Electric Fuel Pump Placement

Discussion in 'Workshop Forum' started by dcioccarelli, Apr 10, 2018.

  1. Hi all,

    when I replaced my mechanical fuel pump with an electric one, I followed the recommendation to mount it as low as possible (in a similar location to the FI fuel pump) so that it didn't need to fight gravity too much (i.e. as opposed to mounting it in the classic location of the carb blower fan bracket).

    Last night I realised the downside of this approach. I came back to the car to be greeted by a strong smell of petrol and a pool of petrol under the car. The fuel line that was exiting the pump had perished and broken at the clamp (even though it was only 2 years old!). The fuel was then wicking along the outside (cloth) sheath and syphoning the petrol out of the tank (as the pump was low down). So now I'm not so convinced about the advantages of this mounting location for a carburettor application. I'll be installing an electrically operated check valve very high up to prevent any future occurrence but this is adding an additional component and additional complexity. I may have been wiser just mounting the pump high up like most people do.

    Anyway, just an observation for anyone with a similar setup.

    Cheers,
    Dom.

    BTW: The issue of a broken fuel line draining petrol in a stationary car is obviously also pertinent to all FI applications as well, due to the location of the pump.
     
  2. Fiataccompli

    Fiataccompli Chris Granju

    Location:
    Knoxville, TN
    In my experience, the failure, the sudden pool of fuel, and the hassle is a risk in all our cars. Obviously, rigorous preventative maintenance will avoid this, but if you are like me & have a lot of cars & a busy life, sometimes we miss.

    I recently replaced a high mounted box pump with a low mounted Carter pump on my 79 X.
     
  3. carl

    carl True Classic

    Location:
    Virginia
    Most of us mount the cube pumps on the mounting base located just below the gas tank sending unit plate with absolutely no problems. Your experience is enough to convince me not to mount the pump low.
     
  4. Dr.Jeff

    Dr.Jeff True Classic

    Location:
    Sin City
    Any electric pump should be able to draw the fuel up. After all the pick up tube on my carbed '79 goes from the bottom of the tank up to the top of it where the level sender enters. That's about as far up as any pump mounting location. Another inch or two higher won't make a difference.
     
  5. Fiataccompli

    Fiataccompli Chris Granju

    Location:
    Knoxville, TN
    I don't doubt that much, except for absolutely optimized setups.

    I have had some cubes fail when mounted relatively high (or high & forward in the engine bay on 124s) fail...I don't know if it was the product of the cheap pump or the placement.
     
  6. Dr.Jeff

    Dr.Jeff True Classic

    Location:
    Sin City
    Chris made me think of another factor. The X's run from fuel pick-up to carb is very short, so there is little resistance for the pump to work against. Especially when compared to a front engine, rear tank vehicle like the 124. All the more reason why the placement on the X shouldn't make that much difference.
     
  7. kmead

    kmead True Classic

    Location:
    Michigan
    A bad hose will behave the same way regardless as the siphon will work in all cases if there is a slight downward cant of the hose from the tank to the pump.
     
    Dr.Jeff likes this.
  8. Daniel Forest

    Daniel Forest True Classic

    Location:
    Montreal,Canada
    Dominic,

    I'm following your initial thinking. I mounted my electric fuel pump in the carb air pump position in the past. I went thru 3 different pumps in a year. A Facet cube, a Carter and a Holley. Next one will be down low. I also read article about why it should be mounted low.

    But it was maybe something else I didn't do well:oops:
     
  9. LarryC

    LarryC LarryC-Albuquerque

    I have used one each of both Facet and rotary pumps mounted high and at the top of the engine compartment. Decades. No problem. The whole "fuel pump needs to mounted low or at X or at Y" is a speculation with no facts behind it as far as my results have shown. Mount it where you want it.
     
  10. Thanks to everyone for all the comments!

    I'd agree that the placement of the pump probably has little impact on the performance or longevity. That said, from a purely theoretical perspective, the "low mounted" position will obviously have the advantage of atmospheric pressure even with a nearly empty tank. This advantage is reduced as the pump is mounted higher. Obviously, this added advantage should be minimal compared to the suction produced by the pump itself.

    As for Karl's comment:
    This is certainly correct, although note that the amount of fuel that will be siphoned out will vary depending on the lowest point before the first resistance in the line: which could be the pump (depending on the design), or the carburettor. The siphon won't be able to draw any fuel that is lower in the tank than this point. In my case, that point will now be this device mounted up high:

    [​IMG]
     
  11. carl

    carl True Classic

    Location:
    Virginia
    I think this is a classic case of science says on thing (and the Facet pump instructions) but reality says we can install the pump in the "wrong" place and it works fine. The reason we all install the pump up high is because Fiat handed up a really nice bracket to mount it!
     
    kmead likes this.
  12. Dr.Jeff

    Dr.Jeff True Classic

    Location:
    Sin City
    Dom, you'll be fine either way. Follow your plan.

    That is an interesting shut-off valve. Please tell us more about it.
    I will make one comment that sometimes adding more components to a system creates more complication than benefit. But I'm certainly not saying you should not use it; after your experience with a leak I understand the desire for added safety.

