No Start...(I've diagnosed it to a point)

Hey guys, our 98 died, It turns over but does not start. I've got fire to the spark plugs and fuel pressure at the rail but the injectors aren't being fired, which tells me it is probably a sensor I suppose. Is that true? I forgot the actual code already but It popped a TPS code. I remembered reading awhile back that if i unplug the the tps that it should start if it is bad I suppose. Any Idea's? No other codes popped and no check engine light of course.

CKP (Crank position sensor) 3-prong/2-wire connector. Driver side, rear of engine. Unplug it and plug it back in see if it starts.

Johnnie Walker said:

CKP (Crank position sensor) 3-prong/2-wire connector. Driver side, rear of engine. Unplug it and plug it back in see if it starts.

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If he is getting fire, most likely the CPS is fine. You can verify this by squirting some starting fluid or carb cleaner down the throttle body. If it starts and runs for a minute, the CPS is fine.

Under what circumstances did this problem start?

This is my wife's Jeep so I didn't get an elaborate explanation but she said it just died while driving down the road at speed and under a load I presume since she was headed to work. I'm 99% certain it's getting fire since I've got voltage all the way to the plugs, but I'll give starting fluid a try.

Aw crap. A woman was envolved. We will never be able to fix it. :anon:

I'll keep my mouth closed on that one, but she does drive it like she hates it (because she does).

Check the wiring for the o2 sensors. Twice they've shut me down; once the rear one when the harness dropped on the driveshaft and wore through (created a short, and immobilzed me), and once on the front O2 when the harness, through heat and fatigue, shorted internally and crumped on me during a blizzard.

Both times, a little 15amp mini fuse in the PDC was the clue...It would pop every time I turned the key, and keep tripping the ASD (auto shut down?) relay under the hood.

Steve

So it turns out that she said when it died the radio and gauges all died for a moment and then it wouldn't start. I need to check all the fuses in the morning.

Mosephus said:

So it turns out that she said when it died the radio and gauges all died for a moment and then it wouldn't start. I need to check all the fuses in the morning.

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1. If the radio and gauges all died and it wouldn't start, you could have a problem with "grounds". Freshen them. Don't want to be chasing your tail for a simple ground issue. More on freshening grounds below.

2. Get us that code number as it may be important here. We need the EXACT number, not just the circuit it is related to, as with OBD, the devil is in the details. Can't ever ignore codes, as your Jeep is trying to tell you something and it could easily be related to your symptoms.

3. When you check for spark, you must have a strong, blue, snapping spark. Yellow/orange/white indicates a weak spark, which may not be strong enough to start the engine
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Grounds can be the root cause of many electrical gremlins. Refreshing grounds is NEVER a bad idea!

You can't just check or look at these grounds. You must remove, scrape, clean until shiny the cable/wire ends and whatever they bolt to. The one on the back corner of the head, and where it attaches to the firewall. Scrape the paint from the firewall. Best to replace that woven cable with a #4 or #2 gauge cable. You can attach the one end to the intake manifold if you would like.

Next go over to the engine dipstick tube stud. Remove the nut and clean the wire ends and scrape the block until shiny at the stud. Reattach tightly.

If you are so inclined, add at least a #6 cable from the negative terminal of your battery to one of the bolts on your radiator support. Scrape the paint off first.

Haven't had time to mess with it but learned I'm not getting any spark (even though my multimeter got a signal) and am getting fuel. Also I apparently left the door open and the batt died so when I went to run the codes the Batt was dead and when it was charged the codes were cleared other than a converter clutch code that it usually has.

So does anyone know of the sensors that kill the spark if the sensor fails?

Cam Position Sensor.

Before you buy any parts from anyone, clean all of your grounds including the PCM ground adjacent to the PCM itself. A few others to look at are the block grounds (rear of cylinder head and below the coil).

FWIW,
Cam or Crank Position Sensor codes will not be thrown until the error occurs for 50 engine rotations. You'll have to crank it for a while before any eror codes are reported.

No Spark = CPS

Mosephus said:

Haven't had time to mess with it but learned I'm not getting any spark (even though my multimeter got a signal) and am getting fuel. Also I apparently left the door open and the batt died so when I went to run the codes the Batt was dead and when it was charged the codes were cleared other than a converter clutch code that it usually has.

So does anyone know of the sensors that kill the spark if the sensor fails?

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#1 cause of no spark is the crank sensor. #2 cause is the ignition coil

Be sure that your battery is verified (load tested) and charged before trying to start your vehicle again.

Ok guys just to give alittle more info, it's now got a brand new battery (store clerk didn't want to wait to charge it so he just gave me a new one.) The Crank positioning sensor is ok, I keep a brand new spare and installed it and no dice and I also tested both of them and they both check out ok.

I'll have to check again since it was a few days ago but I think I was getting full batt voltage to the coil.

Mosephus said:

So it turns out that she said when it died the radio and gauges all died for a moment and then it wouldn't start. I need to check all the fuses in the morning.

Click to expand...

This particular sympton, matched my situation; except that I went to start my '98 XJ when everything died.

In my case, it turned out to be the fan relay. Here's why...

I was checking grounds when I bumped the Main Relay box that houses the ASD, Strarter, Cooling Fan, Fuel pump and other relays/fuses. When I bumped it, my cooling fan spun...hmm. I pulled the cooling fan relay, found that stuff rattled in it when I shook it. I believe the shorting relay was causing the ASD relay to trigger and shut the system down. I removed the positive battery cable for about 10 minutes to reset the PCM, and replaced the dead relay with a new one. It started right up....

The point to all this, is to check all your relays; or if nothing more than good preventative maintenance, replace them all. They are not really all that expensive. Relays are electro/mechanical devices that will eventually fail.

And....from what I've read...check to make sure you've got good spark. It's not hard, pull a plug, plug it into the wire...hold the plug against the block, and have wife crank it..look for spark. I like basics....fuel....spark...compression. If you've got all of them, it will run. Unless they're not at the right time/order.....