Shuts down when warm

[LRPZ]

1978 280z; having problem with engine starts to run rough and then shutting down after driving 20-30 mins. Leave it for a while to cool down and can get it started again.

- put on new set of wires

- new dizzy rotor

- new dizzy cap

- plugs were recently replaced by PO (I have car 2 months), but will be replacing those tomorrow

- getting good spark from ignition coil itself

Thoughts? Is this more symptom of fuel injectors than electrical?

Thanks.

[hr369]

some say its the one way valve at the fuel pump that keeps the fuel line

from emptying back into the gas tank and the rest of the fuel boiling off

in the fuel line. then when restarted you get popping lean hard starts.

i replaced that valve and no change in my difficult hot starts. i even put

a bypass on the ignition so that i could turn on the fuel pump and recirculate the fuel in the rail to cool it off prior to starting. NO improvement.

i then got to thinking that the wires to the fuel injectors might be getting less electricity when they're hot. heat=more resistance so i cleaned and put

dielectric grease on the fuel injector pigtails and it did improve hot starts but still sometime i get a little stumble when hot starting.

Edited July 1, 2011 by hr369

[hr369]

gads my reading comprehension sometimes. i thought you wrote after you shut it down.

your problem sounds like it could be the electronic ignition module

[FastWoman]

Yeah, it sounds like something electrical/electronic is overheating.

I'd suggest having a can of starter fluid close at hand. When your engine fails again, you should immediately pop the hood, pull one of the vacuum hoses off of your intake manifold, and squirt some starter fluid inside. Reattach the hose, and give it a crank. If it fires up briefly, you have a fuel problem and should start scrutinizing your EFI. If it doesn't fire at all, it's probably an ignition problem, and you should check out your ignition module and coil. If it fires up and keeps running.... well... then you're going to have to wait for it to fail all over again, because you weren't fast enough to catch the problem.

Edited July 2, 2011 by FastWoman

[LRPZ]

Thanks for all the feedback...Latest update: pulled the plugs from PO and replaced. Previous plugs had seen better days. Car started but took a while to smooth out (burn off fuel residue etc from earler). Ruuning nice and smooth, then started "wigglying" the injector (electrical) connectors and three of them seemed looser that others. At one point rpms dropped significantly on # 6 and stalled as before. Looked further and a couple of exposed wires as well where tape had come away.

So now thinking need to splice in new set of connectors to the injectors. Any recommendations on where to source?

Thanks again.

[FastWoman]

This ebay seller (f0rrest) puts together a good little kit:

http://cgi.ebay.com/ebaymotors/injector-connector-kit-6pc-datsun-280z-280zx-300zx-_W0QQcmdZViewItemQQhashZitem43a04f8954QQitemZ290452375892QQptZMotorsQ5fCarQ5fTruckQ5fPartsQ5fAccessories

The heat shrink he provides is of very high quality, and he even throws in a packet of dielectric grease. The connectors themselves seem a bit flimsier (or at least more flexible) than the original Bosch, but I don't think that's a significant issue. If you give them a hard wiggle, you can pull them off without first undoing the wire retainer. I suppose that can be either a good thing or a bad thing. All of mine have performed quite well over the past year.

I'd recommend getting additional connectors for your cold start valve, air regulator, thermotime switch, and coolant temp sensor, as well as one spare. Why a spare? It will make testing of these components soooooo much easier! I just picked up a separate 4 cyl kit from him (I think it was for a Jeep), but maybe there's a 5 cyl kit. Either that, or just ask him to put together a kit with 11 connectors. He's a pretty nice guy and will surely do it for you.

The 3-conductor throttle position sensor connector is best obtained at a junk yard. You'll probably have to live with your AFM connector in whatever condition it is. The good news is that it's in a pretty protected place and is probably in good condition.

But yeah, while you're into rewiring the injectors, I'd just do the whole engine. If your engine harness is like mine was, you'll make a couple of discoveries in the process.

[LRPZ]

Appreciate the feedback....will add to the post as I progress along; will be first major set of repairs I'm attemtping myself.

[LRPZ]

Finally got back to taking care of biz and went to try and start up the Z...now it cranks but won't turn over and start. Rechecked coil to dizzy to plugs etc and getting spark all the way thru. Plugs look fine (not fouled), checked gap in all. Finally got all the FI Connectors and will (hopefully) get them installed this weekend and see what happens.

I'm beginning to also think fuel related again...after running & heating up, fuel line/filter getting clogged with "stuff"? Maybe now blocked completely? Guess will start at the fuel filter (easiest to get to) and work backwards.

Any other thoughts?

Thx

[FastWoman]

Well, do dump out your fuel filter to see if you have @$% in it. If you do, then you'll want to see what's in your tank next. There's a drain plug on the bottom of your tank. Put a pan underneath it, and drain just a bit of fuel. You'll want to see whether there's rust/@#$% in it. Another way to check is to remove the 5" dia (?) inspection plate on the passenger side of your hatch area floor. Underneath it is the fuel sender unit. You'll turn a locking ring by tapping it with a screwdriver, and then the entire sending unit will lift out. Then you can peer down into your tank with a flashlight (no sparks!!) and view the bottom.

It's worth mentioning that your '78 has a pickup screen in the tank that will be eaten away by any acid wash or clogged with POR15. Obviously if you eat huge holes in the screen there will be nothing to clog, so perhaps that's OK. Then you'll want a coarse fuel filter between your tank and fuel pump to protect the pump.

You might need to clean out your tank. You certainly wouldn't be the first person. There are descriptions here and there about how to do it. Basically you'll drain it, pull it, perhaps acid-rinse it, perhaps pressure wash it, dry it, perhaps apply a coat of POR-15 to the inside to line it, replace all your hoses while you're at it, and reinstall. Obviously replace your filter at the same time.