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706 wont start

D

Diesel1

New User
I have a 706 gas that i bought. Tractor has sat for over 10 years and engine was froze up. Just rebuilt engine and it wont start. New pistons, sleeves, reconditioned head. Cranks and tries to fire but wont run. After cranking, gas just pours out of carb. Installed new carb-same thing. New carb does not have solenoid on it. Adjusted needle out that is in place of solenoid. Plugs are not getting wet. Installed new manifold-same thing. New points, condenser, cap, rotor, plugs, wires, coil, and resistor. 160-165 psi compression on all cylinders. Good vacuum at carb when cranking. Disassembled front cover to verify timing. ok. Distributor is timed properly to oil pump. Removed head to verify pistons are in properly. They are. Valves are all adjusted properly. I am a mechanic by trade and this is very frustrating. We have to be overlooking something very simple. Any help on this would be great.

Thanks.
 
Sounds like you flooded it. Shut the gas off, put in new plugs or heat the ones you have to burn off the fouling. Does it have a good hot spark? I don"t know why you took it apart again. Don"t you trust your own work?
 
The plugs are dry. We have good spark and tried new plugs. The only reason we took it back apart is because we had no other direction to go. We wanted to make sure we werent a tooth off on the timing.
 
Your distributor needs to be timed to No1 piston when its at TDC on the compression stroke. Remove the sparkplug near the radiator and bring that piston to tdc on the compression stroke. Hold your thumb over the plug hole while a helper slowly cranks the engine until you feel pressure against your thumb then drop a long plastic straw on top of the piston. Then you watch the straw rise while the helper keeps slowly cranking the engine until the straw quits rising. No1 piston should now be at tdc on the compression and your timing marks should now be aligned with the pointer.

Remove the cap on the distributor and see where your rotor is pointing. It should at the No1 plug tower on your cap. If its off you need to pull the distributor and rotate the rotor until its at the No1 on the cap. Hal
PS: Make sure your wires are in the correct firing order on the cap.
 
your comment cranks and tries to fire but wont run.. i hate to ask this question but when putting plug wires on are you installing them in proper rotation i dont remember if distributer turns clockwise or ccw sounds like spark or ignition related
 
What does a small amount of ether do--if you've tried that? Do you have 12 volts to the dist. terminal while cranking? Less with the ignition switch on & not running [resistor in circuit]?
Have you got the plug wires in the right order in the dist. cap?
If you've got that good of compression & vacuum, it should fire. You do have good spark, don't you?
I'm assuming you have tried advancing & retarding the dist. while cranking?
 
The wires are installed on the cap in the firing order that is stamped in the side of the block. We verified the rotation of the distributor and the cylinder numbers are actually stamped in the cap also. Timing is right on and we tried turning the distributor while cranking. I have also cranked the engine with the plugs out holding my thumb over the hole and watching the spark plug for that cylinder at the same time. Verifying that the spark plug is firing at the same time the compression blows my thumb off.
 
When the piston is at the top on compression is the rotor pointed to #1 tower on the dist cap if it is it will start you dont time the dist to the oil pump. Remove #1 plug so you can see when the piston is at the top with a mag lite then you will see if the rotor is pointed at the tower.
 
When we had the front cover off, we verified timing marks, piston on TDC compression(both valves closed) and rotor pointing to #1.
 
Just thought about the neighbor down the road who put in a set of points on his 706 & couldn't get it to run--only fired randomly. I went down & he had the coil wire stuck in the #2 dist. cap hole & the #2 plug wire in the coil. Small thing, but it had him baffled for a whole day.
 
The plugs are dry?

That means fuel is not getting from the carburetor to the cylinders.

Pull the air cleaner off the carb, put your hand over the hole, and hit the starter. Any suction?

No suction means you've either got a blockage in the intake manifold, or your intake valves aren't opening.
 
You may have the cam and crankshaft gears timed correctly, but you may have timed it to No6 piston. By bringing No1 piston to TDC on the compression stroke will show that if the rotor is off. The oil pump has nothing to do with timing your engine. Hal
 
The carb has good suction while cranking. We also tried a new manifold thinking there was a problem. Checked all of the valves and the adjustment. Cam lobes are all good. After cranking gas just pours out of the carb??? Thats why we installed another carb. Same thing. ???
 
Hold your hand over the throat of the carburetor
while a helper makes an attempt to start the engine. You should be able to choke the engine when doing this. If there's very little suction
means you have low intake manifold vacuum and that's needed to suck that fuel into the engine.
Hal
 
The distributor drives off of the oil pump. According to the IT manual, the engine has to be at TDC #1 compression, and it then gives you a location that the drive cog for the distributor has to be in when installing oil pump. If that drive cog is not in the proper location, the dist will not be in time with the engine.
 
