Hard to start when cold

[dltalfa]

Here's my problem: My stock 1972 240z runs great. It has plenty of power, idles very smooth, takes the gas well and overall performs great.

However, if it sits for a couple of days, it is very hard to start. The choke works fine, it has a recent tune-up and everything seems to be working well.

But after a couple of days sitting, it has to crank and crank for a long time before it will start, (several seconds, maybe a minute). It seems almost like it's not getting gas. Once it starts, it runs perfectly.

As soon as it runs long enugh to let the chock off,...you can turn it off and it fires up on first turn for the rest of the day.

Any ideas?

[dltalfa]

I had read somewhere that the early Z's car's had two fuel pumps,...one mechanical in the engine bay and a second electrical one located near the fuel tank in the rear.

My car does not seem to have the electrical pump in the rear. Could this be the problem?

[lady24d]

The mechanical pump will take a little cranking to get your fuel lines and the fuel bowels filled after being parked for a while the eclectic pump was added to help against vapor lock. But should help this problem since it pumps right away vs having to crank the motor over and over to get fuel up to the carbs

[olzed]

Not too difficult to wire up an electric pump just in front of the tank.

[Captain Obvious]

after a couple of days sitting, it has to crank and crank for a long time before it will start, (several seconds, maybe a minute).

Before you get all wrapped up in fuel pumps trying to fix this issue, I will point out that it should not be that difficult to start the car after sitting for just a few days.

I can let my 260Z sit for two weeks and it will start within the first ten seconds. Later that same day once the engine has been "freshly started", it will fire off within the first two seconds, so I do see a reduction in cranking. But having to crank for a minute or so? Come on!

Requiring 60 seconds of cranking to get the car to start after sitting for two or three days? That's a problem. And not the kind of problem that a fuel pump should be used to fix. The only problem a fuel pump "could" fix is if your float bowls are going dry over a couple days of sitting... And if that's the problem, then you better spend some time trying to figure why your float bowls are going dry after sitting just a couple of days.

[chaztg]

I agree with the captain. As I was reading this, it didn't sound like fuel to me. It sounds like an ignition problem. My 73 Z has an annoying problem much like it. I've figured out different ways to get around it, but my car does it too (not starting seemingly with endless cranking). I've tracked it down to the ignition key switch, not the mechanical one where the actual key goes in and turns, but the electrical switch mechanism behind it which contains the plug leading to the wiring harness. Change that part. You can use the switch out of other early Z's, they are all the same--but like everything else with cars, it could be symptomatic of some other problem as well. Changing out the switch hasn't fully solved the issue in my car yet, but it helped.

[olzed]

This sounds like many other 240s that I know of, running SUs, including mine. I have an electric pump at the rear, and no mechanical pump. If I hav'nt used the car for a few days or even a month, the pump will click for 15 seconds, then it will take another 10 or 15 seconds of cranking for the engine to fire. This can SEEM longer. My car starts first time when it has been recently going. (the same day) and it has had the same symptoms for the last 12 years. No better, no worse.

The mechanical pump alone has to drag the fuel all the way from the tank with the engine cranking, and then fill the bowls, so it seems logical that it will seem take a little longer than an electric pump that is pushing the fuel with no cranking.

When cranking it can seem like a long time, when in reality it may not be long at all.

He states that his car starts perfectly after it has been running. If the problem was ignition, would it not show the same hard start symptoms at any old time? Half day. one day. one week.?

When I first got my 240 twelve years ago, I thought it unusual that it took longer to start than a modern car, but now it is quite normal for it.

Just my observation.

Edited January 8, 2012 by olzed

[kenz240z]

Air, fuel, spark. I think we can rule out air, since the engine runs once you do get it started. That leaves fuel & spark. Both easy to check. Before doing so, have you verified that the choke is indeed working properly?

With the choke lever pulled all the way back, the fuel nozzle at the bottom of each carby should be pulled about 1/4" down from the bottom of the carby. Have a helper pull the choke lever while you watch/feel the fuel nozzles to make sure they move. Your hard start issue could simply be that one or both nozzles are stuck. If the choke is indeed working properly, then check for spark & fuel.

Pull a plug wire and put it about 1/4" from a good ground (not touching). The strut mounting nuts at the top of the strut tower work well for this. Crank the engine and look for a spark. You may need a helper to crank the engine for you. You should see a nice, healthy spark. If not, you need to dig into the ignition system. Check the cap, rotor & points and all the associated wiring. Could be a sketchy connection at the ballast resistor or at the coil.

To check the fuel, pull the coil wire and remove the dizzy cap and secure it out of the way so that it doesn't get hit by the the fan or something. The idea here is to prevent a spark, as the next step involves working with raw fuel. Next remove the fuel delivery hose from one of the carby bowls. Wrap a rag around the hose as you pull it off to catch any fuel that spills out. Hold the hose in an empty soup can (or similar container) and have a helper crank the engine. Fuel should flow from the hose within a few seconds. If no fuel flows or it takes a while for the fuel to flow, then check the fuel filter, fuel pump and fuel lines. Could be a clogged filter, defective pump or cracked fuel hoses that allow air to get sucked into the lines. Also check that one of the carbies doesn't have a stuck needle/seat in the float bowl. There should be enough fuel left in the float bowls to start the engine after sitting a couple of days. My car can sit undriven for weeks, yet the engine will start on the first turn of the key.

Hope this helps. Keep us posted on what you find.

[zKars]

The mechanical fuel pump is the fault. weak when cranking, takes forever to pull fuel from the tank. This is likely made made worse by a weak check valve in the pump that lets the fuel drain back. The pump works adequately when the rpms are up.

[Captain Obvious]

The mechanical fuel pump is the fault. weak when cranking, takes forever to pull fuel from the tank. This is likely made made worse by a weak check valve in the pump that lets the fuel drain back. The pump works adequately when the rpms are up.

It's not the fuel pumps fault. You guys are missing my point...

When you shut the car off, the carb bowls are full to the proper level. When you go to restart the car a couple days later, the bowls should still be full to the proper level. You don't need ANY fuel pump when you first start the car because the bowls are already full! You should not HAVE to pull fuel from the tank.

And it's not like that fuel in the bowls gets sucked in all that quickly. How do I know this? Because there has been occasion where I want to pull the carbs off my car and I want them to be as empty as possible before I pull them. Just less mess, that's all. So I disconnect and plug the fuel input lines to the carbs and then start the engine. It will idle for a good minute or so before it starts to sputter from fuel starvation.

In other words, when you first start your car, you should have about a minutes worth of fuel already in the carbs. It should be able to run for quite a while with NO fuel pump before it runs dry.

So, if your bowl levels are already low, or if you're percolating the fuel out of the bowls on hot shut-off, or if you've got very low compression, or a weak spark, or your carbs aren't functioning properly, or, or, or... The point is that the underlying problem is not the fuel pump.

[Captain Obvious]

This sounds like many other 240s that I know of, running SUs, including mine.

Now that you mention it, I don't usually actually time my cranking time. I was guessing with my ten second estimate. So out of curiosity, I timed it this afternoon. Today was the first start in about two weeks:

First cold start - about four seconds.

Warm restarts - Less than one second.

Granted, I'm running the flat top SU's which supposedly aren't as good as the round tops, but I'm content. Even thirty seconds of straight cranking without so much as a "pop" would seem like an eternity to me. I'd be looking for a problem!

[olzed]

He can easily check this by spraying some gas into the carb mouths, and then crank it over. I'm thinking it will fire right up.

We seem to be 50-50 on this.

It will be interesting to see his result.