timing problem-4.3 TBI on 2f motor

Joined
Aug 30, 2014
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157
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Colbert, Oklahoma
5/16 direct return to the tank is perfect.

The timing however...
The timing is stored in the PROM and is controlled by the ECM and the ignition module. Disconnecting the bypass wire tells the computer that the timing is at 0 degrees. When you reconnect the wire the ECM should advance the timing by whatever value is stored in the PROM. You may be 12-14 degrees off.

Do you know which wire is the jumper?
hey again-well, as I have been working on the timing the tan wire to ECM has been hooked up. was wondering if it should be. you're saying to unhook it to time it or leave it hooked up? really wish I could get an answer on my dist. mod. did it like tom Quinn did his, took all advance off[weights and springs and advance pod], marked breaker plate and outer ring with a scribe line, but failed to mark line all the way to dist. housing, and welded breaker plate and outer ring moved when I was adjusting gap on star wheel to pick-up coil. and I didn't have a reference line to move it back to, so think I kind of lost my" home base" position, or 0 degrees spot. used the place where tom locked his down as a reference point. just don't know how critical that is. think ive got it close. just freaks me out. never had this problem. got to be something simple. been trying to find answers today, ill hit it again tomorrow. maybe that thing will bust right off before the day is out. Ha- sure hope so. thanks for your help.
 
Joined
Apr 7, 2005
Messages
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Afton VA
hey again-well, as I have been working on the timing the tan wire to ECM has been hooked up. was wondering if it should be. you're saying to unhook it to time it or leave it hooked up? really wish I could get an answer on my dist. mod. did it like tom Quinn did his, took all advance off[weights and springs and advance pod], marked breaker plate and outer ring with a scribe line, but failed to mark line all the way to dist. housing, and welded breaker plate and outer ring moved when I was adjusting gap on star wheel to pick-up coil. and I didn't have a reference line to move it back to, so think I kind of lost my" home base" position, or 0 degrees spot. used the place where tom locked his down as a reference point. just don't know how critical that is. think ive got it close. just freaks me out. never had this problem. got to be something simple. been trying to find answers today, ill hit it again tomorrow. maybe that thing will bust right off before the day is out. Ha- sure hope so. thanks for your help.
 
Joined
Apr 7, 2005
Messages
1,202
Location
Afton VA
Hey Mike,
On my 5.7, TBI; I would disconnect the Tan wire, time the engine at 0 deg, ~550RPM. At this point the engine is hardly running. Then I would plug the tan wire back in and the ECM advances the timing and everything smooths out.

Of course that's for stock configuration. I think if I were in your shoes. I would leave the tan wire connected and time to the 2F specs (7 deg bubble on the flywheel??).


Hopefully someone with a similar setup as what you are trying to do will chime in.


I don't know if this works on all PROMs but another thing you can try is temporarily removing (& plugging) the vac line from the MAP sensor. I do this often for troubleshooting. My ECM will revert to a fixed fuel map and bypass the MAP sensor. The MAP sensor is very finicky.
 
Joined
Aug 30, 2014
Messages
157
Location
Colbert, Oklahoma
Hey Mike,
On my 5.7, TBI; I would disconnect the Tan wire, time the engine at 0 deg, ~550RPM. At this point the engine is hardly running. Then I would plug the tan wire back in and the ECM advances the timing and everything smooths out.

Of course that's for stock configuration. I think if I were in your shoes. I would leave the tan wire connected and time to the 2F specs (7 deg bubble on the flywheel??).


Hopefully someone with a similar setup as what you are trying to do will chime in.


I don't know if this works on all PROMs but another thing you can try is temporarily removing (& plugging) the vac line from the MAP sensor. I do this often for troubleshooting. My ECM will revert to a fixed fuel map and bypass the MAP sensor. The MAP sensor is very finicky.
Hey there jcj- thanks. man, I stabbed dist. again and it fired. had stabbed it several times, with no luck but I guess I finally got it right. man that makes me feel so dumb. stabbed them lots of times and never had a problem, guess you have to be real careful. going to try and time it like you said. thanks a lot for your help. im going to post a thread for all the guys who tried to help me and for all the guys that may run into what I did. sure appreciate it. Happy Trails!
 

Stumpalama

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I did the same with my dist. It took too many times to get it just right.
 
Joined
Sep 18, 2005
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This may have been said already, but it can't be said too many times. Make sure you have oil pressure as soon as the motor fires up after having had the distributor out. This may be an automatic thing to do for many people, but too many have lost an otherwise good motor over forgetting to do this. Just make sure the distributor is fully engaged into the oil pump.

Don
 
Joined
Apr 7, 2005
Messages
1,202
Location
Afton VA
I did the same with my dist. It took too many times to get it just right.
Ever tried static timing? I have recently come across a few posts and videos. Ingenious, can't believe I didn't learn this years ago.

Hey there jcj- thanks. man, I stabbed dist. again and it fired. had stabbed it several times, with no luck but I guess I finally got it right. man that makes me feel so dumb. stabbed them lots of times and never had a problem, guess you have to be real careful. going to try and time it like you said. thanks a lot for your help. im going to post a thread for all the guys who tried to help me and for all the guys that may run into what I did. sure appreciate it. Happy Trails!
Awesome! hopefully you have decent idle. Not to be discouraging but I too would be surprised if the 4.3 PROM will make you happy without some tuning.
A running 2F is a great start. Best of luck:beer:
 
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