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Old 06-16-2010, 07:58 AM
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RicardoJM RicardoJM is offline
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Default FJ40 Backfire, stall no start

I drove the FJ40 into work this morning and when decelerating off the freeway it started to backfire and stalled. I was not able to get it to start back up and a co-worker (in a big Dodge diesel) strapped me in the last 1/2 mile to the office. Actually, a bunch of co-workers stopped to see if I needed a hand, there are a bunch of real nice people out there.

I have yet to spend much time troubleshooting but may be able to get out there during the day. There is fuel in the carb bowl, the engine is turning over - so I am thinking it may be spark. What are some of the other items, steps that I should look at?

Worst case, TheBoomBoom or HutHut will bring the tow bar out this evening and we'll get it back to the house for further diagnostics.

The drive in is 12 miles, most of it up University and then I-25 to 6th Avenue. Prior to the backfire, the truck was running very well. There were no odd noises, oil pressure is consistent and good, temperature is consistent and good. The ammeter is on the charging side of the line, which is expected considering how much we have cranked it versus how little it has been running and charging the battery. Acceleration had a bit of hesitation early on when the engine was choked and warming up, but once it reached operating temp and the choke was opened it accelerated and decelerated very smoothly. When warm the idle speed seemed right and I would guesstimate it between 500-800 rpm.

Regarding the new engine and drive train on the freeway, on I-25 it got up to 75 mph and still had a bit more that it could go before it would top out. It is still a far cry from V8 powered UZJ100 or Bronco, but much better than the engine and drive train that I pulled out of the truck.
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Old 06-16-2010, 08:12 AM
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Sounds like timing. Check to make sure that your distributor didn't get loose and rotate. Other thing might be your carb loading up if your air/fuel mix isn't right.
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Old 06-16-2010, 09:18 AM
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Quote:
Originally Posted by MDH33 View Post
Sounds like timing. Check to make sure that your distributor didn't get loose and rotate. Other thing might be your carb loading up if your air/fuel mix isn't right.
I'll second the timmimg. And it's problly flooded which is why it didn't start up again. Let it sit till lunch and I bet it will fire right up
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Old 06-16-2010, 02:04 PM
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This is a 60 series distributor and the clamp is built into the base. The position of the base is securely attached to the block and does not appear to have moved a bit since I stabbed it in. The dizzy cap also does not seem to have rotated at all.

To check the timing I rotated the engine to get the pointer mid-way between TDC and the 7 DBTC mark while watching the rotor make its way to the #1 plug position. Yowsers - the timing is off, way off.

The rotor is pointing to the #4 plug and not the #1 plug. The #4 plug is to the left of the #1. I don't have many tools, so I am not certain that the engine is on the compression stroke (versus 180 degrees off) of cylinder #1. Either way, the timing is way off and this engine is not going to fire this way.

My understanding of root cause would be an issue with the distributor. That is to say, with the flywheel where it is the rotor should be pointing to the #1 plug and because it is not the internals of the dizzy are not right. Is this understanding correct? Am I overlooking some other potential cause?

I have not checked for spark. I am on my own for the debugging and my arms aren't long enough to turn the engine over from the cab and still hold a plug wire up to the block.
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Old 06-16-2010, 02:41 PM
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Thinking out loud here.....

I think the gear on the distributor is pinned to the shaft. For the timing to shift that far out of whack, something broke. Maybe the pin sheared and the gear moved on the shaft? I think you need to pull the dizzy and examine it. There isn't any damage to the rotor is there? The flat on the shaft still lines up with the flat in the rotor?
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Old 06-16-2010, 03:12 PM
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Mechanical faliure. Either the teeth sheared. The pin sheared. Dist shaft sheared inside. Or rotor isn't bolted in properlly causing to spin.
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Old 06-16-2010, 03:13 PM
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The rotor just spins around, so it looks like something did break. I'm on my way home now to get the tow bar to get it home. Will pull the dizzy, check the cam teeth and try the old dizzy. The rotor does turn when the engine is spinning, but it is not keeping up with the engine rotation.
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Old 06-16-2010, 04:24 PM
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How does the inside of the rotor look? This is what happened to my 40 on the Outlaws Run this year. Cheap aftermarket rotor (Bosch) didn't key well with the distributor shaft and it wallowed it out and allowed it to spin on the shaft which made it impossible to keep the timing set.
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Old 06-16-2010, 07:08 PM
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The rotor is good. The dizzy shaft, not so much


I took the tow bar, spare dizzy, my tools and HutHut with me. The first thing we did was pull the distributor. It sure came out easy, well the top half did. Using the needle nose pliers the other two pieces were removed. We inspected the pieces to see if there were any smaller pieces that may have fallen into the pan. The pieces fit together and there is nothing in the pan. We then took a look at the cam gear and it looked good.

So we went about setting the engine to TDC and stabbing the spare dizzy, making sure we had oil pressure and then it fired right up. Went into the office long enough to wash our hands and then took the slow, long route home with wide shoulders all the way home.

The tow bar never made it out of the truck. I drove the 40 in to the office and drove it home as well.


I'm at bit of a loss as to what to make of this event. This was a used dizzy that I tested for spark operation, but really don't know any of its history. I didn't ever think to closely inspect the shaft for any damage. I just put it in and off I went. So it could be that the dizzy was on its way out and this morning was its time. I know the spare dizzy I put in is good, I've been running it since last year.

Have any of you ever had a dizzy shaft snap? Was there an underlying root cause?
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Old 06-16-2010, 07:35 PM
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Any chance you tweaked the shaft and fractured it while trying to force it in when you were having dist seating issues?

It could be that shaft was hosed all along and why you were having troubles getting oil pressure.

I have no idea how the shaft could have been broken while it was in the motor, unless there is enough end play in your cam that it was shifting back and forth and putting lateral force on the dist shaft. Seems like an unlikely scenario but we'll know if the current dist breaks too
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