Surely the manifold gaskets are sealing up, aren't they?
Be sure you let us know when you get this thing running, & what the fix was. There's got to be something really simple that is getting over-looked here.
 
Would be nice to find a down-draft intake manifold from an older IH truck to put on the engine so you could dump some gas in while cranking.
 
I agree, i am starting to wonder if the head is cracked in an intake port?? I might try taking the manifold back off then pressurizing each port with the valves closed. This tractor did sit outside for 10 yrs uncovered. Maybe water got in there and froze?
 
Squirt some starting fluid in the area where your intake manifold mates to the engine block
while a helper makes an attempt to start the engine to see if the engine fires. Hal
 
I like to do it that way having the wire hooked to the plug then turning engine over and watch for the spark when its on compression then you know if everything is in time and if you have suction at the carb there is something realy screwed up cause if you are in time and have gas they run.. Acts like my engine on the aircompressor ran last time i used it now it just wont fire and run tried all the tricks.
 
had the same trouble with a 706 of my uncles it would fire if the starter was engauged but let up on the starter switch and she would quit,I found a wire on the ballast resistor broken off under the insulation real hard to spot! might be something to check.
 
You may be loosing your spark when it switches to the ballast resistor circuit. Throw a timing light on it as you try to start it.
 
You may be loosing your spark when it switches to the ballast resistor circuit. Throw a timing light on it as you try to start it.
 
Remove No1 sparkplug and pour several tablespoons of gas on top of the piston then reinstall plug and see if the engine will run for a few seconds. Also open that adjustment needle some more where they usually have a solenoid. Hal
 
Have you checked your valve lash? Neighbor had a IH pickup,late '60s model with a 6 cylinder in it all overhauled but did the same thing you described. Had valves set too tight, zero lash, loosened them up to .020 and it started right up!
 
i have had tractor that would not hit on ether and discovered that i had water in gas.

check spark at plug, had faulty coil wire once.

remove resistor and try, will give you a bit more spark. they say this will shorten point life. ??
 
You said, "we had a steady 12 volts at the coil while cranking." That is impossible unless you have a battery as large as a refrigerator. A normal starter will pull system voltage down to slightly below 11 volts while cranking. Hook a test light between the distributor side of the coil and ground. It must blink while cranking. Pull a spark plug wire off and insert a piece of metal. You should get a fat, blue spark almost a quarter of an inch while cranking when held against the block.
 
Diesel1
When you tore into that engine did it by any chance have the old style intake manifold gasket, a one piece all metal gasket 1/8" or so thick. Then you replaced it with the thinner gasket. You"r problem then lies in the fact that the manifold has to be separated by the four bolts holding the intake and exhaust halves together. A new gasket installed between halves, bolts installed and left fairly loose, while manifold is installed, by the way with the three rings for the intake ports tapped into the head ports. Then remember the two end manifold bolts are longer, and make sure you have the heavy washers installed, torque it up and after tightening, don"t forget to tighten the four bolts holding the manifold together. If that doesn"t get the plugs some gas, you don"t have it timed correctly. Good luck.
Anon
 
Well you may have the dist set accordingly to the oil pump but you are more then likely 180 out . If you say you have the timing marks correct and the rotor set at #1 then it will run. Now as not having the FUEL SHUT off solenoid in place ya had best get it back in place as it was put on them tractors for a reason . You did not say if this is a C 263 or a C291 . Timing has to be set for the engine as they do not set the same. Next do you have it wired correctly ?? Myself i have never had one that did not fire the first time even if i was a little late or a little advanced on the timing.
 
The manifold gasket that we installed is 1 piece and it is about 1/8" thick. We never seperated the manifolds, but have tried 2 different manifolds. What are the "3 rings" you are reffering to??
 
Did you pour that 2 tablespoons of gas on top of No1 piston? If the engine fires and runs a few seconds your engine is probably in time with N0 1 piston. If doesn't fire you don't have the distributor in time with No1 piston. Hal
 
Diesel1
The rings fit in the intake ports on the head. Their may have been three or just two, not sure if they used one in the center port. It will have a shoulder in the head that you tap them up to, Smaller diameter out. You said reconditioned head, maybe they didn"t reinstall them and still have them or didn"t know where they went. Take a straight edge and line it up with face of manifold and see if intake ports stand away, if so that is you"re problem. You need the rings and the new style thin gasket. The new gasket has fiber material on each of the intake ports to seal better. If you have carb leaking gas and no wet plugs when trying to start that has to be it. Let me know what you find.
Anon
 
Crazy idea here----could the throttle plate be shut & not letting gas up into the intake manifold? I know you said it had good vacuum at the carb inlet, but something is causing the unit to not fire off.
 
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