Mechanics

F250 NO ACCELERATION

1986 Ford F-250

1986 Ford F250 V8 Two Wheel Drive Automatic

I switched from mechanical fuel pump to electric Airtex E8012S, 5-9 psi, 30gph, new fuel filter, connected to 10amp fuse. I spliced into the 10amp fuse wire for the " aux fuel solenoid". Engine starts and idles fine. When I put the truck in gear and take off it spits sputters and gags and its a no go. It will idle in gear just fine.
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Captanron
April 25, 2010.



Update: I called Airtex. The electric fuel pump manufacturer and discussed the problem. Turns out that the above fuel pump does not put out enough volume for a 460ci motor. Airtex suggested a E84070 pump. So went to O'Reilly's and got an Airtex #E84070 electric fuel pump. I will be installing it today.
Wish me luck!

Tiny
Captanron
Apr 26, 2010.
Good luck!

Merlin2021
Apr 26, 2010.
I installed the recommended pump from Airtex. Idled like crap. I re-adjusted the float level and tinkered with idle screw. Now it idles at least. Fuel pressure at the carb is almost 5psi. No leaks. Still no acceleration.
Bogs out when you rev the engine like its starving for fuel.
Help me out here guys, cuz i'm lost for causes and running out of money and patience. I have faith in you guys.

Tiny
Captanron
Apr 26, 2010.
How did it run with the mechanical pump? If not good, your carb may need a new accelerator pump. This gives a shot of fuel for take off. Which carb is on it and I will see if I can locate a diagram.
Here are the specs and testing info for the fuel pump. Mechanical, you electric should be set to deliver this pressure.
FUEL PUMP
NOTE: 5.0L MPFI models use electric fuel pumps and 5.8L 4-Bbl. Models use
mechanical fuel pumps. On 7.5L 4-Bbl. Models, the Hot Fuel Handling
application uses in-tank mounted electric fuel pumps. All other
applications use mechanical fuel pumps.
Mechanical Fuel Pump (Volume Test)
On 5.8L and 7.5L 4-Bbl. Models, remove air cleaner. Slowly disconnect fuel line at filter. Using
a suitable container (one pint minimum), place at end of disconnected fuel line. With high
tension wire disconnected from coil, crank engine 10 seconds. If fuel flow is within
specification, proceed to pressure test. If not, proceed to next step.
1.
If fuel flow is low, repeat test using remote vented can of gasoline. Remove fuel pump inlet
hose. Connect a length of fuel line hose to fuel pump inlet and insert other end into remote can
of gasoline. If fuel flow is within specification, problem is plugged intake fuel filter or a kinked,
leaking or plugged fuel line or hose.
2.
Mechanical Fuel Pump (Pressure Test)
Remove air cleaner. Connect suitable pressure tester to end of fuel line. Start engine and let run for at
least thirty seconds. Read pressure and if not within specification, replace fuel pump. Reinstall air
cleaner.
Electric Fuel Pump
On 5.0L MPFI models, disconnect fuel return line at fuel rail. Connect hose to container. Connect
pressure gauge at diagnostic valve on fuel rail. Disconnect wiring connector at fuel tank and apply 12
volts to pump with jumper wire.
On 7.5L 4-Bbl. Models, disconnect fuel line just before the vapor separator unit. Connect a hose from
fuel line to a suitable container. If fuel flow is not within specification, electrically check fuel pump.
If still not within specification, replace pump-sender assembly.
FUEL PUMP SPECIFICATIONS
Application Specification
Electric Fuel Pumps
5.0L MPFI
Pressure (1) 39 psi (2.7 kg/cm2 )
Volume (1) 1 pint (.5L) in 30 seconds
7.5L 4-Bbl.
Pressure (1) 4.3 psi (.30 kg/cm2 )
Volume (1) 1 pint (.5L) in 20 seconds
Mechanical Fuel Pumps
Pressure 6.0-8.0 psi (.42-.56 kg/cm2 )
TUNE-UP - V8 -1986 Ford Pickup F250 Page 1 of 2
4/28/2010
Application Specification
Volume 1 pint (.5L) in 20 seconds
(1) Delivery capability averages.

