Mechanics

FORD F-350 RPM PROBLEM

1993 Ford F-350 • 175,000 miles

I have a f350 with 351w standard trans I had edelbrock fuel injection with 24lbs injectors could never get it to tune. Pulled it all off replaced with edelbrock victor jr intake, BIGS carb jetted 800cfm, msd 6a, fuel regulators, and pushing 40psi intake fuel pumps. My fuel pressure gauge is all over the place, had to retard my timing to 5 btd to get it to stop deiseling, and when I adjust my air fuel at an idle runs great tell you try to drive it, starts to back fire and acts like its running out of fuel, so I idle it up to 2000rpm reset floats, drove again did same thing except now the fuel pumps are pushing past my regulators and over running the floats Do you have any idea's
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Nate2084
February 28, 2013.




CARB.W/ 40 PSI?

MY CARBS REQUIRE LESS THAN 5 PSI

DEISELING IS DUE TO EXCESSIVE IDLE SPEED.I'M GUESS 800-1000 RPM WOULD BE THE LIMIT, PROBABLY CLOSER TO 700 WOULD SUIT ME

TIMING SHOULD BE SET WITH THE IDLE LOW (AS NOT TO HAVE THE MECHANICAL ADVANCE WEIGHTS SLINGING OUT AND ADVANCING IT)

WITH YOUR IDLE SPEED WAY UP YONDER, YOU ARE RUNNING OFF OF YOUR MAINS---NOT THE IDLE CIRCUITTRYING TO TUNE THE IDLE MIXTURE IS POINTLESS, AS YOU ARE NOT "IN" THE IDLE CIRCUIT AT ALL

I'M STILL USING THE OLE MECHANICAL FUEL PUMP ON BOTH OF MY JEEPS----YOU CAN GET A LOW PRESSURE ELECTRIC PUMP, BUT YOU MUST INSURE WITH A REGULATOR AND/ OR A RETURN LINE BACK TO THE TANK. OTHER WISE YOU WILL OVER POWER THE FLOAT/ NEEDLE AND SEAT

I'LL SEND YOU PICS OF HOW MY '77 JEEP CJ 5 SYSTEM WORKS

KEEP US POSTED

THE MEDIC


CJ MEDEVAC
Mar 1, 2013.
Thank you for you response, I have a high dollar regulator on it thats suppose to be able to handle the fuel injection pumps that are in the tank and keep the pressure at 8 lbs witch is what the BIGS carb needs and it does have a return line, all the work on the timing was done with the idle around 800 rpm, I started at 10, set the carb but was dieseling, played with it over and over and ended up at 5 degrees with an idle of about 750-800, tuned in the floats in the shop it sounds great you could hold the Rpm up, rack it, but as soon as you try to drive it it goes bad, it would go maybe 50 yards and start acting up, I cycled the key three times to let the fuel pumps refill the bowl and it would go again for about 50 yards that's why I held the rpm at 2000 rpm and reset the floats only but no change, I'm starting to wonder if the msd system is acting up or if the distributor is not advancing or the plus sating fuel injection pumps can't keep up with the demand of the carb
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Tiny
Nate2084
Mar 1, 2013.
WHAT ABOUT INSTALLING A LOW FUEL PRESSURE GAUGE IN BETWEEN THE CARB AND THE REGULATOR ====JUST TO VERIFY THE PRESSURE?.......LIKE MINE

YOU ARE TIMING WITH THE VACUUM ADVANCE HOSE LOOSE AND PLUGGED OFF?

YOU CAN VERIFY YOUR ADVANCES LIKE THIS:

VACUUM ADVANCE LINE OFF AND PLUGGED----INCREASE THROTTLE WHILE WATCHING THE TIMING MARKS WITH YOUR TIMING LIGHT..........TIMING SHOULD ADVANCE (LARGER NUMBERS).........THIS WILL VERIFY "MECHANICAL ADVANCE"

THEN HOOK YOUR VACUUM ADVANCE LINE BACK UP TO THE DISTRIBUTORTHEN HOOK THE OTHER END OF IT UP TO "MANIFOLD VACUUM" (CONTINUOUS VACUUM)............WATCH YOUR MARKS AGAIN, WHILE UNHOOKING AND HOOKING THE LINE A FEW TIMES........AGAIN IT SHOULD ADVANCE!

I HAVE FOUND THAT WITH MY JEEP, AFTER TIMING IT CORRECTLY, HE'LL PERFORM MUCH BETTER USING "MANIFOLD VACUUM" FOR MY VACUUM ADVANCE (PERMANENTLY) INSTEAD OF "PORTED VACUUM".........THAT'S NOT JUST ME, BUT I'VE SUGGESTED THIS TO OTHER CJ OWNER'S.......THEY AGREE IT PERFORMS BETTER!

WHEN TIMING IS DONE, IDLE IS HIGH (FROM THE ADVANCE) BRING DOWN THE IDLE SPEED TO SPECS THEN TUNE THE MIX SCREWS....THEN GET THE IDLE SPEED RIGHT AGAIN.

I PREFER USING MY DWELL/ TACH METER TO TWEAK MY SCREWS. WATCHING THE TIP OF THE NEEDLE (MOST SENSITIVE) FOR "IMPROVEMENTS" OR "DROPPING OFF"...........KEEPING BOTH SCREWS "EVEN" AS YOU GO...............I, MYSELF, JUST DON'T SEE THE GAUGE MOVEMENTS ON A VACUUM GAUGE, AS WELL AS I SEE THE DWELL/ TACHs MOVEMENTS

MY DAD DIED IN DEC '10---I INHERITED HIS TRUCK---'76 FORD F-150 W/ 351 WINDSOR, IT HAS ABOUT 4 OIL CHANGES ON THE REBUILD WE DID, I STILL HAVEN'T BEEN BACK OVER TO MAMA'S HOUSE TO GET HIM YET, FROM TIME TO TIME, I DRIVE IT AROUND THE YARD

ARE YOU SURE THERE ARE NO VACUUM LEAKS?

AS FAR AS TUNING THE CARB ITSELF---MY HOLLEY WAS TOO LEAN, RIGHT OUT OF THE BOX

I'VE TRIED BUNCHES OF WAYS TO "JET" MINEYOU NEED YOUR RUNNING BETTER BEFORE YOU EVEN THINK ABOUT JETTING!!!!!!!

THIS IS WHERE I FOUND THE VERY BEST METHOD (FOR ME, ANYWAY)HENCE THE "O2 SENSOR" AND AIR/ FUEL RATIO GAUGE........AND INCLUDING THE VACUUM GAUGE I ALREADY HAD ON MY DASH.......ALL SORTA USED TOGETHERSEE THIS LINK

http://www.bob2000.com/carb.htm

YOUR TURN

THE MEDIC


CJ MEDEVAC
Mar 1, 2013.

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