Lotus Elan

Fuel priming device for mechanical pump

PostPost by: Emma-Knight » Thu Aug 07, 2008 6:34 pm

I just read in some 356 network they do have the same cranking up fuel issue as many of us have. One found a simple cheap device:

a ballon pump as used for small boat motors - for less than $ 15 :shock:
Could be fitted between tank outlet and boot fuel line. They reported no fuel starvation up to tested 100 miles an hour - and no silli cranking battery flat and starter sick.
I will try within the next weeks and report!

Some also used a small electric fuel pump in line. Just for priming, then switched off and went on with the original mechanical pump, fuel beeing sucked through the electric pump. Again no problem.

Anna
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PostPost by: neilsjuke » Fri Aug 08, 2008 1:11 pm

A few seconds of cranking lets the oil get up to the cams if the pump and fuel lines are in good nick that all it should take .
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PostPost by: garyeanderson » Fri Aug 08, 2008 1:16 pm

A can of starting fluid is a couple dollars, if this is only a problem with its sitting for a week or more I would give it shot of starting fluid to get it running and let the fuel pump prime the carbs. But thats just me. I went with the electric fuel pump in the 1700 cc twin cam as it runs with a shortened jackshaft and the option of running a mechanical fuel pump has been eliminated.

Gary
Last edited by garyeanderson on Sat Aug 09, 2008 2:18 pm, edited 1 time in total.
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PostPost by: freddy22112211 » Fri Aug 08, 2008 7:34 pm

As a trial I have blocked the Dellorto air 'ports' on the top of the carbs several times with some very thin pieces of a particular sort of foam, backed up with some very thin spring metal, when I park the car. I believe this makes quite a difference when not using the car for a week or two. Over several months however I couldn't notice any difference, and presume the fuel still manages to evaporate over longer periods. And perhaps the fuel line empties somehow as well.
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PostPost by: Foxie » Fri Aug 08, 2008 10:41 pm

Why not just convert to an electric pump ?

Fit it in the boot, no more cranking problems, easy to troubleshoot, and swop it in 5 minutes if it fails.

A failing mechanical pump can fool you for quite a long time; I know, I was that soldier ! :cry:

I fiited a Facet many years ago, it's been another "Fit and Forget"

I bought two back then, but the original is still ticking away. :D

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PostPost by: hatman » Sat Aug 09, 2008 9:44 am

As neilsjuke already pointed out, the prolonged cranking needed to prime a mechanical pump also has the very worthwhile benefit of pumping oil up through the engine prior to it firing up. If it's been standing idle long enough for the carbs to empty through evaporation, it's certainly been standing long enough for all oil to have drained from the top end, leaving dry metal-to-metal contact for a few seconds after starting :shock:

Winter time cold-cranking is eased and the load on the battery, starter motor etc lessened by initially operating the starter motor with the throttle wide open, waiting till there's a first sign of ignition then taking your foot off the accelerator pedal, giving it two or three pumps, then operating the starter with the throttle closed. Leastways, that's what I do. :D
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PostPost by: Foxie » Sat Aug 09, 2008 10:57 am

I agree with Hatman that getting the oil pressure up before the engine fires is a beneficial effect of slow starting.

However, doesn't using full throttle when starting allow complete filling of the cylinders, and maximise starting load rather than reducing it ? :)

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PostPost by: garyeanderson » Sat Aug 09, 2008 11:35 am

hatman wrote:As neilsjuke already pointed out, the prolonged cranking needed to prime a mechanical pump also has the very worthwhile benefit of pumping oil up through the engine prior to it firing up. If it's been standing idle long enough for the carbs to empty through evaporation, it's certainly been standing long enough for all oil to have drained from the top end, leaving dry metal-to-metal contact for a few seconds after starting :shock:

Winter time cold-cranking is eased and the load on the battery, starter motor etc lessened by initially operating the starter motor with the throttle wide open, waiting till there's a first sign of ignition then taking your foot off the accelerator pedal, giving it two or three pumps, then operating the starter with the throttle closed. Leastways, that's what I do. :D


