Electric Fuel Pump Problems

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AZScott
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Electric Fuel Pump Problems

Post by AZScott »

Hello, having some problems with my fuel delivery (On a 63, with 65 4 carb motor). Reserving judgement on if my pump is bad until I check out everything. The car as I bought it had an electric pump with oil pressure and inertia cut out system. I believe could be a stock Clark catalogue part. Before I start replacing parts I would like to understand the wiring. Does anyone have a wiring diagram for this setup you can send me? I can see some generic wiring diagrams on the internet but they look different from what I have. Thank You
Attached is a picture of the switch, and the oil pressure switch off the oil filter.
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66vairguy
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Re: Electric Fuel Pump Problems

Post by 66vairguy »

You did not state what your "problem" specifically is.

Shame on the modifier for not supplying diagrams. I always give folks diagrams of wiring changes I make.

The oil pressure and impact switch shut off the fuel pump in an accident to minimize fire.

The first issue is simple - unless there is a by-pass switch to activate your electric fuel pump it WILL NOT TURN ON until AFTER the engine starts and oil pressure comes up. Needless to say this is a problem on a car that sits more than a day or so as today's fuel easily dry up in the carburetor if the car is shut off after it warms up. One of the main reasons for an electric fuel pump is to prime the carburetors after a car sits for awhile for a quick start up.

A good electrical person would have installed a timed by-pass circuit or relay for start ups. Are you getting the impression this gets complicated (and why new cars have computers to do all this).

I'm not recommending this, but many DO NOT use the low oil pressure fuel shut off switch and the impact switch must be relied upon to shut off the fuel pump in an accident.. If the engine stalls you must either re-start the engine or TURN OFF the ignition key to shut off the fuel pump. Due to the fact that engines don't always shut off in an accident, but fuel lines do get damaged, the impact/inertia switch is important.

There are three prong oil pressure switches (replaces the standard switch) and two prong, like you have, that are separate from the regular oil pressure warning light switch.

At this point I'd suggest finding a good electrical troubleshooter to do the following: First check to see if the fuel pump is fused and fuse condition. IF the fuel pump does not turn on when you turn the ignition key on (before starting) you can isolate the problem. Carefully connect the two contacts on the oil pressure switch to together (wire or test lead) and turn on your key and the fuel pump should work - same for the impact switch as they do sometimes trip open due to vibration. If all else fails the fuel pump could be faulty.

Good luck.
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bbodie52
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Re: Electric Fuel Pump Problems

Post by bbodie52 »

:dontknow: Your initial post provides some information, but leaves many unanswered questions about the details of your electric fuel pump installation. It is very difficult to troubleshoot such a system without specific details of the components, plumbing, symptoms, and wiring. I will try to describe to you how the system should be wired and how it should be functioning. You will have to perform some physical examination and testing with a multimeter to determine the cause of your problem.

:think: I noticed the physical presence of the original mechanical fuel pump. Do you know if this pump is still serviceable, or whether or not it had failed? Has the mechanical pump plumbing been completely bypassed? Do you know the name and model number of the electric fuel pump that was substituted? Also, where was the electric pump physically mounted? Mechanical pumps like the original Corvair fuel pump do a good job of creating a vacuum to pull the fuel long distances from the fuel tank. However, electric fuel pumps are better at pushing fuel than pulling it, so the electric fuel pump normally should be mounted as close as possible to the fuel tank, so that fuel is essentially a gravity feed from the source that would only be a few inches from the pump. Then the electric fuel pump pressurizes the fuel line all the way to the engine compartment and carburetors.

From what I can determine, the inertia switch acts like a circuit breaker. The default would be to permit electrical continuity through the switch unless it has been tripped. This means that there should be a voltage input and voltage output at the switch location, and you should be able to measure 12 V DC with a multimeter at the input of the switch when the ignition key is ON. If you measure voltage going in but nothing coming out the inertia switch may have tripped. You can try pressing the reset button on the top of the switch to restore power.

