1977 Chrysler 90 hp no start

[truckerray]

Inherited this engine last year after it had been sitting for a few years. Got it running after replacing the cdi box, distributor preamp. It ran great for two weeks straight out on the lake. Shut it off in the middle of the lake to help another guy with engine trouble and have not been able to get it to start since. Have checked the fly wheel key, replaced the preamp again (cause I'm told theres no real test for it), cdi box is good according to tests. Getting good spark at what appears to be the right time, getting good fuel, compression is 135 on all 3 cyl's.it will pop (fire) occasionally when I let go of the key when trying to start. Frustrated a few guys already. Little help????

 

[Nordin]

Outboardignition has the troubleshoot guide.

Check that you have 12VDC at the blue wire at distributor. This is 12VDC from the ignition keyswitch and should only be hot when key is in IGN position.
Check that you have 12VDC at blue wire that goes to CD box. This wire should be hot all time. It is charging the capacitors in the CD box.

To determind if preamp is bad, set the piston #1 in TDC pull plug #1 out and ground it to engineblock. Set throttle in idle position.
Loose the white/black wire from distributor and set keyswitch in IGN position .
Scratch the wire to ground. Each time you scratch the plug should spark. If it sparks the preamp is bad. If no spark check the HT wires in the distributor cap.
Clean and reattach.

Check that the distributor/timingbelt is set correctly. The curved line at the dist.pully should line up with the flywheel rim when #1 piston is at TDC.

Do you have a ground wire connected between the dist.mount bracket and the dist.housing?
The swivel has grease in it and it may insulate from ground. The preamp need ground to work properly.

 

[truckerray]

Those are all things I have checked and just rechecked again now. I get awesome spark on all three as I rotate the flywheel by hand to the corresponding positions,as well as when I'm cranking it over. The two perplexing things to me are that after I shut it off with the key in the lake that was it! Wouldn't fire again. The second is the pop/ fire when I let the key go when I'm cranking it over. Kinda like an old ballast resistor failure in the older cars. Plugs get wet when cranking. Fuel will run back out of carbs when choking by hand (over carb intake) or with actual choke.

 

[Nordin]

Have you checked the compression?
Have you checked if you get spark under compression? Use a timing light and see if it flash and check if it flashes near TDC at #1 plug at idle.
What plugs do you have?
Should be surface gap typ, they can foul easy if you run at idle for long time and also if you try to start with choke when it is warm.

Do you use fast idle position when you try to start it.

If all this is okey, check the fuelpump diaphragm. If it has holes you get fuel directly from pump into crankcase and it will "flood" the cylinder.

 

[truckerray]

as mentioned compression is 135 on all 3 cyl's. Have surface gap type plugs.Have tried starting with throttle wide open. Put 12v to the blue wires (to the distributer and cdi box) from a different charged battery to make sure I was getting at least 12v to them (measured with a multi meter) and then it would try to fire occasionally, and it would backfire after choking it while cranking. Can a fuel pump diaphragm with holes cause backfiring?

 

[Nordin]

No normally a crack in the diapraghm flood the cylinder. The plug gets really wet.
Backfiring is a timing issue.
Is the timing set right? Is the distributor pully/drive belt set right? Is the flywheel key shared?