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  #1  
Old June 19th, 2009, 12:49 PM
texmoto
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david summers
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One for the EXPERTS

I will try to keep this short. For background, see my '1300 miles from home' thread. Here's the problem:
94 Defender stalls when the engine is hot, and I slow down and come to a stop. Will restart after sitting for 5 - 25 minutes, depending how hot it is. Constant reving of the engine usually will prevent or delay the stalling.
Also occasionally misses at hwy speed, especially when it's really hot out I (90+degrees), and under load.
Vehicle starts and runs fine, as long as it's not too hot.

Here's whats known. THE problem is loss of spark. I bought a spark tester, and there is NO spark from the coil, after the engine stalls. The engine just cranks and cranks. Plenty of spark, from the coil, when the engine is cool. SO, this is what has been done:

Replaced coil - no change in the problem.
Replaced Ignition control module - no change in the problem.

Have also changed the steeper motor (twice, don't ask), changed the fuel filter and checked most all of the vacum hoses. These things were done prior to getting the spark tester.
BTW, this vehicle has the ignition module relocation kit in place. I have also cleaned the aux ground wire contact off the distributor.

I have done multiple searchs, but I'm missing something. What else could be causing the loss of spark? The problem is consistant, and heat related. Open to suggestions.
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  #2  
Old June 19th, 2009, 01:07 PM
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Chris Snyder
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Is there anyone around that you could try swapping distributors with? It seems strange that it would cause something like this, but if you know that the ignition module is good, the coil is good, and its connection to the coil is good, the next logical step in that chain is the distributor.

Also, while the problem is happening it might be a good idea to get the ohm meter out and make sure your connection between the ignition module and coil is good. In my experience this connection is quite finicky. However I have never had it cause this problem, just a no start situation.The more you check and can rule ou the better.

Hopefully it's something trivial and not a repeat of Ron's wacko shorting starter wire.
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  #3  
Old June 19th, 2009, 01:13 PM
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Quote:
I bought a spark tester, and there is NO spark from the coil, after the engine stalls.
Where exactly are you checking for spark in this step? From the coil to the center of the cap or from the cap to the plug?
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  #4  
Old June 19th, 2009, 01:33 PM
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It could be the little black square thing in the harness on the way to the MAF.
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Old June 19th, 2009, 02:04 PM
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MAF causing no spark?
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  #6  
Old June 19th, 2009, 02:11 PM
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If the problem really is no spark, then it limits the number of possible components. The EFI system wouldn't be the problem, as they are separate systems except for the one connector between the coil and the ECU that tells the ECU your RPM. No spark, and the ECU doesn't supply fuel.

It's got to be the hall sensor, module, coil, cap/rotor, plug wires, or the connections between them.

I'd also suggest testing spark differently like Joel suggested, from the coil wire and not a plug wire. Take the distributor side of the coil wire, and hold it about 1/8" from the intake manifold (or exhaust, or block). You should have a good hot spark there. If not, then the coil isn't even firing. If the coil isn't firing , we've already eliminated a number of components from the issue. How old are your plug wires by the way? I'd also pull the boots back and inspect where the center conductor meets the connector, every OEM type replacement set I've tried has had the conductor burn back, causing intermittent spark on that wire. Since going with quality aftermarket stuff (Mallory), that problem hasn't re-appeared.

Now, did you have any temporary success in fixing the problem when you replaced the coil and module, only to fail again later? Or they didn't help even for a short time? I had a similar problem, and every time I thought it was fixed, the problem just came back a week later. I eventually tracked it down to possibly having blown diodes in the distributor, which were randomly frying components. (I suspect my own welding on the exhaust at one point may have contributed to this, always disconnect everything when welding. oops.)

-Hans
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  #7  
Old June 19th, 2009, 02:15 PM
texmoto
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david summers
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I have checked the spark between the coil wire and the distributor cap, as well as between the coil and the coil wire itself. No spark in either.
Also, replacing the coil and the ingnition module saw no improvement. BTW, what is a Hall sensor? My self, I was thinking it could be a crankshaft position sensor, till I found out that that 94s don't have them.
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  #8  
Old June 19th, 2009, 02:25 PM
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Ok, sounds like the coil isn't firing.

Time to check the signal coming out of the distributor I think, could be a bad hall sensor. Let me get my manual out for the procedure.

Follow-up Post:

Oh, and have you checked the system voltage, to see if you're getting full alternator output when hot?

