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Re: Electric fuel pump push fuel through a mechanical pump
[Re: RUNCHARGER]
#1769598
03/04/15 06:50 AM
03/04/15 06:50 AM
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Joined: Jan 2005
Posts: 3,699
Newport, Mi
Evil Spirit
master
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master
Joined: Jan 2005
Posts: 3,699
Newport, Mi
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If the engine just will not start unless the bowls are hand primed, that's one thing - I would certainly fix that issue. But I never understand why people want a stone cold engine that has sat even overnight to start instantly in the first couple rotations. Pretty good chance that all the oil has drained back into the pan, possibly draining the oil passages and the oil filter. There is also the possibility of lifters bleeding down. If they have sat overnight, I rarely attempt to fire any performance engine until I've cranked it and seen oil pressure. IMO an engine that needs to crank 10 seconds or so on that first startup after sitting any length of time is actually doing itself a favor and priming the oil system before it starts, and eliminating any possible dry startup damage. Many hydraulic cammed engines will sound totally different on startup if you "pre-lube" them first, since it gives the lifters on open lobes that have bled down a little a chance to pump up fully and "tighten" the valve train up. Just a little food for thought about starting that engine that has sat for a while - do you REALLY want it to start first roll? 
Free advice and worth every penny...
Factory trained Slinky rewinder.........
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Re: Electric fuel pump push fuel through a mechanical pump
[Re: RUNCHARGER]
#1769603
03/04/15 10:24 PM
03/04/15 10:24 PM
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Joined: Jan 2007
Posts: 7,664
IN
ahy
master
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master
Joined: Jan 2007
Posts: 7,664
IN
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Quote:
My plan is to loop off at the sending unit, build a bracket that bolts to the tie down attachments (E body) that mounts a 110 GPH electric pump and use the stock 3/8 fuel line up to the HP mechanical pump. All the repro stainless steel fuel lines will be uncut and if I have to run the electric pump all the time that's what I'll do but it sounds like I'll be able to just use it for a cold start and maybe when using WOT in 3rd and 4th. I'll let everyone know after I test it. I'll tie strap a fuel pressure gauge to the cowl when I first install the extra pump.
Sheldon
In general the electric pump will not flow fuel when turned off. The mechanical pump will not be able to "suck" through it. An electric pump bypass line with check valve is needed to allow the engine to operate with electric pump off. I used a brass check valve from the hardware store on my truck... more compact automotive type valves are available from Summit and others.
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Re: Electric fuel pump push fuel through a mechanical pump
[Re: Dr Dave]
#1769606
03/04/15 11:36 PM
03/04/15 11:36 PM
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Joined: Mar 2008
Posts: 1,913
central P.A.
HEMIDOG 70
top fuel
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top fuel
Joined: Mar 2008
Posts: 1,913
central P.A.
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Quote:
Please let me know what you come up with. I have a similar setup, 528", dual quads, shaker, not easy to prime the carbs and want to do something with an electric pump.
X2 no shaker here but I too would like to add a electric pump to prime for starts due to evaporation. I'm running a 528 hemi with dual quads and solid lift cam. I have extended crank times after the car has sat for longer periods.
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Re: Electric fuel pump push fuel through a mechanical pump
[Re: gdonovan]
#1769616
03/06/15 07:19 PM
03/06/15 07:19 PM
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Joined: Jan 2003
Posts: 25,755
Rio Linda, CA
John_Kunkel
Too Many Posts
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Too Many Posts
Joined: Jan 2003
Posts: 25,755
Rio Linda, CA
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Quote:
Quote:
Quote:
Sorry to disagree, but the mech pump WILL pull through an elec pump. I have a Holley pump mounted by the tank that only runs when switched on.
As I stated earlier, not true on some pumps...Carters in particular.
I have a Carter pump, no problem.
You must have a vane-type pump, Carter gear rotor pumps are different:
"IMPORTANT NOTE:
When using a gear rotor type pump....
These pumps cannot be used as a secondary unit ie, on a dash switch. They MUST be wired to run continuously from the IGN circuit as your PRIMARY and ONLY PUMP.
This pump type uses a DRIVEN gear and a RING gear to create a positive displacement and force fuel through to the carb. The gearing is similar to your oil pump. They do NOT have any check valves like a mechanical fuel pump, thus if they aren't running, you cannot DRAW fuel through them via a mechanical pump, etc ( at least, enough to have the engine remain running)."
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