1970 Buick Skylark Fuel Problem

B

Big Country

Newbie
Would appreciate any help/suggestions to my fuel problem. Quick background - I have a 1970 Buick Skylark covertible that I recently restored. Motor was completly rebuilt bottom to top by a very reputable machine shop ( Performance Build - 10.1:1 cast pistons, moly rings, clevite bearings, 1.60 roller rockers, 284/296 Erson Cam, etc. All has replaced regarding the fuel system - new fuel tank, sending unit, SS fuel lines and mechanical fuel pump. Car ran great - put about 1100 miles on new motor - followed break in procedures to a T!! Pulled car into my garage in early December after taking a short cruise - shut it off - went to start it 5 days later and it started but barely ran - no power - could tell it was starving for fuel. Checked spark and all was well. Replaced mechanical pump - looked into pump mount area and all looked fine - old mechanical pump - (1100 miles old) when removed looked fine. Installed new pump and unhooked line from carb ( Edelbrock Performer 600) and cranked motor and not a drop of fuel. Hooked up a hand driven suction pump to line from gas tank and had no problem receiving fuel. Obviously the mechanical fuel pump is not working - but why? I can't believe the lobe is wiped on the cam. If it is and I go to an electrical fuel pump - are there dangers of metal filings in the engine from the wiped lobe - and if so, what is the best procedure to address this issue. Any help or thoughts would be greatly appreciated. P.S. - I did compare the arms of the fuel pump to make sure they were the same length. Thanks in advance for help!!!
 
350 or 455?

You might not have placed the pump arm under the cam, so it might not be pumping.

On a side note. The carb you have is too small for your Buick. Sell it to a chevy guy and get you a 750 or 800cfm. Your buick engine will love you for it.
 
I would be willing to bet my life savings that it's not the lobe on the cam. There is not enough spring pressure on the pump arm to wipe it out in that amount of time. You need to keep looking for another problem. You can test your mechanical fuel pump by hooking a hose to it and putting the hose in a container of fluid and working the arm manually. Does your new fuel lines follow the route of the factory one? Do you have any filters installed before the pump? Mechanical pumps are better at pushing fuel than pulling it. Too many bends or kinks or a routing that has raises or lowers too much might make it tough for a factory pump to work right. Although I would expect that problem to show up right away. Look for a loose connection that is sucking air and make sure that debris isn't being sucked into the mechanical pumps. Electric pumps rarely give long term satisfactory performance.
 
the arm on the mechanical pump makes it difficult to put it back on the lobe. I agree with the above that it's probably not the lobe, because when a lobe goes it does it gradually.

I don't agree about electric fuel pumps, they've come a long way in reliability - and most new cars use electric pumps only and last at least 100k miles... however, they are noisy.

Back to your pump, it does sound like the diaphram has gone bad... it's hard to believe it did it so quickly, but if it had fuel in it once, then sat for a long period of time the blend fuel may have eaten the rubber away... they are easy to check, even on the car, remove the easiest line to get off... crank the motor over with your finger over the hole. Depending on which line you removed it should suck or push... if it does neither, there's your issue.... good luck
 
Thanks guys for all of the responses! Thought I knew how to install a fuel pump (lol) but maybe missing something. The new pump I put on bolted up fine, but do I need to go in at a certian angle - should I have to apply some upward pressure on the pump to compress somewhat the arm of the mechanical pump? Thanks - Big Country
 
if you do have to apply upper pressure, best practice would be to bump the starter over to reduce/eliminate that pressure. If you don't, you run a slight risk of either breaking the flanges or bending the arm.
 
I was told that this mechanical fuel pump for this engine (350) is a gravity feed pump. Also suggested that the problem could be the vented gas cap on the fuel tank not functioning properly. The gas cap is the old cap from the previous tank! Any thoughts
 
I'm not sure what a gravity feed fuel pump is - after all, if it's gravity fed (like the Model As and Model Ts) it won't need a pump.

Your tank has a vent on the front right corner of the tank - most times its problem is it leaks. The rubber that is attached to the vent breaks down.... however, it could also plug. As you can see by the picture (vent is on the left) below, I fastened the vent up and above the tank after replacing the vent lines....

P2210009.png

The cap is not a vented cap, don't use a vented cap. If you do, when you accellerate your fuel will go sloshing out of the back.... in fact, that cap is almost a replace every 5 years kind of item.
 
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