I don't agree with your assumptions, Cranking an engine with out fuel adds little other than wear and tear on that poor old design of a starter the Joseph Lucas made million?s of. If you pulled the spark plugs and performed this its not quite as bad but still not of much value. With a running engine, oil pressure comes up in a second or less, if not there are other issues present. When you hear the commercials that 50% of all wear happens in the first 15 seconds, that happens regardless of whether it running or cranking on the starter. That is unless you have some form of pre-pressurized oil system. A couple of my friends use to say that the twin cam would need a valve job and water pump at 40k miles and not necessarily because the water pump was bad but because you were 90% of the way of doing the job. At 80k miles repeat this again with the bottom end looked after, first crank grind, and maybe first overbore. At 120K repeat valve job and water pump, at 160k miles top and bottom repeat. Ed Loveday drove his Elan quarter million miles before he died not long ago, the car is being restored by a new owner and will start its second life soon.
Starters were never designed for continuos cranking, 10 or 15 seconds is more than likely the safe cranking time. You don't have to believe a word I write or do any of it. I used to have the biggest battery I could buy positioned in-between the rear strut towers and it was still a crapshoot whether it would start or not when it was sub-freezing. I finally learned. An Electric fuel pump, regulator, and most important an accident cut out switch will do the job. Maybe even that Joseph P. Lucas starter will get the job done. But the Japanese derived nippen-denso starters is just the thing that works great. The battery draw is minimal that a battery that is half of the weight will start when the stock setup won't. If you consider starting fluid ?cheating? then I?ll be gone while you are still trying to get fuel in the float bowls. Elan in neutral, Key on, bonnet up, pull the trunk tubing back give it a small sprits of starting fluid and hit the manual button on the solenoid. Another sprits or two to keep it running, when its running on fuel your off. With an Elan that is used every day you can probably get away without any of the above (except the 40k, 80k, top end, bottom end dance).

Gary
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PostPost by: freddy22112211 » Sat Aug 09, 2008 11:40 am

Just to be a bit ornery/split hairs, I think: "... it's certainly been standing long enough for all oil to have drained from the top end, leaving dry metal-to-metal contact for a few seconds after starting" is not quite right. Firstly modern oils coat everything with a very good film, even if most of the oil has drained off, and secondly there are plenty of pools of oil left in the head - the cams, for example, immediately hit oil on the first turn. Still I guess there may be a spot somewhere or other that gains from 'churning'.
Gordon
By the way - I like the colour Anna - light blue (non standard?) I guess.
And also - you can go way more than 40K miles on modern oils before any work is needed.
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PostPost by: ppnelan » Sat Aug 09, 2008 1:35 pm

Use it almost every day
And the fuel won't get to drain away...

When it's cold in the wintertime
Use the choke & s/he'll start just fine...

:lol: Matthew
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PostPost by: stuartgb100 » Sat Aug 09, 2008 4:13 pm

Matthew,

I reckon "Norfolk" cold would be like springtime in Florida to Gary !

BTW, just returned from an uneventful 400 mile trip to collect the +2 chassis (on the roof).

Just got to figure out how to free all the knots (was wet all the way, and wet knots are a begger), then offload and dry it out.

Regards,
Stuart.
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PostPost by: bcmc33 » Sat Aug 09, 2008 6:30 pm

I seem to remember Anna's car being a very nice pale blue over white - much better than this photo.

Or is it just another senior moment?
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PostPost by: Emma-Knight » Mon Aug 11, 2008 5:28 pm

it's Ice Blue metallic over Cirrus White. I was thinking of using it more or less as my daily car from april to october. So maybe I should go the electrical fuel pump (or electrical priming?) way :roll: . I would agree to what Gary says - getting up oil pressure as fast as possible.

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PostPost by: bcmc33 » Mon Aug 11, 2008 7:58 pm

I fitted a Facet 2.5/3.0 psi pump to feed the mechanical pump which has eliminated the cranking prime time, and she sure does start quicker. I intend to remove the mechanical pump at some convenient time.

I can?t believe the point that long cranking primes the oil as being a major benefit ? I?ve viewed my car to see that the oil gauge shows 45 psi from 2 seconds on the starter. To my mind it?s of no issue if a car is used reasonably regularly with modern oils.
If an engine is not started for some considerable time ? then long cranking may be of some benefit.
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PostPost by: denicholls2 » Mon Aug 11, 2008 10:20 pm

Lots of old salts seem to favor doing stuff like disconnecting the main coil lead on startup until oil pressure comes up, as though this is a magic panacea for engine wear elimination. Logic says the opposite, but canards die hard. Against:

- Modern oil film strength, probably good for sitting a year
- Higher RPM of the fast start building guts-saving pressure faster
- Ease of use

... We have, at best, some notion that bearing surfaces undergo measurably less stress when the engine is cranking than when it is running. Anybody got some real data to suggest this might possibly be true? I'm pretty dubious.

The place this is most likely to be true is on the crank throws, where the pounding of a firing cylinder imparts a shear load that isn't present when the engine is coasting under starter power. But how many of you, regardless of starting method, find that the reason you need to tear down your engines is low oil pressure indicating bottom end issues? :?

Sound of chirping crickets expected...
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