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Erratic/Intermittent Voltage Drop while Cranking when warm 88' 4.0


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I bet I know what the problem is. Happened on my wife's xJ. When the fuel level gets high, it sloshes against the ground wire from the fuel pump to the mounting plate of the fuel sender. The ground wire goes all intermittent and quits grounding the fuel pump. The photo shows the ground wire all melted on the XJ.

 

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I bet I know what the problem is. Happened on my wife's xJ. When the fuel level gets high, it sloshes against the ground wire from the fuel pump to the mounting plate of the fuel sender. The ground wire goes all intermittent and quits grounding the fuel pump. The photo shows the ground wire all melted on the XJ.

 

 

Probably caused from long term ethanol rot.

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I bet I know what the problem is. Happened on my wife's xJ. When the fuel level gets high, it sloshes against the ground wire from the fuel pump to the mounting plate of the fuel sender. The ground wire goes all intermittent and quits grounding the fuel pump. The photo shows the ground wire all melted on the XJ.

 

 

Probably caused from long term ethanol rot.

 

I don't think so. The terminal at the fuel pump flange was burned looking and wasn't tight. Definitely a thermal issue.

 

Ran great as long as fuel wasn't sloshing against the wire.

 

All this said, no better time to perform the fuel pump ground wire upgrade in the link below:

 

http://cruiser54.com/?p=249

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Ok, Makes sense except for one thing. Why would it also be loosing spark as well? Does the ECM kill the spark when it reads intermittent/no voltage from the pump?

No. You may have more than one issue. 

 

The ECM is also clueless as to whether you just filled the tank. 

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Ok, Makes sense except for one thing. Why would it also be loosing spark as well? Does the ECM kill the spark when it reads intermittent/no voltage from the pump?

No. You may have more than one issue. 

 

The ECM is also clueless as to whether you just filled the tank. 

 

 

I figured the ECM was clueless of the fuel level. I'm asking if the ECM recognizes voltage or a lack of voltage from the fuel pump. 

 

I could believe there may be more than one issue. But it has not lost spark at any other point except for these 3 times. 

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  • 1 month later...

Got a little update on my Comanche. 

 

It's been running "Ok" since the last post. Not running perfect, But hasn't left us stranded or thought it would. Until this past weekend. Big local Car Cruise near our home was over the weekend. My fiance was going to take it up to our car club's spot( I was at work). But it just cranked and wouldnt start. A friend came by and put some gas in it, and it started up. So she drove it up to our spot. I get there about an hour or so after. And hop in it to go drive in the cruise, Again it just cranked. So I started checking around. Fuel pump: Didn't hear it priming. Checked for spark: None.

 

And finally, It hit me...

 

I never checked the CPS other than a "Visual" inspection...its there and plugged in. Even after hours of looking through this forum and others. And Cruiser's Renix tips for an answer that was obvious lol. So I unplugged it and plugged it back in. And she fired up. Drove it home, And checked it with my volt meter. Of course, Averaged less than .29V AC. Picked up a new one from Napa and now she's running great. I'll try an post pics of the old CPS...Because my visual inspection wasn't good lol. This was a lesson learned for sure.

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