The second safety switch in the circuit is an oil pressure sensor. Most of these have three connectors. One connector is an output that provides power to the electric fuel pump. The other two connectors provide electricity from two sources. One of these allows electrical continuity through the switch when there is no oil pressure. It is normally connected to a temporary voltage source that is provided by the starter solenoid. When the engine is cranked to start the engine, the starter solenoid also provides voltage to the oil pressure safety switch, which passes through the switch and on to the electric fuel pump (but only when the engine is being cranked and needs fuel for initial startup). When the operator releases the key when the engine starts, the starter solenoid disengages and also discontinues providing voltage to the fuel pump. At this point, with the engine running, oil pressure from the engine triggers the safety switch to allow electricity from the ignition switch (and possibly from the inertia safety switch, if one is used) to reach the electric fuel pump.

With this dual safety switch arrangement, the inertia switch would be passive and would normally allow electricity to pass through it unless a sudden vehicle impact causes the switch to open and cut off the electric fuel pump. The oil pressure safety switch only allows electricity to pass through it from the startup source (the starter solenoid) or, when oil pressure is present, from the primary voltage source (normally the ignition switch circuit, which should also be fused).

Obviously, the electric fuel pump system is much more complex than the original mechanical fuel pump system. Possible points of failure include the pump itself, the fuse in the circuit, wiring faults, the inertia safety switch, or a faulty oil pressure safety switch. The photographs you provided only show a small portion of the overall system. Since the installation is undocumented, I have tried to describe what you should expect to find if you examine your specific installation. You will need a multimeter to test for voltage at different points in the circuit, but you will only find that voltage under the conditions where it would be expected (such as ignition key on, engine being cranked, or engine running). You could also try running a temporary bypass to test various components. This might include a voltage jumper from the battery positive terminal to the electric fuel pump power input wire. This would allow you to hear and see whether or not the pump is activated when a known voltage source is applied. If you confirm that the pump does work, but does not appear to be working under normal running conditions, you may find a circuit interruption such as a blown fuse or a tripped inertia switch.

If you find that voltage is present at the input to the inertia switch, but is not passing through the inertia switch, you can try resetting it. If this fails it should be easy to wire a temporary bypass around the inertia switch to see if that restores service to your electric fuel pump.

You did not describe the symptoms that are apparently causing your engine problem. What makes you think that your problem is fuel delivery? Could there be an ignition system failure?

The material I found below about the inertia activated fuel pump shutoff switch indicates that this switch has a reset button on the top. If you suspect that your electric fuel pump is not delivering fuel, have you attempted to reset the inertia switch? There may be a possibility that the switch was accidentally tripped and may need to be reset to restore power to the fuel pump.
:link: https://www.pegasusautoracing.com/produ ... oCZcHw_wcB
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Pegasus Part No. 1108 - Fuel Pump Shut-Off Switch - Inertia Activated
Our Inertia Activated Fuel Pump Shut-Off Switch will cut power to an electric fuel pump after an impact of 10 to 12 G's or higher*, reducing the risk of post-crash fires caused by pressurized fuel sprayed from ruptured fuel lines. Resets with a simple push on the top of the switch.

This is such a cost effective safety item that many production cars have similar switches installed as original equipment. (Note: Although our switch is similar in operation to the switches found on street vehicles, it is not intended to be a replacement for any OEM switch.)

10 Amp continuous load rating allows the switch to handle the current of most electric fuel pumps (such as Facet low-pressure pumps) directly. Fuel pumps drawing 10 amps or more (such as the Bosch 044 and Aeromotive A1000 pumps) should use this switch to break contact on the fuel pump relay coil circuit. Includes switch, connector kit, and full instructions. Installation time averages less than 30 minutes. The kit is a universal fit for any vehicle with an electric fuel pump.

* A "typical" 8 mph fender-bender might generate a 2 g impact. Most OEM air bags are set to deploy in a 7 g impact, equivalent to hitting a solid wall at about 15 mph or a stationary vehicle at about 25 mph.
The inertia switch is a dependable car component, as long as it is in good condition and is working well. But, once it gets damaged, it will be giving you a whole lot of trouble. You may experience sudden dying of your vehicle engine, with no fuel reaching your motor.

