how to turn up fuel...in pictures?

Scottd9990

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I by-passed my FDC last night and Wow, what a difference. Pyro and boost gauges inbound for install. I now get a quick puff of black smoke with each gear shift. Smoke clears right right away as the rev's come up. I now have some power at least!!! I will temper my fun until gauges are installed.
 

yagenrok636

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just be advised if you turn the fuel up too far the FDC will do strange things to the engine like, stuttering shuttering missing popping through the exhaust bad fuel mileage loss of power extreme amount of black smoke and high EGT's at least this happen to me not saying it would happen to you. I also do know this from experience if the FDC is still attached and working when you turn it up and if you start using waste oil for some reason it counteracts with that system and it doesn't run properly when. Now, when I bypassed it runs good and doesn't stutter doesn't miss runs excellent but I still have an issue of running straight diesel fuel, not sure why that is but that is one of the issues I'm still having. I can only run waste oil without the FDC and can only run diesel fuel with the FDC as long as its not turned up....
I'm experiencing all of these things. Exhaust pops weird. Lots of black smoke at idle. Truck takes a long time to start on a 70 degree day. I only by-passed the FDC and didn't adjust the fuel at all. I went down 10 flats on the fuel, and it still has a really hard time starting, pops out the exhaust, runs really hot (1200 degree EGT) and acts like it has no power with 10 psi.
 

RAYZER

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I'm experiencing all of these things. Exhaust pops weird. Lots of black smoke at idle. Truck takes a long time to start on a 70 degree day. I only by-passed the FDC and didn't adjust the fuel at all. I went down 10 flats on the fuel, and it still has a really hard time starting, pops out the exhaust, runs really hot (1200 degree EGT) and acts like it has no power with 10 psi.
Have you had your injectors pop tested? They may be worn out and leaking.
 

RAYZER

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Location
sanford/florida
I'm experiencing all of these things. Exhaust pops weird. Lots of black smoke at idle. Truck takes a long time to start on a 70 degree day. I only by-passed the FDC and didn't adjust the fuel at all. I went down 10 flats on the fuel, and it still has a really hard time starting, pops out the exhaust, runs really hot (1200 degree EGT) and acts like it has no power with 10 psi.
Were you able to resolve this issue?
 

Shane 1971 M35A2

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Travelers Rest. S.C.
I did the 50 cent trick or "quarter crap" on my 1971 M35A2 with C turbo, and saw a noticible improvement in power. When I upgraded to 11-20 tires I stacked another quarter for a total of 3 in the fdc. I am pleased with the improvements in power, streetability, turbo spool sound, hill climbing improvement, overall driveability, and it has been about 2 years. Maybe turning up the fuel in other ways and bypassing the fdc would give even better results. What I can say is it worked for me and thats "my 75 cents".
Shane
 

Floridianson

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I do not understand why someone would do the quarter thing on there own truck. Best thing is to bypass the FDC and add a pyrometer. From then on we do all the fuel adjusting from the main fuel control or twin nuts under the triangle cover. When we bypass the FDC the droop screw is not changing positions because it rides on the FDC wedge stop plate that use too move. So all we can do is adjust the main fuel / twin nuts and have to deal with the extra fuel on the lower end of the RPM scale.
 
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Shane 1971 M35A2

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Travelers Rest. S.C.
I did the 50 cent trick or "quarter crap" on my 1971 M35A2 with C turbo, and saw a noticible improvement in power. When I upgraded to 11-20 tires I stacked another quarter for a total of 3 in the fdc. I am pleased with the improvements in power, streetability, turbo spool sound, hill climbing improvement, overall driveability, and it has been about 2 years. Maybe turning up the fuel in other ways and bypassing the fdc would give even better results. What I can say is it worked for me and thats "my 75 cents".
Shane
Well I have since discovered I don't have a G code fuel pump that is harder to turn up than later models. I watched Tatical Repair's tutorial and learned that it is very easy to turn up a non-G code pump without the chance of the "innards" dropping into some hard to retrieve place. So I adjusted the fuel screw...and for the time being have the "fuel screw" turned up four "peaks" on the inner fuel nut. It increased performance again about the same difference as adding the 3 quarters to the FDC did. Now I still have the 3 quarters in the FDC and have turned up the fuel screw four peaks. By the way it moves out now and holds its speed going up hills, I probably should get around to getting a pyrometer installed.
Shane
 

Floridianson

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Interlachen Fl.
Well I have since discovered I don't have a G code fuel pump that is harder to turn up than later models. I watched Tatical Repair's tutorial and learned that it is very easy to turn up a non-G code pump without the chance of the "innards" dropping into some hard to retrieve place. So I adjusted the fuel screw...and for the time being have the "fuel screw" turned up four "peaks" on the inner fuel nut. It increased performance again about the same difference as adding the 3 quarters to the FDC did. Now I still have the 3 quarters in the FDC and have turned up the fuel screw four peaks. By the way it moves out now and holds its speed going up hills, I probably should get around to getting a pyrometer installed.
Shane
The quarter thing was done when the trucks were still under control of Uncle Sam and I bet the FDC's were still hooked up. They did it so they did not have to cut the safety wire on the tin cover and twin nuts and get caught increasing the fuel. Now that you own the truck I do not think you will get in trouble for bypassing the FDC, cutting the safety wire on the tin cover and throwing it away. Now all fuel control is the main fuel control / twin nuts and since the FDC is bypassed the smoke cam and droop screw long longer change positions when the FDC servo changes positions. So forget the quarter as you will get better control of the fuel when we adjust the main fuel / twin nuts. We mark one of the flat with a marker so we can make fine fuel adjustments. Yes the engine is going to smoke more now that we bypassed the FDC at lower rpm scale till the turbo can spool up. So bypass the FDC and just adjust the main fuel control to your altitude and terrain and put your quarters in your piggy bank.
 
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