Fuel Pump Won't Shut Off

mike knight · #1 (**permalink**) 09-30-2006, 04:39 PM

Here are the facts:
Electric fuel pump (weldon 2025) which is easily heard at idle starts to rattle loudly. I drain the tank and pull the pump checking the brushes. Brushes show some wear but not excessive. I didn't want to lose any drive time this time of year in the midwest so I bought another pump. What the heck I put the new pump in service and it runs perfect. While test driving the car in my neighborhood the engine quits abruptly. I check the fuse and it's blown so i replace it. Pump is working again but it won't shut off when i kill the ignition.
I replaced the relay but that doesn't solve the problem. In order to kill the pump I have to pull the relay after engine shut down. This is becoming a big PIA. I put a meter on the disconnected battery to see if I have any draw down but the meter reads 0. Since there are only two wires coming out of the pump, one orange and one black and it's wired exactly as the old pump, orange to positive and black to a frame ground, I feel confident that I didn't wire it incorrectly.

Any ideas out there about what might cause this? I really don't like the idea of draining the fuel tank again as that is a huge PIA not to mention safety. I do have a 4 post lift so I can get under the car easily. The original pump is on its way to weldon for inspection and rebuild if necessary.
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strictlypersonl · #2 (**permalink**) 09-30-2006, 05:48 PM

It sounds like the relay is toasted. The contacts were welded together by some intermittant short before the fuse blew.

mike knight · #3 (**permalink**) 09-30-2006, 07:44 PM

I had the same thought and bought another relay and it acted the same way.If I plug the relay in with the key out of the ignition the fuel pump turns on. It never did this before. The only way the pump is not on is if the relay is removed from the plug.
Thanks,

Mike

Ron61 · #4 (**permalink**) 10-01-2006, 06:56 AM

Mike,

You might try this until you track down your problem. I have my fuel pump connected to a toggle switch on the dash so I can shut it off if I want to do some work with the key on. Much easier than pulling the relay.
As for what changed, try checking for voltage with the relay out and if you have it on the relay winding, find where it is coming from. Sounds as if the minute you plug in the new relay it is operating. Also measure through the relay contacts of the new one with an ohm meter to be sure they aren't welded together. If you haven't blown any more fuses, then they should be ok. It is possible that while your old pump was going bad, it drew enough current to cause a short between the winding lead and another lead that has power on it. I would start by pulling the relay and checking right at the relay plug terminals.

Ron

mike knight · #5 (**permalink**) 10-01-2006, 09:13 AM

Thanks ron, I'll try that today. If I can't uncover the problem I'll take er' out since it is an absolutely georgous day in chicago, 75d, low humidity,no wind and no clouds. I am going to drive today and hopefully the system will hold together until I can shut it down for winter inspections and work.

neverwouldof · #6 (**permalink**) 10-01-2006, 09:51 AM

What happens when pump starts to go bad? I believe i started having issues yesterday with mine. Guage usually sits at 6psi then it started twitching to 3psi and engine was running badly, before yesterday it would go up towards 10psi after driving awhile when running lower rpms. yesterday something quit and i was braking to turn into neighborhood and engine quit. I tryed to crank engine with clutch in while coasting and no deal.... had to push the rest of the way past the neighbors! Let everything sit over night thinking it might be flooded and tryed to crank this morning and nada.... starter while turning engine over sounded like it was under load and killing battery or something else went wrong.

any thoughts?

Keith

mike knight · #7 (**permalink**) 10-01-2006, 10:39 AM

Hey Never,
I would pull a plug and while out check for spark. If the plug is clean and has spark, fuel delivery would be next. Disconnect the fuel line at the carb , put the fuel line into a catch can and with the coil pulled bump the ignition and see if its pumping fuel. if you've got spark and fuel at the carb what do your plugs look like, Are they wet then you may have a seriously flooded engine. My car is fuel injected so I really don't know much about carb setups and what can happen to make them quit pumping.
When my engine quit there was absolutely no warning and when I tried starting I got no pop at all. I located the fuse in line with my relay, it was blown, replaced it and the engine lit off immediately. The reason it wouldn't even bump is the engine had drawn off all of the fuel in the system forward of the pump and regulator. Is your engine even firing on a couple of cylinders? if you've don't even get a couple of cylinders firing then check your wiring from the pump and see if when your trace it that you don't have a fuse close to a relay like mine. If you do get some popping and from what you've said about your engine sounding as though its laboring on start up its possible that its seriously flooded at which point you should let it sit for a couple of days or pull all of the plugs and clear the cylinders. I won't presume to give you all of the timing precautions to take when you pull all of your plugs and wires.
Keep in touch with all of the guys on this site someone knows enough to help you out with your exact setup. This sit is an absolutely incredible resource you just have to be patient and persistent.

mike

Ron61 · #8 (**permalink**) 10-01-2006, 10:44 AM

First off are you running an electric pump or the mechanical one? If it is an electric one, you should be able to hear it running and if the pressure is varying that much, be sure your fuel filter is not full of crap. Then if you have a pressure regulator check it and the gage to be sure they are ok. You can also remove the gas line at a convenient place and turn the pump on and see if you get gas coming out at a good rate. A bad gage wouldn't cause the car to run bad, but a bad regulator or filter that is blocked would.

