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flathead electric fuel pump
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motobobby
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May 7, 2013, 10:11 AM
Post #1 of 37
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flathead electric fuel pump
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Howdy - I've had an airtex electric fuel pump on my 49 merc - 6 volt positive ground - for years and it has performed admirably. When I started having problems, I replaced it with same, but it only pumps when the ignition is in acc. position or start position - when the engine starts the pump quits. I am baffled by this as the other accessories hooked the that ignition post keep on working perfectly. I have the pos lead well grounded with the neg. lead on the acc. post of ignition.Apparently I didn't need a new pump. Any thoughts on this would be sincerely appreciated - motobobby
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Discretesignals
Ultimate Carjunky
/ Moderator
May 7, 2013, 1:28 PM
Post #2 of 37
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Re: flathead electric fuel pump
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Did you check with a volt meter to see if the pump has power and ground at the pump terminals?
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
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motobobby
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May 7, 2013, 7:54 PM
Post #3 of 37
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Re: flathead electric fuel pump
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Sorry for the delay in my response - I am worse with computers than I am with cars! I'm not getting this - the pump is operating properly with the key in start and acc. positions, but quits when the engine starts and runs. It has a starter button. I'm guessing that there is proper voltage when it's working and none when it's not, but obviously there is something I'm not getting. The pump has always worked in this exact situation, but no more. The manufacturer recomends an inline oil pressure safety switch, which I now have, but I thought that might further confuse the issue, so I've chosen not to hook that up yet. Does this make any sense, because I'm at a total loss.
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Discretesignals
Ultimate Carjunky
/ Moderator
May 7, 2013, 8:12 PM
Post #4 of 37
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Re: flathead electric fuel pump
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Without knowing how the pump is wired up it is kind of hard to give you an answer.
Do you have a wiring diagram?
Does the pump get power directly from the ignition switch or does it go though a relay that is turned on when the ignition switch is in the on position?
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
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motobobby
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May 7, 2013, 8:21 PM
Post #5 of 37
(3897 views)
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Re: flathead electric fuel pump
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First let me say that you're a great guy! I really appreciate your time. It is grounded (pos.) at the pump location to the frame and the neg. lead runs up to the acc post on the ignition switch. It pumps when in this position until the engine starts, then it quits, however all the accessories(fuel,temp,etc.gauges) still work fine
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
May 8, 2013, 3:36 AM
Post #6 of 37
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Re: flathead electric fuel pump
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How wired in might be the issue. Right where you connected power from ignition switch does it have power in plain "run" position? It really shouldn't be wired to run in accessory position at all.
Question and comment: Own a 6V pos ground tractor with about no tricks. Switches and wiring needs to be double gauge as that for 12V set ups. Wild guess is the ignition switch itself has a problem inside. Finding a 6V switch could be tricky as it would be better made than one for 12V.
Question on the pump: How did you find an electric fuel pump to tolerate 6V for long? The lower voltage is hard on electric motor items with lower voltage. I'm a bit surprised it worked well for quite a while if a 12V pump,
T
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motobobby
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May 8, 2013, 8:05 AM
Post #7 of 37
(3878 views)
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Re: flathead electric fuel pump
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What you say makes sense to me, even with my limited knowledge of electricity. The pump is a 6-volt solenoid type designed for an application like mine. I will wire it up as per the manufacturer's instructions with the safety switch and see what happens. The 6-volt switch is available in the event that needs replacing,but it works in all other functions,so I'm hoping it is OK. I'll keep you posted.
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motobobby
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May 8, 2013, 8:26 AM
Post #8 of 37
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Re: flathead electric fuel pump
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One more thing just came to mind - my switch has three terminals; acc.,ammeter, and coil. Would I be more likely to hook up the hot wire to the coil?
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
May 8, 2013, 8:40 AM
Post #9 of 37
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Re: flathead electric fuel pump
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Roger on the 6V pump. I had no clue they were specifically made for 6V still. What has been tough is light bulbs. Tractor just has front and rear headlights (sealed beams in rubber now) and still available. No ign switch on that nor fuel pump - gravity feed to updraft carb.
I've had that thing since about 1969 and is a 1948. If ignition switch in yours has been replaced I bet the quality plummeted vs the original. It may be all messed up inside and guessing (ya - these things are quite old now) that it's meant to be very HD, brass, real copper etc. Both metals and many others are expensive so the cheating is rampant out there.
General and hard to find is very fine stranded copper wire and made to flex helps. Why - thick strands break with even vibrations too easily.
Side note on that. Check the cord to your vacuum cleaner or even a toaster. Feel how flexible it is - that's fine stranded. Hardware stores even just stare at me asking for it.
Do wire up this pump with the failsafes suggested already. Wherever the problem is right now I would run it thru oil pressure to enable it except for just crank position or you could find an empty tank and all the fuel all over where it's parked - not good of course.
Good luck with the project - I'm watching----------- Tom
PS: out of my boating days but marine grade genereric products are twice (or more) the price but made to both be tough and for marine not to make sparks for any motor or switching odds and ends....
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motobobby
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May 8, 2013, 8:52 AM
Post #10 of 37
(3859 views)
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Re: flathead electric fuel pump
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Tom - Airtex makes the pump and you might check out Mac's antique auto for everything Ford.
