Dan_in_WA

Hi everyone, I'm new to Jeeps but not at all new to cars that won't run right!

The Jeep in question has the 4.0L engine and automatic trans. Just bought it used; drove it home and now it won't start! Cranks over just fine. Battery is good, and I've kept the charger on it between starting attempts.

I checked for spark, that appears good. I've replaced cap and rotor, as they looked pretty ratty and needed to be changed anyway.

Plugs are wet when they come out, seems to be getting fuel ok. I even put a tiny bit of fresh gas down the intake manifold, to eliminate the possibility of bad gas. It didn't even try to fire.

I checked the position of the distributor rotor, it points to #1 cylinder from roughly 25 deg. BTDC to just after TDC.

I did have the distributor out for a bit, but have since verified it's not 180 degrees out.

I had another guy take a look today, he verified it's not 180 degrees out, and checked spark and fuel. All are there.

The only code of note that comes up is 24 - and I found the TPS is open. But that won't keep it from firing, will it? (The only other code was 12.)

If it's got spark and fuel, and the timing's ok, it has to run, right?

What am I missing?

Thanks,
Dan

Ender

CPS* CPS* CPS*
(Crankshaft Position Sensor)
What I've done in the past is just unplug the connection, then recconect it, then she fires right up! Good Luck!

Dan_in_WA

Thank you!! I'll try that tomorrow.

Little update; I put new plugs in it. The old NGK's weren't all that bad, but very wet. Fresh Autolite platinums went in, gapped at .035".

It coughed and sputtered this time, but the battery is now a little low from all the attempts tonight.

Could I simply have too much fuel flooding the thing? Maybe the Powertrain Control Module thinks the driver's foot is on the floorboard because the TPS is shot?

Thoughts? I really appreciate the help.

This is the first car problem to get me down and stomp on me for awhile.

Dan

freegdr

do you have injector pulse that tells the injectors when to open and squirt fuel

tjwalker

Yes, you can flood the engine. If the plugs are wet and stink of fuel, it is likely.

Be sure that the battery is up to the job. Load testing is the only real way of confirming that. Any parts store will do this for free.

Spark + Fuel + Compression + Air = Start.

For most vehicles, compression and air is okay, so you should keep focusing on spark and fuel.

EXACTLY how is the spark? By that, I mean you are looking for a strong, blue, snapping spark. Yellow/orange/white indicates a weak spark which may not be strong enough to start the engine (test your ignition coil).

Going back to your distributor issue....why did you remove the distributor? And did the no-start occur IMMEDIATELY after reinstalling the distributor? If it did, you need to focus on indexing of that distributor.

Dan_in_WA

The no-start happened the next day after we brought it home. The previous owner said it was hard to start when cold.

The distributor looked like it was one tooth advanced, when the engine was at TDC the rotor was already well past the #1 tower on the cap. The cap and rotor were dirty, a little oily or wet with who-knows-what and the center button on the cap was badly worn. These aren't expensive, so I changed 'em.

I tested spark with an old Autolite plug I had laying around, it was a blue spark. I tried pulling a couple of the NGK's out of the engine and testing them, to see if they were fouled or whatever. YELLOW spark, on both of them. The gap was a little wide, but under .045". Fouled? Whatever. I changed them.

I'm heading out now to take another run at it. Thank you for your replies!

Dan

Dan_in_WA

I think I'm finally on the right track. Crank Position Sensor, or at least the wiring that goes to it.

Following the instructions in the Chilton's manual, I checked resistance of the middle terminal (A terminal in the pix) to battery ground. Should have been 5 ohm or less, getting about 6.3K ohm.

This looks like the orange wire in the back of the connector. I am on the correct terminal, aren't I?

Man, I hope that PCM is okay.

Dan

MATT 87 CHEROKEE

He has spark typically when a cps goes out it doesn't have spark... I've got a friend who needs 2 replace his cps any tips for replacing it? Back to the topic.... how is your timing, or possibly even the computer. Are you sure you didn't flood it?

Dan_in_WA

It was flooded.

I replaced the Throttle Position Sensor this morning, and it started (pretty much) right up.

The TPS had failed completely open. No continuity between any pin, anywhere.

The PCM apparently thought that the throttle was all the way open, and was dumping fuel into it. That would also explain why putting a little gas down the intake manifold didn't help it fire.

I checked out the Crank Position Sensor; the Chilton's manual was wrong. The center pin isn't ground, but "+" power. And I had 5.02V at pin 7 (gray) of the PCM, and that would momentarily drop to near 0 as I rotated the engine by hand.

Thank you all for your help and suggestions!
Dan

Dan_in_WA

Which engine does he have? The Chilton's manual, which has proven itself less than reliable, says to remove a bolt and pull it out. On my 4.0L.

But here's a tip that might be worth something: Your local library probably has Professional Motor's Manuals or another series similar to that. Going down there and making myself a few photocopies has saved me lots of time and swear words more than once!

My local library recently put all that stuff online, but for whatever reason, their server is down right now and I couldn't get in to their Research section. It's worth a Google of your local library system...

My local one is www.ncrl.org for anyone interested, go to Research and Homework, find Auto Repair and then get the message "Diagnose Connections Problems", as of this writing.

Hope that helped.
Dan

MATT 87 CHEROKEE

Thanks he has a 4.0 and I think in going to have to use around 4 feet of
Extensions to get it out