F Motor Explosion - Bent Push Rod? (1 Viewer)

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Hi All,

I'm trying to keep my FJ40's F motor from going to the scrapper.

After sitting for a week, it would not start. I spent all weekend tracking it--no spark. Timing was off.

I got it running again, and it ran good around the block. I was adjusting the timing when there was a big explosion and engine shut off.

Smoke came out of the Carb, valve cover and side cover on the block. I had never seen such a thing.

It took me a while, but I was able to get it running again. Now there is a knocking noise at higher RPM. No knocking at idle.

Power is still good--but is sounds horrible.

Any ideas? Maybe a bent pushrod after explosion?:bang:

I haven't torn into it yet--I wanted to get some pointers from the experts at IH8MUD before I go overboard.

Thanks guys!
 
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By explosion do you mean backfire, which could be very common if messing around with the timing?

Does the engine have points or electronic ignition?

Is the engine knocking because the timing is off?
 
Joined
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By explosion do you mean backfire, which could be very common if messing around with the timing?

Does the engine have points or electronic ignition?

Is the engine knocking because the timing is off?

Hi FJforty...the knocking sound too loud to be timing.

I just uploaded a video to YouTube that might show the sound better.

Here's the link everyone: YouTube - FJ40 metal slapping - possible bent pushrod

What do you think...pushrods or something else?
 
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Sounds like a bad rod bearing. Not good to run it. If you want to do a quick test before tear down you can try this. Do the same thing ( rev it a little) but pull one spark plug wire at a time to help ID the bad cylinder. One thing though, I have heard sounds like this from the fuel pump, if the return spring in the pump breaks the arm smacks around. I would at least pull it off first and check it.
 

Trollhole

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And while your at it spend all of 2 min and remove the valve cover and look and see if it's a bent push rod. Run it with the cover off and see if you can see the problem. What ever you do don't drive that cruiser until that is fixed.

Also while you were screwing around with the timing you didn't happen to pull the dristributor up out any? If so you could have disengaged the oil pump and wrecked your motor. Can you confirm you have oil pressure?
 
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I was listening to that video thinking "sounds fine to me, what the hell is this guy talking abou... oh, THAT!"

Sounds like a pooped rod bearing to me. Forgive me if this is ignorant (I've never adjusted timing myself), but you do so by fiddling with the dizzy, right? Any chance you pulled it out of engagement with the oil pump while doing so?

EDIT: Wow, shoulda read Trollhole's post right above me. s***, now I'm That Guy.
 
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fwiw My dizzy came up and the no oil thing happened (I turned it off quickly), but it would only knock at idle. I pulled the pan and replaced the bearings, cleared the oil paths in rods and hardware clothed the shaft and its been good ever since. But it didnt do it at seed tho.........
I would try to look at easy thing 1st like the fuel pump and valve cover. pulling the pan would hurt neither...
 
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San Diego, CA
Compression on Cruiser

How about getting a compression tester and posting up the results.

Hi Trollhole, took your advice here's what she gave me:

Cylinder #1: 115 psi
Cylinder #2: 135 psi
Cylinder #3: 130 psi
Cylinder #4: 120 psi
Cylinder #5: 125 psi
Cylinder #6: 140 psi

#1 is barely scraping by on the minimum according to my Chilton book (114 mininum, 150 psi optimal on 1969-71). The others are all over the place.

Any thoughts?:wrench:
 
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I was listening to that video thinking "sounds fine to me, what the **** is this guy talking abou... oh, THAT!"

Any chance you pulled it out of engagement with the oil pump while doing so?

EDIT: Wow, shoulda read Trollhole's post right above me. ****, now I'm That Guy.

Hi amaurer,

As for disengaging the oil pump with dizzy--I don't think so (I hope not). It was in place and still is.

I didn't drive it very far...less than a mile before it happened. I was taking it out for a test spin when I started loosing power at higher RPM. I pulled off to the side and tried adjusting it by ear. It was less than 1 mile from home--so I hope damage is minimal.

Like I said, the clanking sound didn't start until after it backfired while I was adjusting (turning) the dizzy.

Thanks for all your ideas and suggestions--I'm following them to a T.


:steer:
 
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fwiw My dizzy came up and the no oil thing happened (I turned it off quickly), but it would only knock at idle. I pulled the pan and replaced the bearings, cleared the oil paths in rods and hardware clothed the shaft and its been good ever since. But it didnt do it at seed tho.........
I would try to look at easy thing 1st like the fuel pump and valve cover. pulling the pan would hurt neither...


Thanks Kyle,

I'll try the fuel pump next and take your fix into consideration.

Pulling the oil pan off is probably next. But at that point I need to find a place to park it--as this might turn into a big project.

Thanks again for your insight.:)
 
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After spending some more time trouble shooting the knock, this is what I found under the oil pan in cylinder #4.

4603521370_f4bc2cd0ca_o.jpg

The cotter pin and bolt holding this rod assembly together came apart--well 1/2 of it did. The knocking noise was coming from the bolt tapping on the piston rod itself.

There are some metal shaving in the bottom of the pan, along with the nut from the bolt that came loose.

Is this salvageable, or is the Toyota F motor shot?

Any ideas or advice is appreciated on what my next step should be.

I really want to get this cruiser back on the trail.

Thanks!:wrench:
 
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Southeast Overland

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I'm not the expert here - but - have you looked at the crank and bearings at #4?

Maybe a crank polish, new bearings and fix the piston and???
 

jfz80

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That assembly should not have had a cotter pin; just a bolt and nut.

Your sound may also be from the gap b/w the bearing surface and the crank, however that ground down side of the washer supports that it was striking the rod or piston as well.

MY F met a similar fate. However the bolts retaining all connecting rods were in place and tight. I assume the bearing got spun blocking the oil passage and the friction ate the bearing up completely (as in there were no halves to remove upon dissasembly) Sounded about identical but and became much worse very quickly to a knock at any rpm a howl and a tow home.

since #4 is low as well and your in there I'd check all your caps and retaining bolts.
If you can remove that bearing cap, inspect the crank for scoring. If your there to replace one, you might as well replace all the bearings. NO fun, but more fun than diving back in after you wrap up a partial project.

Comparo vid: This was #6 running w/out connecting rod bearing... doh

 

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