4.3L Vortec swapped motor no spark **Long with details** - Pirate4x4.Com : 4x4 and Off-Road Forum

79CJLongmont · 08-04-2005, 01:08 PM

I have a 1995 4.3L Vortec out of a GMC Jimmy. It has been swapped into a 1995 Jeep Wrangler. I used a Painless wiring harness. I am getting no spark from the coil. The engine was running when pulled from the donor. The distributor has not been removed or moved. Here is what I have checked:

1. Injectors are firing, you can smell fuel from the header outlets (no exhaust yet).
2. I have 60psi of fuel pressure
3. Coil is getting 12 volts in start AND run key position
4. Coil is good. I tested primary, secondary and body ground with ohmmeter
5. There are no computer trouble codes
6. For the heck of it I disconnected the knock sensor and tried to crank to make sure the computer would detect its absence. It did. I erased the trouble code. Still no spark.
7. I have double and triple checked all grounds and harness connections.
8. Painless has no idea and only suggested that I go through the alldata ignition troubleshooting sheets. I can not do this effectively since their system is different (it bypasses the ESC).
9. The only thing I noticed was over 30,000 ohms resistance on the coil to distributor wire, BUT I get no spark from the coil with the wire removed and a screwdriver held to ground and extremely close to the coil.
10. I have tried a new coil with no luck.
11. I tried disconnecting the timing plug with no luck/spark occurring
12. The battery is fully charged
13. It does not change anything if the distributor is unplugged.
14. This painless system does not use the crankshaft position sensor. The function of determining that the motor is being cranked is instead accomplished via the Camshaft Position Sensor (or so they say).
15. The computer is new as is the MEMCAL. The MEMCAL was accidentially dropped on concrete before it was installed, but was subsequently inspected for any visual problems. I have not ruled this out as a problem yet except that everything else works fine and the coil is getting 12 volts.

Sorry for the long post, but I am very close to banging my head against the wall and setting the thing on fire then calling the insurance company. Any suggestions are appreciated!!! I figure if anyone can figure this out, someone on the PBB can!!!!!!

THANKS!

xxkptdeuce40xx · 08-04-2005, 11:50 PM

hey i just installed a new 4.3 CPI vortec in my s-10 blazer... and the mechanic i talked to after installing it told me these engines need some exhaust back pressure to run.... so just a guess... but i would say hook up your exhaust and see if it will fire... this is what he told me but im not posstive about it... hope it works for ya... lemme know

3/4ton62gmc · 08-05-2005, 07:45 PM

Check the ignition module this is a common problem. If it is bad it will not set any codes. It seems as though you have checked every thing else and this module will cause no spark. Of course with the painless harness its hard to say if it is being triggered properly. just something to try if you have another one or buy one. My .02$

79CJLongmont · 08-05-2005, 09:19 PM

Alright, I have an update. Thanks for the suggestions, though. Painless is not using and SWEARS that they do not need to use the ESC/Ignition Module that is next to the coil. There is not even a plug in the harness for it. Although, the plug labeled "distributor" does not work with this distributor. It actually fits the ignition module. I pulled the distributor today and noticed that although the harness plug fits into the distributor it is a 4 wire plug and the distributor has a 3 wire.

This motor is supposed to be out of a 1995 GMC Jimmy 4x4. I did not pull the motor from the donor. I am just wiring it up.

Alldata depicts the 1995 Vortec's distributor as having a module in the base with a 4 wire plug and a 2 wire plug. The 2 wire plug on the distributor is supposed to go to the coil. The 4 wire goes into the harness and back to the computer. That is what is SUPPOSED to be the scenario.

This engine actually has a single 3 wire connection that is nothing more than a hall effect camshaft position sensor. There is NO 2 wire or 4 wire connection. Half of the 4 sockets in the coil are actually blocked off by plastic. There is only a place for the 12 volt and tach lead plug on the coil. This engine also has a seperate ESC/Ignition module next to the coil. The ESC has a 4 wire connection like the distributor is SUPPOSED to have and the painless wiring harness's plug fits it.

Does anyone have any idea what this ignition setup is actually from? My 1992 454 TBI has the distributor that this thing is supposed to have and also has the ESC module. Not that it matters, though. It just looks like the 1995 Vortec is supposed to have a TBI style ignition sysytem perhaps minus the seperate ESC module??? Anyone have any idea on this??

lumpdog · 08-05-2005, 11:28 PM

Sounds to me like you have the newer Vortec engine, 96 and up. They have a plastic upper plenum, a single four flat wire connector to the coil, a plastic base distributor, and a cap on the distributor that has the terminals straight out towards the sides of it. From what you are describing, I would guess that is what you have.

