Runs great....when it runs, 1986 351
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Runs great....when it runs, 1986 351
A week ago, I was out of town when I started my truck, and it started as usual. Once the engine started the starter kept going. I replaced the solenoid switch, then the starter, found it to be the ignition switch on the column. 400 mile trip home went of without a hitch. Day after I got home, I saw a puddle of gas under the truck, leaking fuel pump. I replaced the fuel pump, and the truck ran fine for about a hour. Seemed to be running out of gas, both tanks full. Another fuel pump. Wont start at all. Turns over. Plugs and wires are new. Carb is a new Holley 600 4bbl. Carb is wet with gas inside, smells like its flooding, but wont start. I am on the verge of setting the truck on fire, or sending it on a cliff dive. Please, if you have an idea, let me know!
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From: Denver Metro Area, CO
Are you getting spark? Pull a plug wire and hold it near a ground (might wanna hold it using
insulated pliers) while somebody tries to start it, there should be strong zaps as that cylinder
tries to fire.
Check the fuel pump's output pressure and flow rate at the carburetor, just cuz the carb
is wet inside doesn't mean much.
insulated pliers) while somebody tries to start it, there should be strong zaps as that cylinder
tries to fire.
Check the fuel pump's output pressure and flow rate at the carburetor, just cuz the carb
is wet inside doesn't mean much.
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I havent checked the spark, but I plan to later today. Got my son coming to help. As far as checking the fuel pressure, I wouldnt know where to begin. My truck has a mechanical fuel pump, and its new, so my assumption is that the fuel pressure is correct. At least I would like to hope so. Thanks for the advice!
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From: Denver Metro Area, CO
You'd need a fuel pressure gauge (some are dual-purpose and double as vacuum gauges,
e.g. Amazon.com: Actron CP7803 Vacuum and Fuel Pressure Tester Kit: Automotive)
you'd disconnect the fuel inlet from the carb and attach it to the gauge, then crank the
engine after disconnecting the ignition. That'd check the output pressure; a brute-force,
seat-of-the-pants method to check flow rate would be to attach a long hose from the pump,
crank the engine and pump the gas into a container and see if ti looks like "that should be
enough."
The real method involves a flow meter and is generally too expensive for the
average home mechanic to buy.
I had a mechanical pump crap out on me just after one year, the diaphragm inside sprung a
leak and my crankcase ended up filling with gasoline.
e.g. Amazon.com: Actron CP7803 Vacuum and Fuel Pressure Tester Kit: Automotive)
you'd disconnect the fuel inlet from the carb and attach it to the gauge, then crank the
engine after disconnecting the ignition. That'd check the output pressure; a brute-force,
seat-of-the-pants method to check flow rate would be to attach a long hose from the pump,
crank the engine and pump the gas into a container and see if ti looks like "that should be
enough."
The real method involves a flow meter and is generally too expensive for theaverage home mechanic to buy.
I had a mechanical pump crap out on me just after one year, the diaphragm inside sprung a
leak and my crankcase ended up filling with gasoline.
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Looks like I have a great spark, but the cap and rotor were worn so I replaced them. Still no good. Cranked the engine with the breather off with my son, and gas was pouring into the carb. I guess the mix is way too rich now, with the new pump. Gonna try to adjust the carb. Never done that before, so I will have to read up. Here's hoping. Thanks.
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From: Denver Metro Area, CO
My guess is the float in the bowl is sticking open, there are no external adjustments that will
remedy this (that I know of, anyway). If it were mine, I'd remove the front bowl and see if
the mechanism inside (kinda like a toilet tank float) is sticking or not closing properly.
remedy this (that I know of, anyway). If it were mine, I'd remove the front bowl and see if
the mechanism inside (kinda like a toilet tank float) is sticking or not closing properly.
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I give up. Today I discovered gas in my crank case. Changed the oil. The spark plus were fouled, so I cleaned them. The truck will start, but gas is literally pouring into the carb. It is running way too rich. I dont have the skills to adjust the carb, so i will have to pay someone that knows how. Thanks for all your help.
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From: Denver Metro Area, CO
I don't know how you'd get gas into the crank case through the carb unless your valves &
rings were shot. My mechanical fuel pump developed a leak in the diaphragm, the truck being
parked at an angle for something around 1-2 months resulted in gas siphoning into the crank
case (made for an interesting day).
rings were shot. My mechanical fuel pump developed a leak in the diaphragm, the truck being
parked at an angle for something around 1-2 months resulted in gas siphoning into the crank
case (made for an interesting day).
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You most likely have a leaking needle and seat. If the carb is flooding over, you will also be dumping more gas into the engine than it can burn which causes the oil dillution you experienced. Replacing the needle and seat on a Holley is actually very easy, you can do it without even removing the carb or fuel bowls. Look on top of each carb bowl (Holleys have two bowls and two needle/seat assemblies) you should see a large slotted screw with a nut below it. Loosen the screw slightly and turn the nut counter clockwise to remove the needle/seat assembly. Install the new one, making sure you have the gaskets above and below the nut. Remove the plug on the side of the carb bowl, then start the engine and turn the nut to adjust the fuel level until it is at the bottom of the plug hole and tighten the large screw. Sounds more difficult than it is, but the whole job only takes about 5 minutes.
