1985 460 Fires but doesn't stay running
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1985 460 Fires but doesn't stay running
I have my 460 with 4bbl carb and when I turn the truck over the fuel pump pumps fuel into the carb but after it fires the solinoid no longer sends power to fuel pump and the truck dies, is the fuel pump suppose to constantly pump to keep the truck running or is it suppose to run off just straight pressure?
pedant
Joined: Jan 2008
Posts: 23,576
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From: EXTREME southwest CT
The fuel pump relay is bypassed from the 'I' terminal while the starter relay is engaged in order to prime the carburetor.
The 'Hot Fuel Handling' system is safetied through the inertia switch and an oil pressure switch.
For the relay to close, power routes through a fuse, through the inertia switch and to the relay, which is pulled closed when the oil pressure switch connects to ground.
Check the fuse.
Check the button on the inertia switch.
Check the oil pressure safety switch.
Check the relay.
Since the pumps prime when the starter is engaged you know it is not the switch valve or the pump itself.
The 'Hot Fuel Handling' system is safetied through the inertia switch and an oil pressure switch.
For the relay to close, power routes through a fuse, through the inertia switch and to the relay, which is pulled closed when the oil pressure switch connects to ground.
Check the fuse.
Check the button on the inertia switch.
Check the oil pressure safety switch.
Check the relay.
Since the pumps prime when the starter is engaged you know it is not the switch valve or the pump itself.
Moderator
Joined: Nov 2007
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From: Denver Metro Area, CO
Might jiggle the key switch/tumbler a bit towards your body and see if that fixes your problem; the springs wear out and/or the linkage gets gooped up and it doesn't spring fully to RUN from START.
Laughing Gas
Joined: Apr 2013
Posts: 1,049
Likes: 65
As stated previously it sounds like your fuel pump is not getting power in the run circuit.
First, does the truck have oil and oil pressure? Did you just change the distributor? There's a safety device that prevents power from getting to the pumps if you don't have oil pressure. If you just pulled the distributor and dislodged the oil pump drive shaft that could be your problem.
Okay,
I think the fuse in the fuse panel is #18. Maybe 15 amp. Should be hot with the key on.
Next check the main power supply wire at the starter solenoid. Its attached to the same big hot lug as your positive battery cable. If there's a burnt up wire there your fusible link may have blown and there's your problem.
And yes check the inertia switch.
Otherwise you'll need a test light to see if you've got constant power to the fuel pump relay.
If all that checks out you can try disconnecting the oil pressure switch at the very back of the motor and jumping the plug with a jumper wire. Then the pump should run with the key in run, even with the motor not running.
First, does the truck have oil and oil pressure? Did you just change the distributor? There's a safety device that prevents power from getting to the pumps if you don't have oil pressure. If you just pulled the distributor and dislodged the oil pump drive shaft that could be your problem.
Okay,
I think the fuse in the fuse panel is #18. Maybe 15 amp. Should be hot with the key on.
Next check the main power supply wire at the starter solenoid. Its attached to the same big hot lug as your positive battery cable. If there's a burnt up wire there your fusible link may have blown and there's your problem.
And yes check the inertia switch.
Otherwise you'll need a test light to see if you've got constant power to the fuel pump relay.
If all that checks out you can try disconnecting the oil pressure switch at the very back of the motor and jumping the plug with a jumper wire. Then the pump should run with the key in run, even with the motor not running.
Laughing Gas
Joined: Apr 2013
Posts: 1,049
Likes: 65
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New User
Joined: Sep 2011
Posts: 14
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As stated previously it sounds like your fuel pump is not getting power in the run circuit.
First, does the truck have oil and oil pressure? Did you just change the distributor? There's a safety device that prevents power from getting to the pumps if you don't have oil pressure. If you just pulled the distributor and dislodged the oil pump drive shaft that could be your problem.
Okay,
I think the fuse in the fuse panel is #18. Maybe 15 amp. Should be hot with the key on.
Next check the main power supply wire at the starter solenoid. Its attached to the same big hot lug as your positive battery cable. If there's a burnt up wire there your fusible link may have blown and there's your problem.
And yes check the inertia switch.
Otherwise you'll need a test light to see if you've got constant power to the fuel pump relay.
If all that checks out you can try disconnecting the oil pressure switch at the very back of the motor and jumping the plug with a jumper wire. Then the pump should run with the key in run, even with the motor not running.
First, does the truck have oil and oil pressure? Did you just change the distributor? There's a safety device that prevents power from getting to the pumps if you don't have oil pressure. If you just pulled the distributor and dislodged the oil pump drive shaft that could be your problem.
Okay,
I think the fuse in the fuse panel is #18. Maybe 15 amp. Should be hot with the key on.
Next check the main power supply wire at the starter solenoid. Its attached to the same big hot lug as your positive battery cable. If there's a burnt up wire there your fusible link may have blown and there's your problem.
And yes check the inertia switch.
Otherwise you'll need a test light to see if you've got constant power to the fuel pump relay.
If all that checks out you can try disconnecting the oil pressure switch at the very back of the motor and jumping the plug with a jumper wire. Then the pump should run with the key in run, even with the motor not running.
