Delayed start problem

You are giving the classic description of a bad main power connection. I would suspect the body's ground connection first.

The power takes time to arc the bad place and connect. Heat can expand connections tightening them up. Once arced the connection can work for a while also. This will get worse usually sooner than later.

Mike

Following your advice posted in previous threads I have done the following:

There are a few more ground straps though. That about the heat expanding the connections makes sense. Thanks!

I forgot to mention I removed the relays, cleaned the connections, moved them around, then decided to replace both the fuel pump and ASD relays. No change in behavior, but now I have spare relays! Thanks

Sounds normal to me, you must give the computer time to run it's diagnosis. A common reason why the on board error code is not displayed, people won't wait before starting the on and off sequence. God Bless America, Bill O|||||||O mailto: snipped-for-privacy@aol.com

Thanks, I'll keep this in mind but I'm afraid that one day it just won't start if I let it go on like this. In fact, on a recent trip to the mountans where it was pretty cold, I had to be towed part way down until it just decided to start again. It seems the cold is a major factor here.

How's the battery voltage and fluid level?

Bill, The starter always works fine (always cranks). But if the computer has not provided a ground to the fuel pump relay, it won't start and run. Both the check engine light and the ASD and fuel pump relays are supposed to get a ground from the computer. I don't know if it is because the computer is not getting 12v from the ignition switch or if it is unable to get a good ground.

Latest test: I put a test light on pin 5 on the computer data link connector to see if that point was getting 12v as soon as the ingnition switch is turned to run. It checked out fine, but the check engine and relays still have a (this time) 6 second delay before it turns on. I'm now thinking it is either:

I got a new battery soon after the problem started. It checks out fine, I'm pretty sure it must be something else.

One more thought for you.

There is a recall on your emergency brake lever and the ground for the fuel pump bolts onto the frame of this lever on your 95 YJ. There have been posted 'fuel pump' and 'ECM' 'failures' right after this job is done if the wire doesn't get hooked back up. Maybe your ground there is bad?

Mike

I'll check that one ASAP. Thanks.

too:

cranking:

I cleaned the CPS connector but the sensor itself could be bad. Can a bad CPS keep the check engine light from turning on right away? I think the computer allows about 3 seconds to get at signal from the CPS but I don't know if others have reported the check engine light not lighting due to a bad CPS. Thanks

The FSM says that not all '95 YJs have this ground wire. Mine doesn't seem to have it (but it still worked fine for a long time before this problem started).

Here is an update: I checked directly at the PCM connector for ground on all the ground cavities, 0.3 ohms on all three. Checked for 12v on the cavity that always has 12v from the battery, perfect. Checked if the PCM gets 12v from the ignition switch as soon as it is turned to run, perfect. If this problem is due to a bad connection I would say it has to be in the PCM connector itself or in the PCM itself or the computer is taking a long time to run its diagnostics as Bill suggested. Any more ideas? Thanks

One more idea for you I just remembered.

I have had a bad fuse connection cause a 'no red dash light means no start' issue on several vehicles over the years. It was corrosion on the fuse's legs and their socket causing it.

Mike

Thanks, I'll check the fuses again. Maybe it's that dome light fuse that seems to affect much more that what it says it does.

Mike,

How likely do you think it is that this could be due to a bad PCM? Can computer faults be made worse by cool weather?

Thanks