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post #1 of (permalink) Old 10-20-2003, 06:24 PM Thread Starter
 
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Mechanical or electric fuel pump?

After a hard day in the mud with my Jeep, the in-line electric fuel pump stopped pumping on the way home. I towed it to my daughter's, since it was 30 miles closer. The next day the fuel pump was working again. A couple of days later, I was going to take the Jeep home and only made it a couple hundred feet and the fuel pump stopped pumping. I could hear and feel it trying, but no gas. The filter doesn't have any trash in it so I don't think the gas line is plugged. I didn't have an air compressor to blow in the line.
So I'm finally to my question. Is there any advantage to an electric fuel pump over a mechanical one? Unless there is an advantage to the electric pump, I am leaning towards going back to a mechanical pump. I will have to install a roll over switch if I stay with an electric pump, since the PO didn't think one was necessary and I do.
79 CJ7 - 304 - Edlebrock intake - Holley 600
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post #2 of (permalink) Old 10-20-2003, 06:55 PM
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Re: Mechanical or electric fuel pump?

I prefer mechanical. They seem more reliable.

The big advantage with electricals is that they're handy for restarting after running out of gas. [img]images/graemlins/grin.gif[/img]
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post #3 of (permalink) Old 10-20-2003, 08:16 PM
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Re: Mechanical or electric fuel pump?

Electrical feeding a TPI system on a SBC. Oh, that wasn't exactly the question.

I've had less problems with an electrical. I've only had to change one on an MGA. I've had to change several mechanicals. Check connections and grounds. I believe the pump should be no more than a couple inches above the bottom of the tank on an external.
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post #4 of (permalink) Old 10-20-2003, 09:24 PM
 
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Re: Mechanical or electric fuel pump?

From my experience, unless needed for FI, I prefer mechanicals.
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post #5 of (permalink) Old 10-21-2003, 06:57 AM
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Re: Mechanical or electric fuel pump?

Taz, I had several MGBs, and several friends with them, and one with an AH 3000. I don't recall ever replacing a pump, but several of them would stop working occasionally and require a single whack with the handle of the KO hammer to get them going again.

I was spooked about that for a while, thinking that some day the fix wouldn't work and I'd be stranded. I couldn't really afford to replace it though, and it never died.

I've only experienced one failure with a mechanical, and that was on my '55 Chevy 265. The diaphragm ruptured and caused a gasoline fountain spurting out the vent hole on the top of the housing. It soaked the entire engine compartment. That it didn't ignite is one of life's little mysteries.

Since then I periodically replace the pump on everything I own. They're cheap and easy to swap.

I suspect that one reason we hear about problems with electricals is that they're often aftermarket items that have been installed by guys without the knowledge and tools to design and build a really good wiring harness.

On the other hand, I've had two electricals die on Volvos I've owned, and one REALLY nasty problem on a Volve where the relay that powered the pump was intermittent. The car would die without warning. Coast to the shoulder, wait 10 minutes and it would fire up and run fine. We chased that for several months, and only found it when it happened to die while the dealer mechanic was looking for the problem.
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post #6 of (permalink) Old 10-21-2003, 09:08 AM
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Re: Mechanical or electric fuel pump?

Do you have a filter before the pump too?
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post #7 of (permalink) Old 10-21-2003, 09:25 AM
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Re: Mechanical or electric fuel pump?

1. I'm amazed that electric fuel pumps are as reliable as they are.
2. They're like the energizer bunny, they just keep workin'...
3. And when they do start to fail... they usually give a warning.
4. They outlast mechanical fuel pumps,
5. IMHO they give much better service over life than a mechanical fuel pump....
6. But there's something Jeepers like about seeing and holding a hard part.
7. The electric fuel pump, because it's electric,
8. Is something of a bridge to a nether world of parts.
9. You know it works, but you don't know how because it's not mechanical,
10. That leads to mistrust.
11. Usually when an electric fuel pump goes out the owner ignores the warnings,
12. Then they're really PO'd when it fails and wondering why?
13. And blaming the darned thing for the towing bill.
15. When a little preventative maintenance would have helped.[*] So quit hittin' it with a hammer[*]Sometimes wacking thing don't make 'em work (see ... Children)[*] Run SeaFoam through two tanks of gas every 6 months[*] Listen for that tell tale noise (hummm...) it makes when it goes south[*] Change the input filter to the pump once in a while (it is filtered isn't it?)[*] Keep the pump cool[*] Keep the pump clean[*] Keep the pump as free of vibration as you can.
16. How many of us carry a spare mechanical fuel pump in a trail parts kit?
17. Why not carry a spare electronic fuel pump in a spares kit?
18. IMHO... most of the bias against an electronic fuel pump,
19. Is fear of the unknown...
20. And a lot ignorance thrown in on top of it.
21. Give me an electronic fuel pump any time,
22. And a spare for the spares kit.
23. It ain't no different than preparing for a mechanical repair,
24. Only a lot more expensive to carry a spare.

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post #8 of (permalink) Old 10-21-2003, 10:45 AM Thread Starter
 
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Re: Mechanical or electric fuel pump?

No, I do not have a filter before the pump. I thought there was a filter in the tank so I put what I thought was a second filter near the carburetor. Looking at my manuals this morning, I find that the only filter in the tank is a strainer on the fuel pickup. Now I am wondering if the strainer is clogged since the pump does pump fuel for a little while. The next day when I cranked the engine after pulling it to my daughter's, I let it idle for about 10 minutes and all was fine. When I started to take the Jeep home a few days later, the engine had only been running about 3 or 4 minutes when I went over a couple of rough places in the road. That's when the engine died. I could feel and hear the pump, but no gas coming out. I removed the gas cap thinking that maybe the vent in the cap was closed, but nothing that simple.
I am going over there tomorrow, so maybe I'll find the problem.
Thanks everyone for the input.

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post #9 of (permalink) Old 10-21-2003, 11:19 AM
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Re: Mechanical or electric fuel pump?

Leve, you're probably right about the fear of the unknown and electrical stuff, at least in many cases. In my case however, I fully understand the electricals of a fuel pump but still prefer mechanical. Could be that I'm turning into an old fart.

When I think of the components that could cause a failure - a switch, should be at least two, a fuse, several connectors and several feet of wire under the Jeep in the mud and slop, electrical ground, plus the pump (brushes, armature, bearings and the pump itself) - I just feel more comfortable with a mechanical.

The Lucas pumps on the sports cars I mentioned don't whine, they're clickers. They're just like a mechanical pump except that they use a solenoid instead of an eccentric to compress a spring, which pushes on a diaphragm which moves the gas. When the spring is relaxed it closes a set of points which activates the solenoid again. It's about as simple as it can get.

I never took one apart to see why the points would occasionally not complete the circuit, because one never failed hard, but I suspect that it was that the spring sometimes would get stuck. As I recall they would usually fail when the car was parked, so I think that bumping down the road kept them running.
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post #10 of (permalink) Old 10-21-2003, 07:51 PM
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Re: Mechanical or electric fuel pump?

My Lucas failed by the points welding together. I could turn the key on and off and hear the pump make one cycle each time. On the MGA, the pump and batteries (yes plural) are behind the seats. I disconnected the pump put a piece of wire on it and touched it to the battery negative (yep, pos. ground). Started it up and drove away. Each time the engine started to sputter, I'd just touch the wire to the battery a few more times. It got me to somewhere I could get a new pump and back home. Those pumps were about as simple as you can get.

The MGA had no starter solenoid either. There was a knob on the dash attached by a cable to a big heavy duty switch in the engine compartment. Pull the knob to start.
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