time checked the firing order checked the plug, relays, fuse everything I can think of

 

[greg92jeepxj]

To recap , you've changed the crank sensor , distributor and pcm . To your knowledge , all previous posted checks performed and are correct. So , the only spark your getting is from the #1 & #4 spark plug wires ? This is somewhat pcm related . All grounds and wiring harness connections are good ? Are all sensors getting a 5 volt reference ? Need to know if pcm is communicating with sensors . Especially the cam and crank sensors. Reference and signal , 5 volt and return between pcm and cam and crank sensors needs to be in good order . Interested in what kind of spark your getting , quality and to how many cylinders. Also , is there voltage read at the injector harness positive and are any of the injector harness grounds responding when engine cranking. Need to know if pcm is grounding injectors to fire them. Cam and crank sensors have all to do with that function .

 

[drewbuddy]

:agree: Injectors were on my brain as well. I would do a resistance check too. If you can find what spec is for injectors you're using, an ohm reading will tell you if they are bad, out of spec or not to eliminate that factor. Proper gap on your plugs too (long shot, but it happens)

 

[robsyz426]

To recap , you've changed the crank sensor , distributor and pcm . To your knowledge , all previous posted checks performed and are correct. So , the only spark your getting is from the #1 & #4 spark plug wires ? This is somewhat pcm related . All grounds and wiring harness connections are good ? Are all sensors getting a 5 volt reference ? Need to know if pcm is communicating with sensors . Especially the cam and crank sensors. Reference and signal , 5 volt and return between pcm and cam and crank sensors needs to be in good order . Interested in what kind of spark your getting , quality and to how many cylinders. Also , is there voltage read at the injector harness positive and are any of the injector harness grounds responding when engine cranking. Need to know if pcm is grounding injectors to fire them. Cam and crank sensors have all to do with that function .

Well after checking everything 3 more time I went and bought a new distributor (the only thing that wasn't new) it fired right up. Purrs like a kitten now. Thanks for all the advice