Why is it hard to Start when Cold

[awg]

I dont think the PCM will work the same way, as the '96 does not have a keychip based immobiliser, which the 99 does, so no reliance could be placed on a test...but it might yield something.

If you do have a bad PCM, with cooked internal solder joint perhaps,
then imo the best bet is to try and get one from the same year

They have the part num clearly written on them..a bunch of small nums starting with 5, then 3 BIG numerals..the 3 big numerals are easy to see, and could be obtained from a wrecker, they should match if possible, probably cost $100, there is a few specialist wreckers

[LuluBelle]

about right awg that plus some postage I am really grasping at straws now I suppose.... the closest auto electrician is at Longreach 215k away so its up to me ...
I think I am going to spear it and test for the pulse at least it will be another piece of the puzzle
I will also back probe the iac map and cam sensors to test for voltage already done tps and crank and the o2 well the wires are fine
results tomorrow night
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[awg]

Originally Posted by LuluBelle

... the closest auto electrician is at Longreach 215k away so its up to me ...

_____ooooo
/__l_l_,\____\,___
l_---l_l__l---[ ]llllll[ ]
_.(o)_)__(o)_)--o-)_)

they wont want to know you, my mate got one free from a reputable auto elec, sat in his shop for 1yr..stuck a new computer and it fired right up

I see a Gumtree advertisor, he he is from Mittagong or Bowral, and must be a wrecker..knows his sh!t..I would get in contact and discuss get the matching num computer

Its very comforting for me to have a 59 digits off VIN spare sitting right here, the computer part num is an exact match, color and interior match
(except its a Limited, nicer interior, so I am pimping my ride with upgrades)

[LuluBelle]

today yielded nothing I found the wire at the comp plug speared it with a pin hooked my test light to positive and got the missus to turn the key no light? no earth pulse?
tried it a couple of times and back at the relay I even went over and did the test on the 99 and WTF it had no pulse and I know it was running fine when I parked it there a couple of months ago......
so once again ????
_____ooooo
/__l_l_,\____\,___
l_---l_l__l---[ ]llllll[ ]
_.(o)_)__(o)_)--o-)_)

[Jonny Jeep]

Dies the 99 still run? if it does you will have a pulse. Maybe the ground can't supply enough current to light a test bulb? a multi meter should be able to show the pulse as it's two seconds long.

Don't forget to check the fuel pump relay ground too. You would only need one working ground to activate both relays by splicing between the relay coil ground sockets.

Just thought... Will the 96 start if you pull both fuel pump and ASD relays and jump the contacts so fuel pump and ASD circuits get constant power? You'd have to pull the jumper wires to stop the engine, so this would just be a test to see if all else is OK.

[LuluBelle]

"Maybe the ground can't supply enough current to light a test bulb? a multi meter should be able to show the pulse as it's two seconds long."........good idea Jonny Jeep I will try that.......................

"Don't forget to check the fuel pump relay ground too. You would only need one working ground to activate both relays by splicing between the relay coil ground sockets.".......? I don't understand what you mean?.....my fuel pump stays on after priming

"Just thought... Will the 96 start if you pull both fuel pump and ASD relays and jump the contacts so fuel pump and ASD circuits get constant power? You'd have to pull the jumper wires to stop the engine, so this would just be a test to see if all else is OK.".......A Really Good Thought actually!
As my fuel pump runs on though? I will try jumping 30 to 87 and see what happens .........thanks for your input

I have been trying to understand the wiring diagrams in the fsm concerning where the pcm gets power from and grounds?
reading everything about pcm failures I can
I think the issue might be the pcm......Why?
originally when this first started apart from low fuel pressure ... you had to turn the key on and off several times the check engine light flashed like crazy it wasn't until the light slowed down and stopped flashing and stayed on like normal for a few seconds then you could start... harder when cold... it got worse over a few months fast forward to now when I cleaned all the earth wires I found a damaged wire I repaired it ..... the check engine light no longer flashes it comes on for a micro sec and that's it? its like something gets power and trips straight away? my scanner wont link anymore and I cant get codes using the key..
maybe it is fried ?

_____ooooo
/__l_l_,\____\,___
l_---l_l__l---[ ]llllll[ ]
_.(o)_)__(o)_)--o-)_)

[Jonny Jeep]

Originally Posted by LuluBelle

"Don't forget to check the fuel pump relay ground too. You would only need one working ground to activate both relays by splicing between the relay coil ground sockets.".......? I don't understand what you mean?.....my fuel pump stays on after priming

Occasionally I've seen on the TJ section on Jeepforum.com PCM ground has failed on either the fuel pump or ASD relays. When this has been diagnosed, and pulse confirmed on the other relay, the 'fix' has been to tap the working ground over to the relay with the non working ground.

This means the PCM is using only one relay ground to operate the two relays. This can be done as both grounds operate in exactly the same way, ie. initial pulse on, then on during cranking or running.

Hope that's a better explanation for you. Possibly it was getting ahead of where you are up to since pulse and continuity hadn't been fully confirmed.

As far as the fuel pump relay sticking on, we know the relay coils grounds so I would remove the relay and check what the coil ground does at ignition on. If the ground is continuous I'd check the output from the PCM. If it pulses as it should I'd swap the relay, as it could be bad.

A couple of times recently I've had my engine stay running after removing the key from the ignition. The first time it happened the engine stopped as I pulled the relay. The hood was open at the time as I was just doing initial cam break-in. I'd replaced cam and lifters while the head was off to replace pistons due to a broken skirt. The second time it happened was the next day but the engine stopped before I could get the hood up to get to the relay. I swapped my ASD relay for the horn relay and the problem hasn't recurred. I did have problems starting before and after the break in which could have also been down to bad relay contacts. I've now replaced my bad relay and will probably replace the others too for peace of mind.