Long Cranking, 1977 280Z

[503Alex]

I'm currently having a long cranking issue with my 1977 280Z. On a cold start I have to try to start it 5 or 6 times sometimes before it starts. Sometimes it starts for a second (goes to about 500 rpm) and then dies. I have replaced the spark plugs (properly gapped), rotor, fuel filter (twice in 700 miles), distributor cover, plug wires (NGK), and properly set the air gap. The weird part is sometimes when I started it again just a couple hours after driving it, it starts immediately. My timing needs to be adjusted somewhat though. Any advice for me getting it to start up more consistently?

Thanks in advance,

Alex

Edited October 15, 2010 by 503Alex

[FastWoman]

I'd almost be willing to bet money that your fuel is leaking out of your fuel rail. It might be draining back into the tank because your fuel pump check valve is bad. Or it might be dribbling out into the intake manifold through leaky/dribbly injectors. (Don't forget the cold start injector!) Anyway, the end result is approximately the same. You end up with a lot of air that has to be purged from the fuel rail when you start the engine. If your engine is like mine was, it runs very roughly when you finally start it, and then it evens out after 10 sec or so (at least if you don't rev the engine). Right?

Possible cures: Check/replace your check valve. Those are becoming NLA; however, you can get an aftermarket check valve to insert inline in your fuel line. Also check/replace your injectors. If all else fails, you can install a priming switch somewhere that will run your fuel pump for several seconds before you start the engine.

[Pomorza]

I'm currently having a long cranking issue with my 1977 280Z. On a cold start I have to try to start it 5 or 6 times sometimes before it starts. Sometimes it starts for a second (goes to about 500 rpm) and then dies. I have replaced the spark plugs (properly gapped), rotor, fuel filter (twice in 700 miles), distributor cover, plug wires (NGK), and properly set the air gap. The weird part is sometimes when I started it again just a couple hours after driving it, it starts immediately. My timing needs to be adjusted somewhat though. Any advice for me getting it to start up more consistently?

Thanks in advance,

Alex

I'm going to agree with fastwoman here. You have fuel leaking out of something or back into your tank. I installed a fuel pressure gauge after it started doing this as I suspected I was loosing pressure. Long and behold, when I turn the car off for a long period of time the pressure drops to ~0.

I would first check the injectors, and cold start valve. For what I remember the check valve in 280z's is in the actual pump (of course) which means a new pump may be the way to go if that's what it turns out to be.

Jan

[503Alex]

I'd almost be willing to bet money that your fuel is leaking out of your fuel rail. It might be draining back into the tank because your fuel pump check valve is bad. Or it might be dribbling out into the intake manifold through leaky/dribbly injectors. (Don't forget the cold start injector!) Anyway, the end result is approximately the same. You end up with a lot of air that has to be purged from the fuel rail when you start the engine. If your engine is like mine was, it runs very roughly when you finally start it, and then it evens out after 10 sec or so (at least if you don't rev the engine). Right?

Possible cures: Check/replace your check valve. Those are becoming NLA; however, you can get an aftermarket check valve to insert inline in your fuel line. Also check/replace your injectors. If all else fails, you can install a priming switch somewhere that will run your fuel pump for several seconds before you start the engine.

Thanks for the advice! That's what mine is doing too, it is rough initially. I will check these things out.

I'm going to agree with fastwoman here. You have fuel leaking out of something or back into your tank. I installed a fuel pressure gauge after it started doing this as I suspected I was loosing pressure. Long and behold, when I turn the car off for a long period of time the pressure drops to ~0.

I would first check the injectors, and cold start valve. For what I remember the check valve in 280z's is in the actual pump (of course) which means a new pump may be the way to go if that's what it turns out to be.

Jan

I'd like to install a pressure gauge too at some point. Thanks for the info!

[FastWoman]

Jan, Alex, the fuel pump check valve unscrews from the body of the fuel pump. The check valve is actually inside the fuel outlet nipple. If you can't find a replacement, just leave the leaky valve where it is, and install something like this in the fuel line:

http://cgi.ebay.com/ebaymotors/5-16-Check-Valve-Diesel-Gas-8mm-One-Way-Fuel-Flow-_W0QQcmdZViewItemQQhashZitem3cb0e0fc82QQitemZ260665572482QQptZMotorsQ5fCarQ5fTruckQ5fPartsQ5fAccessories

I suppose you could also pull the nipple/check valve and remove all of the valve stuff from the inside. That should be easy enough. It might reduce the back pressure on the pump a bit.

[503Alex]

Jan, Alex, the fuel pump check valve unscrews from the body of the fuel pump. The check valve is actually inside the fuel outlet nipple. If you can't find a replacement, just leave the leaky valve where it is, and install something like this in the fuel line:

http://cgi.ebay.com/ebaymotors/5-16-Check-Valve-Diesel-Gas-8mm-One-Way-Fuel-Flow-_W0QQcmdZViewItemQQhashZitem3cb0e0fc82QQitemZ260665572482QQptZMotorsQ5fCarQ5fTruckQ5fPartsQ5fAccessories

I suppose you could also pull the nipple/check valve and remove all of the valve stuff from the inside. That should be easy enough. It might reduce the back pressure on the pump a bit.

Good stuff, I'll check that out. Thanks.