Why is it hard to Start when Cold

[LuluBelle]

Well that Fixed Nothing ...... Idiot Lights don't Flash any more ... another small step I suppose
I also pulled out the airbox and there 2 small Earth Points on a 8 ml bolt under the ECU.... cleaned and refitted .....
There are 2 more earth Points front Lower on the Engine I will have to take the battery out to get my arm down there "WHY IT IS ALWAYS HARD".........................
I don't know anymore ... on some US Forums a dude says the PCM Earths at the Dipstick Tube Earth Point ?.. FIXED
another Dude says it earths at the front of the engine ... where as another Dude says that's where the starter and alternator Earth out? I will clean them anyway that way I can say I have no Earth Issues........................
But the Fuel pump RUNS ON...Does not Prime then turn OFF......Ready to Start....When it Does it Starts and runs Perfectly?................ So its Not a Sensor
24 HRS until the Mechanic comes around and it costs me $$$
And I bet he scratches his head?$??
I guess its the PCM Next?...aka ASD Relay ??
I Guess I am Lucky I Make HomeBrew
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_.(o)_)__(o)_)--o-)_)............................................... ...........And Now It Wont Start!

[LuluBelle]

Engine to Battery Negative .. Engine to Alternator... Clean No Change.... had to take the battery and battery tray out just to get to them ... But all Earths are Clean Now!
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_.(o)_)__(o)_)--o-_)................................................ ...And Now It Wont Start!

[awg]

are you able to swap over the ASD relay with one from your other truck?

also jiggle each individual harness wires at both ends, insofar as possible

without refering to the FSM, relays sometimes operate when the earth leg is switched, so a short circuit somewhere would cause the relay to stay on. Relays can also fail in that mode (rarely)

[LuluBelle]

awg there are a few relays in the PCM to play Chess with Believe Me I have tried every Move ......
the mechanic was a No Show Today I will have to chase him tomorrow .....
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_.(o)_)__(o)_)--o-)_)

[LuluBelle]

Ok Forget the Mechanic ...
I did some tests I saw on a US Forum
Pull ASD and Fuel Pump Relays
1..Ignition Off..Check for Power at Cavity 30 in PDC..Check!
2..Ignition On..Check for Power at Cavity 86 and 30..Check!
3..Ignition Off..Reverse test light clip it onto the Positive on the battery probe Cavity 85 When the Ignition is turned On there should be a pulse for 2 to 3 seconds (Prime Fuel Pump) and the Light will come On then go Off?.....FAILED!
85 on the fuel pump relay the light stays on on the asd the light never comes on?...
So apparently from what I have read and using the FSM pin 85 on the ASD should get a ground signal from the PCM ... test 85 to pin 51 on the ECM?
Now I thought the ECM is what the PCM is now called?.....
Pin 51 is in a 60 Pin Plug?.... My 96 and the Red 99 both have 3x32 Pin Plugs at the Computer/PCM/ECM?...So where the F*_K is Pin 51?.................
New Theory....Fresh BEER
Now I Read Somewhere on a USA Wrangler Forum about ASD Failures (Fuel Pump OFF)..... That a Dealer had fitted a Immobiliser connected to the ASD?........I found the Secret Switch and the Wires that go to No Where.....?????
WTF??..No But sorta makes sense If I could test pin 51? I could establish ground so I think the next step is to go inside the PDC (Engine Fuse Box)
How Do You get the Yellow Bit out to check the Wires Underneath?
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_.(o)_)__(o)_)--o-)_)

[Jonny Jeep]

Good work with the diagnosis.

Just had a look at the 97 XJ FSM in case it matches your 96. The ASD ground is circuit K51 at pin C3 (connector C pin 3) which should be a dark blue/yellow wire. The fuel pump relay control is a brown wire at C19.

With the connector attached you could try pushing a pin in the rear next to the wire to back probe the connector and see if those grounds pulse on with the ignition.

I know in the past there have been TJs and possibly XJs too where one of these grounds can fail in the PDC. Since they should operate in the same manner the wires can be linked to get round that issue.

There can also be corrosion getting into the crimps at the PDC terminals which can result in loss of connection as you have with the ASD terminal. It's a long time since I've been at the wiring in my TJ's PDC and I don't remember exactly how it all clip together. I'll have a look and see if I can find a TSB that exists for later TJ's which should give a pretty good idea how it comes apart.

Edit: found a copy of the 05-06 TJ TSB which explains the repair for the issue they get. It doesn't show pics of the PDC disassembly but this is the text explanation, which I hope helps you get to the wiring in there...

REPAIR PROCEDURE:
1. Remove and isolate the positive and negative battery cables from the battery.
2. Remove the Power Distribution Center (PDC) cover from the PDC.
3. Locate the ASD (Auto Shut Down) and the Fuel Pump relays in the PDC.
4. Remove the two nuts used to secure the positive battery cable to the PDC. Remove
the positive battery cable from the PDC.
5. Remove the PDC from its bracket and remove the cover from the bottom of the PDC
to expose the underside wiring.

[awg]

good post ^^

if a failure to earth is the problem, due to a PCM (ECU) wiring issue

In some cases the problem can be rectified by providing a separtae earth wire

this would not work if the earth is "switched" though

to probe the PCM wires, I would be inclined to use a homemade backprobe, which is a small safety pin, attached to my multimeter probe with an alligator clip.

If you cannot backprobe the cavity, it is acceptable practice to pierce the wire with the pin