Pinging (1 Viewer)

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My 1977 FJ40 constantly pings. At first , it was pinging on a load and I found out the timing was advanced 7 degrees. The timing was put back to spec and now it pings all the time.

Any ideas ? I just had the carb rebuilt and valves adjusted as well. Thanks
 
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Isn't 77 when they changed from points to electronic ignition? What do you have?
When you say it was "put back to spec", how many degrees advanced are you now?
You may have advanced the timing too much.
 
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What do you mean by all the time? Idle, just sitting there? Pinning is bad. Lets get this fixed before it blows a hole in one of your pistons.
Pinning is caused by pre-ignition. You can get some pre-ignition if an engine is really hot or if the timing is firing to early.
 
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The pinging occurs when driving in 2,3 and 4th gear under power. The timing had been advanced 7 degrees above the stock setting. At that time it only pinged in 4th gear under load. Now the timing is set to the factory setting.

The the ignition was changed to a Pertronix system. I have added a can of seafoam to try to clean any carbon buildup.
 
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Ignition system needs 2 things, spark at the right time and advance of the spark. If your timing is set OK then maybe your advancing too much.
 
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If the only thing you changed was the timing, then I would venture to say that is where this new problem is. Although vac advance could be involved, too.

Low octane fuel can bring on the ping, have you tried a higher octane?
7* BTDC is the "factory" setting for your timing at idle, you can adjust it a bit either way to make it run optimally.
How are you determining the timing? There should be two marks on your flywheel, a line that shows TDC, and a BB that shows 7* BTDC. Your timing should be set to the BB when at idle, about 650 RPM.
 
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Lean conditions in a hot cylinder can cause pinging too. The Fj40 has a unique problem with the vacuum brake booster in that it is tapped off of the manifold runner for the number six cylinder. If the seal on the booster goes bad, it can cause a lean condition in that cylinder, and if left unchecked can burn the exhaust valve. Make sure the seal is good. This is checked from inside the cab. Idle the engine, then get your head down by the brake pedal and slowly press it. Listen for a hissing noise. If you hear hissing, then get the booster overhauled or replaced.

Mine hisses, but I have a V-8 and the lean condition is spread out over 8 cylinders, so I don't face the same issue as the stock six. Still, it's something that I need to address one of these days.
 
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I had to take the truck to the shop as I will going OCONUS in a couple of weeks and don't have the time to mess with it. The shop said right off the bat that there was an intake manifold leak and that needed to be fixed first. That could be a large part of the problem. I will let you know. Thanks
 

bsevans

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I experienced pinging when I was in the White Mountains and the only fuel available was regular octane. I have always used premium in my 40 and never have pinging when running premium octane fuel.
 
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The "pinging" you hear may be your tappets....if timing is at the BB. When was the last time you adjusted the intake and exhaust valves?
 
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I am still pinging. I had a intake maniford leak fixed . I had hoped that could have been the cause. I ran a can of seafoam through the tank. I then filled up with high test and still pinging. It is better but it still pings in 3rd and 4th while under a load.

The trucks runs better than it ever did but the pinging is bothersome.
 
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I didn't notice if you had tried any kind of adjustment with the timing at all since the initial time you reset it. The higher octane fuel improving the issue points towards timing as you are using a fuel that burns "slower" than lower octane stuff which can help buffer out too much ignition advance. I'd try retarding the timing little by little to see if it helps as the pinging means you are hammering the hell out of your pistons.

I'd also try moving to slightly fatter jetting as running lean can cause pinging as well, it doesn't hurt to have slightly too much fuel but too little can destroy a motor.
 

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