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Old 03-30-2016
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Ranger backfires

Hey there my 1985 ranger 2.8 v6 runs but backfires when you give it gas I am wondering what the problem is?
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Old 03-30-2016
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Check firing order on the distributor first, easy to cross wires, follow each wire back to its spark plug.
Firing order here: Ford Ranger/Bronco II 2.8 liter Engines

I have been doing mechanics since......well forever, and I STILL goof up firing orders, and never ever learn, lol, I have chased my tail on a misfire or other similar issue for hours, because I KNOW firing order is correct.
Well it wasn't..............they say you learn from you mistakes, but I must have a moron blind spot for firing orders

Then disconnect SPOUT jumper and reset spark timing at 10-12deg BTDC
After setting the spark timing reconnect SPOUT jumper and then start engine, check spark timing again, it should be different, rev engine a few times and spark timing should change according to RPM, if not then TFI module may need attention.

Next would be the accelerator pump.
A carb adds fuel to the air flowing in using Jets, the air sucks fuel from the tips of the jets as it passes by.
And on a carb there needs to be a way of adding more fuel quickly when accelerating because the Jets will lag behind the air flow slightly because opening the throttle plate quickly drops the vacuum quickly, so an accelerator pump was added.
When you push down on the gas pedal the accelerator pump squirts extra fuel into the engine, the harder or faster you press down the more fuel is squirted in.

If accelerator pump isn't working like it should the engine will get a Lean air/fuel mix, this lean mix can self ignite when entering a hot cylinder causing a back fire.
I would think you would also have some pinging/knock associated with this issue as well.

Engine OFF
Take the air cleaner off the carb so you can see inside the throat, open throttle manually and you should see fuel squirting in, that's the accelerator pump working.
IF there is little or no flow then the accelerator pump diaphragm is bad, these used to be available separately, but now-a-days you often have to buy the whole rebuild kit.

Last edited by RonD; 03-30-2016 at 10:29 AM.
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Old 03-30-2016
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Thanks for your help

Quote:
Originally Posted by RonD View Post
Check firing order on the distributor first, easy to cross wires, follow each wire back to its spark plug.
Firing order here: Ford Ranger/Bronco II 2.8 liter Engines

I have been doing mechanics since......well forever, and I STILL goof up firing orders, and never ever learn, lol, I have chased my tail on a misfire or other similar issue for hours, because I KNOW firing order is correct.
Well it wasn't..............they say you learn from you mistakes, but I must have a moron blind spot for firing orders

Then disconnect SPOUT jumper and reset spark timing at 10-12deg BTDC
After setting the spark timing reconnect SPOUT jumper and then start engine, check spark timing again, it should be different, rev engine a few times and spark timing should change according to RPM, if not then TFI module may need attention.

Next would be the accelerator pump.
A carb adds fuel to the air flowing in using Jets, the air sucks fuel from the tips of the jets as it passes by.
And on a carb there needs to be a way of adding more fuel quickly when accelerating because the Jets will lag behind the air flow slightly because opening the throttle plate quickly drops the vacuum quickly, so an accelerator pump was added.
When you push down on the gas pedal the accelerator pump squirts extra fuel into the engine, the harder or faster you press down the more fuel is squirted in.

If accelerator pump isn't working like it should the engine will get a Lean air/fuel mix, this lean mix can self ignite when entering a hot cylinder causing a back fire.
I would think you would also have some pinging/knock associated with this issue as well.

Engine OFF
Take the air cleaner off the carb so you can see inside the throat, open throttle manually and you should see fuel squirting in, that's the accelerator pump working.
IF there is little or no flow then the accelerator pump diaphragm is bad, these used to be available separately, but now-a-days you often have to buy the whole rebuild kit.
Thanks for your help I rebuilt the carburetor and the pump seems to be working fine I'm going to check the firing order now.
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Old 03-30-2016
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Fireing order is correct

Quote:
Originally Posted by Elijahnichelson View Post
Thanks for your help I rebuilt the carburetor and the pump seems to be working fine I'm going to check the firing order now.
When I start the truck it seem to work fine then after about a minute I starts to backfire I think I need to a just the mixture screws.
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Old 03-30-2016
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Do you still have the stock Motorcraft 2150A feedback carb, or has it been swapped for a 2150, non-feedback?

And did the back fires start just after the carb rebuild?


After the first minute the cylinders can get hot enough to self ignite lean fuel mix.
Assuming you mean cold start and then after a minute you start to get back fires

A back fire(out the carb) or forward fire(tail pipe "bang") are also different things and have different causes.
Back fire is generally a spark plug firing when intake valve is still open or the fuel self ignites on the way into a hot cylinder while intake valve is open.

Exhaust system "back fire" is when a cylinder misfires on the power stroke but gets spark while exhaust valve is open or the unburned fuel is self ignited by hot gases when it is pushed into exhaust manifold.
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Old 03-30-2016
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Backfire

The back fire is out the exhaust and it was happening before I rebuilt the carburetor and is still happening now after I built the carburetor it is the original carb I'm thinking timing is off now. Can you can you adjust the timing on this engine?
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