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sprinkles08
sprinkles08, ASE Certified Technician
Category: Jeep
Satisfied Customers: 21586
Experience:  Chrysler/Dodge/Jeep Master Certified, ASE Master and Advanced Certified, Trans and Hybrid Specialist
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My name is ***** *****. I have a 1995 Grand Cherokee 4.0

Customer Question

Customer: My name is ***** *****. I have a 1995 Grand Cherokee 4.0 Liter with a Crank-No start problem. Had same problem in late May this year and diagnosed as bad Crank Position Sensor. Installed new and problem solved, until recently. Jeep has cranked but failed to start three times in the last two weeks. Cranked-No start the 23rd. We left it and came back today the 26th to tow her home. She fired right up and ran for 45 minutes. Tested Crank-Start a dozen or so time without fail. Tried again an hour later and Crank-No start again. Good plugs, Wires, Cap, Rotor and Coil. I'm getting good coil spark but no Plug Wire Spark. Any Ideas what would cause the intermittent failures.
JA: Thanks. Can you give me any more details about your issue?
Customer: I'm not sure what you need to know, but I'd happily share any info. Jeep has 230k, runs High Mileage Oil, doesn't go Off Road (2wd). Has ample power when it it running.
JA: OK got it. Last thing — JustAnswer charges a fee (generally around $18) to post your type of question to Jeep Experts (you only pay if satisfied). There are a couple customers ahead of you. Are you willing to wait a bit?
Customer: I don't mind waiting
JA: OK. Now I'm going to take you to a page to place a secure deposit with JustAnswer. Don't worry, this chat is saved. After that, we will finish helping you.
Submitted: 11 months ago.
Category: Jeep
Expert:  Amedee replied 11 months ago.

Hello and welcome! My name is ***** ***** I can assist you with your question. Are you saying that there is spark going into the distributor cap but no spark coming out? If so, this would indicate a bad cap and or distributor rotor.

Customer: replied 11 months ago.
The cap is new the wires are new
Customer: replied 11 months ago.
The rotor button is new.
Expert:  Amedee replied 11 months ago.

Just because they are new does not mean they are good. I have seen bad new parts right out of the box.

Expert:  Amedee replied 11 months ago.

Unless of course they were installed wrong.

Customer: replied 11 months ago.
I'm way past the cap, rotor and plug wires. They are definitely not the problem.
Expert:  Amedee replied 11 months ago.

So there is spark leaving the cap going to the plugs correct?

Expert:  Amedee replied 11 months ago.

If not, something simple is being overlooked

Customer: replied 11 months ago.
There's good spark leaving coil, no spark from distributor when crank·no start happens. When jeep does start, it runs great. So if the dist cap, rotor or plugs and wires were bad it wouldn't run great.
Expert:  Amedee replied 11 months ago.

It is possible that they are going bad intermittantly. The reason I ask is because it is very common to have a no spark condition intermittantly caused by a bad coil, ASD relay or engine speed sensor.

Customer: replied 11 months ago.
Is this legit, or just a scam?
Expert:  Amedee replied 11 months ago.

Ww have an A+ rating with the better business bureau

Expert:  Amedee replied 11 months ago.

Sorry, meant to say we

Expert:  Amedee replied 11 months ago.

As a matter of fact, I have helped a lot of customers today.

Expert:  Amedee replied 11 months ago.

Shall we continue?

Customer: replied 11 months ago.
Well which of these would cause no voltage coming from dist cap when the coil is producing?
Expert:  Amedee replied 11 months ago.

battery voltage or spark? There is a difference. Big difference

Customer: replied 11 months ago.
Coil produces 3/4 inch spark off ground. I would estimate 15k or more volts.
Expert:  Amedee replied 11 months ago.

Thats good. So, this spark goes into the distributor cap but does not come out of the cap to the other wires when this happens? Is this correct?

Customer: replied 11 months ago.
When crank·no start happens, coil is producing good spark, but no spark from dist cap
Expert:  Amedee replied 11 months ago.

Then you have bad tune up parts. Thats the only possible cause.

Customer: replied 11 months ago.
Why does the Jeep start and run great for a week a and all of a sudden tune up parts are so bad it won't fire at all, then Jeep starts fine and runs great for a couple days, then crank·-no start again?
Expert:  Amedee replied 11 months ago.

Most likley because of something else causing a no spark condition. I bet there is no spark coming out of the coil when this condition occurs.

Customer: replied 11 months ago.
You would not want to bet that. There is very good spark coming from the coil when the crank-no start occurs.
Expert:  Amedee replied 11 months ago.

Based on what your telling me and my 15 years being a diagnotic tech, something is not adding up here. I am going to leave this question open for other experts as another expert may be able to assist you. Good luck.

Customer: replied 11 months ago.
Sorry for the troubles. I've tested the ASD Relay and engine speed sensor. Maybe the CPS I replaced back in May is intermittently going bad.
Customer: replied 11 months ago.
Don't feel bad, if it is in the book, I've already tried it.
Expert:  sprinkles08 replied 11 months ago.

Hello and welcome to JustAnswer!

If you have spark at the coil but not leaving the distributor then the problem has to be with the coil, coil wire, or a cap/rotor issue. Either the spark is too weak to make the jump at the rotor or spark is being lost internally in the distributor. It will often ground through the distributor shaft due to an issue with the rotor. I would first suspect the coil is weak but it's very possible that it's the cap or rotor. If the wires, cap and rotor were replaced in an attempt to repair this issue then they are less likely to be a factor, if that's the case then I'd recommend replacing the coil with a Mopar part.

Customer: replied 11 months ago.
Sorry guys, but you seem hung up on rotor, cap, etc. The Jeep starts and runs great one day and crank-no start the next and then start great later in the day. Rotors, caps and wires don't fail and then magical repair themselves. I found a proper testing procedure and it was the Crank Position Sensor. Seems this is responsible for a majority of Jeep 4.0 engine crank-no start problems. No hard feelings, but I am not satisfied with you guys answers. My original question should have answered the rotor, cap, plugs diagnosis.
Expert:  sprinkles08 replied 11 months ago.

Yes, any electrical part can have an intermittent failure. If you're losing spark that's an electrical issue, and you're losing spark intermittently therefore you have an electrical part failing intermittently. If you have spark leaving the coil then the only parts of the ignition system that could physically cause the problem are the coil, coil wire, cap or rotor.

If the crank sensor wasn't functioning then there would be no spark or injector pulse. The cam and crank sensor signals have to be present and in sync for the ASD relay and coil drivers to turn on. If the crank sensor was truly the issue then the information supplied in your post was not correct and spark was not actually present.

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