My 85 Z won't fire up on a hot day in the afternoon.

[Ken Lis]

Hi, guys.

In the morning my Z starts fine before I go to work. Or cold day it start fine, but in the heat of the day in the after noon, my Z have a hard time firing up. I crank it many times and it would not fire up. I checked everything including fuel line, Cap and rotor, spark plug and wires, gas fuel filter and so on. Everything is fine.

It has been like this sinse I put in the new starter to the motor. Any suggestion why is happening like this? I'm open for suggestion.

Ken

[phleb]

Welcome to NICO ken! This here be general chat. You'll probably have more luck with you question here in the classic Z forum zeroforum/194

[amolao]

Do you also replaced the battery???

If your battery (old or new) does not have crank amperes it will not let your computer and relays energized properly. It only affects the battery and makes it worse during hot days. Something to check, trust me it happened to me...

oh and welcome to NICO!!!

[Ken Lis]

Thanks, I'll check that.

[evildky]

when you say it won't start what won't it do? is the starter turning the engine? if not then look long and hard at your wires and connections at eigher end, if the engine is turning but not firing, I'd look at the ignitor, please tell us more

[Ken Lis]

I checked the end wire to the starter, fuel pressure regulator, and so on. It look like there is no fuel coming to start fire when I turned the key.

Every time I turn the key the starter and and entgine turn and it won't fire. There are sparks on the plug and I check that too. So I have my friend do the short cut to see if it start. He shoot some fuel mist into the valve and start the engine, it zoom and got it going.

Could it be the fuel pump, not pumping enough pressure to the regulator and to the injectors?

All this happens in the afternoon when it's warm or hot.

In the morning it start up fine.

Well, any ideas fellas, I'm really appreciated for your help and your expertise.

[Ken Lis]

Yes, I have my battery check and is still good. The ampeg are good and strong.

Thanks.

[Glorywagon]

Sounds like mine run fine till it warmed up real good than you shut it off and wouldn't start. Had it towed home and it fired right up. checked and posted everything sent it to the shop they said bad MAF. Took them another one off my other z that was running said it was bad too. Tow it home sent the ECU to Micro-Teck to have it checked it was junk. Went to Autozone and got a rebuilt one $220.00 hooked it up no more problems.

[Glorywagon]

Oh yeal Micro-teck in Louievill ky. will rebuild your ECU for $125.00 and warrent it. (If its rebuildable) if not they ony charge $25.00 to check it out plus freight. Danny

[evildky]

hehe, you kinda butched my city spelled Louisville, pronounced looavul if you've fever been here you get it, I would also suspect the CHTS, but these ecu's have been known to fail after 30 years of use

[Glorywagon]

Sorry about the louieville but I had baseball on my mind. I know better to I drove a Truck for 40 years been tru there hundreds of times . Danny

[Glorywagon]

The funny thing is I put the ECU off my 85 z turbo on it and it run fine after it warm up.but I did buy the right one for it.

[evildky]

not sure on the differences in the ecu's i'd guess the turbo pulls timing for bst? which would have to be calculated form the maf, tps and rpm, so Iguess an n/a could run fine on a turbo ecu but a turbo can't run on an n/a, or at least runs the risk of a lean condition

[Ken Lis]

I replaced the fuel pump and it still doing the same thing. It won't fire up. this time I'm gonna change the Fuel pressure regulator, if it still doing the same thing, then I have to spend some time to have it diagnois by some mechanic.

Or maybe getting a use ecu from the junkyard and use it, try to see if that'll work.

[evildky]

fuel pressure regulator won't keep it from running, unless the internal diapham completely gave up and it's puumong fuel into the vac line, ...highly unlikely

[evildky]

ecu or fuel injector relay are your more likely causes,

[AZ-ZBum]

fuel pressure regulator won't keep it from running, unless the internal diapham completely gave up and it's puumong fuel into the vac line, ...highly unlikely

Actually.... I've had that happen twice now. And it seems to be a fairly common occurance on the Z31. It's one of the first checks to do when a fuel related issue is happening.

There are no fuel injector relays. All fuel injector stuff is done internal to the ECU.

[evildky]

them new fangled contraptions, I've only heard of a few fprs failing internally, maybe nissna's line about our nasty usa gas had some real foundation