96 GM 5.7 thunderbolt 5 ign timing

[jwkoehn]

When I try to set the timing I ground out the ign timing lead to a ground to put it in base timing . when I check the timing It is still jumping around and sitting at aprox 10 deg btc. Does this make any sense ? I am following the service manual from merc. It does not seem to be in base timing . any thoughts ? Jim The wire I am grounding is the purple /white and am grounding it out to the Black wire in the harness which is sitting next to the ign timing lead wire and looks to be there for that purpose .

 

[Reel Poor]

Re: 96 GM 5.7 thunderbolt 5 ign timing

Here is the timing procedure. If your doing it like the diagram says it could be jumping around due to misfiring or timing chain wear/stretch. Connect the timing light to the number six plug wire and check it again to see if it still jumps around if it does not jump, number one wire, plug, or cap may be misfiring.

 

[Don S]

Re: 96 GM 5.7 thunderbolt 5 ign timing

Did you ground out the lead BEFORE you started the engine?

Also, use a meter and make sure that black lead is actually grounded.

 

[jwkoehn]

Re: 96 GM 5.7 thunderbolt 5 ign timing

I rechecked the timming and it is at 10 btc 96 350 thunderbolt 5 ign rebuilt into a 383 stroker the timming is steady @10 deg. however I am having a problem w/ cold starts while cranking it kicks back into the starter but does start It restarts great when warm . When I check w/ a light it advances very little also I don:t seem to have the power while accelerating and sometimes get a little hesitation. I am wondering if we may have the dist off by a tooth or 2 .
It seems like I have too much advance at starting and not enough at higher RPM.

 

[Don S]

Re: 96 GM 5.7 thunderbolt 5 ign timing

If it's at 10? BTDC, it can't possibly be off a tooth.

timming is steady @10 deg.
When I check w/ a light it advances very little

Did you disconnect Purple/white lead you grounded to set the timing? How little advance did you get and at what rpm????

IMPORTANT: Timing jumper wire has to be removed or the Ignition Module will stay locked in the Base Timing Mode and it will not be able to advance the ignition timing correctly when the engine rpm is increased.

The timing will also jump around quite a bit when idling when not in base timing mode.
You may have a other ignition problems if the jumper was removed.

 

[jwkoehn]

Re: 96 GM 5.7 thunderbolt 5 ign timing

Yes lead is disconnected 20 deg total advance at 3000 rpm

 

[jwkoehn]

Re: 96 GM 5.7 thunderbolt 5 ign timing

would an ignition module partially fail?

 

[John_S]

Re: 96 GM 5.7 thunderbolt 5 ign timing

Was you engine built from a 5.7L (2brl alpha) or 5.7LX or 350mag? The 5.7L wouldn't have a knock sensor or module, but the rest would.

 

[jwkoehn]

Re: 96 GM 5.7 thunderbolt 5 ign timing

it was built from a 5.7 lx and it does have a knock sensor on it

 

[John_S]

Re: 96 GM 5.7 thunderbolt 5 ign timing

Ok, do you have a service manual to go through the knock system tests? That purple/white wire should have an 8-10 volt signal on it. If no signal, line is grounded or you do have an issue with knock system. I'd check with the engine warmed up at idle and at 3K, simultanously watching what the timing is doing.