Electric Fuel Pump Shuts Motor Off

-
gtsdon

gtsdon

Well-Known Member
Joined
Jan 15, 2012
Messages
47
Reaction score
36
Location
Hampton VA
Had a weird thing happen today. Took the Dart out for a ride and after I shut the engine off it was hard to restart. Several times the engine would start but as soon as I turned on the electric fuel pump it would kill the engine (like someone turned off the ignition switch). This happened several times in a row until I finally gave up.

Again, I could use the pump to fill the carb bowls without the engine running but if I turned the pump on with the motor running the engine would shut off.

Anyone else ever had anything like this happen? Any ideas?
 
67cudafb said:
Stuck float?
Click to expand...

It doesn't act like a stuck float in the carb. I drove the car for 30 minutes before shutting it off. On the second restart is when the trouble started. Its weird- I can start the motor and it will run until I turn on the electric pump. As soon as the pump comes on the engine will die like someone cut off the switch.

Its an old holley blue pump thats been on the car for a few years. Was wondering if the fuel pump motor is shorting out or something and causing some type of interference with the ignition.
 
Abodybomber said:
You need a mechanical pump, let's start there.
Click to expand...

I thought about troubleshooting with a mechanical pump but rerouting the fuel lines would be a pain. Guess I will just replace the old electric pump and and see what happens from there.
 
The pump has to be working or the engine wouldn't run at all cause it wouldn't be getting any gas. Did your on/off switch somehow get turned around so when you think it's on it's really off?

BTW: why are you turning the fuel pump on and off while you start it anyway? Needs to be on to get fuel to the engine.
 
Wild guess... electric pump robbing current from ignition circuit ?
 
Regulator might be stuck...over powering the needle and seat, then flooding the motor. I've had this happen with my Holley blue pump before. Take your air cleaner off and try it again, if you see fuel coming out your vent tubes like a fountain then you either have a stuck float, bad needle and seat, or a regulator issue....just something to try. Good luck.
 
Abodybomber said:
You need a mechanical pump, let's start there.
Click to expand...

mechanical pumps suck theses days; with an electric pump you don't even need a choke, pump once start and go!


sounds like the OP's pump maybe drawing too much power and is hooked into the same power source as the ignition, or the regulator went bad and the carburetor is getting more then 9 PSI (MAX)
 
What ignition system do you have? MSD? The pump might be taking so much current that the ignition shuts down. They are both on the same circuit i'll bet. The pump needs a relay and it's own separate circuit with fuse protection. Sounds like a frustrating problem. Good luck. tmm
 
electric pumps often times have an ignition cutoff switch.

it's a safety feature so that if you are in an accident, and the engine cuts off, the fuel pump does not keep pumping.

basically it's an oil pressure dummy switch. it's wired so that when your key is in start position (cranking starter) the pump is always on. when it's the key is in run position the pump is on unless oil pressure dies, then it cuts out.
 
Lots of good responices guys. Looks like I have my work cut out for me trying to diagnose. Thanks for the help and suggestions.
 
Try a different pump...i don't throw the switch until the engine lights up.the crab has enough gas in it to start the engine.you might have to resolute your power source for the pump.....
 
bad440 said:
Try a different pump....
Click to expand...

Nope. This is called "throwing parts" at a problem. It's expensive, time consuming, and sometimes, doesn't even fix the problem.

I'm leaning towards Redfish.........a wiring problem that is robbing current from ignition

There's only so many things can go wrong.

1....Might be something wrong in the pump. Unless the pump (motor) started magically running backwards, I don't see a pump flowing LESS when running

2....Might be a wiring problem killing ignition power

3....Might be stuck needle and seat

I can't see no1 so leave it for last

No3......Seems to me if it were flooding you would KNOW it. You could smell fuel, the engine would be "dogging down" and hard to start again after flooding.

No2. Easy to check. Why is this taking so long, LOL? Just "rig" a test light or multimeter to the ignition power and SEE what the joltage is doing
 
The circuit must not be fused if it draws so much and on 1 Circuit then kills the engine unless it has a very large fuse. The factory wiring under the dash for keyed hot is not designed for such a load on its own. The Fuel pump can be on the same circuit "keyed-switched" but it needs its own power source by using a Bosch Style Relay. The ignition will pull the coil closed in the Relay and then it will draw its power straight from the battery. The keyed on or switched on to power the relay will draw under 1 amp to pull the coil in the relay and bring power to the fuel pump. Regardless of your problem. It needs to be wired in this way. Something to check.
 

Attachments

  • boschrelay.jpg
    30.5 KB · Views: 231
I don't believe any type of fuel problem will shut the engine off immediately like a light switch…especially after the car has been running and the bowls are not full just yet. It would usually run on and die out from flooding the engine which would not be immediate.
 
If the fuel pressure regulator is heat soaked, turning the fuel pump on will push the boiling fuel into the bowls causing vapor lock. The OP stated a hard hot start condition.
 
You must log in or register to reply here.
-

Back
Top