Random stalling/no restart issue

[cothran]

I posted a thread here regarding this, and one of the members thought I might be able to get some better answers here. I won't make you all read that 5 page long thread, so here is the gist of the issue.

After buying the car and driving it daily 60 miles roundtrip to work for about 2 months, it suddenly started dying without warning. Sometimes it will restart immediately, sometimes I have to wait an hour, or overnight. Most recently, for example, I drove it on Saturday all over the place for about 1/2 hour. I started and stopped it multiple times, got gas, etc. and it was perfectly fine. The next day i went to drive it to a local car show and I made it about 500 feet before it died and wouldn't restart. I checked for spark (good), fuel pump was engaging, but no ignition. A couple of times, after about 10 tries, it started and ran extremely rough for about 2 seconds then died again. I drove my other car to the show, came back about an hour later and tried to start it and it fired right up. I have since driven it 3 more times without issue.

Here's what I have done so far:

• New coil

• New plugs and wires

• New fuel filter

• Replaced all fuses, cleaned terminals

• Cleaned all relays under hood

After the last time it died I pulled the fuel pump/dampener assembly and pulled the small fuel filter out of the fuel pump. It was crystal clean. My next step was going to be dropping the gas tank, but if there was crud in the tank wouldn't at least something have made it into the pump filter? I mean, it definitely ACTS like a fuel starvation problem.

However...

The only time I've been able to replicate the problem myself was when I noticed in a video I made that the voltage light was coming on when I put the turn signal on. The next day I drove it, every time I used the turn signal it died immediately. That was the problem that drove me to replace all the fuses and clean all the terminals. After I did that, that particular problem no longer occurs and I can no longer cause it to die by doing anything myself.

So, is it electrical or mechanical? Anyone have any ideas? My next step (after I drop the fuel tank) will be to tear out the fuel injection and replace it with carbs. I find it odd that I can drive it for miles with no issues but then it will die after only 30 seconds of driving some days. If it was crud in the lines/filter, wouldn't it stay clogged up? I really thought I solved it by replacing the fuses/cleaning because it ran for about a week just fine, but the morning I tried to drive it to work I didn't make it 2 miles.

[cothran]

Forgot to mention that I also tested the fuel pressure (before the regulator, after the filter) and was consistently getting about 32psi. There have been a few instances after it dies when the pump won't turn on, but the times that it does it still doesn't start. It really makes me think it's an electrical issue, which I'm mediocre (at best) at diagnosing.

[JohnnyO]

Tim, Glad to see you made it here. Hopefully some of the members here will be able to chime in and get you going reliably.

Welcome to the club.

John

PS. You going to grumpy's tomorrow night?

[Arne]

Year and model? Any mods? From the fuel pressure you note, I'm guessing a 280Z, but no idea about anything else.

[cothran]

Sorry, I always forget that. 1978 280z, no mods aside from aftermarket exhaust (twice pipes) and 4 piston calipers.

[Walter Moore]

Do you have a factory service manual? If not you can download one here:

http://www.xenons30.com/

It is always difficult to diagnose these things from a distance. I have noticed that if there is an electrical issue related to the fuel pump the car will run for a short distance after the pump shuts down, then stall. (But you say that the pump engages... Hmm..)

There is also a screen in the fuel tank that could be clogged.

Then again it might still be a connector on the ECU or a bad fuel pump relay. Sounds like you have some research to do.

Good luck.

[Zed Head]

Forgot to mention that I also tested the fuel pressure (before the regulator, after the filter) and was consistently getting about 32psi. There have been a few instances after it dies when the pump won't turn on, but the times that it does it still doesn't start. It really makes me think it's an electrical issue, which I'm mediocre (at best) at diagnosing.

32 is low for the fuel pressure, unless you were testing while the engine was running and the vacuum line to the FPR was hooked up. It should run about 36 psi without the engine running (just the fuel pump powered), or with the engine running and FPR vacuum hose disconnected.

You could have an FPR problem or a fuel pump problem.

Of course, this might not be related to your stalling issue at all.

[FastWoman]

Check your main wiring harness connector, on the inside (cabin side) of the firewall on the passenger side. There's a plastic trim piece that covers it. You might find that the fuel pump contact in that connector is charred. (Mine was.) I cleaned up the connection a few times before deciding to abandon it. I broke that one wire out of each side of the connection and connected through a bullet connector instead. Works fine now.

Hard starting after the hot engine has sat a while could be due to old, dribbly injectors. When you shut off the engine, the fuel pressure contines to dribble fuel into the intake manifold. Then when you try to restart, you're already flooded. I think that's been my problem for a while. I'll soon know for sure (replacing injectors).

[cothran]

I just ordered some replacement fusible links, so we'll see if that helps. I also just read about hogie's problem up above where his turn signal was causing the ignition to cut out - I'll have to take a look at my turn signal unit, too.

[BrianL1987]

Did you test fuel pressure test while car was performing normally? I would carry a phillips head screwdriver & drive until car dies the, open top of one of the carbs & look for fuel. I know there are many possibilities but, I think you stand a pretty good chance of fixing with a new electric fuel pump.

[BrianL1987]

Sorry, I missed the make/Model. Still think it sounds like fuel

[cothran]

It isn't the fusible links. I drove it about 50 miles this weekend - ran perfectly fine. This morning I decided it was ok to drive it to work. As I got near the last parking lot before the freeway, I said "ok, one stop left" as in 'if you're going to die, now is the time to do it.'

And she died.

Now I might be imagining this, but the last time it died and this time it seemed to be related to giving it gas in third gear while at a fairly low rpm, maybe 1500. I gave it gas and it seemed to just not respond then a few seconds later it died. Even if that's what caused it I don't know what that would mean. The thing is, if it's going to die it does it within the first couple of miles. If it doesn't die within that time it will run all day.

I haven't had time to open up the turn signal and check that, but aside from that I think it's time to tear out the fuel injection. That way the entire FI electronic system is out of the picture. The fuel pump will be replaced, so I can cross that off too. Which would leave the alternator, the gas tank (which I doubt is the cause), the fuse box and the fuel pump relay unless I'm missing something.