Fuel Pump Will NOT Stop Clicking!!!!

[78MGB]

Greetings,

Hopped in the MGB this morning for a quick spin before the HEAT. Turned the ignition and heard the friendly chirp of the fuel pump, but it will not stop until I turn the ignition off. The car starts great and I do not smell any exess gasoline. The gauge shows about 3/8th or more. Did clamp the fuel line near the Weber carb. Felt the pressure build, but the pump would not shut off./ubbthreads/images/graemlins/cryin.gif

Thanks for your input.

 

[Steve_S]

Sounds like a leak in the lines before the pump. An air leak here will allow air into the lines and cause what you describe. I would replace all the rear hoses since it only takes a few minutes.

 

[Bruce74B]

Mine does that occasionaly too...then sometimes it doesn't. All my lines are solid and seal well...had them apart yesterday and removed the in line filter that was there. Still, the pump kept on running /ubbthreads/images/graemlins/crazyeyes.gif

Bruce /ubbthreads/images/graemlins/cheers.gif

 

[Keoke]

Hi Bruce 74B/78MGB, as stated earlier you have an air leak some place on the input side of the pump.--Fwiw---Keoke /ubbthreads/images/graemlins/yesnod.gif

 

[Steve_S]

Could be a leak in the check valve then, but it's less likely.

 

[Guest]

Well, the things that I can think of that can cause this are:
1. needle valve in carburator not closing or trash in it.
2. leaking hose between the pump and carb.
3. something bad in the pump not building up enough pressure.
4. leaking hoses in the pick up side including the tank pick up.
5. tank low on fuel
6. tank pick up not in gas for some reason

With mine, any gas starvation problem at the tank would result in the pump running a lot faster than normal and the gas stop flowing.
Any leak in between the pump and carb should result in a smell of gas plus gas running out. Of a sufficient quantity to make the pump run all the time should be detectable fairly easily.
The needle in the carb not closing would result in the car running rich and/or hard to start and black smoke coming from the exhaust depending how much gas was getting through.
A bad pump that would not build up enough pressure can be measured with a pressure gauge and should register around 2 lbs at the carb input. Probably 1.5 to 2.5 lbs would be normal. Too much more than that will force the needle valve open in the carb.
Another thought would be the float in the carb bowl could spring a leak and not close all the way but this would also run rich and have black smoke out the exhaust and also run rough and be hard to start.
The other possibility is what Steve said.
That's all I can think of at the moment. Maybe someone else can think of more.
Bob

 

[Dave Russell]

[ QUOTE ]
Could be a leak in the check valve then, but it's less likely.

[/ QUOTE ]
This is NOT so unusual. The slightest bit of contamination will prevent the pump valves from completely sealing, as could a slightly warped pump valve or seat.

Not a problem if the pump slows considerably but just does not completely stop.

Some non original type pumps, of different design, never stop.
D

 

[Tullamore]

The one in my sprite clicks all the time, never been a problem.

 

[AlamedaMGB]

[ QUOTE ]
[ QUOTE ]
Could be a leak in the check valve then, but it's less likely.

[/ QUOTE ]
This is NOT so unusual. The slightest bit of contamination will prevent the pump valves from completely sealing, as could a slightly warped pump valve or seat.


[/ QUOTE ]


All the more reason to have a filter between the tank and the pump.. I went through several pumps until I replaced my rusted gas tank!!! Seriously, chunks of rust were getting picked up and work their way through the line until they lodged in the fuel pump check valve. You can check with a pressure tester to see what pressure is building at the carb.. My guess is that it's low.

it can be R & R'd .

good luck.

 

[Steve_S]

FWIW, I was informed recently on another BBS about the dangers of placing a filter before an SU pump. Dave Dubois, the guru of fuel pumps sent this reply...

[ QUOTE ]
The SU fuel pump will pass all but the big chunks with no problem. If a present day paper filter in between the tank and the pump, it will trap any fine rust particles and can clog up rather quickly. When it does clog up, it will cause the pump to stall in a current on condition. If left with the power on very long when this condition exists, it will burn out the internal swamping resistor in the pumps coil. Once the filter is changed, everything appears to be normal and the owner goes on his/her way thinking that the problem has been solved. Unbeknown to him/her, is that the burned out swamping resistor just defeted the arc suppression circuit in the pump and the points burn out a short time later. No big deal, the owner gets a new set of points and installs them, only to have them burn out in a short period of time. Owner then places a posting on the BBS decrying the lousy SU fuel pumps. I would say that about half or better of the pumps that I get to work on have just this situation present when I disassemble them.

If you want an additional filter int he system, place it after the fuel pump. If it gets clogged in that position, the pump just thinks that it is trying to pump into a full float bowl and guits pumping in the normal, current off idle position. result is no harm done.

Not all fuel pumps work the same. If you have a Facet pump, it has a bypass valve in it to set the pressure. This bypass valve is why the pump runs continuously even whe the float bowl is full. This pump is not harmed by a clogged filter on the inlet side, because the pump never stalls out. Other pumps may operate even differently, so they may ar may not be affected by a clogged filter ont he inlet side.