Follow-up Post:

Here's the next test for you.

Check your battery voltage.
Check the positive connector on the coil and make sure the voltage is same as battery.
Check the negative connector on the coil, should also be same as battery voltage.
Check between the housing on the ignition module to ground, should be zero volts.

-Hans
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  #9  
Old June 19th, 2009, 02:28 PM
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david summers
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Thanks Hans. I will do that now.
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  #10  
Old June 19th, 2009, 02:33 PM
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FWIW: I have found using a timing light to check for spark is easier than holding the end of a wire close to some piece of metal to determine if it is sparking. You don't get zapped that way either and the motor runs normally instead of not running at all in the case of the coil to the distributor wire.
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  #11  
Old June 19th, 2009, 02:42 PM
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Quote:
Originally Posted by landrovered
FWIW: I have found using a timing light to check for spark is easier than holding the end of a wire close to some piece of metal to determine if it is sparking. You don't get zapped that way either and the motor runs normally instead of not running at all in the case of the coil to the distributor wire.
For a quick check, I agree. But sometimes you also need to see the spark itself to determine if it's strong or weak.

-Hans
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  #12  
Old June 19th, 2009, 02:42 PM
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david summers
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Sorry, I can be a little dense. Make the coil checks with enigne on, yes? And when checking the coil leads, what should I be connecting the other wire to? Electrical is not my area of expertise.


Also, my spark tester gap is adjustable, if that could be of any help.
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  #13  
Old June 19th, 2009, 02:44 PM
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Not a problem. You want the ignition turned on, but the engine not running.

When checking the voltages, put the positive lead for the meter on the thing you're testing and the negative lead to a known good ground. The engine block or intake work pretty good for this.

-Hans
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  #14  
Old June 19th, 2009, 03:09 PM
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ok. voltage for the + coil terminal, the - coil terminal are equal to the battery voltage. Zero volts for the ingition module.
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Old June 19th, 2009, 03:15 PM
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Ok, that means the coil tests ok for now. What was the battery voltage? 11.5 or more is good, lower than that is bad.

Assuming good battery voltage, next step is the module. With the switch off, you want to test between the positive terminal on the battery and the negative terminal on the coil. Should be zero volts. Then crank the engine, the voltage should come up a little bit but not much.

-Hans
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  #16  
Old June 19th, 2009, 03:17 PM
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Quote:
Originally Posted by evilfij
It could be the little black square thing in the harness on the way to the MAF.

That would be my guess if you have replaced the ign. module already.
Often overlooked part, but does exactly what you say is happening.
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  #17  
Old June 19th, 2009, 03:37 PM
texmoto
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david summers
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Will do. New info, difficult to explain, wish I had a digital camera. The ground for the ingnition module is the aluminium relocation plate, mounted on the drivers fender well. I have determined that the only grounding contact for the PLATE is the two threaded mounting studs, which are slightly grungy. Any chance this less than optimal ground could be the problem? When I isolate the plate from the studs, the ground is lost and the engines dies and won't restart. Just like when its stalls when hot.
And, battery voltage is 11.5. Little low due to Engle fridge running for 36hrs.

Follow-up Post:

And what is this little black thingy that you speak of?

Follow-up Post:

Ok. Red to + on battery and black to - on coil equals 12 volts with engine off.
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  #18  
Old June 19th, 2009, 03:42 PM
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It's very possible that you don't have enough ground there. I've never worked with the Rover remote style module, only the on-distributor ones. But the distributor mounted ones had a ground connector that ran straight to the engine block. I would both clean up the existing studs as well as run an additional ground wire if there is a place to do so on the case of that module.

Also, how good is the physical contact between the module and the plate it's mounted on? I do wonder if possible the module is getting too hot, and perhaps would need a heat sink on there somewhere?

-Hans

p.s. little black box? Silly rover, all these parts that AREN'T in the book that I keep finding.
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  #19  
Old June 19th, 2009, 03:46 PM
texmoto
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david summers
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I will try clean the bolts. But what does the 12volts when there should be no volts between the coil neg terminal and the battery + terminal mean?
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  #20  
Old June 19th, 2009, 03:54 PM
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Very possible that it's a sign of the bad ground, and the voltage is finding an alternate route to ground.

Couple other things are possible as well, but right now I'd focus on ensuring that module gets a good ground.

-Hans
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