Crank no start!

[KatahGii]

Ok so I’ve been working on this MJ for moths now. I have a Duralast Gold group 35 battery with 800 CCA just bought today because the old group 58 battery was toast! It starts if I jump it but if it’s just the battery it cranks and cranks and cranks but no start. Any ideas?

[JustEmptyEveryPocket]

When you are jumping it, where do you put the ground clamp on the MJ?

 

I'm wondering if you are missing some body or engine ground points, and by completing a circuit from a good ground and power source you are getting around that.

 

Could also be way off. Electrical is not my strongest area. But this is what jumped (haha un-intended pun) to mind first.

[eaglescout526]

Have you tested your CPS for Volts AC? Should put out above 3.5VAC.

 

 

Huh, I mustve not submitted my reply when I typed what to check.

[KatahGii]

7 hours ago, JustEmptyEveryPocket said:

When you are jumping it, where do you put the ground clamp on the MJ?

 

I'm wondering if you are missing some body or engine ground points, and by completing a circuit from a good ground and power source you are getting around that.

 

Could also be way off. Electrical is not my strongest area. But this is what jumped (haha un-intended pun) to mind first.

No when I jump it it’s positive to positive and negative to negative.

[KatahGii]

7 hours ago, eaglescout526 said:

Have you tested your CPS for Volts AC? Should put out above 3.5VAC.

 

 

Huh, I mustve not submitted my reply when I typed what to check.

I have not

[KatahGii]

11 hours ago, eaglescout526 said:

Have you tested your CPS for Volts AC? Should put out above 3.5VAC.

 

 

Huh, I mustve not submitted my reply when I typed what to check.

Oh if you are talking about the crank sensor I replaced that a few weeks ago. It just dawned on me.

[eaglescout526]

Usually that is a culprit for a no start condition. The aftermarket CPS's are a hit or miss and can fail right out of the box.

[JustEmptyEveryPocket]

3 minutes ago, eaglescout526 said:

no start condition

But OP says it will start if jumped. That is what has me puzzled. What would be different about (in essence) hooking up another good battery versus a new battery?

 

OP: What is the resting voltage of your new battery? If you jump the truck and get it running, what is the voltage of the new battery then?

 

Easiest test (IMO) right now would be to pull a plug, ground it to the block, crank the engine, and watch for spark. If you have spark, then we need to move to something new. If you do not have spark then CPS becomes suspect #1. 

[eaglescout526]

2 minutes ago, JustEmptyEveryPocket said:

But OP says it will start if jumped

I missed that. Brain is kinda burned from the ECU thread.

[cruiser54]

19 hours ago, JustEmptyEveryPocket said:

But OP says it will start if jumped. That is what has me puzzled. What would be different about (in essence) hooking up another good battery versus a new battery?

 

OP: What is the resting voltage of your new battery? If you jump the truck and get it running, what is the voltage of the new battery then?

 

Easiest test (IMO) right now would be to pull a plug, ground it to the block, crank the engine, and watch for spark. If you have spark, then we need to move to something new. If you do not have spark then CPS becomes suspect #1. 

 

Cranking SPEED is important to the Renix system. The CPS generates a signal to the eCU. Slow crank= low signal. 

[KatahGii]

Sorry I leave this thread for dead I’ve been dealing with some personal stuff and on top of that the friend who’s house my Jeep is at is having some issues with her husband. I’m going to have it towed when I get the money and the sheriff to go with me. I haven’t checked the battery like y’all said yet since I haven’t been able to go over and look at it. But it is a brand new Duralast Gold with I believe 800cca. And it only starts if jumped. Could it possibly be the engine ground or the starter ground and I’m grounding it through my friends car when we jump it?