Ok, got one that's pulling my hair out and need some help from you smart guys. Consistently my 401 loses fuel pressure and the fuel filter empties after it's run to operating temperature(even without actually driving it). It dies at idle but if I kick the idle up to 1200-1500 I can keep it running. The fuel pressure will be 0-1 at this point and the fuel filter is empty with only splashes of fuel coming in. I've seen the threads about vapor lock but as you can see from the pictures I'm running straight from a fuel can, with the hood up, with a shop fan blowing right on the engine, in 60 degree weather, and it still does it. Could it still be vapor lock right at the carb? If so what can I do to fix it? Electric fuel pump w/regulator the only way to go? Any help will be greatly appreciated! Engine info- - '63 401, originally 2V. Prior owner converted to 4v intake and added Edelbrock 600cfm #1405 (gonna buy a bigger carb if I can fix the fuel delivery). - Prior owner also swapped Cam and lifters. - timing is good/plugs and wires are new/carb has been gone through. - Brand new mechanical fuel pump has the same issue
Dave are all the fuel lines in use at the moment new and unobstructed? Is the pump making any noise? Loud tapping sound. Just because it is new doesn't make it good. Cut a V shape on the end of the hose, in the fuel can, to prevent the hose from becoming restricted as it sucks in fuel. A cheap electric fuel pump/ pulse pump 6-7 psi. can be used to help diagnose your fuel issues. Once your fuel issues are remedied replace your plastic filter with a metal or sight glass style as they are a safer type. Let us know if any of these things have been tried or help. Hope that helps
Does it have the metal heat shield gasket (https://www.ebay.com/itm/333981294731?hash=item4dc2d6208b:g:xUMAAOSwClRZ4jZp) under the carb?
you can't go by the fuel filter mine look like there empty but runs fine. did you check the fuel pressure cold and then warm. make sure your gauge is right also.
Sounds just like my Wildcat before I found the sock filter on the end of the pickup tube in the tank was about 80% plugged. It was plugged due to about a pound of very fine rust in the bottom of the tank, so fine the inline filter didn't catch it. I noticed a thin layer of rust in the bottom of the float bowl. Only fix was to have the fuel tank cleaned and coated.
Hello again, guys. Sorry for the delayed response. Had unexpected health problems pop up. Just got back on my feet this week and was able to work on the car today. Anyway, to answer the questions presented: - are all the fuel lines in use at the moment new and unobstructed? Everything is new but the steel line running along under the body. I used some extra hose to blow air through the steel line...seems clear. - Is the pump making any noise? Loud tapping sound. Just because it is new doesn't make it good. No noise from the pump - Cut a V shape on the end of the hose, in the fuel can, to prevent the hose from becoming restricted as it sucks in fuel. No effect - A cheap electric fuel pump/ pulse pump 6-7 psi. can be used to help diagnose your fuel issues. I bought a $25 electric that is doing the same thing straight from the gas can. - Also who changed the fuel pump? Do you still have the old pump? I did and I put the old one back in to make sure. Same result. Does it have the metal heat shield gasket under the carb? Yes is the sock filter on the end of the pickup tube plugged? I checked it when I replaced the lines. It's clear did you check the fuel pressure cold and then warm? make sure your gauge is right also. fuel pressure cold is 5-6 and drops to 0 when the filter empties. car doesn't want to run at that point either so I believe the gauge is good. the eccentric the fuel pump rod rides on could be worn. This is something I didn't even consider. Wouldn't the pressure be low all the time though? At this point I'm considering just dropping the money for an electric pump and regulator unless someone has any other ideas? The fuel lines in the engine bay are really hot and I can't see any other way of rerouting them to cooler areas other than getting that mechanical fuel pump out of the loop.
Another possibility is that you have some cracked / split hoses or clamps that are not as tight as the need to be. A pump will suck air if given the choice over fuel because air is much lighter. More then once I have had this issue rear it's head and since it's on the suction side of the fuel system it may never even show a drop of fuel leaking, especially when the vibration from driving the car is opening up whatever small cracks there maybe in dry rotted hose lines and any small drops of leaked fuel just evaporates away in 4 seconds. Even where the steel line on the suction side of the system off the frame screws into the pump can be the source of the air sucking issue if that nut is not tight, or the seat on that steel line as scratches or gouges in it. BTDT! PS,you do not need a bigger Carb. A 600 cfm Carb can support 400 hp. What's needed with the factory intakes is more Plenum volume, and NO not just a notch ground into the upper and lower Plenum on the secondary side. That's just crutch!
wow great, you covered a lot of bases. try some insulation like the foam one you use for home pipes or anything that works for testing. you lost me on trying the electric pump that did not help but you want to buy a electric pump and regulator ? yes the eccentric can't be the problem that's why just wanted make sure you had good pressure when cold.
My thought is if I don't have to run the fuel line up to the front of the engine past the headers, heater hoses, etc...then I can just run it up the firewall in the back of the engine bay and greatly reduce the amount of area the fuel is exposed to excess heat. The lines are cool running up to the engine bay but get almost to hot to handle from the mechanical fuel pump to the carb. True, the cheapo electric I tested with didn't fix it but I'm out of ideas at this point and getting frustrated with it.
This is possible with the steel line running up the frame. All the rubber lines are new and solid on both the tank end and into/out of the fuel pump. The lines in the engine bay are all rubber starting from just behind the passenger wheel well and the fittings on the fuel pump and carb are well seated and clean. Guess I can get ahold of some steel line and build a new one. I've got all the tools from rebuilding the trans lines already. ...or I might try to put my tester electric pump in the back by the tank and see if it "pushes" any leaks into sight. I'll try one or both of these this weekend. Thanks. (And the carb discussion is for another thread. that convo would completely derail this I think)
Disconnect and cap the line at the tank and disconnect it from the inlet side of the pump. Then pressurize the line with low pressure 5-10 lbs, and use Leak-Tek or mix a few drops of dishwashing soap in water and spray on with a bottle to all fittings and the line to see if there is any leak, split or pinholes in the line from the back to the front. Pushing fuel from the rear will do the same thing, and especially reveal the area the line runs above the rear spring perch and bottom of the body where the line is hidden. Just try to use a low GPM setting pushing fuel.
I must have missed something but I don't understand why the frame rail fuel lines are in question when you are bypassing those by using the gas can? If you suspect vapor lock you could use an A/C fuel filter with the extra fuel return line nipple and run a return line back to your temporary gas can...that was the factory remedy.