Oil pressure switch is jumped and both front and rear pumps run in key-run position. Engine starts and will run forever with gear in park or neutral but will die in about a minute when in gear and moving. When engine dies, I can hear the fuel pump running BUT the pumps sound like they are laboring or running weak at a variable speed (not a strong whir). Apparently the pumps are running okay in the key-start position because the engine will start right up again. There is something wrong with the pumps delivering enough fuel to carb with key in run position. I am not good with electrical wire tests regarding continuity, voltage etc, so if you have some suggestions, please walk me through the details of troubleshooting. Thanks.
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From: Virginia
Here is a diagram of the 460 dual tank system. If it's easy to get to, put your meter on ground and the terminal leaving the fuel shut off switch, and fire the engine and see what voltage you have there.
Laughing Gas
Joined: Apr 2013
Posts: 1,049
Likes: 65
If the pumps run check your fuel filters. If they're clogged you won't get enough fuel flow to the carb to make power. Besides the little filter at the carb inlet my E350 has a larger canister style fuel filter mounted on the frame rail. Be sure to check / change them both. 460's be thirsty and need good flow.
Did you drop the tanks to replace the pumps or are the pumps mounted externally? As far as I know the stock pumps were inside the tank but after all these years who knows how things could be hacked up and modified...
Beyond that I wonder about the carb. What kind do you have and what kind of shape is it in? If you post a picture we can see... If the floats are set too low that can also cause you to "run out of gas" under power.
If you're running out of gas it will cut out, sputter, and lose power. But if it's dying like you turned off the key the problem might be something other than fuel delivery.
Did you drop the tanks to replace the pumps or are the pumps mounted externally? As far as I know the stock pumps were inside the tank but after all these years who knows how things could be hacked up and modified...
Beyond that I wonder about the carb. What kind do you have and what kind of shape is it in? If you post a picture we can see... If the floats are set too low that can also cause you to "run out of gas" under power.
If you're running out of gas it will cut out, sputter, and lose power. But if it's dying like you turned off the key the problem might be something other than fuel delivery.
New User
Joined: Sep 2011
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There is no fuel filters between the tanks and the carb.
Both tanks have been dropped, cleaned and new fuel pumps installed.
Fuel Selector Valve Switch on the rail replaced. Fuel Relay replaced. Fuel line vapor separator replaced. Oil pressure switch and Oil pressure sender replaced but not the wires.
Replaced Neutral Safety Switch and the Ignition Starter Switch on top of steering column.
Carb is a stock Holley 4 barrel has been rebuilt by a carb professional, so I'm hoping that the float level is set correctly. (note: engine runs beautifully when running). It will idle or run at higher speed without hesitation when in neutral or park, but will run for about a minute in DRIVE then sputters. Starts right up again.
Carb is starving for fuel when sputter stops, not like the key turned off.
Is there any connection between the shift lever and the key lock in RUN mode ?
As I mentioned before, both pumps will operate in Key-Run position with the oil pressure switch jumped. When engine dies, pumps do not sound strong.
Both tanks have been dropped, cleaned and new fuel pumps installed.
Fuel Selector Valve Switch on the rail replaced. Fuel Relay replaced. Fuel line vapor separator replaced. Oil pressure switch and Oil pressure sender replaced but not the wires.
Replaced Neutral Safety Switch and the Ignition Starter Switch on top of steering column.
Carb is a stock Holley 4 barrel has been rebuilt by a carb professional, so I'm hoping that the float level is set correctly. (note: engine runs beautifully when running). It will idle or run at higher speed without hesitation when in neutral or park, but will run for about a minute in DRIVE then sputters. Starts right up again.
Carb is starving for fuel when sputter stops, not like the key turned off.
Is there any connection between the shift lever and the key lock in RUN mode ?
As I mentioned before, both pumps will operate in Key-Run position with the oil pressure switch jumped. When engine dies, pumps do not sound strong.
Laughing Gas
Joined: Apr 2013
Posts: 1,049
Likes: 65
I can't think of anything related to gear selection that would change the power supply to the fuel pumps.
If it sputters and dies the minute you put it in gear I don't think it's fuel delivery. There should be enough fuel in the float bowls to keep it running for a couple minutes even without the pumps running.
Review the carb tuning. If the idle speed is too low and your choke doesn't work that would explain it stalling out when you drop in into gear...
- Bone Cold with the choke on the idle speed should be around 1250 rpm in neutral and 900 in gear.
However the fast idle cam will reduce idle speed gradually as the engine warms up, so if you live someplace that's warm all the time it might not get cold enough for the fast idle to get that high.
- Fully warm with the choke off idle speed should be 850 rpm in neutral and 650 in gear.
If you're idling 500 rpm in neutral and you drop it into gear I'd expect it to sputter and die. Especially if the motor is cold.
If it sputters and dies the minute you put it in gear I don't think it's fuel delivery. There should be enough fuel in the float bowls to keep it running for a couple minutes even without the pumps running.
Review the carb tuning. If the idle speed is too low and your choke doesn't work that would explain it stalling out when you drop in into gear...
- Bone Cold with the choke on the idle speed should be around 1250 rpm in neutral and 900 in gear.
However the fast idle cam will reduce idle speed gradually as the engine warms up, so if you live someplace that's warm all the time it might not get cold enough for the fast idle to get that high.
- Fully warm with the choke off idle speed should be 850 rpm in neutral and 650 in gear.
If you're idling 500 rpm in neutral and you drop it into gear I'd expect it to sputter and die. Especially if the motor is cold.