Instead of preventing any problems, a filter on the inlet side of the SU fuel pump can cause problems. The bigest problem being that it is an unseen problem.

[/ QUOTE ]

 

[78MGB]

Steve,

Thanks for the forward. Got under the MGB this evening and found the problem. (hopefully). The fuel line hose connection at the pump from the tank had a BIG gash in it. So, hope it was just trying to pump air.

WAS going to ask for suggestions for a pre-pump fuel filter, but thanks to Steve's forward, I will just replace the fuel line hose.

Thanks to all!!!

 

[Steve_S]

Glad to hear it worked out. I would recommend replacing all the hoses, at least the ones in the rear. If one split, the others may not be far behind. It's a cheap and easy fix and it's better to do it in the garage than on the side of the road. Trust me, I know!

 

[Dave Russell]

[ QUOTE ]
FWIW, I was informed recently on another BBS about the dangers of placing a filter before an SU pump. Dave Dubois, the guru of fuel pumps sent this reply...

[ QUOTE ]
The SU fuel pump will pass all but the big chunks with no problem. If a present day paper filter in between the tank and the pump, it will trap any fine rust particles and can clog up rather quickly. When it does clog up, it will cause the pump to stall in a current on condition. If left with the power on very long when this condition exists, it will burn out the internal swamping resistor in the pumps coil.
Not all fuel pumps work the same. If you have a Facet pump, it has a bypass valve in it to set the pressure. This bypass valve is why the pump runs continuously even whe the float bowl is full. This pump is not harmed by a clogged filter on the inlet side, because the pump never stalls out. Other pumps may operate even differently, so they may ar may not be affected by a clogged filter ont he inlet side.

Instead of preventing any problems, a filter on the inlet side of the SU fuel pump can cause problems. The bigest problem being that it is an unseen problem.

[/ QUOTE ]

[/ QUOTE ]

Partially true. Very few SU pumps have the "swamping resistor". Early ones had a capacitor/condenser & later ones had a diode. neither of these types have the resistor burn out problem.

The "big chunks" are definitely a problem & even small chunks will reduce the pump valve sealing ability. The small chunks will pass through & collect in the bottom of the carb float bowls. Some of them will cause float inlet valves to fail to seal. It is also true that a good filter will clog if enough small chunks collect in it. That's what it is made to do.

Lots of opinions on this subject.

If you want good filtering with long filter life, use a high capacity filter on the pump inlet. An example is the Fram G3802A shown in the attached pic.
D

 

[78MGB]

Finally cooled off this evening and I had a few minutes so I crawled under the MGB and cut off the bad end of the hose. Hooked it back up and it fired right up without the fuel pump continuing to run. Hope I really got luck this time. Off to the auto parts store for a few feet of hose.

I replaced the fuel hose up front, but obviously failed to look at ALL the fuel hoses about a year ago. Out of site out of mind sort of thing is what got me in this mess. Thankfully, it was in MY OWN garage and not on the road some place. Hopefully, I learned that I need to look at a problem as a system, not just one part of it. Muffler goes bad, look over the entire exhaust system and so on.

Thanks for the input to all who posted replies.

Did find a black (I think) wire with a connector on the end just dangling back there. Fuel pump wires hooked up as was the fuel gauge sending unit. Both seem to be working just fine. Hmmm... a PO no doubt and unfortunately not the only "dangling wire" I have found. What to do???/ubbthreads/images/graemlins/rolleyes.gif

/ubbthreads/images/graemlins/cheers.gif

 

[Steve_S]

Sounds like a ground wire.

 

[78MGB]

To what, I know not. /ubbthreads/images/graemlins/eek.gif

Thanks for your help on the pump gang!

 

[Bruce74B]

It is probably the ground wire to your fuel pump or the sending unit that was replaced with another wire to ground. I have seen this on several cars. More likely the fuel pump, where a short ground wire to the mouning bracket is used to get a good ground.

Bruce

 

[Bugeye58]

As long as you haven't found any lamp cord being used yet, I'd say you were lucky!!
Jeff

 

[jcatnite]

LOL...lamp cord...although I think about 20 years ago I might have used some when I was trying to install some home component speakers in my Mustang...LMAO...Been trying to supress that memory..
JC

 

[martyc]

[ QUOTE ]
...Turned the ignition and heard the friendly chirp of the fuel pump, but it will not stop until I turn the ignition off.

[/ QUOTE ]

A tale of (averted) woe...A couple of weeks ago, I had a similar problem. Turned on the TD's ignition... the usual tick-tick-tick as the float bowls filled, then a tick every couple of seconds. I opened the bonnet and found that the bolt holding the overflow tube and lid on the forward float bowl had loosened sufficiently to allow fuel to run down the outsided of the bowl! /ubbthreads/images/graemlins/shocked.gif

Lessons learned: Remember to go back frequently, check and re-torque bolts after you rebuild carbs or replace lines...and check the fuel lines/carbs before every trip. Mine could have easily been a car-b-que!