Hot-start issue with EFI - who has it, who doesn't

[rossiz]

today i had what i think was a hot-start episode:

warm, sunny afternoon, car up to full operating temp, went into the grocery store for about 20 minutes, came out and the car would not start at all - nothing, not even a pop after much cranking. i pulled the solenoid wire off the starter and turned the key to start to run the fuel pump, trying to circulate some fresh fuel around the rail - could hear it going and saw my pressure gauge blip up a little while the pump ran, but still no starting even after a few tries at this. maybe priming doesn't work because the fuel just runs around the rail and recirculates, without actually going down the short 90 degree hose runs to the injectors. took out a couple plugs and they were bone dry.

let it sit for 5-10 min with the hood up, and then it started - ran rough for a moment until i reved it up above 2k and then it was as if nothing had ever happened.

so i'm thinking - what if i set up a momentary push button switch to fire the cold start valve, even though the engine is hot? it's pretty far away from the block, so maybe it would be cool enough to provide enough fuel to get things started? i don't know how injectors work, but i thought they opened up when they received a pulse of power - if this is the case, wouldn't it just take a few cranks to pull some air/fuel in?

i'm really not digging the feeling that it's just pot-luck whether my car will start when i come out of the store. especially since i had just gotten the car washed and it was looking SOOO nice, attracting admiring glances, then (sigh) hood up, fettling in the parking lot, hoping i could get home before the ice cream melted...

[EuroDat]

I wonder if its sticking injectors. They are after all just a coil activating to pull on a magnet to open the neddle. The temperature could tighten the tolerances when they sit in high temerature and sieze shut until they cool off. Worn surfaces on the needle and the injector housing could grap easily and cause this problem.

Vapour lock with 36psi, cranking the engine and even flushing cool fuel past the injectors seems unlikly, but I do mean seems.

Manually pulsing the cold start injector could be a way around this.

Chas

[FastWoman]

Running the fuel pump will cool the "trumpet," and the legs leading to the injectors might also fill with fuel, but the injectors will still be hot. Actuating the cold start valve wouldn't cool anything down, any more than running the pump (which would do much more good), but it might spray enough fuel to run the motor. That would be a very fiddly way to start the motor, but it might work.

Rossiz, for the sake of this thread... Yes, you indeed had a hot restart issue. What is the configuration of your engine?

[ZCurves]

After lurking on this Thread and suffering from these symptoms (Stock 78 setup), I am changing out the Injector Insulators to the plastic style and adding the ZX injector fan. I feel that with all of the heat shields in place that this might make the most difference. It is going to be a HOT summer here in Houston.

[hr369]

yesterday i decided to do a little experiment. i detached my fuel rail leaving the injectors still attached to the rail. i then turned on the fuel pump and used a 9v battery to turn on and

the injectors one by one. i thought i would have had at least one leaking injector. not even one little dribble could be seen. i also checked the cold start valve for a leak.

i then pulled the injectors off the rail and soaked them in an ultrasonic bath of solvent.

ran solvent both directions thru the injectors. its been 10+ years since i replaced these

injectors so they were due for a good cleaning anyways.

car ran more smoothly at idle but the real test will be when i go for a long drive

and try to restart.

btw i have the plastic injector insulators and a new check valve.

the 280z exhaust manifold looks quite a bit more meaty than the zx manifold.

perhaps a zx manifold would help the heat soak problem. does anyone in a 280z run

a zx exhaust manifold?

Edited April 10, 2014 by hr369

[rossiz]

Actuating the cold start valve wouldn't cool anything down, any more than running the pump (which would do much more good), but it might spray enough fuel to run the motor.

my point exactly: get some fuel in to start the engine and draw the vapor from behind the injectors.

yes - it would be fiddly, but maybe it could be controlled more effectively by the HellFire? just a thought from a non EFI guy...

Rossiz, for the sake of this thread... Yes, you indeed had a hot restart issue. What is the configuration of your engine?

