Wont start, back fires a lot, after installing new ignition system. LOST!?!?!!

[hezzy602]

1985 VIP Mercruiser MCM 205 GM 4.3 V6
Ok here it is, I just replaced the old Thunderbolt ignition system after troubleshooting it FOREVER, narrowed it down to a faulty system. So I bought the 4.3L Delco Voyager EST Marine Electronic Distributor Kit from Michigan Motorz (new distributor and coil). Installation went good I believe. Only one problem in the install, didnt have 12 volts on the purple wire that hooks up to the new coil. So I just ran a new wire from the Battery. Went to fire it up, it just cranks and cranks, and then back fires real loud. it seems like it wants to turn over but just doesnt. I'm sure the timing is a little off but it should still start, RIGHT?
Spark plugs & wires are only a year or so old. Its getting gas.

--Why isnt it turning over..(I know its a really broad question)
--How come its back firing real bad?
--It came with new spark plug wires but I left the old ones one because they are almost brand new. Spark plug wires are spark plug wires right??

I'm so lost :facepalm::mad-new:. I really dont have the money to go get ripped off by some shop that will end up charging more than what my boat is worth!!

 

[Oshkosh1]

Re: Wont start, back fires a lot, after installing new ignition system. LOST!?!?!!

Re-check your plug wire routing. Sounds like firing order is off.

 

[hezzy602]

Re: Wont start, back fires a lot, after installing new ignition system. LOST!?!?!!

Thats what I thought too but that has been doubled checked. Its stamped right on my engine block, firing order and which cyclinder #. Also referenced my shop manual. I would figure its the same with the new ignition system.

Might be a stupid question but only way to check timing is while its running right.

 

[Jonnybbad]

Re: Wont start, back fires a lot, after installing new ignition system. LOST!?!?!!

I would suspect that you have the distributor installed off some teeth in there. See if these vids help ya get it right or at least confirm its on target. You could find top dead center on the compression stroke of one of the cylinders and see if the rotor lines up with the correct cap doodad for the cylinder. That will tell you if you're teeth are clocked correctly. If so, I would leave the distributor loose and slowly rotate it while cranking to see if you can get it to start and run decent and then you can time it and tighten it down.

Installing a Distributor Part 1 - YouTube

Installing a Distributor Part 2 - YouTube

 

[achris]

Re: Wont start, back fires a lot, after installing new ignition system. LOST!?!?!!

Sounds like the dissy is 180 degrees out. You're firing on the valve overlap stroke, not the compression, that's why it's backfiring. Take the dissy out, turn the rotor 180 degrees and put it back in, (very easy mistake to make).

Chris......

 

[hezzy602]

Re: Wont start, back fires a lot, after installing new ignition system. LOST!?!?!!

Ok thanks, when I get off work today I will pull the dist. and rotate it 180. If that doesnt work I will try what Jonnybbad suggested.
Thanks, EVERY little thing helps!!

 

[hezzy602]

Re: Wont start, back fires a lot, after installing new ignition system. LOST!?!?!!

Ok thanks, when I get off work today I will pull the dist. and rotate it 180. If that doesnt work I will try what Jonnybbad suggested.
Thanks, EVERY little thing helps!!

I do have to admit, I made a rookie mistake and didn't mark the old dist. Before pulling it out. I thought I got pretty close but I guess I was wrong.

 

[Bt Doctur]

Re: Wont start, back fires a lot, after installing new ignition system. LOST!?!?!!

You need to read the manual first.
You need to have #1 piston at TDC , line up the rotor to where #1 is on the cap and insert dist body. Once inserted the rotor should line up with #1 spark plug wire.install dist cap, install wires in correct firing order

 

[Glastron_V210]

Re: Wont start, back fires a lot, after installing new ignition system. LOST!?!?!!

^^^^Do not guess!!!!

It sounds like you are way advanced, or the order is off, or both.


To find #1 TDC (Or close enough anyway) is easy. Pull the spark plugs to reduce compression forces. Have someone hand rotate the engine with a wrench/ratchet. Stick your finger in the #1 plug hole. When it is on compression stroke, it will push air past your finger. When you get this, remove finger and insert a small screwdriver. SLOWLY rotate the engine. The piston will push up the screwdriver, and you can feel the approximate TDC. Check your harmonic balancer timing marks. If the balancer has not shifted, they will be better than your approximation above. Allign to the marks if they are good.

There is no #1 position physically. It depends on how you installed the distributor. It will work in any location, as long as your #1 matches the engine, and the order is correct.


Now, and only now, pull your dist. cap and check the rotor position. It will be at/close to one of the posts. Allign it to a post which will give you adjustment to advance/retard and check your firing order one more time.

Now, it should fire up. It may run rough, but it will fire up if everything else is right. Time with a timing light!!!


Chay

 

[hezzy602]

Re: Wont start, back fires a lot, after installing new ignition system. LOST!?!?!!

Ok I understand about doing it the right way by finding TDC and I do have a manual and have read it. I was going to do it that but figured to try rotating it 180 degrees, it didnt start up so tried rotating a couple more times. Finally started up and ran rough, loosen up the clamp holding the dist. and slowly rotated it till it sounded like it was running good. sounds good now. Went to go get my timing light and go figure it took a sh*t on me so tomorrow I will be getting a new light and timing it exact.
Sounds like I got lucky???? or is this a redneck way of getting it close enough before using a timing light??

 

[achris]

Re: Wont start, back fires a lot, after installing new ignition system. LOST!?!?!!

There is 2 TDCs in a 4 cycle engine.... One is the top of the compression stroke when you have a fuel charge in the cylinder and need to fire it, with the spark. The other TDC is after the exhaust stroke has finished (blowing the dead exhaust gases out of the cylinder through the exhaust valve) and the intake stroke starts (sucking a new fuel charge into the cylinder through the intake valve). You needed to find the TDC of the COMPRESSION stroke. Apart from the fact that the valves are on 'overlap' the crankshaft will be in exactly the same position on BOTH strokes. Are you sure you had the distributor on #1 cylinder of the COMPRESSION stroke?

Find a post by 'Bond-o' and have a look at his avatar... That is a perfect 4 cycle engine. You will see the piston travel to the top of the cylinder twice in each cycle. One to fire the charge, the other to close the exhaust valve and open the intake valve.

Chris.......

 

[Bondo]

Re: Wont start, back fires a lot, after installing new ignition system. LOST!?!?!!

or is this a redneck way of getting it close enough before using a timing light??

Naw,... A Redneck would do it Right, 'n find TDC 1st, then stab the distributor....

 

[Silvertip]

Re: Wont start, back fires a lot, after installing new ignition system. LOST!?!?!!

If the engine had not been turned over AFTER removing the original distributor, the new modified one should slide back in provided the rotor was pointing in the same direction. But since the rotor position was not marked, all bets are off and you must revert to the TDC procedure and that's where folks tend to go wrong.

 

[Jonnybbad]

Re: Wont start, back fires a lot, after installing new ignition system. LOST!?!?!!

Sounds like I got lucky???? or is this a redneck way of getting it close enough before using a timing light??

A redneck would have marked the distributor position before he took it out. A redneck also wouldn't use a timing light. He would just set his half empty beer on the motor and turn the distributor until the waves in his beer smooth out.