    On a side note, have such fuel leaks been frequent occurrences for others? I ask because I had not considered this before. But maybe I should (guess I've been lucky to never had a single leak after 45 years of building cars). I recall there were frequent engine fires on the old air-cooled VW's due to the fuel line crossing over the hot engine. They used fabric covered hose and the rubber inside would dry out and start leaking, soaking the fabric cover until it finally caught fire.
     
  13. carl

    carl True Classic

    Location:
    Virginia
    If you have the original fuel line hoses or don't know how old yours are, you should replace them. I got a 124 coupe whose fuel lines had the consistency of balsa wood. Pin holes in old lines are fun to watch as they shoot tiny streams of gas all over the engine bay.
     
    kmead likes this.
  14. Dr.Jeff

    Dr.Jeff True Classic

    Location:
    Sin City
    I guess that's where my OCD, ADD, ADHD tendencies have a benefit. Before even attempting to start a newly acquired old car I service the complete fuel system; clean out the tank, flush the hard lines, replace all soft lines, replace/add filters, clean the carb/injectors, etc. So there aren't any old components remaining to cause such events. But I also do similar services to the ignition and oil systems, so its more a part of my personality disorders than necessity.
     
  15. Fiataccompli

    Fiataccompli Chris Granju

    Location:
    Knoxville, TN
    I have been guilty of having some "look okay " lines that have been too old in cars. Usually that has materialized in the form of an easy to detect & repair connection at the carb or the fun sudden failure of the filler neck hose when parked. These days I also replace lines and also routinely check for leaks.

    I had a mechanical fuel pump fail on a 124 when parked & it dumped a lot of fuel.

    If the connections are sound and there are no cracks in lines, I can't think that elevation makes a difference. This is an interesting nod at where the theory we learn and practical reality/experience meet. Guess I am still learning that stuff.
     
    Dr.Jeff likes this.
  16. Hi Dr. Jeff,

    I agree that I'm adding extra complexity and would probably be better off simply relocating the pump. I'm just stubborn!

    The electro-valve is actually an Italian made unit (purely coincidental) from a company called Tomasetto. It is intended for LPG installations in carburettor cars to cut the fuel supply when the car is running on LPG. These conversions are surprisingly common in eastern Europe (I even drove an LPG powered X1/9 in Poland!).

    In terms of fuel leaks, my only experiences up until now have been:
    • The fuel inlet barbs separating from the carb body on 2 X1/9s (a 32 DATR and a 34 DMTR). This is a known issue and is rectified by using screw in barbs.
    • The fuel line betwen the tank and pump becoming punctured in my FI X1/9 after having it transported. This is because the line is so low where it enters the fuel pump and I'd neglected to replace the plastic cover that is supposed to protect it :oops:
    • This latest incident.
    The fuel lines that I'm using are the fabric covered ones that you refer to, specifically these:

    https://www.ebay.de/itm/201661822333

    I bought them in 2014, so to have them perish and break within 4 years doesn't attest to their quality. I went for the fabric covered ones for "originality" although I may need to revisit the wisdom of that choice as well :(

    Dom.
     
  17. MikeHynes

    MikeHynes True Classic

    Location:
    Goodfield, IL.
    I've experienced the same. The SCCA requires that all Weber carbs receive this simple mod.
     
  18. Dr.Jeff

    Dr.Jeff True Classic

    Location:
    Sin City
    Dom, interesting solenoid valve. It seems LPG conversions are popular in may parts of the world (outside the US). I guess it comes down to the cost of petrol vs LPG.

    I agree with you and Mike, Weber carbs are prone to the nipples coming loose. Typically it happens when I'm removing a stubborn hose and have to work at it. Using screw-in barbs is an excellent idea.

    I'm really surprised the new'ish hose failed so quickly. Honestly I don't think that it being fabric covered has anything to do with it. Much more likely some sort of defect in the rubber. I know there is a lot of talk in the US about fuels and rubber hoses deteriorating, mostly referring to chemical additives and ethanol. Not sure if there might be some similar issue with the fuels there? But I know the quality of many automotive products has significantly degraded in recent years. Most of the major manufacturers have gone global with their production facilities and quality has suffered as a result. Even lots of the famous big-name companies with very long-standing, highly-regarded reputations are now providing extremely inferior products (but at the same high prices...likely in the name of profits). In some cases it is a crap-shoot what you will get in the 'branded' box. Unfortunately many countries have laws that allow manufacturers to sell products labeled as made in their home country when in fact they were made elsewhere (interesting stories behind how that works). But the point is it is difficult to say "buy brand 'X' and you won't have any problems", because it may no longer be true.
    One option might be to use teflon (PTFE) lined hose? I'm referring to the stuff that usually has a stainless braided cover and used in high pressure systems (e.g. brake lines). It requires different fittings to go with it, but eliminating the rubber core might avoid fuel issues? I've not tried it, but I've seen it marketed at recent SEMA shows as hose specifically designed for ethanol fuel.
     

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