1987 Ford Other motorhome

Tiny
REBECCA ARMER
  • MEMBER
  • 1987 FORD
  • 2WD
  • AUTOMATIC
  • 200,000 MILES
We have a 1987 Ford 460 automatic in a Motorhome. It runs OK until you hit 55 mph then it starts cutting out and back firing. It will not go over 55 mph (up hill or down). So far we have put in a new carburetor, changed the fuel filter, rotor, distributor cap, plugs, wires and check the timing. Any idea on what else our problem could be?
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Monday, March 10th, 2014 AT 12:19 PM

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Tiny
CJ MEDEVAC
  • EXPERT
SAY IT'S A CARB. NOT FUEL INJECTION?

MECHANICAL FUEL PUMP?

DID JA JUST OBTAIN IT?

HAS IT DONE BETTER IN THE PAST?

RECKON SINCE IT'S A BIG OLE ROAD MONSTER IT COULD HAVE A GOVERNOR ON IT.'COURSE THAT WOULD NOT EXPLAIN THE BACKFIRING

I HAVE OTHER POSSIBILITIES. REALLY SOUND FUEL RELATED. WHAT CARB DOES IT HAVE?

ARE YOU ABLE TO USE A TIMING LIGHT W/ CONFIDENCE. MAY WANT YOU TO DO SOME OTHER CHECKS ON THE 'STRIBUTOR

YOUR TURN

THE MEDIC
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Monday, March 10th, 2014 AT 4:10 PM
Tiny
REBECCA ARMER
  • MEMBER
Yes, it has a carburetor and we just replaced it with a brand new Edelbrock 3 days ago. My husband also dropped the fuel tank last night, checked the filter in the tank (the sock), pressure washed the inside of the tank and dried it with an air hose and it still did the same thing. He looked for a governor but was unable to find one. We bought this from his uncle's preacher about a month and a half ago and he told us that it had been working fine until his last drive to the deer lease so it just started the issues about 3 or 4 months ago, which with a motor home, they do not get driven a lot. So if the carburetor is new and the filters/tank are fine, what else is there in the fuel system that could be causing the back firing?

Oh, and yea, he used the timing light with confidence : )
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Tuesday, March 11th, 2014 AT 6:32 AM
Tiny
CJ MEDEVAC
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BEFORE WE GO INTO YOUR FUEL SYSTEM. WHICH I HAVE LITTLE INFO AVAILABLE TO ME."SEEMS MITCHELL I" IS LIMITED ON OLDER STUFF

DO Y'ALL HAVE A CHILTON/ HAYNES/ OR ANY OTHER KINDA REPAIR MANUAL FOR THAT PUPPY. SOMETHING W/ SPECS OR TESTS?

IT'S STORY/ NOVEL TIME!

EVERY THING WE DO FROM HERE ON, NEEDS TO BE W/ YOUR ENGINE AT OPERATING TEMP!

LET'S DISCUSS MR. DISTRIBUTOR AND TIMING!

YOU HAVE A VACUUM LINE GOING TO THE DIST. THIS IS THE VACUUM ADVANCE VACUUM LINE.

. DID YOU TIME IT WITH THIS LINE DISCONNECTED FROM THE DIST AND THIS LINE (NOW LOOSE) PLUGGED OFF WITH A BOLT OR SCREW?

. WHEN YOU WERE DONE. DID YOU HOOK THAT PUPPY BACK UP?

. DID YOU HAVE THE IDLE SPEED CORRECT AND/ OR ADJUSTED IT AS YOU WENT, SO THAT THE END RESULT WAS "X" DEGREES" @ "X" IDLE SPEED, THIS INFO MAY BE ON A STICKER UNDER THE HOOD (AFTER YOU'VE TIGHTENED THE DIST HOLD DOWN BOLT AND THE VAC LINE IS RECONNECTED, YOU MAY HAVE TO ADJUST IDLE SPEED AGAIN)

. IF YOUR IDLE SPEED IS TOO HIGH. MECHANICAL ADVANCE STARTS MOVING. YOU END UP TIMING IT WRONG

. NOT DOING THIS STUFF MAY HAVE YOUR TIMING WAY OFF!

NOW THEN, CONFIDENCE W/ THE LIGHT!

