Hard To Start

[MAX]

After my 73 240Z sits for more than a couple days it is hard to start. I wonder if I'm having a problem similar to that as posted by Mark Dixon where the mechanical fuel pump takes a while to prime the fuel lines.

HD240Z...you indicated that you corrected your problem by adding an electric fuel pump. Could you advise me as to the type and manufacturer of your electric fuel pump. My car used to have the OEM type electric pump added by the dealer to fix the 73's fuel problems but it had long since died and I didn't add one back after doing my restoration. And now I see that the OEM pumps are way expensive....

By the Way .....I'm also running duel Weber DGV carbs.

Would a simple one way valve do the trick instead of adding an electric fuel pump as mentioned by HLS30.com in the same post by Mark Dixon?

Thanks Guys....

[hd240z]

My electric fuel pump is an Airtex similar to this one, but probably higher quality as it cost more 20 years ago. Be sure to get one that is low pressure (2 to 5 psi) and high flow. Mine is a little noisy, but I find that useful for priming the fuel system prior to start up, the sound changes slightly as the fuel pressure comes up in the system. I mounted mine with a rubber isolator and once the engine is running you can't hear the pump.

You should also install some sort of pump safety shutoff, like a Ford inertia switch to reduce fire potential if you have a crash.

I question that adding a one way valve in the fuel line would help the hard starting problem. I don't think fuel can flow backwards through the mechanical pump anyway, so you already have this feature. I suspect the fuel is evaporating and/or leaking from the carbs when they set for several days or weeks.

[MAX]

HD 240Z:

Thanks for the info. Did you mount the electric fuel pump back near the gas tank where the OEM unit was originally mounted?

And did you remove the mechanical fuel pump or do you use them together?

[hd240z]

Yes, my electric pump is mounted next to the gas tank.

I have run my fuel pumps several different ways. When I first got the car it had just the stock mechanical pump which worked good except when I got into some mountain driving in Colorado. It seemed to be having problems delivering enough fuel, so I installed the electric pump and removed the mechanical which I felt was starting to fail.

When I ran it with the electric pump only I was getting about 2 psi of fuel pressure at the rear carb. It ran ok up to about 5,000 rpm then you could feel the power drop off most likely because it was running lean (duh).

I now run both pumps and I have 4 psi throughout the rpm range which makes the engine feel much stronger on the high end.

Initially I was concerned about having too much pressure with the two pumps in series, but the mechanical pump seems to regulate the pressure very well.

As a side note, the way I monitored the fuel pressure was by teeing into the rear carb hose and running another short hose section with the gage out from under the rear of the hood and temporarily securing the gage to the cowl grille with plastic ties. The gage was oriented so I could read it through the windshield. If you do this sort of thing, even temporarily, be very careful to use the proper size and type of hose to prevent leaks or the hoses blowing off the fittings. Watching your car burn up by the side of a road is no fun especially if you are inside.

[MAX]

Thanks for the input hd240Z.

Since I'm running dual Weber DGV carbs I did some checking around for Weber carb technical information and ran across the following web site:

www.webercarbs.com

They recommended using a Carter 4070 Electric fuel pump.

thanks again....

[beandip]

I have been running a RX-7 pump for several years. It is quiet and pumps right at 5 psi. $15.00 at the bone yard . We tried it on a stroker engine running triple Mikuni and it supplied it great with no problem . I don't know what they are new . I added a oil pressure switch that cuts the power to the pump when the oil pressure drops below 5 psi. I am running SUs and I have not had any trouble starting even after the car has set for weeks . Inertia switch is a vary good addition as well. My friend had a electric pump fail and shorted . As soon as the oil pressure dropped the power was cut and saved the wiring and the possibility of a fire. The in line fuse and holder malfunctioned and didn't blow the fuse , which resulted in the melting of the holder. I am not running a mechanical pump. I also have '73 but with a ZX engine . Gary:knockedou

[beandip]

I have been running a RX-7 pump for several years.

[MAX]

Thanks for the input beandip. The cutoff switches are very good suggestions.....

[Go240Zags]

I have been running a RX-7 pump for several years.

Gary, Do you have a part number for the RX-7 pump, which years this pump came on? Gary D

[beandip]

I don't have a part number but mine came off a '79 or 80 . It just needs to be from a carburated RX- 7 . You will need to make a simple mount . I used a length of 1/8'' X 1'' steel strap . I bought it a Home Depot and I used a couple of rubber grommets to insulate the pump from the metal to eliminate any sound . I can take a picture and send it to you if you want. Send me a PM with your email address . Gary