Fuel supply issue...

[Nunyas]

Hi again folks,
Fisrt off, I'd like to thank those that gave me pointers on my brakes causing my idle to go up issue. I pulled the servo assemly, after I got the parts and immediately found that the vaccume seal between the servo and the master cyclinder was installed incorrectly in the past. I replaced it and I think it's fixed... for now.

However, in my testing of the effects of applying my breaks I encountered a new issue. Although, I'm not entirely convinced that it is new. In my thread about my brakes I mentioned that I could not sustain "high-way" speeds (i.e. 60+ MPH for more than a minute or two) without my B acting like it stalled and then picking up again a second later. The car has also been stumbling off the line. Over the past week starting from a dead stop has become more and more difficult. Starting the car period has become alot more difficult since I've acquired it, most noticeably over the past week. While poking around under the bonnet, I noticed that my fuel filter looked like it barely had any fuel in it. It seems kind of odd to me for it to not be full of fuel at all times. While checking my brakes in my drive way the car stalled, and starting it is like trying to start a car that has not fuel. However, the tank was just filled recently, and the guage still reads 1/2 tank. I can hear the fuel pump clicking when I turn the power on in the car, but I don't always get rapid clicks that slow down. Right now, all I get are slow clicks that average about 2 clicks every 5 to 10 seconds. Watching the fuel filter under the hood I see no new fuel entering it at all anymore. I checked under the car for spilled fuel (incase a line has been punctured) but I did not see any wet spots on the ground at all.

I'm thinking that my fuel pump may be bad, but the clicking from it makes me think that it could still be working, and I might just have some sort of blockage in the line. The pump that is currently in the car is definitely not an original, as I can see the hackish work that was done to install it. The gromet in the trunk above the pump is missing and I can see the wires for it were spliced into the harness.

Are there any "common" points to check in the fuel lines for blockage? Also, do any of you have any recommendations for replacement or even performance parts? And lastly, is there anything else that I should check in the fuel sytem before I go running off to buy new parts?

Thanks again for any information you guys can give me. /ubbthreads/images/graemlins/smile.gif

 

[usasma]

I used to have to "tap" the fuel pump in my old B with a hammer occasionally to get it working. Not hard, but not soft either - and it would then start easily.

 

[aeronca65t]

On my car, the pump doesn't tick very much unless it has been sitting for a few weeks. And the clear fuel filter I use is rarely more than half-full. My car runs fine.

Check to see that an extra fuel filter has not been put inline somewhere and is plugged up.
Be sure that the metal fuel line from the gas tank to the fuel pump is not plugged up with "muck" from the bottom of the fuel tank (remove it from the fuel pump and use a low amount of compressed air to "back-blow" this line).
Be sure that your fuel tank is vented somehow.

Occasionally, previous owners will plug various emissions devices....someone may have plugged the tank vent to the canister. If in doubt, run the cap "loose" and see if things improve.

Be sure that the float bowl level in the carb is set at the correct height (bend the float lever to adjust this....refer to your manual for the setting height).
Be sure that you do not have weak ignition (coil, plugs, wires, etc.). If a car "runs out of breath" at higher speeds it may be fuel starvation but it can also be misfire.

Check ignition timing (this can also limit a car at higher speeds). A "long shot" would be stuck timing weights in the distributor (but I'd check all the other stuff above first).

 

[Geo Hahn]

Fuel filters just fill enough to reach the outlet then no more... so it is usual to see them half full or less.

Sure sounds like a blockage, I would disconnect a fuel line and run it into a can to see what the flow looks like... first with the filter, then w/o the filter, etc working back to the pump. Usual disclaimer about ventilation, no flames, extinguisher handy, etc.

Sorry I don't know specifics about your car but is the fuel filter stock? If not, is a fuel filter really necessary for SUs? Some say yes, some say no.

 

[Guest]

Take the fuel line from the filter, put it into a container to catch the gas and turn the ignition on. You should get rapid clicks from the pump that keep going as long as the key is on since it is not on the carb. There should be plenty of flow. Also check the pressure. An SU pump should show around 1 1/2 to 2 1/2 pounds approximately. Mine is slightly less than 2 lbs and runs great. If that is what you get look somewhere else.
Bob

 

[MGTF1250Dave]

Aloha Nunyas,

As previously suggested, check the fuel flow to the carbs. If it is slow, work down the fuel line toward the tank to find where the obstruction is. If you remove the gas tank cap, that may be a simple way to see if the tank vent is plugged. A possible problem area could be the filter screen that is internal to the SU electric fuel pump may need to be cleaned. Also see if any additional fuel filters have been installed under the car. If you find more filters, I would recommend you remove them. This is one of those times when more is not better. Good luck.

Safety Fast,
Dave

 

[screenprinter]

My 2 cents worth and a LONG LONG shot to boot - I recently redid the tank on my Sprite and I noticed it had a nylon mesh strainer over the supply tube inside the tank which is the major reason I didn't use tank sealer and risk plugging it - to get to the point, I had a 70 Monte Carlo once that would start fine, run great for about 5 miles and then die - after sitting for ten minutes, start fine, run 5 miles, die -
I pulled filters, installed electric fuel pump, nothing - A good old boy shade tree mechanic told me that the "sock" inside the tank had gotten old and collapsed - so we drained and dropped the tank , pulled the supply line out and sure enough, there was a little conical nylon mesh strainer that was as limp as overcooked spaghetti - after the pump built up some pressure ( suction at that end) the strainer collapsed and choked the fuel flow - I chucked the "sock" and everything was fine ( There's an inline filter, so the sock was a little redundant)
So, Not knowing B's I don't know if you have an in-tank strainer - One of these forum guys can , no doubt, tell you yes or no - and it's a long shot but something to consider.

Good Luck!

 

[NGW]

Have recently had a very similar problem with my 78mgb, which finally culminated in intermittent complete failure, the fault was diagnosed to the fuel pump which was failing to supply enough fuel to the engine. whilst the original fuel pumps can be serviced and repaired there is still the inherant problem.

I have fitted a new contactless fuel pump to the car and the problem has been completely resolved - hope this helps.

 

[Guest]

Please don't think I am disputing using new type fuel pumps. I just had some bad luck with one years ago. I was having continuous problems with my stock pump and thought a new solid state pump would get rid of problems completely as the old one was going through points rather quickly.
The new pump would not cut off when up to pressure and lasted about one week before it quit completely.
I then took the old one apart and decided to try the diaphram since it seemed a little stiff. Not having a new one to compare, I didn't know for sure.
Well the new one was a lot more pliable and that and a new set of points and condensor fixed the problem and the points usage went down dramatically. The condensor could also cause premature point failure. The original is still in there and the car is 32 years old.
Bob