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35HP Vanguard engine won't start


Rinso21's Avatar
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01-12-15, 02:37 AM   #1  
35HP Vanguard engine won't start

Hi, I'm new here. I hope someone can help me out.

Briggs and Stratton Vanguard
35 HP
model: 613477
Type: 0135-E1

Engine turns over but won't fire up.

Back ground:
Engine was running ok. Had an electrical issue when the ignition/starter switch fell apart and shorted. Fried everything!

I have:

Replaced the switch,
Replaced both ignition coils,
Replaced or repaired most of the wiring harness and checked the rest for continuity and shorts.
Repaired burned contacts in harness plugs etc.
Cleaned plug contacts and checked wiring to fuel solenoid and checked solenoid operation OK

I now have spark at the plugs.
Fuel pump is working fine.
I have checked the compression (Good and even)
I have set the valve clearances. They were very wide. Though I didn't measure them, the valves seem to operate through a large enough range of travel (I have seen these engines with the exhaust lobes worn right down on the camshaft)

Engine spins over but won't start. I put some fuel into the intake. NO difference.
I removed the carby and put fuel directly into the manifold. All I got was a backfire. I pulled all the fan cowling etc. off again and removed the flywheel nut, just to check if the key had somehow sheered off but all appears to be ok.

This thing is doing my head in! What am I missing?????????

Any constructive input will be greatly appreciated.

 
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01-12-15, 05:05 AM   #2  
The wide valve clearance may be an indication of the excessive cam wear you noted from past experience. Since the compression is good and it was running when it went down you're probably OK.

There is a diode in the wiring in some twins to keep the kill from crossing coils, I believe. That has come up a number of times here and proved to be a problem in ruining coils and the running of the engine. That may be a possibility.

 
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01-12-15, 05:32 AM   #3  
Have you checked the anti backfire solenoid on the carburetor to make sure it is not engaged or stuck in the extended position? It must receive power to retract the solenoid pin and allow fuel to get to the jets in the carb. You can remove the solenoid and power it with 12v or even a 9v battery works much of the time. When testing it though make sure you hold the tip close to something to prevent the pin from over extending. When it's installed in the carb it hits the orifice before full extension so it's not meant to go to the end of it's stroke.

 
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01-12-15, 12:13 PM   #4  
Thanks for the replies.

marbobj, thanks for the tip regarding the diode. That too may have been fried in the original disaster but shouldn't be causing the engine to not start now. I have spark at the plugs.

Pilot Dane, yes I have checked the solenoid. It works fine as the key is turned on and off.

 
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01-12-15, 12:42 PM   #5  
I have spark at the plugs.

 
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01-12-15, 03:02 PM   #6  
If the diode is fried you could have cross firing. It could cause a no start.

 
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01-12-15, 10:38 PM   #7  
marbobj, You are right. I thought of that today and when I checked it, sure enough the diodes were fried. Continuity in both directions. I disconnected the grounding wire at the coils and the engine fired up right away. I have ordered a new harness [diodes aren't available separately here}.
I just came home to let you know what I found, only to find your reply. Spot on!

I feel really stupid for not thinking of that possibility earlier.

Thanks everyone!

 
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01-13-15, 03:58 PM   #8  
Don't think that way. Those things are usually a part of a fairly technical discussion here and the full time shop guys sort it out.

Sounds like you've got it licked, take care.

 
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