Ron

neverwouldof · #9 (**permalink**) 10-01-2006, 11:18 AM

Thanks guys, i'm not getting any pop at all now. Just sounds clunky and i stop. So i'll check the plugs. Should fuel pressure vary when driving normal when it was running? I don't hear my fuel pump at all anymore. Holley High Pressure Mechanical Fuel Pump by the way....

mike knight · #10 (**permalink**) 10-01-2006, 11:56 AM

mechanical pumps are pretty bulletproof. I am running an electric which is very noticeable while running. i have fuel pressure at the regulator and the fuel logs so i know that's o.k. as for mechanical do you have a gauge in your engine compartment so that you can verify your dash gauge?

Ron61 · #11 (**permalink**) 10-02-2006, 06:17 AM

Never,

Mike is right. Pull a wire and make sure that you have a good spark at the plug. If so then I would remove all of the plugs and look at them and also turn the engine over if they are black or gummy to blow out any gas that is in the cylinders. If you have gas in any of them. it wouldn't hurt to squirt a small amount of oil down in there so it can coat the walls as the gas will have washed them clean. I am running the high pressure Holly Blue Pump and have to have a regulator. I have a pressure gage mounted on the regulator just in front of the carb., and it only varies when I really get on it. The pressure will drop for a second or so as the opening of the carb. lets more fuel flow. but at a steady driving speed, the pressure should stay at whatever you have it set at. But be sure to check any fuel filters and make sure they aren't plugged. Also check you oil for any signs of gas as a mechanical pump can let gas into the oil if the diaphragm is starting to split.

Ron

neverwouldof · #12 (**permalink**) 10-05-2006, 05:58 AM

Quote:

Originally Posted by Ron61

Never,

Mike is right. Pull a wire and make sure that you have a good spark at the plug. If so then I would remove all of the plugs and look at them and also turn the engine over if they are black or gummy to blow out any gas that is in the cylinders. If you have gas in any of them. it wouldn't hurt to squirt a small amount of oil down in there so it can coat the walls as the gas will have washed them clean. I am running the high pressure Holly Blue Pump and have to have a regulator. I have a pressure gage mounted on the regulator just in front of the carb., and it only varies when I really get on it. The pressure will drop for a second or so as the opening of the carb. lets more fuel flow. but at a steady driving speed, the pressure should stay at whatever you have it set at. But be sure to check any fuel filters and make sure they aren't plugged. Also check you oil for any signs of gas as a mechanical pump can let gas into the oil if the diaphragm is starting to split.

Ron

Ok.... have some updates. It started up after letting sit a couple days and recharging the battery which was run down from starter use i'm guessing. The 2nd 735 Holley is leaking gas when engine is shut off. When i take air cleaner off the inside of carb is soaked with gas and i'm guessing it is flooding engine. There was actually gas dripping out of muffler on passenegr side when i got it started up which i'm guessing is from being flooded. Is there a website where i can get details of adjusting the carbs for proper fuel flow. The engine shop i was going to take it to is so backed up i've been waiting 3 weeks just to try and get an appointment. Still don't have one yet. I can't believe it is running well and then all the sudden it is going nuts on me... how does this happen so quick. Thanks for any help or direction!!!

Keith

Ron61 · #13 (**permalink**) 10-05-2006, 06:31 AM

Keith,

Is this a vacuum opened secondary carburetor? Also you say it is soaking wet when you take the air cleaner off. Can you see gas dripping or coming from either end? If you have had a back fire or anything like that, unless your carb. has the blow by protection, you could possible have blown a power valve. The older Holly's were famous for this and I used to carry two or three all the time to put in when I was out and one blew.
After it set for a couple of days and you started it up, how did it run then? any black smoke or sputtering?

Ron

neverwouldof · #14 (**permalink**) 10-05-2006, 10:34 AM

http://pg.photos.yahoo.com/ph/northf...e2.jpg&.src=ph

Here is the link to photo with location of leak from carb circled. The carb is continueing to flow fuel after engine is cut off and actually starts to come out of location circled in pic. The carbs were rebuilt i was told just 6 months ago. Right when i was purchasing car. It was running well and then all the sudden this pops up. Any more suggestions helpful.... last time i started it up some gas actually dripped out passenger side muffler which cant be good can it?

Keith

Jerry Clayton · #15 (**permalink**) 10-05-2006, 10:50 AM

Kieth

Change the needle seat assy on the seconaries of that carb
when a holley runs over the vent tubes with the engine not running and the throttle blades closed, it will run out around the throttle shafts

Check your fuel system for debries that is fouling your pressure regulator and needle seat assy

Flush all the hoses in the system, check all screens, set the regulator at 5-6 #, make sure your pump is shutting off

Jerry

Ron61 · #16 (**permalink**) 10-05-2006, 11:50 AM

Jerry pretty much said what the rest of us have been saying. He is correct about the fuel coming out around the throttle shafts if enough goes into the throttle body with the butterflies closed. Also while you are checking all the rest you might want to put what they call whistles in the carbs. They will keep gas from splashing up under braking and going into the vent areas. I had to have that done with mine and what a difference it made. If your pressure has been to great you could have the needle valves all messed up. My book on the 900 Holly I am running calls for just 6 to 8 pounds of pressure. My pump puts out 14+ so I have to watch it and make sure the regulator doesn't back off or the filter get full of crap. The gas out the muffler is just unburned raw fuel which has poured into some cylinders and is being ejected. Not good as some of it most likely went into the oil pan too. I would have both of the carbs checked out completely along with the rest of the stuff Jerry mentioned, and then change the oil and filter to make sure there is no gas in the oil.

Ron

neverwouldof · #17 (**permalink**) 10-05-2006, 12:24 PM

Ok .... will do . Thanks guys for your wealth of info!

I'll update once i get in there and see whats happening.

Keith