hard cold starting in '72 Z

[vtdds71]

(same post on ZCar.com - trying to cover more bases!)

 

My '72 Z is finally back on the road again, and is actually running quite well. But, the engine is slow to fire up when cold, even with full choke engaged. Takes several seconds of cranking, then coughs to life, then immediately runs quite well on choke until reasonably warm. It will re-start instantly when warm, and when the car has not sat overnight. My sense is that the fuel lines are draining to empty after an extended shut-down, and the fuel pump (stock mechanical only) has to start from scratch to pump fuel from the tank to the carbs. Is there some type of one-way check valve in the system that is supposed to prevent this? Is the fuel pump malfunctioning? The engine has been "de-smogged". Carbs have been cleaned and rebuilt and show no sign of leaking, the gas tank was cleaned and re-lined, new fuel lines and in-line filter were installed, etc. Mechanical fuel pump may be original, but it does seem to pump plenty of fuel when tested.

 

On a related subject, I did buy a Holley electric fuel pump from MSA some time ago, but have never installed it. Is this a good add-on for the early Z's? Is it better to use it in conjunction with the mechanical pump, or as the sole fuel pump in the car? Where is it best installed, and can anyone clearly describe the best way to wire it in (relays, etc.)? Thanks.

[Tony D]

My car will boil out the carbs from underhood heat---well this is as much a function of heat as the gas formulations available today...when I'm running ERC or VP Racing gas, this doesn't seem to be as much of an issue. Anyway, it takes some cranking to get the bowls refilled to a level where they will fire the car even with the starter system engaged.

To alleviate this, especially in situations where my car has been parked at the airport for a couple of months and the battery is nearly dead, I installed a small Facet Solid State fuel pump in line between the hardline and the mechanical pump.

When I return, I simply connect the fuel pump to pre-fill the bowls. it has saved me 2X this year on a nearly flat battery allowing me to instantly fire a very slowly cranking engine and get the battery recharging.

 

I don't have it on a switch or anything, I'm usually under the hood to replace the coil wire and rotor that gets pulled and placed somewhere else in the car while it's parked... Not that I'm paranoid or anything.

 

If you hooked up a small toggle switch, you could fire it off and listen for it's pitch to change, signalling the float bowls are full and you are ready to start.

[vtdds71]

Interesting idea. Still need to verify that the float bowls are actually emptying out after an overnight sit in the garage. One responder suggested the flex lines from float bowls to jets might be leaking, or the wrong type. If they are too stiff they could prevent the choke lever from fully dropping the jets during starting, or they could be slowly leaking away the gas in the bowls. I used the tubes that came in the MSA rebuild kits (made by Royce, I believe), so thought they were OK.

 

I mentioned having bought the Holley electric fuel pump from MSA. Since their policy seems to be "no returns on electrical items", I may be stuck with it even though I didn't plan to install it after all. Would this pump do the same thing yours is doing? Granted, it's a "pusher" pump and is supposed to be installed back by the gas tank, not up in the engine compartment. Have you heard of much success using this pump?

 

I am not familiar with the pump you suggested. Any idea where to find one?

[Tony D]

Google it, Summit Racing, Autozone, PepBoys, Kragen, Checker, O'Rilley, Napa....they all sell the Facet Replacement Pumps. Little solid state affairs that go 'tick tick tick tick' Only good for 3-5 psi usually. Self regulating. I think the first generation Mazda RX7's even had them...

 

That Holley, is BIG, and NOISY. The one I'm talking about would likely fit in the palm of your hand and not extend over the edges. I can close my fist around mine and almost conceal it.

 

I have a bunch of them laying around, they work great for pumping fuel out of old tanks, transferring fuel, etc... Self priming. THey work as well up front in this duty as out back as a total pusher. Depends on what you want to do with it. Mine is just there to refill the bowls after it's been sitting and it is easy to get to where I did it, so no switch or anything.

 

If your bottom tubes are really flexible, they are the right ones. You don't want THICK walled hose, they should look almost like aquarium vinyl tubing and be as flexible. And some have a prebend in them. You don't want conventional stuff on there as it's too stiff and it will side-load the jet and can wear it out, or make the needle touch and wear a groove in it if you are using the starter system reularly.

 

Me? I'm helping with an SU EFI replacement...screw all that carburettor business! LOL