Datsun fuels system issues.

[Datsun Clark]

I have a 1977 Datsun 280z that has been acting up. When I drive the car for a lengthy distance and shut it off, or if it reaches full operating temp, and try to come back 10-15 min later and start the car again the car will sputter and die. It usually takes multiple tries with the gas pedal slightly down to overcome the problem. I just replaced the fuel pressure regulator hoping to fix it but it was no help.

Any ideas?

[black gold man]

You might have manifold leak expelling hot exhaust gases under hood.

Try zx injector fan with timer inside car, run for 15 min when parking for that short time.

[FastWoman]

This is one of those "personality" things that commonly plagues the 280Zs. There is very little agreement as to what causes it. The theory I favor is that your hot engine block soaks your injectors with heat after you shut down your engine. (They are no longer cooled by the flowing fuel.) This causes the fuel to boil (which many people argue can't happen when the fuel is under pressure; however, the operating pressure of the old L-Jet systems is lower than pressures of modern systems). Then when you go to restart your engine, you're injecting fuel vapor, rather than liquid fuel. Eventually your engine passes all the vapor, cools the injectors back down, and injects liquid fuel.

This problem will be worsened...

... in hot weather

... in fuel systems that do not properly hold their pressure

... when running more volatile winter mix gasoline during the summer

... when running 10% ethanol gasoline, for which our EFI systems weren't designed.

I've found my hot restart problem has been successfully resolved, for the most part, by the following:

... correcting the pressure leakdown problems (old injectors, worn check valve)

... insulating the fuel rail (very minor improvement)

... running 100% real gasoline -- summer formulation, no ethanol

The following measures have been used by Nissan to address the problem:

... plastic (rather than metal) insulators around the bases of the injectors

... cool-down fan on the ZX models (mentioned by black gold man). These fans will mount up under a Z hood.

[Datsun Clark]

Thanks for the feedback! I'm going to try a few methods and see how they work. Do all ZX's have a fan?

[black gold man]

YEP

[Wade Nelson]

Your vehicle could be:

A) Vapor locking

Losing pressure in the rail (i.e. leaky check valve, bleeding fuel back into the tank)

C) Flooding due to leaky injector or cold start valve

D) Failing to provide the cranking enrichment (failed CSV, wiring, ...

or E) some combination of the above.

Tee-ing in a fuel pressure gauge and seeing if your rail is losing pressure after shutdown will point you in the right direction before you spend a lot of $ on a set of new injectors

Testing the CSV (and signals from the ECM controlling it) with a DVOM or "noid light" and having it "pee in a cup" to verify proper operation might save you the $71 RockAuto currently gets for a replacement.

You might verify operation of the "auxiliary fan" which is SUPPOSED to blow air over the injectors after shutdown. Mine never kicked in, the coolant temp switch simply never hit 210 degrees. I wish I could buy a 180 or 190 switch but none is available. So I wired in a toggle switch in the cockpit so I can FORCE it to run the fans after shutdown --- they still shut off after 15 minutes giver take a minute or too.

Occasionally a "deal" will come along on a set of new injectors (*picking up another rock*) but some well-intentioned do-gooder will sometimes spoil the deal, preventing you from getting a bargain.

You CAN send your injectors out for re-building for about $130 IF that's the direction your diagnosis takes you.

These cars have ALWAYS been prone to hot restart problems, as noted in the original Car/Driver & Road/Track reviews. As FastWoman pointed out (*taking aim*) the fuel pressure simply wasn't high enough on these early fuel injection systems to PREVENT vapor locking, esp with "oxygenated fuels" containing ethanol. Modern systems tend to run 35-85 psi.

My personal ZX starts "Well enough, often enough." But nothing like a newer Toyota or Nissan which starts and catches the very instant you twist the key to "crank." Every single time.

Throwing rock at do-gooder.... (* A DIRECT HIT *)

Edited August 2, 2012 by Wade Nelson

[grantf]

I have the same problem. My current solution is to rev the car after startup to get the gas flowing. I know this is not a cure. but it's what I do, at least for now.

No problems when the engine is cool though.

[FastWoman]

Throwing rock at do-gooder.... (* A DIRECT HIT *)

I'm thinking you were in the market for a set of injectors!