XJ40 ( XJ81 ) 1986 - 1994

Issues with starting

 
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Old 05-27-2018, 12:55 PM
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Default Issues with starting

Just recently purchased a 1994 XJ6 and I'm beginning to have issues with starting, especially the first try in the morning. It seems that if I wait around 12 hours to start it from the last time it ran.. it just won't start.

I know it's not the battery. It's turns and turns for as long as I try but that's it. This happened to me just a couple of days ago first thing in the morning, so I ended up taking another vehicle to work. Then when I got home I tried starting it first thing and it started up just fine.

Thanks for the help in advance!
 
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Old 05-28-2018, 08:58 AM
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Default Starting issues.

Sounds like your distributor is taking in moisture. Pull off the the dist cap and wipe it down. First thing in the morning is dampest time of the day, I think that might be your issue.
 
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Old 05-28-2018, 11:47 AM
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Thank you for the reply AbstractCustoms,

I just took a look at the dist cap and it was bone dry.. still no start. It's starting to look as if the time of the day doesn't matter as much. I have no issues once it does start or with idling. Also, I can cut it off and then start it back up right away with no issues. So I don't think it's a power or alternator problem.

Yesterday, I sat out there trying to get a start for about 10-15 minutes and I eventually did. I'm no expert mechanic by any means but I'm wondering if it could be the fuel filter or fuel pressure regulator?
 
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Old 05-28-2018, 03:29 PM
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My WAG would be that the problem is your fuel pump, although there are two relays affecting fuel delivery that may be the problem. The fuel pump relay and (more likely) the O2 sensor heater relay.


Try swapping out and cleaning the connectors sockets of the O2 sensor heater relay on the passenger side firewall. I think that relay has a light blue socket, third from the left.


Worth a check anyway.


Larry
 
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Old 05-28-2018, 10:04 PM
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Casey,

Welcome to the Jaguar Forums! It's great to have you with us.

One simple check you can do when the engine cranks but won't start is to watch the tachometer. It should read about 200 rpm while cranking. If it reads 0 rpm, suspect the Crankshaft Position Sensor (CPS).

Also, just because the battery will crank the engine doesn't mean the voltage while cranking is sufficient. If the voltage sags much below 11 volts while cranking, the Engine Control Module (ECM) may not trigger the ignition to fire.

And following up on Larry's good advice on the fuel pump, Bryan N of the Jag Lovers forum wrote an excellent fuel pump circuit diagnostic routine for the '93/'94 cars that has worked for me every time I have needed it:

With ignition OFF
Remove fuel pump relay (black base, right rear corner
trunk above BFM)
Do you get 12 volts at pin 30 (Brown/yellow) of the fuel
pump relay base from fuse C6 in right fuse box?
If yes, jump pin 30 (Brown/yellow) and pin 87 (Blue/red)
in fuel pump relay base - does the pump run continuously?
If pump does not run, fault is in the wiring / connector
between fuel pump relay and pump
If pump runs, suspect fuel pump relay is defective.
Replace / re-fit fuel pump relay
Remove oxy sensor heater relay (yellow base on firewall)
Do you get 12 volts at pin 30 (Brown/pink) of the oxy
sensor heater relay base from fuse C4 in right fuse box?
If yes, jump pin 30 (Brown/pink) and pin 87 (Blue/purple)
in oxy sensor heater relay base - does the pump run
continuously?
If pump runs, suspect oxy sensor heater relay is defective
Replace / refit oxy sensor heater relay
Remove EMS main relay (black base on firewall)
Do you get 12 volts at pin 30 (Brown/yellow) of the EMS
main relay base from fuse C1 in the left fuse box?
If yes, jump pin 30 (Brown/yellow) and pin 87
(White/brown) in EMS main relay base
Turn ignition ON
Do you hear the fuel pump give its half-second priming
burst? [You can repeat this many times and you (or an
assistant listening at the open filler neck) should hear the
half-second 'whirr' of the pump every time you switch the
ignition ON]
If yes, suspect the EMS main relay OR the EMS ECU is
defective (the latter, very unlikely but possible)
Turn ignition OFF
Replace / re-fit EMS main relay
Remove Ignition 'ON' relay (on a '94 it may be in a
white base on the firewall or it may be buried under the
dash behind the radio, which may make the following rather
difficult!)
Do you have battery voltage at pin 30(Brown) of the
Ignition 'ON' relay base?
If yes, temporarily jump pin 30 (Brown) and pin 87
(White/pink) in the Ignition 'ON' relay base
Do you hear the half-second priming burst from the pump
each time you jump those pins in the Ignition 'ON' relay base?
If yes, suspect the Ignition 'ON' relay is defective or
even fuse A5 in the left side fuse box - but if either is
defective, you will get NO dash lights when you turn on the
ignition, so you should have already noticed that.

Cheers,

Don
 
 
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