Fuel Starvation

Tait

New Member
Hello all! It seems I have ran into a problem with the fuel system that I cannot solve. So here's the deal the fuel tap, inline fuel filter, fuel line, and fuel pump are brand new. The fuel pump will manually pump gas IF the fuel pump is off the block and the outlet hose is off. Once the fuel pump is on the block and outlet hose to attached to the carb, the car will idle fine. However if I proceeded to give a good amount of gas (on accelerator, off accelerator, on accelerator....and so on doing this fast) the car will starve of fuel and the pump seems to not fill the in line fuel filter. I have taken that inline filter off, used a fuel pump spacer, rebuilt the carb and none of these change anything. Anyone have any suggestions?
 

Jon March

Member
seems as tho there is a restriction that is only able to flow enough for lower demand. Youve eliminated the fuel filter as a possibility.
Other guesses that could cause it: 1) fuel tap open/flowing fully? (try bypassing it with a direct hose from fuel outlet to block mounted fuel pump- open fuel:keep fire extinguisher ready/dont drop tools/prevent sparks/etc) 2) ethanol/age narrowing of rubber fuel lines?(if any) 3) defective fuel pump 4) carb /seal issues?
 

Steve

Member
When you rebuilt the carb, did you set the float level to factory spec's? Not enough fuel in the float bowl will cause the engine to starve under load.
 

Jon March

Member
Steve hits on a real possibility that i wasnt aware of. Get me thinking, since i had my carb worked on (new accel pump gasket, o-rings, etc_ I wonder if he did anything to the bowl level setting. Steve - hwere is this setting?/ how can a person check it, etc?
 

Tait

New Member
seems as tho there is a restriction that is only able to flow enough for lower demand. Youve eliminated the fuel filter as a possibility.
Other guesses that could cause it: 1) fuel tap open/flowing fully? (try bypassing it with a direct hose from fuel outlet to block mounted fuel pump- open fuel:keep fire extinguisher ready/dont drop tools/prevent sparks/etc) 2) ethanol/age narrowing of rubber fuel lines?(if any) 3) defective fuel pump 4) carb /seal issues?
Thank you for the fast reply! I would say 1-3 are not what I would assume to be the causes as the fuel line is new of yesterday, the tap was open when checked out of tank, and the pump works when the outlet hose is off to pump up gas to the rear. Not sure about the carb seals because I had someone else rebuild the carb for me. This could be a possibility that I need to investigate.
 

Tait

New Member
Could be problem Dave once had here ..

https://amphicar770.com/threads/carb-or-help.14604/

I do not know the factory spec but someone else can chime in. I use a drill bit of same size to measure float bowel distance.
So a problem with the gaskets under the carb would cause a loss of fuel pressure? I can monitor fuel pull from the pump with a clear in line filter in the rear before the pump(also thought the filter might be a problem but no difference with or without it) and the car just begins to run on fumes it seems.
 

Steve

Member
Steve hits on a real possibility that i wasnt aware of. Get me thinking, since i had my carb worked on (new accel pump gasket, o-rings, etc_ I wonder if he did anything to the bowl level setting. Steve - hwere is this setting?/ how can a person check it, etc?
I've never set my float level on this car because I've never had a problem like this. I did however with a Holley I had on my old Rambler years ago. It was a combination of a screw and locknut on the float bowl. I'd have to check my Amphicar manual to see how it's done. It's not something that normally requires maintenance but changing a needle and seat could create the issue.
 

jfriese

Active Member
Once I added an inline fuel filter to my Amphicar and mounted it just ahead of the mechanical fuel pump. From that point on I was plagued by weird fuel starvation problems under various load conditions of the engine. After what seemed like endless fiddling around with the system, an old time mechanic said you can't mount the filter at that point and that it must be mounted after the pump or up near the tank. This made no sense to me at all but I switched it's location to right after the fuel shut off solenoid and that fixed the problem. I still have no idea why this worked, but it did. Thank God for old time mechanics.

John Friese
67 White
78 Red
 

Jon March

Member
perplexing- but at least it worked! And did you say you also shoehorned a 3psi fuel pump in somewhere, or no? Wonder if that would help him...
 

Jon March

Member
is the accelerator pump on the side of the carb squirting fuel when you depress the lever? look down inside - i dont think the car even needs to be running, as long as therr is fuel in the bowl, i THINK? it should squirt visibly?

or maybe the in-tank fuel screen pre-filter is gummed up?
 

jfriese

Active Member
Jon,

At the time of the problem I simply moved the secondary fuel filter as I mentioned in the above post. Much later I added a low pressure electric pump by the fuel solenoid and as a priming device for when the car has sat awhile. I put a switch on it and only use it to fill the float bowels and then turn it off. The electric fuel pump comes with a fuel filter of it's own so I ended up adding a second filter anyway. Since I have always run Pertronix electronic ignition modules, they don't use a condenser. The simplest thing is to simply remove that second filter. After that, if you still have a problem, I might try changing the condenser, as Gord suggested. I simply don't have any idea what that might do.

John Friese
67 White
67 Red
 

Tait

New Member
Once I added an inline fuel filter to my Amphicar and mounted it just ahead of the mechanical fuel pump. From that point on I was plagued by weird fuel starvation problems under various load conditions of the engine. After what seemed like endless fiddling around with the system, an old time mechanic said you can't mount the filter at that point and that it must be mounted after the pump or up near the tank. This made no sense to me at all but I switched it's location to right after the fuel shut off solenoid and that fixed the problem. I still have no idea why this worked, but it did. Thank God for old time mechanics.

John Friese
67 White
78 Red
I have tried running no inline filter and it didn't change anything unfortunately but thank you for the suggestion.
 

Tait

New Member
Ok so I think I might have fixed my problem due to a "new" hose in the front that may have been bad or the new condenser I tried(Thank you for the suggestion SNOWBIRD). I will have to recheck the symptoms again this weekend. Thank you for all the help! Quick semi related question, the bolt hole on the Intake Manifold under the carb towards the muffler, should that be opened or closed off with a bolt of some sort?
 

SNOWBIRD

Amphicar Expert
There should be a open ended tube in there. it is U shaped (upwards)so fuel can run out onto the Street. Not good for Amphi thou. I attach a hose and bring up above carb, When started fuel will be sucked back into manifold.
 

Tait

New Member
There should be a open ended tube in there. it is U shaped (upwards)so fuel can run out onto the Street. Not good for Amphi thou. I attach a hose and bring up above carb, When started fuel will be sucked back into manifold.
Is there anyway you may be able to share a picture of it? I just found it on Gordon's but if it's simple enough for a local parts run, that would be ideal so I can get going sooner. :) I'm mostly interested in the fitting part and how that works on the stock one.
 

SNOWBIRD

Amphicar Expert
Lots of pics of it the the other posts just started today>>> you'll see it. a small pc of brake line..
 

Similar threads


Top