1975 Ford F250 with a 390, crank, no start
#21
08-26-2012, 11:08 PM
There is another way to find TDC of the compression stroke of #1 piston.
Remove the valve cover on cylinder bank, 5-6-7-8. Driver's side.
Turn the crankshaft by hand and watch cylinder #6 intake valve.
Right when cylinder #6 intake valve just begins to open, and I mean you just barely begin to see that valve open, the #1 piston is near TDC of its compression stroke.
Look at the timing mark. It should be near the zero mark on the scale. But you will need to move the crank some, since the valves have a certain amount of overlap.
The reason this method works is because the 390 is a four stroke, even firing engine. It fires every 90 degress. (90*8=720. Two complete revolutions of the crankshaft for all eight pistons to complete their four stroke cycle. One complete turn of the cam.)
An even firing engine means each piston has an opposing piston that is in the same place in its cylinder bore at all times. In the case of the 390 the opposing cylinder of #1 is #6.
The rotor on the dist. turns counterclockwise. The firing order is 1-5-4-2-6-3-7-8. The cylinders are from front to rear, passenger side 1-2-3-4, and driver's side 5-6-7-8.
Once you find TDC of the compression stroke of #1 piston the dist. cap only fits on the dist. one way. Install the dist. so that the rotor is pointing to the sparkplug wire of #1 cylinder on the dist. cap.
Upon start up attempt have some one crank the engine and turn the dist. advanced and retarded a little while the engine is cranking.
It should fire up. As long as the timing chain hasn't jumped, it's getting spark, and it's not flooded.
Cheers.
Remove the valve cover on cylinder bank, 5-6-7-8. Driver's side.
Turn the crankshaft by hand and watch cylinder #6 intake valve.
Right when cylinder #6 intake valve just begins to open, and I mean you just barely begin to see that valve open, the #1 piston is near TDC of its compression stroke.
Look at the timing mark. It should be near the zero mark on the scale. But you will need to move the crank some, since the valves have a certain amount of overlap.
The reason this method works is because the 390 is a four stroke, even firing engine. It fires every 90 degress. (90*8=720. Two complete revolutions of the crankshaft for all eight pistons to complete their four stroke cycle. One complete turn of the cam.)
An even firing engine means each piston has an opposing piston that is in the same place in its cylinder bore at all times. In the case of the 390 the opposing cylinder of #1 is #6.
The rotor on the dist. turns counterclockwise. The firing order is 1-5-4-2-6-3-7-8. The cylinders are from front to rear, passenger side 1-2-3-4, and driver's side 5-6-7-8.
Once you find TDC of the compression stroke of #1 piston the dist. cap only fits on the dist. one way. Install the dist. so that the rotor is pointing to the sparkplug wire of #1 cylinder on the dist. cap.
Upon start up attempt have some one crank the engine and turn the dist. advanced and retarded a little while the engine is cranking.
It should fire up. As long as the timing chain hasn't jumped, it's getting spark, and it's not flooded.
Cheers.
#22
08-27-2012, 12:59 AM
That's what I tried earlier this morning. Did almost exactly that and it's not igniting any fuel at all. I checked for spark and it's good, I have compression, and I have fuel(well, it's all blowing out of the carb but still) I can only assume the timing chain jumped and everything is all out of whack.
Fuel blowing out the carb' like a valcano? Hissing and spewing gas?
With the dist. installed, disable the iginition, and crank the engine. Does it still blow fuel out the carb' the same way?
If it does that means an intake valve is open, most probably, on a compression stroke. Which means the timing chain has in fact jumped time or suffered failure.
Also, the dist. rotor should turn right when you turn the crank by hand in the direction of a running engine. Shouldn't be any lag.
Be interesting to know too, where the timing mark on the crank pully is when #6 intake valve just begins to open. Or when you bring the mark to zero can you see, or feel the piston top of #1 through the sparkplug hole with a long thin screwdriver. Or vice-versa. When you can see/feel #1 piston top where is the mark.
#23
08-27-2012, 10:04 AM
put number 1 piston all the way up and turn the crank by hand until the O on the timing scale lines up with the line across the crank damper and pull the distributor cap and check the rotor button ! the rotor button should be pointing to number 1 plug wire on the cap ! if it,s off pull the distributor and set it back down in with the rotor pointing to number 1 plug wire on the cap ! it should start there, then hook up a timing light to set it at the degree it calls for ! if the distributor don,t want to drop in all the way take a long screwdriver, reach down in and turn the oil pump !
#24
08-27-2012, 01:03 PM
put number 1 piston all the way up and turn the crank by hand until the O on the timing scale lines up with the line across the crank damper and pull the distributor cap and check the rotor button ! the rotor button should be pointing to number 1 plug wire on the cap ! if it,s off pull the distributor and set it back down in with the rotor pointing to number 1 plug wire on the cap ! it should start there, then hook up a timing light to set it at the degree it calls for ! if the distributor don,t want to drop in all the way take a long screwdriver, reach down in and turn the oil pump !
Also, the dist. shaft to oil pump may not be a slot. Ford used a hex on many of their engines. Perhaps the op. will enlighten us.
#25
08-27-2012, 09:41 PM
put number 1 piston all the way up and turn the crank by hand until the O on the timing scale lines up with the line across the crank damper and pull the distributor cap and check the rotor button ! the rotor button should be pointing to number 1 plug wire on the cap ! if it,s off pull the distributor and set it back down in with the rotor pointing to number 1 plug wire on the cap ! it should start there, then hook up a timing light to set it at the degree it calls for ! if the distributor don,t want to drop in all the way take a long screwdriver, reach down in and turn the oil pump !
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