So you may be chasing down diagrams for the wrong style motor.... On those engines, they do use a hall effect sensor that is an input to the ecm, and the ecm controls the ign coil. On the earlier years (like you truck) the coil was directly controlled from the distributor. Also, the later years will have a crank sensor down by the balancer in the timing cover, and uses the distributor for the cam sensor.

79CJLongmont · 08-06-2005, 01:22 AM

Quote:

Originally Posted by lumpdog

Sounds to me like you have the newer Vortec engine, 96 and up. They have a plastic upper plenum, a single four flat wire connector to the coil, a plastic base distributor, and a cap on the distributor that has the terminals straight out towards the sides of it. From what you are describing, I would guess that is what you have.

So you may be chasing down diagrams for the wrong style motor.... On those engines, they do use a hall effect sensor that is an input to the ecm, and the ecm controls the ign coil. On the earlier years (like you truck) the coil was directly controlled from the distributor. Also, the later years will have a crank sensor down by the balancer in the timing cover, and uses the distributor for the cam sensor.

Sounds right to me. The guy told me it was a 1995, but it appears that it is a 1996. That would explain it. This motor has a Crankshaft Position Sensor and the distributor cap like you described. However, it is a 3 prong connector on the distributor and an aluminum intake manifold. This motor looks like a frankenstein version. The MAP sensor is an older style MAP sensor and not the smaller version like the ODBII. It is speed density and does not have a MAF. Weren't 1996 and newer MAF systems and not speed density? The wiring harness has a "set timing" connector, but the distributor is not movable due to a roll pin in the rear of the block at the distributor base and a fork on the distributor base that slides down onto the roll pin. Can you swap in a 1995 or older Distributor and coil with this and have it actually work?? It seems that it is either that or try to run a newer 1996-up wiring harness, but I can almost guarantee that won't work if for no other reason that I don't think the MAP sensor plug will work, maybe the coil plug and probably other sensors.

79CJLongmont · 08-06-2005, 01:21 PM

FYI...

I did some more research on ALLDATA and found that this is a 1995 Vortec 4.3L. It is evidently a late 1995 model that is OBDII compliant. This is the reason for the 1996 and newer style ignition system but the 1995 and older cast aluminum intake and lack of a MAF sensor, etc... Evidently GM frankesteined the newer style ignition system on these in late 1995 to be ODBII compliant without yet doing all of the modifications that ended-up going into the 1996.

Now, I am guessing I can obtain and install the older style distributor and coil on this engine to obtain the desired result. Otherwise, the Painless wiring won't work, the computer for the wiring won't work, etc... It is quicker, easier, and less expensive to replace the distributor and coil than it is to replace many other things.

Anyone know if this will work? One hurdle I see is that there is not a timing indicator tab on the timing cover. I'd prefer to not have to pull the front end of the motor down to replace the timing cover. Also, the roll pin in the back of the block for the later distributor *might* get in the way. I can cut that off or pull it out, I think, if it does interfere.

Thoughts?

08-04-2005, 01:08 PM	#1 (permalink)
79CJLongmont Registered User Join Date: May 2003 Member # 19662 Location: Longmont, CO Posts: 115	4.3L Vortec swapped motor no spark Long with details I have a 1995 4.3L Vortec out of a GMC Jimmy. It has been swapped into a 1995 Jeep Wrangler. I used a Painless wiring harness. I am getting no spark from the coil. The engine was running when pulled from the donor. The distributor has not been removed or moved. Here is what I have checked: 1. Injectors are firing, you can smell fuel from the header outlets (no exhaust yet). 2. I have 60psi of fuel pressure 3. Coil is getting 12 volts in start AND run key position 4. Coil is good. I tested primary, secondary and body ground with ohmmeter 5. There are no computer trouble codes 6. For the heck of it I disconnected the knock sensor and tried to crank to make sure the computer would detect its absence. It did. I erased the trouble code. Still no spark. 7. I have double and triple checked all grounds and harness connections. 8. Painless has no idea and only suggested that I go through the alldata ignition troubleshooting sheets. I can not do this effectively since their system is different (it bypasses the ESC). 9. The only thing I noticed was over 30,000 ohms resistance on the coil to distributor wire, BUT I get no spark from the coil with the wire removed and a screwdriver held to ground and extremely close to the coil. 10. I have tried a new coil with no luck. 11. I tried disconnecting the timing plug with no luck/spark occurring 12. The battery is fully charged 13. It does not change anything if the distributor is unplugged. 14. This painless system does not use the crankshaft position sensor. The function of determining that the motor is being cranked is instead accomplished via the Camshaft Position Sensor (or so they say). 15. The computer is new as is the MEMCAL. The MEMCAL was accidentially dropped on concrete before it was installed, but was subsequently inspected for any visual problems. I have not ruled this out as a problem yet except that everything else works fine and the coil is getting 12 volts. Sorry for the long post, but I am very close to banging my head against the wall and setting the thing on fire then calling the insurance company. Any suggestions are appreciated!!! I figure if anyone can figure this out, someone on the PBB can!!!!!! THANKS!

