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

[FastWoman]

Zed, I suppose deposits binding the pintles could explain some hot restart issues, but certainly not all. I'd offer the following thoughts:

1. I continued to have some hot restart issues even after replacing my injectors with new ones. Although the hot restart was improved, I did many things as a part of my intake overhaul, and it's difficult to say specifically what improved my situation.

2. The deposits on the pintles are going to be varnish. Varnish is hardest when cool, so I would think the deposits would cause the greatest problems with sticking when cool. But contrary to this notion, time and cooling reliably resolve this restart issue.

3. One could argue that it's a thermal expansion issue, but that would depend entirely on the materials involved. If all the parts are made of the same material, thermal expansion would have no effect on their relative fit. So a steel pintle in a steel sleeve would not tighten with either heating or cooling. Of course I can only speculate as to the materials typically used in an injector. However, I would think that any thermal expansion jamming that would occur in a heat-soaked engine could also occur in a running engine, particularly when idling on a hot road in the middle of summer. But we don't hear about that.

Edited April 29, 2014 by FastWoman

[Zed Head]

I thought that I would post the link mainly as food for thought. Single pintle versus four hole. I don't even know that the description in the drawing is right, since it talks about a plate but the diagram shows a tapered seat valve.

I'm going to start another thread with the details of what I did. My experience with cooling the injector bodies makes me think the problem is in the injectors but I don't have the definitive experiment done, with other variables controlled.

[Zed Head]

Here's the link to my other thread. Still collecting information.

http://www.classiczcars.com/forums/fuel-injection-s30/52171-modern-injectors-new-fuel-rail-no-heat-soak-problem.html#post455660

[TheCrazySwede]

A few months ago when I was experiencing the hot restart problem, my local Nissan/Datsun mechanic suspected that it had to do with the fuel mixture used during winter time. I wasn't sure if that was true or not, because I can't remember if I experienced it last year. Now that it's summer (I live in CA, so it gets pretty warm) I've been driving my car, just the same way it was during the winter, in much warmer circumstances, and yet I'm not experiencing the hot restart issue anymore. I've tried to replicate it (Drove it hard, parked it in the sun...waited 10-15, and started it) but it just starts right up without a single moment of hesitation.

Anyone else experience this? Perhaps in my case, the guy I spoke to was right.

[rossiz]

i've been quiet on this thread for a while, since last time i chimed in there were electrical issues clouding the problem, and i wanted to be sure i had good, consistent info to report.

it's been warm here in seattle, and i've been plagued by constant hot start problems. the car runs fantastic, plugs seem decent color, i just ran seafoam through the intake the other day and my idle has gotten much more stable, the only issue is starting when it's hot. the car starts like a champ in the morning - almost instant. now that it's hot outside, when i stop for 5-10 min. the car has a very predictable pattern: it fires up for just a second, dies, then will not start at all. doesn't matter if i leave the hood up, it just seems that the initial heat soak is flashing the fuel pretty quickly for me.

strangely, for me priming the fuel actually works consistently to get it going. i hop out, pull the wire from the starter, hold the key for 30-45 sec (a long time, yes, but it does work) and then she'll fire up - if not, i'll get the same sort of 'almost start' and have to repeat the process, but once it starts it revs right up and it's business as usual.

the other odd thing is that if it heat soaks, the vapor will stay behind the injectors for a very long time. i took my daughter to her ballet recital at 4:00 and it was hot out - shut the car off in a parking garage (at the perimeter, sun on the hood) and came back at 6:00 and it did the 'almost start' dance, needed 30 sec. of priming and then fired right up.

i'm going to put a toggle switch in the cabin to cut the starter wire so i don't have to jump in and out of the car every time. hope that will work until i can save up for a header. i'm convinced the header will work to reduce the heat soak. i'm also planning to look into the multi-spray injectors and a different rail.

[FastWoman]

Sorry you're still having hot restart issues, Rossiz! As an alternative to a starter kill switch, you might wire a switch to deliver +12V to the coil of the fuel pump relay. It would be a priming switch, so to speak. (That's what I did on my car.)

I'm anxious to hear what does the trick for you, since you'll be trying a few approaches.

[Zed Head]

I wonder if there's something odd going on with your fuel pump control relays, that gets corrected when you disconnect the starter solenoid. Maybe the voltage drop from turning the engine is screwing up the fuel control system. It might be worthwhile to connect a fuel pressure gauge, then pop it out to where you can see it while you have the no-start condition. The symptoms seem more like no fuel pressure at all. The priming step might just be building up pressure, which allows the engine to start, then fuel pump control returns when you're off the starter.

You're not conforming.

[rossiz]

i have a fuel pressure gauge between the fuel filter and the rail - the pump check valve is holding pressure, the gauge is at a solid 35psi when i go to start. when i pull the solenoid wire off the starter and turn the key, i can watch the needle bump up a psi or two as the fuel circulates, and i can hear it running through the fpr. then when i re-connect the starter, it fires up.

i'm sorry, but i've never been very good at conforming...

[sscanf]

Another Data Point:

1976 280Z, MSA Coated 6-1 Header, new Standard Motor Products FJ707T injectors. I was just out running errands, 84 degree day, one 30 minute stop and one 10 minute stop. Never a hint of this problem, not today and not prior to today since I got it on the road in April (and have been driving it most days). It always fires right up, hot, cold, warm, or luke warm.

Probably not of consequence but I have a rebuilt ZX distributor/ignition module (with appropriate wiring mods) and a rebuilt air flow meter. I believe the fuel pump was recently replaced by the PO.

Dan

Edited June 2, 2014 by sscanf

[Zed Head]

You have the same setup as siteunseen. Header and FJ707T injectors. That's two wins for that combination, but still leaves the question of header or injector.

Here's something generally interesting on injectors. BWD and Standard are made by the same organization, and the high end BWD's have the FJ type of output (see links below). When I bought my first set of new injectors, I went for the cheaper ones,with the single pin pintle design, like Nissan stock. A few more dollars and I might never have had the problem, assuming injectors alone are the solution. The price difference seemed higher back then.

List: Fuel Injector - 1978 Nissan 280Z | O'Reilly Auto Parts

BWD 57519P - Fuel Injector | O'Reilly Auto Parts

Edit - I shouldn't leave out FastWoman's Standard FJ3 injectors either, with stock manifold and heat shields (but a wrapped/insulated fuel rail). Reported to have occasional hot start issues, but not significant, if I recall correctly. That's three FJ injector winners, no FJ losers yet.

Edited June 2, 2014 by Zed Head

[rossiz]

it looks like the 57519P has a different plug/connection - is there a removable insert in there so the oem style plugs will work? i just bought and wired in a complete set of new plugs to fit the oem injectors (and csv)

57519P:

27519:

[rcb280z]

Hey Zed, I also have the FJ3's and exhaust header installed with no hot restarts.