Bad Fuel Pump?

[PLP6400]

This past weekend I took my Ranchero on a little over 1,200 mile round trip. I left early Friday Morning and came back Sunday afternoon. The car ran excellent untill I was about 140 miles from home. I just started going up a 7% grade when the engine acted like it ran out of gas. I pushed in the clutch and started to pull off the highway when for some reason I downshifted into third gear. The engine started up and I continued up the grade. About a half mile from the summit the engine quit again, I down shited into third again and it started. After that the engine would quit every so often on hills or level ground. I know it wasn't vapor lock because the outside teperature was in the high 40's When I got home I was to tired to do anything about it. Yesterday I changed the fuel filter and drove the car to see if that solved the problem. The car seemed fine and I thought the problem was solved. Today the problem came back. The whole fuel system is new with only 5,600 miles on it. The Gas tank was boiled out and coated. The fuel filter I removed was clean and there was no particals in it. It is a stock mechanical fuel pump with the filter on it.

Anybody have any suggestions?

 

[Asa]

does it only do it when you're climbing hills?
and if so, is your fuel filter of the type that you can see through?

i know that with mine, the fuel filter is never filled completely, so if the car is at an angle, the gasline might not be sucking enough gas to supply the carb

make sense?

 

[addo]

Fuel pump, or restriction in the lines. Downshift=higher RPM, so more fuel is forced up to the carb.

Could be a punctured diaphragm, sticky check valve or constricted metal lines. At least you weren't running a blower. Lean mix plus forced induction - not good...

 

[Anonymous]

Was there noticable pressure in the fuel line when you took off the filter?
The restriction in the line is a good possibility since you did all that stuff to the tank. Might try disconnecting the fuel line from the pump and see how fast gravity flows fuel through the line. then diconnect both ends from pump to carb and blow through to check for restrictions.While there check the inlet to the carb for trash obstructing that. Also a combo vac /pressure gauge is pretty cheap and not a bad thing to have laying around.
Cowboy way is disconnect fuel line between carb and pump, point it into a coffee can and have someone turn the key- should pulse gas with some authority.

 

[CZLN6]

Howdy PLP6400 and All:

In addition to the previous ideas and suggestions consider-

Sometimes even a new fuel pump is not what you'd expect. It simpler solutions don't do it, I'd be looking to try a different "New" fuel pump.

You didn't say how new the cam is. The fuel pump is driven off of an eccentric, or cam lobe like fixture on the cam. With time and poor maintainance these eccentrics wear and offer less lift to the fuel ump stroke. If that is the case the solution is either a new cam with a new fuel pump actuator, or bypassing the mechanical pump altogether and installing an electric fuel pump.

I'll be anxious to hear how this comes out for you. Keep us posted.

Adios, David

 

[PLP6400]

Howdy back David

The whole engine has 5,600 miles on it now. I do think it is the fuel pump, because one other thing I realized about the problem is it only does it after being driven for over an hour. I think maybe the rubber diaphragm gets soft or distorted.

The reason I just don't change it is that I am considering installing the Holley fuel injection kit (#502-20S). Then I would have an electric fuel pump.

I know a lot of people think it is just a glorified carburator. But GM used that type of fuel injection for about 10 years. Friends that have installed this kit on their non computerized V-8's are very happy with them and claim about 5 MPG increase in milelage. At gas prices over $2.60 a gallon here. It probably will pay for itself.

If any one out there has installed this kit on their 6? I would like to hear your opinions.

Thanks
Patrick

 

[MercuryMarc]

My car nearly died going uphill, but did OK if I kept the speed slow. I replaced the fuel pump, fuel filter, and rebuilt the carb (twice). Eventually I found a small peice of foam in the 1 inch line from the fuel filter to the carb.

Not sure how it got there but it was intermittantly clogging the fuel line, only noticable under maximum load (uphill at high speed).
Just a thought!
Marc in SF
63 Comet Ragtop
69 250/C4/Duraspark
http://mercurycomet.net

 

[PLP6400]

It was the Fuel Pump. About 4 miles from home it did it again. This time I couldn't get it to go at all. I removed the fuel filter canistor and there was no gas in there. Next I removed the rubber line from the fuel pump and blew in the fuel filler tube. Plenty of gas came out.

I probably will just get a new fuel pump tomorrow, but I am still considering going with the Holley Fuel injection.