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08-04-2005, 11:50 PM	#2 (permalink)
xxkptdeuce40xx Registered User Join Date: Jun 2005 Member # 49054 Location: VA Posts: 10	hey i just installed a new 4.3 CPI vortec in my s-10 blazer... and the mechanic i talked to after installing it told me these engines need some exhaust back pressure to run.... so just a guess... but i would say hook up your exhaust and see if it will fire... this is what he told me but im not posstive about it... hope it works for ya... lemme know

08-05-2005, 07:45 PM	#3 (permalink)
3/4ton62gmc Wheeler Join Date: Nov 2004 Member # 38880 Location: Phoenix Az. Posts: 247	Check the ignition module this is a common problem. If it is bad it will not set any codes. It seems as though you have checked every thing else and this module will cause no spark. Of course with the painless harness its hard to say if it is being triggered properly. just something to try if you have another one or buy one. My .02$

08-05-2005, 09:19 PM	#4 (permalink)
79CJLongmont Registered User Join Date: May 2003 Member # 19662 Location: Longmont, CO Posts: 115	Alright, I have an update. Thanks for the suggestions, though. Painless is not using and SWEARS that they do not need to use the ESC/Ignition Module that is next to the coil. There is not even a plug in the harness for it. Although, the plug labeled "distributor" does not work with this distributor. It actually fits the ignition module. I pulled the distributor today and noticed that although the harness plug fits into the distributor it is a 4 wire plug and the distributor has a 3 wire. This motor is supposed to be out of a 1995 GMC Jimmy 4x4. I did not pull the motor from the donor. I am just wiring it up. Alldata depicts the 1995 Vortec's distributor as having a module in the base with a 4 wire plug and a 2 wire plug. The 2 wire plug on the distributor is supposed to go to the coil. The 4 wire goes into the harness and back to the computer. That is what is SUPPOSED to be the scenario. This engine actually has a single 3 wire connection that is nothing more than a hall effect camshaft position sensor. There is NO 2 wire or 4 wire connection. Half of the 4 sockets in the coil are actually blocked off by plastic. There is only a place for the 12 volt and tach lead plug on the coil. This engine also has a seperate ESC/Ignition module next to the coil. The ESC has a 4 wire connection like the distributor is SUPPOSED to have and the painless wiring harness's plug fits it. Does anyone have any idea what this ignition setup is actually from? My 1992 454 TBI has the distributor that this thing is supposed to have and also has the ESC module. Not that it matters, though. It just looks like the 1995 Vortec is supposed to have a TBI style ignition sysytem perhaps minus the seperate ESC module??? Anyone have any idea on this??

08-05-2005, 11:28 PM	#5 (permalink)
lumpdog Rock God Join Date: Mar 2005 Member # 44659 Location: Mtn Home, Idaho Posts: 1,237	Sounds to me like you have the newer Vortec engine, 96 and up. They have a plastic upper plenum, a single four flat wire connector to the coil, a plastic base distributor, and a cap on the distributor that has the terminals straight out towards the sides of it. From what you are describing, I would guess that is what you have. So you may be chasing down diagrams for the wrong style motor.... On those engines, they do use a hall effect sensor that is an input to the ecm, and the ecm controls the ign coil. On the earlier years (like you truck) the coil was directly controlled from the distributor. Also, the later years will have a crank sensor down by the balancer in the timing cover, and uses the distributor for the cam sensor.

08-06-2005, 01:21 PM	#7 (permalink)
79CJLongmont Registered User Join Date: May 2003 Member # 19662 Location: Longmont, CO Posts: 115	FYI... I did some more research on ALLDATA and found that this is a 1995 Vortec 4.3L. It is evidently a late 1995 model that is OBDII compliant. This is the reason for the 1996 and newer style ignition system but the 1995 and older cast aluminum intake and lack of a MAF sensor, etc... Evidently GM frankesteined the newer style ignition system on these in late 1995 to be ODBII compliant without yet doing all of the modifications that ended-up going into the 1996. Now, I am guessing I can obtain and install the older style distributor and coil on this engine to obtain the desired result. Otherwise, the Painless wiring won't work, the computer for the wiring won't work, etc... It is quicker, easier, and less expensive to replace the distributor and coil than it is to replace many other things. Anyone know if this will work? One hurdle I see is that there is not a timing indicator tab on the timing cover. I'd prefer to not have to pull the front end of the motor down to replace the timing cover. Also, the roll pin in the back of the block for the later distributor might get in the way. I can cut that off or pull it out, I think, if it does interfere. Thoughts?