Switching from Volvo TBI to Carb on a 1996 5.7 GI

alldodge

alldodge

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camboat said:
Perfect
You just saved me $400
Do I need to change anything on it for the carb conversion?
I will put a new coil on. The old one looks tired.

Thanks
Click to expand...
As Scott said coil is fine

Timing is done as follows the difference will be DO NOT use timing listed (2*), you will need to use most likely 8* BTDC. You also do not have a shift interrupter

EST Timing.jpg
 
Lou C

Lou C

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I thought of replacing my old Prestolite Points distributor with an EST, the only thing holding me back is the advance curve, I know the 4.3 cannot take as much advance as the V8s can, so I guess I'd have to set the timing by using Total Timing Advance, and then the idle timing will be whatever it winds up at, probably somewhat retarded from the stock setting.
Thoughts? The 4.3 according to my OMC Shop Manual gets only 12* of centrifugal advance, standard curb idle timing is 6* and so the total is only 18* @ 3200 rpm (with 89 octane fuel).
That's how I have run it all these years. Don't mind replacing points, but it would be nice to have something a bit more reliable.
 
Scott Danforth

Scott Danforth

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The EST for the V6 has 2 different curves and the cylinder head determines the curve

Screenshot_20251231-101146.png
 
C

camboat

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camboat said:
Thanks
Click to expand...
Will I had time to pull the VST off the boat and I opened up the distributor cap and here is the model of distributor that is on the Volvo 5.7.
Sierra 18-5484-1

They must of put a new one on when they rebuilt the engine. I looked it up and it needs a control module to make it work. Is that right?

Thanks
 

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alldodge

alldodge

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Just like the Davis one, the EST is self contained and only needs what is in the distributor to run. While Sierra is ok, the standard automotive GM is the same, nothing special
 
C

camboat

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I tried using the stock Volvo pump, but in end I decided to replace it. I picked up a Carter fuel pump. My question is, can I mount it on the engine or do I have to mount it lower for better fuel pickup? I still want to use the Volvo secondary filter. Starting to put everything back together since we have a week of good weather.
Thanks again for the help!
 
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camboat

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Will I got everything installed and wired up today. Everything works but the fuel pump when you turn on the key. Attached is how I wired everything up using the new to me 2005 GL wiring harness and the attached schematic. I checked fuses. Swapped fuel pump relay. Still nothing.
The relay plug has 12 volt on one side, but nothing on the other terminals when you turn the key turn the on.

I must be missing something. Everything was pretty much plug and play with the new harness, other than changing a few alarm ends and temperature sender end.

Thanks for any help.
 

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camboat

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One more question
Does the fuel pump come on for a few seconds to prime the carb when you turn the key on like the throttle body pump did?
 
alldodge

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When cranking you should get 12V on pin 85 of the relay when cranking. If it's not there check to see if your getting 12V on the Yellow/Red wire on the key switch when cranking

If 12V when cranking on key switch and not on pin 85, then it's probably the diode. Check for 21V on both sides of diode when cranking
 
C

camboat

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Thanks everyone for your help. I fired it up today. With a few adjustments to the carb at idle. Dialed in the fuel pressure to 5lbs. It runs great. The Carter fuel pump is loud. I will probably replace it with a better one in the spring. Not sure which pump is better for this application.
Thanks again for everyone that helped with this project.

Cheers!
 

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Lou C

Lou C

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Great work and congrats!
Question:
did you use the bypass or blocking fuel regulator?
 
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