TUNE-UP - V8 -1986 Ford Pickup F250 Page 2 of 2
4/28/2010

Merlin2021
Apr 28, 2010.
A big thank you Merlin for responding!

I have at normal idel 4.5 - 5 psi. At the carb. Starting cold 9 psi. At the carb. Fuel pump puts aout 72 gph. Working fine no leaks.

I discovered yesterday that if I manually close the choke plate almost closed and push the throttle open, it will run like a lion with turpintine on it's rear!

So i'm kinda leaning towards a bad fuel accelerator pump?

What do you think?

Tiny
Captanron
Apr 28, 2010.
That was my first thought, but it might also need a mixture adjustment, fully warm motor should have a fully open choke. How old is the choke thermostat?

Merlin2021
Apr 28, 2010.
I dont know about a choke " thermostat". The choke is electric. I just dont understand why I have to manually hold the choke plate at top of carb almost closed in order to get the engine to run at high speed. Pumping the throttle dosent keep it running unless I almost close the choke plate. Carb is getting enough fuel. Fuel pump puts out 72gph.
Acclelrator pump works. It's just getting enough fuel to keep running. I'm thinking there is an adjustment behind the electric choke. Like a little plastic thing with a tensioning spring. Wish I had a picture. Should be an adjustment for it.

Tiny
Captanron
Apr 28, 2010.
Any black smoke from the exhaust? Could be a vacuum leak or mixture adjustment. Is the carb a carter? holley?
Post a photo if you can. Also check the mounting gasket and hold down nuts, if the base gasket is cracked or loose, you will NEVER get it adjusted right... Snug the nuts down evenly, but not excessively. Here's a few simple things to check, Float is important and can be adjusted on Holley carbs without taking it off or disassembling it...
FLOAT LEVEL - WET 1. Start engine until it reaches normal operating temperature. Place vehicle on a flat surface. Remove air cleaner, if installed. Run engine at 1000 RPM for 30 seconds to stabilize fuel in carburetor. 2. Stop engine and remove sight plug from primary side fuel bowl. Check fuel level. Fuel level should be at bottom of sight plug hole. If fuel spills when plug is removed, lower fuel level by turning adjustment nut clockwise. 3. If fuel level is below sight plug hole, raise fuel level by turning adjustment nut counterclockwise. Turning adjustment nut 5/32" (4 mm) will change fuel level about 1/32" (.79 mm). 4. Tighten lock screw and install sight plug. Start and run engine at 1000 RPM for 30 seconds. Stop engine, remove sight plug and check fuel level. If necessary, adjust fuel level. 5. If fuel level is at bottom of sight plug, install sight plug using a new plug gasket. Repeat procedure for secondary fuel bowl. Secondary throttle MUST be used to stabilize fuel level in secondary fuel bowl. ACCELERATOR PUMP LEVER 1. Place throttle valves in wide open position. Using a feeler gauge, measure clearance between lever adjustment screw head and pump arm with pump arm manually depressed. See Fig. 3 . 2. To adjust, loosen adjustment screw lock nut. Turn adjustment screw in to increase clearance, and out to decrease clearance. Each 1/2 turn of adjustment screw equals .015" (.38 mm). Tighten lock nut. Fig. 3: Accelerator Pump Lever Adjustment
NOTE: Each 1/2 turn of adjustment screw equals .015" (.38 mm). ACCELERATOR PUMP STROKE Accelerator pump stroke has been preset at factory. Setting should not be changed. If original setting has been changed, adjust as follows: Check that plastic accelerator pump cam is aligned with correct hole (top or bottom) in throttle lever. Plastic accelerator pump cam is located behind throttle lever. If not aligned with correct hole, remove screw. Reposition in correct hole. Install and tighten screw. SECONDARY THROTTLE VALVES Hold secondary throttle valves closed. Turn secondary throttle shaft stop screw out until secondary throttle valves seat in throttle bores. Turn screw in until it just contacts secondary throttle valve lever. Turn screw in an additional 3/8" (10 mm) turn. CHOKE PULL-DOWN 1. Place carburetor on a stand which will allow access to pull-down diaphragm vacuum passage on underside of throttle body. See Fig. 4 . Mark choke cap and choke housing for adjustment reference. 2. Using a hacksaw, carefully cut a slot in head of choke cap breakaway screws. Using a screwdriver, remove breakaway screws and conventional screw. Remove retainer, choke cap, and gasket. 3. Temporarily install choke cap and gasket. Line up marks made prior to disassembly and rotate cap 90 ° counterclockwise from this position. Secure choke cap with one screw. 4. With choke plate fully closed, actuate choke pull-down diaphragm by applying at least 17 in. Hg of vacuum. Using a drill or gauge, check clearance between lower edge of choke plate and air horn wall. 5. If adjustment is required, carefully remove diaphragm adjustment screw cap with a small punch or screwdriver. See Fig. 4 . Using a 5/16" Allen wrench, turn screw clockwise to decrease clearance and counterclockwise to increase clearance. 6. Maintain vacuum applied to diaphragm during adjustment. Cycle vacuum from 0 to 17 in. Hg to verify adjustment. When adjustment is correct, apply RTV sealant to adjustment screw cavity and check fast idle cam position. Fig. 4: Choke Pull-Down Adjustment FAST IDLE CAM POSITION 1. Using a hacksaw, carefully cut a slot in head of choke cap breakaway screws. Using a screwdriver, remove breakaway screws and conventional screw. Remove retainer, choke cap, and gasket. 2. Temporarily install choke cap and gasket. Line up marks made prior to disassembly and rotate cap 90 ° counterclockwise from this position. Secure choke cap with one screw. 3. Apply vacuum to choke pull-down diaphragm and cycle throttle. Fast idle speed screw should rest on top step of fast idle cam with throttle closed. See Fig. 5 . 4. If adjustment is required, turn adjustment screw clockwise to position fast idle screw higher on second step. Turn counterclockwise to position screw lower on second step. 5. Remove temporary choke cap and gasket. Install original locking gasket, choke cap, and retainer. Secure choke assembly with 2 breakaway screws and conventional screw. Fig. 5: Adjusting Fast Idle Cam Position CHOKE UNLOADER Hold throttle valves wide open. Apply light closing pressure on choke valve. See Fig. 5 . Measure choke unloader clearance between lower edge of choke valve and air horn wall. To adjust, bend pawl on fast idle cam lever.


