Lately, I have been having some starting issues with my 94 XJ6. Here's the story: I will go to crank the car and it will just keep turning over like its not getting fuel or something. Then I will try to crank it again and it wont crank at all like the battery is out of juice. I will go to jump it with my truck and it will start right up like normal. I have had battery dieing issues but I think that is due to it being in storage for long periods of time from the previous owner I recently bought the XJ from. I have put the battery on a slow charge for about 8 hours and it's been good till tonight. It started doing the same thing again. On a side note, I do run 91 octane fuel only and have recently run a bottle of Lucas Oil fuel system cleaner to keep the system clean. Any thoughts on what it might be thats causing this unusual behavior?

 

Hi bigrig,

If this were my problem, I would check for corrosion or looseness in all of the electrical connections for the Engine Management System (EMS), the Engine Control Unit (ECU), the starter, battery terminals (and ground) and fuel pump, too. All of these can cause inappropriate voltage drops.

If that fails to cure the problem, I would suspect the battery next.

Assuming you do NOT have a maintenance free battery, what is a battery hydrometer test revealing when you feel it is fully charged? You may have a dead cell or low Specific Gravity in one or more cells. It took a day and half to slow charge and bring my Cat's dead battery back to life. It then floated 4 out of the 5 hydrometer ***** in all cells.

If that's ok, then I would suspect high battery internal resistance.

When starting, the amperage drawn by the starter is causing a lower battery terminal voltage due to an increasing voltage drop across the battery's internal resistance - the more current drawn, the larger the internal resistance voltage drop, the smaller the terminal voltage or voltage seen by the car.

Yes, it's enough to power the starter and fuel pump, but not enough voltage to power the ECU and the rest of the EMS.

The next time you experience a no-start condition, have someone measure the number of volts across the battery's terminals with a voltmeter. Do this both before you crank and during. If there is not 12V while cranking, then your sensors aren't getting the proper voltage to tell the EMS to turn on the fuel injectors. Furthermore, the ECU may not be getting the proper operating voltage either.

This battery may be good for another vehicle (or your lawn tractor or jumping motorcycles) but not for your Jag‧u‧ar.

PS And yes, your fuel pump may be going bad and drawing more than rated current.

just my 2₵

Best of Luck

 

bigrig:
These cars are notorious for needing a full charge on a good battery. I'd have it tested to see if that is your problem right there. It might be an easy fix.
Scott

 

Replace all the BLUE relays that control the Engine and Transmission Management.
1988 to 1994 had alot of problems with the Blue Hella relays.

The Blue relays are just simple SPST relays and the Purple ones are different (SPDT???)

You could have 2 faults at once, faulty relays and a low/weak battery.

bob gauff

 

Ok...sounds like I got some work to do on the XJ this weekend. Thank you all for your input!!!