Inertia switches can be found in most cars especially those that use fuel injection. Its main purpose is to prevent any dangerous fuel leaks to occur when you get into an accident. It does this by cutting off the fuel supply fed by the fuel pump to the engine. However, a sudden stop or a vigorous change in direction may activate the switch. When accidentally activated, your car might not start or the engine would suddenly die due to the engine being starved of fuel. To remedy this, you can either reset the switch which is fairly easy or, if it's broken, is to install a new one.
:link: https://www.summitracing.com/parts/atx- ... oCPQTw_wcB

:link: https://www.summitracing.com/parts/crt- ... oCxGjw_wcB
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The Carter A68301 pressure switch is a single pole double throw diaphragm actuated switch. Terminals P (Pump) and S (Start) are normally closed, terminals P (Pump) and I (Ignition) are normally open. Start and Pump terminals will be active during cranking and the ignition and pump terminals will be active when 7psi of oil pressure or higher exists. All current will be deactivated if 7 plus pounds of oil pressure or the start switch signal is not present. With a 10 Amp rating across the entire switch.
Brad Bodie
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AZScott
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Re: Electric Fuel Pump Problems

Post by AZScott »

Thanks , 66vairguy, and bbodie52, appreciate you taking the time to respond. My unit has the by-pass plate in the mechanical fuel pump, and the line to the pump is fused, and the fuse is good. I would still like to see if someone has a wiring diagram for the Clark supplied safety cut off system that incorporates both the inertia and oil pressure switch.
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Re: Electric Fuel Pump Problems

Post by bbodie52 »

I put together a theoretical electric fuel pump wiring diagram, as shown below. It includes both an oil pressure safety switch and an inertia safety switch. The oil pressure safety switch allows power to pass through from the starter solenoid to the electric fuel pump when oil pressure is not present. Voltage would only be present to provide power to the fuel pump when the engine is being cranked. Once the engine has started and oil pressure is present to close the safety switch, power from the starter solenoid would be discontinued when the key was released. At that point, voltage would be available to the electric fuel pump from the ignition switch in the ON position. This voltage would pass through the inertia safety switch, which is normally closed unless it has been tripped by a vehicle impact or some other cause of rapid deceleration (possibly hard breaking, impact with an object such as a pothole, etc.) This is how I would expect your Corvair to be wired. Please let me know if you have any questions.

Left-click the image below to enlarge for better viewing…
Electric Fuel Pump Wiring Diagram
Electric Fuel Pump Wiring Diagram

1965-1969 Corvair Engine Compartment Wiring Harness Starter Connections.jpg
1965-1969 Corvair Engine Compartment Wiring Harness Starter Connections.jpg (80.88 KiB) Viewed 1290 times

Click on the link below to view complete Corvair wiring schematic diagrams…

Corvair Combined Wiring Schematics
:link: http://www.corvairforum.com/forum/viewt ... 25&t=12968
Brad Bodie
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AZScott
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Re: Electric Fuel Pump Problems

Post by AZScott »

Bbodie52, Thanks!! Got it running now. I guess my set up was not the type that was sold through Clark’s, since I have the 2 connector pressure switch. My cars could see a period of time between runs, so I believe I need the three connector oil pressure switch, like you and 66vairguy explained. Thanks again.
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acarlson
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Re: Electric Fuel Pump Problems

Post by acarlson »

AZScott wrote: Fri Jun 09, 2017 2:01 pm ... I would still like to see if someone has a wiring diagram for the Clark supplied safety cut off system that incorporates both the inertia and oil pressure switch.
You can just email Clarks Support and ask for the install instructions. They will email them to you as a PDF file. I have done this on a couple of Clarks parts. There is no charge for this.

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66vairguy
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Re: Electric Fuel Pump Problems

Post by 66vairguy »

There may be some confusion over the three prong oil switch. Some can work as Brad's diagram shows, some are wired to turn on the warning lamp with low or no oil pressure and turn on the fuel pump with oil pressure. There are different three prong switches. This is a problem when folks get creative and don't document things they do to a car.

