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Unread 02-20-2011, 09:53 PM   #1
vmhlbjorn
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1990 XJ Cherokee 
 
Join Date: Jul 2010
Location: Arlington, VA
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1990 XJ no start - fuel issue

1990 Cherokee LTD (Renix, 4.0, I6), 180k+ miles. No start (cranks, and cranks… now in Park and Neutral). I’ve been stalking posts for several evenings and weekends, but haven’t found the one that seems to hit home yet (still reading). I’ve read it is a cause of slow-start, but can leak-back through the fuel line check valve cause no start?

Novel follows, but boy is asleep and I want to try and provide full symptoms up front, hoping for your help, and to avoid wasting your time:

Background: For considerable (1-2 yr) time before it died, Jeep would start slow for the first start of the day – sometime needed to prime the fuel system with 2-3 turns of the key. Wouldn’t really even fire to life, but just stumble it’s way to life if I was able to release the key and step on the gas as it began to catch. It would usually be fine after that during short trips, but each additional start on that trip, the engine would roar to life, often with very high rpms for 3-10 sec, a bit higher/longer each start. This seemed to be worse in hot/humid weather, until this winter. After driving and parking at work, it was back to the same slow/lucky start. Usually, if I missed stepping on the gas in time, a few more cranks would get it going. Generally I think it ran rich / smelled of gas – but no visible leak. Also seemed to idle at what I thought was a bit low (400rpm).

I remain concerned about the background problem described above (and found a lot of good posts about maintenance and repairs that should help), but I write because of the following:

Recently, in the week before the no start condition, different symptoms. Car began bogging down at intersections and dying unless I kept my foot on the gas, so I began driving with two feet – waiting on the next warm weekend to dig in. Last day, it died on the way home as my foot was lightly on the gas coming down a hill, but I got into a parking lot and after 5min was able to restart (last time) and get home. The car also began bogging down when trying to accelerate in the last day or two.

Over the past year or so (toddler means limited time to play with the XJ), I have installed a new fuel filter, new CPS this summer (which seemed to fix an earlier no-start, for awhile – although occasionally needed to be in Neutral), and new coolant temp sensor (3 months ago). I also tuned in the last 3 months: new rotor/cap and plugs. Previous repairs (’07) included new injectors from the dealer (one was leaking, they goofed up the repair, so eventually replaced all 6), new wires to the spark plugs, and battery. It seemed to start acting up after that injector repair – random stalling at slow cruising – but that ‘went away’, unless it just became different/current problems. I cleaned the IAC two yrs ago, but after reading posts, I may have done a poor job - and didn’t clean (haven’t cleaned since 2002!) the throttle body.

Now, while cranking, fuel pressure at the rail comes up to just less than 40psi. After releasing the key, pressure drops almost immediately to 20psi, then quickly on down to <10psi (within 1-2 minutes). I pinched off the rubber line from the fuel pressure regulator, but same symptoms. Need to verify spark again, but battery is now charging after getting drained by the attempts to start/test.

Assumption of good spark may be a bad one, but assuming spark is good, and back to the point:
Leak-down test makes me think the fuel line check valve is one of several issues. But could it be the one causing no start?

Opportunities to work on the problem are limited to a few hours on the weekend, but if you can help me get up and running, I’ll do my best to document the fix and subsequent repairs to address the broader issues. Thank you!

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Unread 02-21-2011, 05:44 AM   #2
tjwalker
It's the crank sensor!
 
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1. The problem with having to start your vehicle in neutral is the "neutral safety switch". It is very common. They can often be "refurbished", adjusted and returned to function. Here is a link to a very good article on that.

http://bc4x4.com/tech/2010/jeep-neut...ty-switch-nss/

2. Two quick and dirty tests here to help you isolate your no-start. First, If it doesn't start, check for spark. Never assume you have spark. Pull a spark plug, keep it attached to the plug wire, place the spark plug electrode near a good engine ground, have a buddy crank the engine while you watch. 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.

If you have quality spark, spray a small amount of starting fluid or a small splash of gas into the intake. If the engine starts and runs momentarily, you know you have injector pulse and you have confirmed a fuel delivery problem.

Once you have narrowed this down a bit to fuel, spark or quality spark, the suspect list gets a whole lot shorter........

Good luck and post back what you find!
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Unread 02-21-2011, 04:27 PM   #3
cboccboc
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I just had the exact issue on my '90. I replaced the Crankshaft Position Sensor and she is now happy again. Check the resistance between the two pins on the connector. I believe the required measure should be between 170 and 270ohms. While you are connected to the pins move the wire around. Mine had all of the wire insulation removed close to the sensor so it wasnt visible. The two wires were shorting causing all my fun and heartache. I am about to do my neutral switch as stated before but the only issue that is causing me now is starting in all gears or settings and the back up lights being intermittent.
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Unread 02-21-2011, 04:54 PM   #4
keepishop
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Could be worth testing the fuel injectors for leaks and clogs.
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Unread 02-22-2011, 07:36 PM   #5
vmhlbjorn
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All - thank you. TJ's caution on assumptions seems spot on. After getting the battery back in I did not see spark, but I didn't have much time to test. I will update once I can do some better troubleshooting while jumped. The neighbors will love watching me drive wife's '98 XJ across the front yard to get to the driveway with jumper cables...
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Unread 03-28-2011, 07:25 PM   #6
vmhlbjorn
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Solved! (?)

Wanted to give it some time to be sure, but I think I found the issue...

Spark! I never could do a successful spark test (I need to get better at that), but in testing and cleaning, I found a very dirty/oily connection into the coil. Once that was cleaned up, and with a full battery (and jumper cables), she started right up. Still starts, and hasn't let me down in a month or so now. I still need to load test the battery, as that seems a lingering issue.

Thanks all for your tips and suggestions, across the forum. Researching here got me back on the road.
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