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View Full Version : FJ40 Backfire, stall no start


RicardoJM
06-16-2010, 07:58 AM
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.

MDH33
06-16-2010, 08:12 AM
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.

TIMZTOY
06-16-2010, 09:18 AM
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

RicardoJM
06-16-2010, 02:04 PM
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:eek:.

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.

60wag
06-16-2010, 02:41 PM
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?

TIMZTOY
06-16-2010, 03:12 PM
Mechanical faliure. Either the teeth sheared. The pin sheared. Dist shaft sheared inside. Or rotor isn't bolted in properlly causing to spin.

RicardoJM
06-16-2010, 03:13 PM
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.

MDH33
06-16-2010, 04:24 PM
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.

RicardoJM
06-16-2010, 07:08 PM
The rotor is good:thumb:. The dizzy shaft, not so much:eek:
http://www.risingsun4x4club.org/uploads/ricardojm/4speedengine/w_brokedizzy1.jpg

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.:D

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.:D
http://www.risingsun4x4club.org/uploads/ricardojm/4speedengine/w_brokedizzy2.jpg

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?

Air Randy
06-16-2010, 07:35 PM
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 :eek:

RicardoJM
06-17-2010, 05:56 AM
Any chance you tweaked the shaft and fractured it while trying to force it in when you were having dist seating issues?

Always a chance, but I don't recall an event that would have inflicted that level of trauma, i.e. hitting it sideways with the BFH while it was partially in.

If the camshaft is moving, wouldn't there be other symptoms that would be occurring? I can't afford a new dizzy for each time I put the FJ40 on the freeway.

60wag
06-17-2010, 07:19 AM
I think the difficulty you had putting the thing in indicates that something was wrong with it on install. Maybe the shaft was bent and that was preventing it from seating easily. It still has a bunch of usable parts on it so keep it for spares. I assume the old dizzy dropped in much easier than the later model one did. If its running well now, I doubt there is a problem with the cam shaft.

RicardoJM
08-16-2010, 03:16 PM
I am bumping this back up as I broke the shaft on another big cap distributor.

After the first shaft snapped, I put in and have been running my small cap electronic distributor. The truck has been running great and not having any issues. I've put on over 1k miles in driving.

Last Friday night, I was helping a Air Randy who needs to send his DUI distributor in for service, get his FJ40 running. He was able to get a Toyota big cap distributor, but does not have the dented side cover - so we put my small cap into his truck and the big cap into my truck. Putting the big cap into my truck took "he man strength" to stab, and within 60 miles the distributor shaft snapped. Because of the issue with stabbing the big cap distributor and the small cap goes right in, we took a micrometer to both to see if there were physical differences; the diameters of distributor shafts, gear and bottom blade were the same and I am stumped.

I believe there is an issue with the gear on the camshaft which makes it difficult to stab the distributor and because the mount for the big cap distributor is part of the distributor body when locked in place there is stress placed on the shaft. I believe because the small cap distributor uses a bracket, the stress is still there but because of the bracket it is not enough to cause the shaft to snap - yet. What other issue could be contributing/causing this?

Air Randy
08-16-2010, 04:01 PM
Ricardo,

There is some additional info we need to share that could be critical clues:

1-The small cap distributor Ricardo has that drops right into the motor and has worked fine for 1,000 miles without issue, came with the motor when he bought it.

2-We got another small cap distributor yesterday and tried to install it into Ricardo's engine since his dizzy was in my truck. It went in just as hard as the big cap did, we would have had to whack it with a hammer to get it to drop in. We installed it into my truck and it dropped in effortlessly, we took Ricardo's out of my truck and it dropped right in to his engine. Weird.

I'm beginning to think there is a difference in the drive gear on the small cap unit that drops easily into Ricardo's truck. For whatever reason it matches up with the cam drive gear in his truck. However, if that was the case, you would thing Ricardo's small cap distributor wouldn't drop in easily into my truck?????

frontrange
08-16-2010, 05:36 PM
Have you mic'd the major diameters on both the fitting and not fitting gears? You should check the minor diameters too but that's hard without the right mic. The gear pitch should be alright unless something really weird is afoot, so the only other thing would be the gear engagement distance from top/bottom of the shaft. Does the one that fits have any shaft play? How does the width of the flat at the bottom of the diz shaft compare between the two?

treerootCO
08-16-2010, 05:38 PM
Chinese built aftermarket camshaft?

RicardoJM
08-16-2010, 05:43 PM
Have you mic'd the major diameters on both the fitting and not fitting gears? You should check the minor diameters too but that's hard without the right mic. The gear pitch should be alright unless something really weird is afoot, so the only other thing would be the gear engagement distance from top/bottom of the shaft. Does the one that fits have any shaft play? How does the width of the flat at the bottom of the diz shaft compare between the two?

Randy may be able to address what we put the micrometer on.

The truck is with my son at work so it may be tomorrow before I can pull the distributor and check for any shaft play - but that could also account for why the small cap shaft has not been strained enough to snap.

RicardoJM
08-16-2010, 05:44 PM
Chinese built aftermarket camshaft?

I don't know much of the history of the engine it.

frontrange
08-16-2010, 08:22 PM
IIRC the original cam had a regrind. It for sure was not a cheap knock off replacement.

RicardoJM
08-18-2010, 05:55 AM
I pulled the distributor last night and there is some play in the shaft. This is why it goes into the engine easily and likely why it's shaft has not snapped.

While it was out, I looked around to see if I could determine what is not lined up. Using the snapped end of the shaft, I know the blade slips into the oil pump with no binding. Using a different distributor, I know the binding starts when the gears begin mesh, just after the o-ring starts to go into the block. I removed the o-ring and there was no change. I did not find the cause for the alignment issue.

Air Randy
08-18-2010, 02:31 PM
I laid awake last night disassembling your motor piece by piece in my head and had a thought. From when I rebuilt my spare 2F I seem to remember there is an oil pump mounting block inside the pan that mounts to the engine block. I don't know if it's possible to bolt this on backwards or to get it out of alignment. That would offset the oil pump inlet slightly towards the cam gear. That could explain why everything seems OK until you try and seat the dizzy shaft down into the oil pump. Your existing dizzy has enough play in the shaft to allow it to go into the oil pump slightly out of alignment and still fit without binding.

This fits with your findings from last night where you ruled out the o-ring and the oil pump blade being the issue.

I think the easiest test is to drop the oil pan and see if we can re-align the oil pump and test fit a different distributor to see if it then drops in ok. If it does we can lock the pump down and put the pan back on. You may want to go ahead and replace the oil pump to be safe since you've already got the pan off.

RicardoJM
10-04-2010, 09:30 AM
An update on this issue.

Randy, your diagnoses of the issue was right on. It appears the block that the oil pump attaches to was indeed just a little off alignment. Fortunately the solution was very easy and didn't require the oil pan to be dropped. I loosened the two bolts that hold the block in place, removed my small cap distributor and then put in another distributor and then tightned the two bolts. I needed a long breaker bar to get them loose and I only loosened them a couple of turns. I was concerned that in loosening the bolts, I would create an oil leak so far there has not been any leak.

It took me a while to source another big cap distributor. Last week Dr. Schlegs came through with another big cap distributor (bit dirty on the inside) which went into the truck Friday evening. I put on over 120 miles this weekend and so far it is all good.

Many thanks to all who posted up on this thread and helped me figure this out.:risingsun