Also there is an error in Brad's diagram. The wire to the starter from the key goes to the "S" terminal on the solenoid, not the "R" terminal (that goes to the coil to allow ballast resistance wire by-pass). The "S" terminal supplies voltage only when the ignition key is turned to "START". The "R" terminal is always powered unless the ignition key is "OFF". Basically the fuel pump would run even when the oil pressure dropped, albeit with a reduced voltage via the coil ballast.
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bbodie52
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Re: Electric Fuel Pump Problems

Post by bbodie52 »

66vairguy wrote:...The wire to the starter from the key goes to the "S" terminal on the solenoid, not the "R" terminal (that goes to the coil to allow ballast resistance wire by-pass). The "S" terminal supplies voltage only when the ignition key is turned to "START". The "R" terminal is always powered unless the ignition key is "OFF". Basically the fuel pump would run even when the oil pressure dropped, albeit with a reduced voltage via the coil ballast.
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The "S" terminal is connected to the ignition switch by a purple wire. That wire is only energized when the ignition switch is turned to the START position. Voltage applied to the "S" terminal energizes the solenoid, which physically engages the Bendix drive with the ring gear on the pressure plate or torque converter. At the same time, a large metal contact ring inside the solenoid establishes connectivity between the 6gauge positive battery cable connection on the solenoid to the starter motor connection that is directly opposite it — which energizes the motor itself to crank the engine.

The "R" terminal is wired to a spliced connection with the ballast resistor wire that is in turn connected to the ignition coil positive terminal. When the ignition key is in the ON position, voltage is fed via the resistor wire to the ignition coil at a nominal 7 V DC. When the starter solenoid "R" terminal is energized simultaneously along with the starter motor, the same 12 V DC that is fed via the 6gauge positive battery cable to the motor is also connected to the "R" terminal, which raises the voltage on the BLACK/YELLOW wire above the 7 V DC that is present from the resistor wire. This higher voltage overrides the 7 V DC to temporarily boost the coil output to provide a "hotter" spark at each spark plug (promoting starting of the cold engine). When the solenoid disengages (when the operator releases the key after the engine starts) the solenoid disengages the starter Bendix drive and simultaneously opens the contacts with the starter motor AND the "R" terminal (which allows the supply voltage at the coil positive terminal to revert back to the lower 7 V DC provided through the ballast resistor wire).

However, I was incorrect in indicating that the oil pressure safety switch would be connected to the "R" terminal. Because of the splice in the primary ignition wire, 7 V DC would still be present on that wire and could potentially be fed to the fuel pump as well (via the oil pressure safety switch). Instead, the oil pressure safety switch would be wired to the "S" terminal. When the ignition key is held in the START position and 12 V DC is applied to the "S" terminal to energize the solenoid, that same 12 V DC would be made available at the normally closed "N" pressure safety switch terminal where it would be passed on to the "C" terminal and on to the fuel pump. Once the engine starts oil pressure would be made available to the pressure safety switch, which would close the contacts between the "NO" safety switch terminal and the "C" terminal, which would continue providing voltage to the electric fuel pump (via the INERTIA SAFETY SWITCH) after the engine had started.

I've corrected the wiring diagram to reflect these changes.
Brad Bodie
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AZScott
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Re: Electric Fuel Pump Problems

Post by AZScott »

Thanks Alex, good suggestion, I will contact Clark’s. Clark’s have been very knowledgeable and helpful to me in the past. (doesn’t hurt that I spend a pile of money there as well) Plus I am curious if the oil pressure switch that I have now was sold as a kit through them. I thought it was, but not so sure now. I will need to wire up a 2nd car for an electric fuel pump, and definitely want to have both the inertia and oil pressure switches functional, so all this is helpful. Again thank you everyone for your help and suggestions.
63 Monza Coupe (164-4 carb)
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74 Norton Commando
69 Triumph Bonneville
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