76 280Z fuel delivery issues

[bhermes]

First of all if this posts twice, sorry.

I have recently purchased a 76 280Z and apparently have a fuel delivery issue. I have replaced the fuel pump and fuel filter. The car is driven about 6-10 miles daily and a weekly trip of 20-30 miles. The car has been breaking down about once every two weeks while driving the car spits a few times and eventually stops.

I suspected that I might have a whole in the pick up line in the gas tank. I decided to top off the gas every couple days and would typically add about 1 gallon of gas. The car ran about 2 months without breaking down. I thought that I had solved the issue and would begin looking at fixing the pick up line. A couple days ago during one of my weekly 30 mile trips the car broke down about 15 miles from the house. I waited about 15 minutes and the car started up again and I drove home. I topped off the tank and added about 2 gallons. Basically the tank was only about 1 gallon low when the car stopped. I am now thinking that the problem is not the pick up line.

The only thing I can think of at this point is that I may have rust in the gas tank and that during higher gas demand situations the screen at the fuel pump is getting clogged. Not sure exactly where this screen is located.

Any other thoughts or comments?

[cozye]

Are you sure it's a fuel delivery issue ? Do you have a fuel pressure gauge on the car? How do you know it's not electrical, or ignition related ?

Did you put an inline "pre" fuel filter in just after the fuel pump? You can get a clear fuel filter and a lot of guys just put these in to see if they get rust since it can easily be verified visually.

Have you tried squirting ether in the intake while it's broken ? Verified spark ?

[ansell]

Well I used to have the same problem in my 77 ,and in my case it was a dirty gas tank,

[240260280z]

Sometimes it is the ignition module that is the cause of this. Watch the tach the next time it chuggs to a stop.If the needle drops to 0 before the engine does then it is an electrical ignition problem.

[FastWoman]

It sounds like SOMETHING that's failing because it's heating up. I had a fuel pump go out on me a while back. The pressure would start out strong (enough) and would sag so far that the engine would lean out and stop running. The first time it took 45 min on the interstate. I had the car towed back home, and it started right up in the driveway. Grrrrr. The second time, it took about 20 min around town. The third time was when I hot-wired the pump, put a gauge on it, and watched the pressure. After only 15 min, the pressure went from adequate to practically nothing. Replacing the pump fixed the problem.

You can get a cheap pressure gauge from your local Ace/TrueValue Hardware store ($5) and the brass fittings to connect it inline between your fuel filter and fuel rail. It's a handy diagnostic tool to have in your engine bay when you're stuck.

[siteunseen]

If you still want to know where the pump screen is there is a small cone shaped screen in the "in" port (coming from the tank) on my factory fuel pump. Comes out real easy and is real fragile. I used tweezers. I put the clear $5 G3 Fram fuel filter right out of the tank before the fuel pump.

Edited November 25, 2011 by siteunseen

[bhermes]

I would like to thank everyone for the great replies.

In regards to the heating up issue, I considered this; however, the car has broken down a few times only 1-2 miles after starting for the day.

In regards to the screen and the fuel pump does the screen come with a new fuel pump? I have replaced the fuel pump already or is a seperate piece? Will adding the filter help at all if I have rust in the tank. I am thinking that the screen is getting clogged and reducing the fuel flow.

In regards to the ignition module, would this cause the car to not start at times or only when running?

Does anyone have a suggestion other than dropping the tank and taking it to a radiator shop for cleaning out and repair? I have seem some posts on do it yourself but not sure if this is the right thing to do.

Again thanks.

[FastWoman]

A heat-related failure would probably occur about the same way everytime, so if the failure occurs sometimes after a half hour, sometimes after only 15 min, sometimes after only 1-2 mi, and sometimes as you're trying to start the car, it's probably not heat related. That said, most non-heat-related intermittent problems won't disappear with the car just sitting for 15 min. It was this last observation that made me suspect a heat-related issue (i.e. when a part gets warm from running), and I suspect Blue picked up on the same thing when he suggested the ignition module.

Yes, a new pump comes with a new filter screen, but the screen is very small. There's a much larger intake screen in the tank, at least on a '77/'78. (I don't know about the '76 tank.) Some of us install clear inline filters between the tank and pump.

Before you drop the tank, I'd suggest the following:

First, see what your fuel flow looks like. Pull the hose off of the outlet side of your fuel filter (the one running to the fuel rail), and attach a long, clear, vinyl hose to it. Run the end back to your gas tank filler neck. Then connect a wire from the (+) of your battery to the (+) post on your fuel pump to run your fuel. The fuel will (or at least should) circulate at relatively high volume and of course no pressure. If you have a restriction anywhere, that should reveal it.

Next, you can determine whether there's crud in your tank by removing the round inspection plate in your hatch area over the fuel tank (about 6" diameter, with 2 screws). Removing it will reveal the fuel level sender at the top of the tank. You'll have to use a screwdriver and a hammer to tap on the retaining ring to turn it and remove the fuel level sender. (Vacuum out the area first!) Then you can look into the hole with a waterproof flashlight (no sparks) to see any rust or sediment in the bottom of your tank. Obviously, NO SMOKING, NO SPARKS, ETC! When you reinstall the sender, clean the parts thoroughly, and be sure to align the notch in the sender with the notch in the mount.

BTW, one intermittent fuel problem that gave me fits for a while was from a corroded/melted/arcing connection in one of the big wiring harness connectors, just inside the firewall on the passenger side. Pull it apart to check the condition of that one contact. As I recall, it was a blue/green wire in the corner of one of the connectors. I ultimately snipped the two wires out of that connector and connected them with a bullet connector.

[bhermes]

Sounds like some really good advice. I will update after I look at the items suggested.

Thanks.

[Zed Head]

There's a drain plug on the bottom of the tank. Disconnect the fuel line to the filter and run some extra hose to a spare gas can or two. Use the fuel pump to push the fuel out through the fuel lines (disconnect the starter line and use the key at Start or hot-wire the pump), then drain the remaining gallon or two through the plug and see what comes out. The pump will either stop pumping due to debris buildup while it's running, or you'll find some crud when you drain through the plug hole.

You'll need to do this any way before you remove the tank. If the pump runs fine while draining the tank and no crud comes out, you can always change your mind.

As far as the ignition module goes, when mine was failing (1976 car like yours), I could bring on the failure signs by running over ~3,000 RPM. It was okay below there, but as soon as I went above that number, the tach needle would start bumping around at a higher number than the engine was at, and the engine would start missing, stumbling and wouldn't idle. My alternator was in the middle of its failing process and I think that the stray voltage spikes hurt the module. As Blue suggested, the tachometer will give some signs of ignition module failure.

[bhermes]

Trying to test out the ignition module issue, I went out and ran the engine at around 3000 rpms for about 1 minute or so a couple times. No issues. Based on your experence would this rule out the ignition module or do I need to actually be driving for a longer period? I just had the car out of gear not actually driving.

I am not familiar with the inspection plate on the fuel tank? Is there something under the spare tire? I just removed and I am not sure where to go next?

[bhermes]

I know I am going to more than likely need to drop the tank but really trying to make this the last thing. I drive the car daily and would rather not take out of commission. So bare with me as we diagnose the problem.