78 90 hp straight 6 problems

[Glastron Fisher]

Ok so I had posted a thread about this motor befor and I have since solved original problem... Now il starting a new one with a few more issues. I had bought this motor needing a stator and dizzy belt, replaced the belt to see if it runs and have only gotten it to fire but not run. When I timed the dizzy I set the flywheel to the tdc mark and lined up the dizzy with a mark that was sticking out the side not an arrow on the dizzy. Now my issue is I cleaned the carbs to see if that was my problem but couldn't get any of the jets out so I just sprayed the crap out of it with cleaner. And I did a test showing my condenser is bad in the dizzy is that a part I can replace or is the whole dizzy bad? And can I temporarily bypass it to do more testing and getting the motor to run?

 

[Maxz695]

Re: 78 90 hp straight 6 problems

My experience with a distributor model is Nill and Null but having avid experience in automotive a condeser is relaceable if that is the issue regaurdsless. First of all did you make sure the measurements were as perscribed for you particular engine in the manual?. Needle seats and levers must be set to there perscribed position to work properly. A poorly adjusted float and unlevel lever for the needle will inhibit the flow necesary to start the engine. Even if it is close and under perscribed in it,s position will not have enough gas in the bowl to allow the engine to pull through the port to start the engine efficiently on a few turns. Choking the hell out of it will start the engine in time but it drains the battery and over heats the starter. Change the condeser if you are inclined to believe that is an issue. When changing a belt for a distributor it is usually much tighter than the old worn sloppy belt that may have been redone with a link and sinc for the play of the worn belt. It must be done again as perscribed in the manual for the linc and sinc as well as proper carburetor adjustments.

 

[Faztbullet]

Re: 78 90 hp straight 6 problems

And I did a test showing my condenser is bad in the dizzy is that a part I can replace or is the whole dizzy bad? And can I temporarily bypass it to do more testing and getting the motor to run?

That motor does not have a condenser.. It has a remote mounted mercury filled kill switch that resembles a condenser. If it has points and condenser its a 60's model not a late 70's..

I had bought this motor needing a stator and dizzy belt, replaced the belt to see if it runs and have only gotten it to fire but not run.

If you have good spark nothings wrong with the distributor, your syn & link and timing are off.

 

[Glastron Fisher]

Re: 78 90 hp straight 6 problems

I found out that it only runs when the key is in the crank position for some reason, I've checked power everywhere and only power that changes in crank is the starter solinoid but I don't see how that's what it is...

 

[Lone Duck]

Re: 78 90 hp straight 6 problems

I may be wrong,but if it gets spark when you crank it over,and not when in the run position. Then either the switch is faulty or the wire from your ignition is hooked to the start terminal.

 

[Glastron Fisher]

Re: 78 90 hp straight 6 problems

The only thing I've noticed is that the ground going to the ignition switch through the harness was wired into the ground for the starter solinoid, they are supposed to be grounded separately but I don't see how that could cause it to not run key on but I will be testing that out today

 

[Faztbullet]

Re: 78 90 hp straight 6 problems

Bad trigger... below is testing link.
Troubleshooting Mercury Battery CD Ignitions

 

[buzzm19]

Re: 78 90 hp straight 6 problems

Those older mercs, like yours, 76 to 78 are the same type ignition wiring and you can get the wiring diagram from maxrules.com/oldmercs/wiring/1966ona/50.jpg On yours first I would check your spark box on the starboard side not the dist side the three wires are, red, white, green. The red wire is hot all the time with battery connected, you should have 12v there, with the key on in the run position you should have 12v on the red and white, if you don't have it at the white wire I would start with the key switch, the green wire go's to the coil. That condenser is for the tilt that if you tilt the motor up too far it will kill the motor. For testing purpose just disconnect it from the spark box and go on with your trouble shooting. Make sure all your grounds are correct first and this is very important on those motors. One screw up and you fry either the spark box or the electronic unit in the distributer and those parts are expensive. Buz

 

[Glastron Fisher]

Re: 78 90 hp straight 6 problems

The wires on the starboard side have power like you said, the ones on the port side wich are the 3 from the distributor I have I believe the top one hooked up and the bottom two that come from the distributor I jumped the two posts do I could get spark but I'll do some more testing is it bad if the bottom two are not hooked up at all?

 

[Glastron Fisher]

Re: 78 90 hp straight 6 problems

So I hooked the distributor back up the the port side of the switch box and it has no spark, jump the wires again and I get spark

 

[Glastron Fisher]

Re: 78 90 hp straight 6 problems

So the test I did was for the trigger not condense but would a trigger really cause it to run only when cranking when I bypass the trigger? Doesent seem like it would

 

[Glastron Fisher]

Re: 78 90 hp straight 6 problems

And to replace the trigger I need a whole distributor right?

 

[Chris1956]

Re: 78 90 hp straight 6 problems

Triggers can only be bought as part of the distributor housing. It is less $ than a whole distributor, but still in the $200 range.

 

[Glastron Fisher]

Re: 78 90 hp straight 6 problems

But my question is will it only run when cranking if the trigger is bad? Every other test has passed for the starting issue and I don't want to spend 200 dollars on a dizzy to find out it still will only run while cranking

 

[Maxz695]

Re: 78 90 hp straight 6 problems

Disconect the pigtail at the engine to remove the key switch as a cause and use a remote starter switch or jump the soleniod to see if there is fire on all cylinders or starts and runs as intended. If it does the key switch is bad or the wiring harness has a short in it

 

[Glastron Fisher]

Re: 78 90 hp straight 6 problems

All wires have been bypassed at the main engine plug, bypassed the key switch and put power to the solinoid to start it, runs untill I pull power off the solenoid and just dies, red connector at switch box has power at all times and white terminal has power at all times when key on cranking or not, I'm stumped... And if I'm not mistaken the trigger just jumps the two terminals on the port side doesent it?

 

[Glastron Fisher]

Re: 78 90 hp straight 6 problems

i did some more testing on it tonight with my volt meter instead of test light, was getting 12v at red post and 12v at white post key on and 9 volts both places cranking, but only getting -.8 volts at the green wire going to the coil? it got .8 volts when it runs as well but isnt it supposed to have 12 volts? i connected it directly to 12 volts and tried it and it just smoked a connection as if it was shorting to ground... could this be my problem even tho it still runs while cranking? i also disconnected the stator thinking that might be a problem and its not

 

[Faztbullet]

Re: 78 90 hp straight 6 problems

Replace the trigger or dizzy as you call it as it is bad. Output to coil is about 125V not .8, you must have a DVA adapter to check this.

i connected it directly to 12 volts and tried it and it just smoked a connection as if it was shorting to ground... could this be my problem even tho it still runs while cranking?

No and you probably smoked the coil.....If you go back and read the troubleshooting page at step 3 you will see your problem...

3) Engine cranks and fires as long as starter is engaged:
This problem usually indicates a bad trigger.

 

[Glastron Fisher]

Re: 78 90 hp straight 6 problems

The green wire going to the coil gets 125 volts? And ya I guess I didn't think about that but I've bypassed the trigger and just didn't know if it did something special or something it just doesent sound right that that's the problem but we will see. Is there a for sale section on this site for used parts? Can't find the dizzy on ebay