difficult starting

[jwkoehn]

Ihave a 96 mercruiser 5.7 bravo3 Rebuilt into a 383 stroker the engine runs great . The problem is in starting.The engine cranks great until I hit the ignition switch At that point the the flywheel kicks back into the starter. So far this summer I tore up 2 starters drives it broke off the end of the casting. I strongly suspect it is in the timing The ignition is a Thunderbolt5 system I have retarded the timing as far back as I can and still get decent performance.Ihave been told that I must time the engine by grounding out the spark advance then set the timing at 8 deg and the ecm will remember this at starting . Is this fact or just wishful thinking? I need help soon before I trash a flywheel. Also the engine starts great if it is warm the problem is only when it is cold

 

[Don S]

Re: difficult starting

The engine cranks great until I hit the ignition switch At that point the the flywheel kicks back into the starter.

What kind of system do you have. Usually there is only one switch. when you turn the key over to start, the starter turns but you have ignition at the same time.
Sounds like you have 2 seperate switches? Is this correct? ? ? ? ? If so, WHY?

And yes, setting the timing on a TBV systems is different than some others.

 

[jwkoehn]

Re: difficult starting

The engine cranks great until I hit the ignition switch At that point the the flywheel kicks back into the starter.

What kind of system do you have. Usually there is only one switch. when you turn the key over to start, the starter turns but you have ignition at the same time.
Sounds like you have 2 seperate switches? Is this correct? ? ? ? ? If so, WHY?

And yes, setting the timing on a TBV systems is different than some others.

 

[jwkoehn]

Re: difficult starting

The gear shift has an ignition kill switch on it If I crank the engine with this off the motor will crank fast enough that I can hit the ignition switch and it will usually fire

 

[Don S]

Re: difficult starting

Just scroll down to the bottom of the thread and use the Instant Reply.
Forget that useless "Reply-Quote" button. It does nothing usefull.

 

[Don S]

Re: difficult starting

The gear shift has an ignition kill switch on it If I crank the engine with this off the motor will crank fast enough that I can hit the ignition switch and it will usually fire

If you have to go through that process to get it to crank and start, then you REALLY need some help.
That kill switch is something you hook to yourself with a lanyard that kills the engine incase you get thrown out of the drivers seat. It's not something used for starting.
Time for you to answer some questions.
1. When was the last time you did a full tuneup. Not just throw some spark plugs at it, but cap, rotor, plugs, comperssion test, timing adjust, carb adjust, you know, the normal maintenance stuff.
2. When was the last time you check the fuel filters?
3. Do you have an OEM service manual? Since you don't know how to set the timing, I doubt you do.
4. What sort of testing have you already done.

 

[jwkoehn]

Re: difficult starting

THe engine was completely gone through last year when it was rebuilt plugs cap rotor cap filters the engine runs great the only problem I have is cold cranking also I do have a Clymer shop manual 95/97 version. Which said the same thing you told me. How ever Using that process did not help the problem

 

[Reel Poor]

Re: difficult starting

Maybe the battery is weak on a cold start, but charges up to full voltage after running, for easier hot starts. Check battery voltage with a volt meter while cranking the engine cold. Should maintain at least 10.5 volts while cranking.

What is the base timming set at?

What octane fuel are you using?

What are the compression numbers?

 

[jwkoehn]

Re: difficult starting

Maybe the battery is weak on a cold start, but charges up to full voltage after running, for easier hot starts. Check battery voltage with a volt meter while cranking the engine cold. Should maintain at least 10.5 volts while cranking.

What is the base timming set at?

What octane fuel are you using?

What are the compression numbers?

 

[jwkoehn]

Re: difficult starting

1/ compression all@ 175-180
2/fuel 87 octane w/ octane booster
3/ 2 batteries 1 600 cca 2 1000 cca both tested great if I keep it on a trickle charger it will start ok anything less and it kicks back at the flywheel

 

[Reel Poor]

Re: difficult starting

With a volt meter, check the battery voltage at the starter (big terminal) while cranking. Should maintain 10.5 volts. Checking here will eliminate any possible battery or battery cable problems. Could also be a bad ground or ground cable. If the cables are green they are not any good and need to be replaced.

You didn't say what your base timming was set at.

 

[jwkoehn]

Re: difficult starting

voltage at starter is at 11.5 0r better engine has 3 ground cables base timing is unknown timing was set at the least advance that would give decent performance without the spark advance grounded

 

[Starflight]

Re: difficult starting

The compression #s you gave would indicate that you have around 9.5:1 compression ratio. my 9.5:1 engine requires that i use 93 octane gas. i cant get 93 in my area, but can get 100 octane. i use 2/3s 91 and 1/3 100 so i can use the recomended timing per specs. otherwise it pings at wot and is hesitant (strains starter)to start because the timing is set at 12 deg btdc.
the octane boost i.e. +104 and others is crap. i read that the usual dose only increases the octane .1 (87 jumps to 87.1) I personally would spend more on the gas and get better performance. Or you could retard the timing some to run 87. try a temporary tank of the high octane and see if it helps.

 

[Reel Poor]

Re: difficult starting

base timing is unknown timing was set at the least advance that would give decent performance without the spark advance grounded

Have the timming set properly to factory specs with a timming light before you destroy your engine.

Also like was mentioned above, trash can the octane booster and run the premium grade fuel.

 

[jwkoehn]

Re: difficult starting

base timing is unknown timing was set at the least advance that would give decent performance without the spark advance grounded

Have the timming set properly to factory specs with a timming light before you destroy your engine.

Also like was mentioned above, trash can the octane booster and run the premium grade fuel.

 

[jwkoehn]

Re: difficult starting

Looking for some help setting the timing from someone who is used to doing it on a thunderbolt 5 system when i ground the white/purple wire i see no difference on the timming mark at idle or at 2000 rpm if it is grounded or not

 

[jwkoehn]

Re: difficult starting

If you know how to deal with this can you leave a phone# I can call you at Thanx Jim

 

[Reel Poor]

Re: difficult starting

Here is a link to an online service manual describing the Thunderbolt V ignition system. It is not specific to your engine but in general describes operation. There is also a wiring diagram showm for this system.

If your ignition system is not advancing or retarding properly you may have a problem with the control module, engine knock module or the knock sensor.

Click on the link below then scroll down to Thunderbolt V Ignition System. It's on page 4B-14 indicated on the bottom left corner of the page.

Online Manual Link

 

[jwkoehn]

Re: difficult starting

Thanks captian

 

[jwkoehn]

Re: difficult starting

Here is a link to an online service manual describing the Thunderbolt V ignition system. It is not specific to your engine but in general describes operation. There is also a wiring diagram showm for this system.

If your ignition system is not advancing or retarding properly you may have a problem with the control module, engine knock module or the knock sensor.

Click on the link below then scroll down to Thunderbolt V Ignition System. It's on page 4B-14 indicated on the bottom left corner of the page.

Online Manual Link

to Reel Poor THanks a bunch for the on line link It was a huge help One more Question about setting the timming . II did the knock control module test as well as the knock sensor test everything points to a bad knock sensor However When I checked the voltage at the Ignition control module it showed 10 -12 volts at the Purple/white timming lead not 8-10 like the manual says Any thoughts Jim