1978 280z - stock i/e manifolds, exhaust, fuel rail, heat shields, original injectors (i think)

recent new parts (in last 6 months):

- entire cold start system (thermotime sensor + connector, injector, AAR + hoses, connector)

- PCV valve + hoses

- FPR + hoses

- AFM boot/hoses/connectors

- all injector connectors (including cold start)

- fuel pump check valve (rebuilt)

- plugs, distributor cap, wires

- water temp sensor + connector

- thermostat

- all fuel lines in the engine bay

- most vacuum lines in the engine bay (vacuum currently measures 19 at idle)

PO replaced parts/service (have receipts):

- AFM (sept 2013)

- ECU (1995)

- injectors cleaned (2006)

- fuel filter (2006)

modifications:

- K&N filter + cold air intake

- EGR system removed and both manifold connections blanked-off

- fuel pressure gauge installed between fuel filter and rail (reads constant 35psi)

- fuel filter between tank & pump

i've included some pics of the engine bay and one of the injectors - maybe you all can tell if they are original and if they are the "plastic insulator" kind (looks plastic to me)

[EuroDat]

- fuel pressure gauge installed between fuel filter and rail (reads constant 35psi)

i've included some pics of the engine bay and one of the injectors - maybe you all can tell if they are original and if they are the "plastic insulator" kind (looks plastic to me)

The fuel presuure seem a bit high. Normally maximum pressure is 36psi, but thats only under full throttle/ high load conditions when the vacuum is very low. At idle is should be under 30 psi. Does it change when you disconnect the vacuum from the FPR?

The injectors don't look like OEM to me. OEM were green (JECS) and white (DKC).

Chas

[Zed Head]

If you blow up the injector picture you'll see the typical A46(I think) - 00000 number of the stock Nippon Denso or Denso injectors. They look like they were probably green when new. Pretty dirty now.

Those are the older style two part insulators, with the aluminum upper half. Hard to tell if they are better or worse for heat absorption. There's an air gap in the middle which might let them transfer heat faster, but the metal piece might hold more heat. Nissan might have changed just because it's cheaper to make a one piece plastic insulator than a two-piece.

And that 35 psi constant is an unknown. Kind of odd, as EuroDat noted.

To hr369 - I picked up a ZX manifold, more just to have a complete ZX engine package than for the heat-soak problem, but have realized that you need a longer head pipe to fit the shorter manifold. You'd have to do some exhaust work, it won't swap straight in.

Back to Post #37 though, I'm not sure that's the typical heat-soak problem. It doesn't usually wipe out all of the injectors, just a few. The engine starts but runs bad. Yours didn't start all. That seems more electronic or electrical. Then when it did start you said it ran rough for a moment. Heat-soak running seems like eternity although it's only 20-30 seconds. But, if you do have it, it will come back, and you'll get familiar.

[siteunseen]

Here's a picture of it, I never can get one on a PM.

[ZCurves]

Thanks! Thats the ticket! PM Sent.

[ZCurves]

i've included some pics of the engine bay and one of the injectors - maybe you all can tell if they are original and if they are the "plastic insulator" kind (looks plastic to me)[ATTACH=CONFIG]70739[/ATTACH]

Hello, It looks like the injectors in your pic are the OEM. The aluminum ring is actually clamps the injector into the manifold. BUT the aluminum transfers the heat more effectively to the metal injector body. Sarah(Fastwoman) had pointed this out earlier in the thread. Since I had to replace a dead injector anyway, I bought new Injector o-ring seals AND the plastic Fuel Injector mounts from Advanced Auto Parts. Below are the part numbers/prices...

BWD/Intermotor Fuel Injector Seal Kit Part #28412 $6.49ea (You will need six).

Beck/Arnley Fuel Injector O-Ring Kit Part #158-0022 $3.29ea (You only need TWO - 4 in each package).

These changes may only make a minute difference - but it is cheap and worth a try. I will keep every posted as to my findings..

Edited April 11, 2014 by ZCurves

[EuroDat]

Here are some photo's of my injectors in the car and an old set on the bench. The ones in the car now are remanufactured and could be from a ZX.

The originals were JECS Made in japan. The text on the back "1148" and "1701B". Its not on the set in the car. The set in the car have "086" and "0 280 150 116".

I think they might be production numbers.

Chas