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Merlin2021
Apr 29, 2010.
Thank you for your response merlin. There are no vacume or fuel, vacume or smoke of any color from exhaust. The float level for primaries was checked and properly adjusted. Cold start; I depress the throttle one time which sets the choke, start the engine. It runs at fast idle. As the engine warms up, it slows to curb idle. Depress the throttle and it sounds like it ran out of fuel and will die. Let off the throttle and it will idle. It will restart and idle. I havnt checked accelerator pump measurements yet or the nylon fast idle cam behind the electric choke yet.And i dont think the electric choke is adjustable. Heres some pics of what i have. This is an 4180C holley/motorcraft carburetor and it takes an Renew kit #3-1346 from Holley.


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Tiny
Captanron
Apr 29, 2010.
Both floats are adjustable on these, I happen to like the mechanical pumps. My old fords had nothing but mechanical. If you have a small ball peen laying around, tap the carb in several spots with the engine running, this may dislodge a small bit of dirt in the carb, if any is in it. It looks fairly new? Rebuilts do not always perform well on the first try, I had a 66 Tbird that I put 5 rebuilts on in one day! If it is a rebuild, it may not have the right jets or metering rods for the application. Have you tried the mixture screws yet? All carbs need to be matched by adjusting the mixture, Use a tachometer and adjust idle as low as possible, then obtain the highest RPM reading on both screws, then rest idle speed. If it sounds like its out of gas it may be set way too lean!

Merlin2021
Apr 29, 2010.
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