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
May 8, 2013, 9:08 AM
Post #11 of 37
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Re: flathead electric fuel pump
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Tractor is a John Deere so stuff available usually easily. Cars I've restored were a lot new than this so plain good auto parts were available. Body parts/trim can be a hunt. No so bad if you choose something popular. Done with all that now, Tom
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motobobby
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May 10, 2013, 4:28 PM
Post #12 of 37
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Re: flathead electric fuel pump
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I had a friend spend the day with his meter on my car and we have determined that although the voltage is good at the pump, no amps get through when the engine is running - in start position the draw is 1.25 amps, but drops to zero when the car starts. Any thoughts you might have on this would sincerely be appreciated-Thanks!
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HT
User
May 10, 2013, 4:42 PM
Post #13 of 37
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Re: flathead electric fuel pump
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The amp reading is the amount of current it takes to operate the component. The same motor doing the same job under the same conditions will draw the same current every time with minor difference for temperature. If the motor is not drawing current, then it has lost either power supply or ground. You can do a voltage drop test to determine if there is a connection problem somewhere in the circuit.
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motobobby
User
May 10, 2013, 6:36 PM
Post #14 of 37
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Re: flathead electric fuel pump
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Let me elaborate. The pump works fine until the engine starts and runs. While running I got 6-volts at the pump but no amp reading. When in the start position on the ignition, the reading is 6-volts and 1.2 amps. When the engine is shut down, with the ignition in start position, the amp reading comes back to normal (1.2). This car has a button starter. We have ruled out the pump as it works fine when I run a lead from the battery and we also have ruled out the switch.Any idea where I should look next?
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HT
User
May 10, 2013, 6:41 PM
Post #15 of 37
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Re: flathead electric fuel pump
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You don't under stand electrical circuits and I doubt you are even reading the amperage correctly. If you have power and ground to the pump, the pump will operate normally. You are missing one or the other The amperage consumption is meaningless here..
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motobobby
User
May 10, 2013, 6:45 PM
Post #16 of 37
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Re: flathead electric fuel pump
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I certainly can't argue that point, but the fact remains that I was holding the leads while my friend was reading the meter. The pump has constant voltage, but quits only when the engine is running. Even with my lack of understanding, I can say that with confidence
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HT
User
May 10, 2013, 6:48 PM
Post #17 of 37
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Re: flathead electric fuel pump
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And I will tell you again............... if the pump quits, it has lost power or ground supply.
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motobobby
User
May 10, 2013, 7:03 PM
Post #18 of 37
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Re: flathead electric fuel pump
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I just got off the phone with my buddy - He has built many high-end street rods and knows this stuff pretty well.He would like to talk to you as he is befuddled by this. My car has new looms and cables, so a ground problem is very unlikely-all the other accessories attached to the post on the switch work fine,running or not. A ground problem would not allow the pump to work at all wouldn't it? off the battery, the pump works,but off the generator /regulator no dice. Can we somehow put you two in contact , as he can follow you whereas I cannot?
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HT
User
May 10, 2013, 7:08 PM
Post #19 of 37
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Re: flathead electric fuel pump
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The problem has to be in that lead coming off the ignition switch or something it passes through on the way to the pump. This is why i recommended a voltage drop test. Connect one lead of your meter to the terminal of the ignition switch and the other where it attaches to the pump and turn it to run and see what the meter reads. It should not read over half a volt or you are losing voltage along that wire.
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motobobby
User
May 10, 2013, 7:21 PM
Post #20 of 37
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Re: flathead electric fuel pump
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my friend is going to contact you in a couple minutes-please stand by
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HT
User
May 10, 2013, 7:22 PM
Post #21 of 37
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Re: flathead electric fuel pump
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Heading to bed soon
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Discretesignals
Ultimate Carjunky
/ Moderator
May 10, 2013, 7:32 PM
Post #22 of 37
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Re: flathead electric fuel pump
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Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
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motobobby
User
May 10, 2013, 7:36 PM
Post #23 of 37
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Re: flathead electric fuel pump
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Thanks - this diagram is tattooed to my brain.
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doggy
New User
May 10, 2013, 8:00 PM
Post #24 of 37
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Re: flathead electric fuel pump
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This is motobobby's friend. We did a voltage drop test from start of wire to wire entering into the pump, not even 1/4 dvc drop. Disconnected wire at ignition switch and hooked directly to battery, pump ran fine. Started engine with pump still wired to battery post and pump kept running. Read amperage which was 1.25. Turned off motor and removed wire from battery post and attached to ignition switch. Turned on switch and pump started running normally, measure voltage and amperage which were the same as when hooked to battery terminal. Pump continued to run during testing and then depressed motor start button and at this point pump stopped running. During this entire period had VOM hooked up on pump electric line to rear to watch for any changes within voltage output. None were observed but pump wouldn't operate, but line voltage at rear of car at pump were reading 6vdc, but pump wasn't operating. Turned off engine by key and then turn key to start position, but not firing engine, and the pump fired right up. For some unknown reason when pump tries to operated off generator and regulator, not battery direct, if wouldn't run, but pump wire when generator in operation (engine running) indicates good voltage (6.25 VDC) going to pump, but pump will not operated. I hope this explains our problem. For some unknown reason when generator in operation, pump won't work.
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Tom Greenleaf
Ultimate Carjunky
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May 11, 2013, 1:01 AM
Post #25 of 37
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Re: flathead electric fuel pump
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This should be more basic than this. The dang key, ignition switch as said way back has probably failed. A stupid test light would show that and put all the junk away. A dang electric start riding mower does the same key/ignition action!
T
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