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 have a comanche 87 , in line 6cylinder 4.0

Battery light comes on when we turn the key on (didn't do that before). It will crank over but doesn't start. The fuel pump does not prime, no power to it. Changed the starter relay and fuel relay.  I am stumped. Need help please.

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No power to it when and where? You only get power for 2-3 seconds while priming and while cranking. Have you checked the ballast resistor on the driver side fender?

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Have you jumpered the fuel relay circuit and listened closely for the fuel pump? Also, check you fusible links on your starter relay. You said the battery light coming on just started happening, so possibly something is drawing hard on the battery and your fuel pump fusible link burned up. I had a similar problem and discovered the link issue, replaced, fuel pump powered up and no problems since.  Link to my thread where Ohm helped me troubleshoot and source the problem. Hope it helps, if anything it may eliminate possible causes. 

 

 

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4 hours ago, Limeyjeeper said:

Don't think the 87 had the ballast resistor but I might be wrong. If an 87 was fitted with one it was due to a noisy fuel pump TSB or recall.

Mine does.

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13 hours ago, Limeyjeeper said:

Don't think the 87 had the ballast resistor but I might be wrong. If an 87 was fitted with one it was due to a noisy fuel pump TSB or recall.

There was a TSB to install a ballast resistor.  Some 87s got this from the dealers.  I have an 87 parts XJ that has one installed.  My original 87 MJ has never had one.

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What if the ground for the fuel pump behind the left taillight was crappy? 

IMPROVING THE FUEL PUMP GROUND

The fuel pump and fuel tank sending unit ground at a sheet metal screw up behind the spare tire on an XJ, XJ-Body-Ground.jpg?resize=300%2C162and behind the driver’s taillamp on an MJ.

Not only is a sheet metal screw a lousy way to ground things, this ground path is long and travels through some connectors that are prone to corrosion and moisture.

Locate the black wire on  the HARNESS side of the fuel pump/sender 3 wire connector. Remove a 6″ length of the split loom covering. Strip back about 1/2″ of insulation from the BLACK wire.1-fuel pump ground MJ

Take your new ground wire, preferably at least 14 gauge and 12 to 18 inches long as needed, strip it about 3/4″, and wrap it around the exposed part of the harness plug wire.1-fuel pump ground mj-002Solder the connection. Tape it up and reinstall the split loom covering.1-fuel pump ground mj-003

At the other end of your new ground wire, add a crimp on eyelet. Attach the eyelet under a bolt that goes directly into the chassis. Be sure to clean the attaching point til shiny and apply OxGard to the contact surfaces.1-fuel pump ground mj-004

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