Startin Issue - any ideas?

[jthill3]

My '77 280z has just had the temp sensor to the fuel injectors replaced and this solved myMPG issue and now the car starts well whether hot or cold - except - when I travel only a short distance (ie 3 to 5 miles) and then it will not start back up.

For example. I traveled from my house to the gas station (about 3 miles), turned the car off, filled up my tank, and then tried to start it up but all it would do is turn over but never catch fire. This story happened to me a couple a couple of times.

Over the last year I have replaced all fuel injectors, cold-start injector, new spark plugs, new spark plug wires. I now have the car at NISSAN looking this over but they asked for my books on the car yesterday and my confidence is waning.

Thanks for any hints........

[sblake01]

I'm assuming that it does eventually start. How long does it take?

[jthill3]

It does start eventually,

In the two instances of this issue, once it started after 1/2 hours and the next time more than 1 hour went by.

[DatsunZsRule]

I'm thinking it could be a faulty Thermotime Switch.

When the coolant temperature is below specs. (71 degrees) the bimetal contact in the Thermotime Switch is closed allowing the signal to the Cold Start Valve so that an additional amount of fuel gets injected for cranking operation. The bimetal is equipped with a heater for when you do repeated starting while coolant is below 71 degrees. Electric current should be flowing through the heater whenever the ignition switch is in the start position so it sufficiently heats up the bimetal allowing the switch to open to prevent an excessively rich mixture during frequent restarts like what your describing doing real short distances. I'm thinking that the heater for the bimetal in your switch is no longer operating like it's suppose to so when you go to quickly restart your Z, it's getting too much fuel and flooding. Once it has a chance to sit for a 1/2 hr. to an 1hr. then it will of course restart again for you. From the way your describing it, that sounds like a possible cause to me so I would look into that.

let us know how you come out.

[sblake01]

I once had a similar problem with my 78 that I solved by replacing the EFI main relay. It's under the hood on and is a single relay on my 78 but on a 77 and earlier it's above the ECU on the drivers side kick panel. And it's a wide relay that's like two relays in one where one side is the fuel pump relay and the other side is the EFI main relay.

Edited May 19, 2009 by sblake01

[jthill3]

Well the thought now after more testing at NISSAN- it was the computer - I ordered one from Black Dragon. Will provide results later I get it in.

[ChrisB77]

I'm interested to see how this turns out for you JT. Doesn't really sound like an ECU problem. These early Nissan systems are so simple and robust that they almost never have ECU failures. I like Jared's thoughts on this. Theromotime switch could easily cause your incident.Keep us all informed when you know more.

P.S. Make sure the guy at Nissan working on the car is the oldest,most experienced tech. Not some young pup who wouldn't know a Z from a Jag;)

[jthill3]

update- 06-02-09 ECU was replaced two days ago and so far it starts alot better than ever. Seems to start almost as soon as the key is turned.

A mechanic friend tells me that if the intermitent "starting problem" reocurrs, that I should look at the Ignition Module (aka Ignitor).

Does this sound right?

Thanks

[DatsunZsRule]

Did you try checking the Thermotime Switch???

[jthill3]

Did you try checking the Thermotime Switch???

Yeah, the thermotime switch was replaced already before this particular issue happened. It was retested though and ruled out.

No starting problems so far since I got the car back.

[sblake01]

update- 06-02-09 ECU was replaced two days ago and so far it starts alot better than ever. Seems to start almost as soon as the key is turned.

A mechanic friend tells me that if the intermitent "starting problem" reocurrs, that I should look at the Ignition Module (aka Ignitor).

Does this sound right?

Thanks

It's possible but I never experienced that with my 78 in the 12 years I owned it. Hopefully you don't have a problem with that. It's one of the most expensive items on the car; if you could find one.

[jthill3]

It's possible but I never experienced that with my 78 in the 12 years I owned it. Hopefully you don't have a problem with that. It's one of the most expensive items on the car; if you could find one.

Thanks - glad to hear from you.