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1948 - 1956 F1, F100 & Larger F-Series Trucks Discuss the Fat Fendered and Classic Ford Trucks

302 started up then backfired....

 
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Old 01-22-2011, 07:46 PM
michaelmilburn
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302 started up then backfired....

and never started again.

ok well it wasn't in that order persay. I installed my new manifold, 4 bbl carb, thermostat ad housing, fuel filter, fuel lines from pump to carb. It took four good turns and some fuel to get her running, she was purring with an occasional rpm jump but once i adjusted the fuel and air ratio it was a steady run, longest was 5 mins before i shut her off .
During it's running trails it would back fire, so i popped off the dist cap and it was off so i put it in the correct firing order ordering to many threads here which I trust is all correct. After a few turns it would start then die. Now it won't even start at all. I know I have to replace the lines from the tank to the fuel pump but right now is not it's time. It was running fine until i started to mess with the dist. Tank has gas and I'm even going to put in another 3-5 gallons of gas tomorrow.


Options or idea's to try tomorrow?
 
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Old 01-22-2011, 07:54 PM
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Undo whatever you did that made it stop running, then start over. You said it was running fine before you messed with it, so there lies your problem.
 
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Old 01-22-2011, 08:00 PM
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Originally Posted by 52 Merc View Post
Undo whatever you did that made it stop running, then start over. You said it was running fine before you messed with it, so there lies your problem.

I did that, i put it back to where it was. We had it on TDC ad took out the plug to see if the piston was up and it was, it pushed air out just like any directions say to do.

Question now lies within this. What else besides wrong firing order and fuel clogged lines or pumps causes backfires ?
 
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Old 01-22-2011, 09:10 PM
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Are you sure the distributer is set to the right top dead center? remember its gotta be set to the one after the compression stroke. if thats not the problem. id try to disconnect the fuel and turn it over a few times to clear the fuel out of the system then hook it back up, tune the carb (rule of thumb 2 turns from bottom), set the distributor and make sure the left bank isnt mixed up with the right, LOL I did that once :P

The main reason why they backfire is because of the timing being too far adjusted

Other than that there is no reason other than valves not seating and cam timing being off, but you didnt touch those so they should be fine.

Hope I was helpful Good Luck!
 
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Old 01-22-2011, 09:22 PM
michaelmilburn
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Originally Posted by TBSS110 View Post
Are you sure the distributer is set to the right top dead center? remember its gotta be set to the one after the compression stroke. if thats not the problem. id try to disconnect the fuel and turn it over a few times to clear the fuel out of the system then hook it back up, tune the carb (rule of thumb 2 turns from bottom), set the distributor and make sure the left bank isnt mixed up with the right, LOL I did that once :P

The main reason why they backfire is because of the timing being too far adjusted

Other than that there is no reason other than valves not seating and cam timing being off, but you didnt touch those so they should be fine.

Hope I was helpful Good Luck!
The first time we messed with the timing it backfired through the carb and wouldn't start.

I am sure it's TDC but only way to tell on my engine is this white line on it.

I have tried the pencil in the hole trick and everything points to it beng TDC and on the #1 cylinder.

so i don't know what to do
 
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Old 01-22-2011, 09:22 PM
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As a reminder, there are two firing orders for the 302/5.0L based on what year (technically what cam) you have.
 
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Old 01-22-2011, 09:24 PM
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Year is unknown and and so is cam, def from an a 60-early 70's mustang
 
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Old 01-22-2011, 09:56 PM
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and I'm a Chevy guy, it took me the LONGEST time to remember that the ford distro order is reverse (COUNTERCLOCKWISE) of chevy (Clockwise)..


Sam
 
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Old 01-22-2011, 09:59 PM
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H.O. or NO ho That is the question

The early year mustangs 77 ,78,79 had a High Output engine. The engine has a roller cam and higher compression. The firing order is diferent on that engine than the "normal" 302's. If you backfired the engine you can sometimes screw up a sensor or two. I forgot which ones give the trouble. Is your engine carbed or is it injected? did you change it over to carb?
 
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Old 01-22-2011, 09:59 PM
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Originally Posted by sdetweil View Post
and I'm a Chevy guy, it took me the LONGEST time to remember that the ford distro order is reverse (COUNTERCLOCKWISE) of chevy (Clockwise)..


Sam

HA! I have a chevy 1500 that i tow this around with.


I'm so pissed at this truck, it was fine then I had to try and fix the backfire!! aRGH
 
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Old 01-22-2011, 10:04 PM
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Originally Posted by Marty Smilt View Post
The early year mustangs 77 ,78,79 had a High Output engine. The engine has a roller cam and higher compression. The firing order is diferent on that engine than the "normal" 302's. If you backfired the engine you can sometimes screw up a sensor or two. I forgot which ones give the trouble. Is your engine carbed or is it injected? did you change it over to carb?


Carb, had the original manifold and 2 bl carb. Replaced with a edelbrock 4 bbl and intake, looks good.

Everything i've read is pointing at the #1 being farthest away from passenger on that side. and the rotor lines up perfect with the #1 spark plug..
 
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Old 01-22-2011, 10:09 PM
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Old 01-22-2011, 10:14 PM
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Originally Posted by havi View Post
Havi

That looks exactly what I have minis the following.


On my tdc there is only a white line and I try to line up that with the black mark on there, makes no sense I know I'll take photos of it tomorrow or Tuesday. What's the easiest way to manually get it there, what tool do I use for this and it's in my truck not on a stand can I still rotate it?
 
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Old 01-22-2011, 10:19 PM
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A timing light. I put a white line on the degree mark I need the engine set at, and when running at the proper RPM, I rotate the dist until the white line is at the arrow. If there is no arrow, but you know the engine is at TDC for #1, you can mark a white line on the block across (above) from the zero mark on the balancer, and still mark the balancer at 11 degrees (as shown in the picture), and time it until they are straight across from each other. Since you have a points dist., there's dwell to take into consideration. And there should be no vacuum line to plug.
 
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Old 01-22-2011, 10:30 PM
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#1 is furthest forward

#1 is furthest forward


This photo shows the 5.0L is diferent than the 302 even tho they are the same displacement they have diferent firing orders.
If you have an air compressor you can put the number one to TDC (white mark on arrow. Blow air into the cylinder. If you hear air coming out the exhaust it is on the wrong TDC. Rotate the engine 360 degrees (cam turns 180) this should put the engine on TDC compression stroke. Insert the wires as firing order states and try again. If you are running points you can also get real close to the timing BDC with a degree wheel and an analog meter.

Now as to the original problem, is this the first time the engine has been run in a long time? Could you have a hanging valve from carbon or rust on the valve stem? is there a weak or broken spring in the valve train? Is the engine just tired? lots of questions there
 

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