IF YOU HAVE AN ADJUSTABLE ONE---STICK IT ON "ZERO" (PLAYING WITH THE DIAL CONFUSES PEOPLE)THIS AIN'T NASCAR.A 1940s PLAIN JANE TIMING LIGHT COULD DO THIS ENTIRE TIMING TASK AND CHECKS

WE WANNA CHECK THE MECHANICAL ADVANCE 1st----UNDO THE VAC ADVANCE HOSE AND PLUG IT (IT WILL NOT AFFECT US NOW) WE ARE CHECKING TO SEE IF IT WORKS/ IS STUCK/ SPRINGS ARE BROKE AND IT "REALLY HAS YOU ADVANCED". ALL OF THE TIME. AND WILL NOT RETRACT (IF THIS IS THE CASE) YOUR TIMING MAY HAVE BEEN "OFF" 'CAUSE OF A SPRING BREAKAGE. NOW YOU "THOUGHT YOU TIMED IT". IT WILL NOT RETRACT. SO "MECHANICAL ADVANCE" IS LIKE IT IS NO THERE. YA?

HERE'S HOW YOU CHECK---YOU ARE AT IDLE SPEED---WATCHING YOUR MARKS WITH THE LIGHTGRAB THE THROTTLE AND INCREASE YOUR ENGINE SPEED SLOWLY (MAYBE TO 2000 RPM) USING YOUR TACH/ DWELL METER. DOES YOUR MARK MOVE MORE AND MORE BTDC. RELEASING MR. THROTTLE SHOULD TAKE YOU BACK TO CORRECT TIMING. WHAT'S HAPPENING IS AS THE ENGINE SPEED INCREASES----YOU ARE THROWING THE SPARK SOONER AND SOONER SO THE QUARTERBACK CATCHES IT EVERY TIME AT THE "INSTANT" THE PISTON STARTS DOWN ON POWER STROKE. WE CANNOT SPEED UP ELECTRICITY--JUST THROW THE SWITCH SOONER!

GOOD?

NOW LET'S CHECK VACUUM ADVANCE. VERY SIMILAR

WE HAVE 2 KINDS OF VACUUM

"PORTED" (VAC NIPPLES ABOVE THE CARB THROTTLE PLATES) THIS IS ONLY ALIVE WHEN YOU CRACK YOUR THROTTLE OPEN

"MANIFOLD" (BELOW THE THROTTLE PLATES) THIS IS ALWAYS ALIVE

YOUR RIG'S VAC ADVANCE COULD BE HOOKED TO EITHER KIND.I CAN'T SEE IT FROM HERE)

IT DON'T MATTER FOR THIS TEST---WE WILL MAKE IT WORK---TEMPORARILY ANYWAY

RIGHT NOW (FROM LAST TEST) THE VAC ADVANCE LINE IS PLUGGED AND A-DANGLIN'

WHILE THE ENGINE IS RUNNING, UNPLUG IT AND STICK YOUR FINGER OVER ITARE YOU AT CORRECT IDLE SPEED, IS IT SUCKING?

IF SO, ITS ON "MANIFOLD VACUUM"

WATCH THE TIMING MARKS WITH YOUR LIGHT AND PLUG IT BACK ONTO MR. DIST. DID IT JUMP BACK 10 DEGREES OR SO, AND THE ENGINE RUN FASTER AND SMOOTH?

. OK (OTHER POSSIBILITY). SO IT DID NOT SUCK AIR WITH YOUR FINGER ON IT

WE HAVE "PORTED VACUUM". IF WE SPEED THE ENGINE UP (TO MAKE THE PORTED WORK). MECHANICAL ADVANCE WILL KICK IN TOO

WE NO WANT THAT!

LET'S FIND A "LIVE" MANIFOLD VACUUM LINE ON YOUR CARB OR INTAKE MANIFOLD

WE ARE GONNA HOOK UP THE DIST VAC LINE. BUT WE ARE GONNA REMOVE THE OTHER END OF THE HOSE (CAP OFF THAT NIPPLE) THEN HOOK THE HOSE TO THE "MANIFOLD" (ALWAYS LIVE VACUUM)

AT THE SAME TIME. WATCH THE MARKS. IT SHOULDA JUMPED BACK 10 DEGREES OR SO, AND THE ENGINE RUN FASTER AND SMOOTH?

ALL IS GOOD. PUT IT ALL BACK LIKE IT SHOULD BE

. BAD ON EITHER TEST. NEED NEW DISTRIBUTOR!

YOU CAN INSTALL IT THE EZ WAY---OR THE HARD WAY----I CAN HELP YOU DO THIS CORRECTLY. IF NEED-BE!

HOPE IT DON'T GET THAT FAR!

YOUR TURN. AM I CONFUSING OR WHAT?

THE MEDIC
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Tuesday, March 11th, 2014 AT 5:35 PM
Tiny
CJ MEDEVAC
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Peek-a-boo

I'm here!

The Medic
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Wednesday, January 4th, 2017 AT 3:06 PM

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