‘74 1.8L L-Jetronic Cold Start Low Idle, Mystery solved! Options

[StarBear]

No. You just need to touch both prongs on the switch itself.

@Van Oh, think I tested the wrong thing. Check the wiring diagram on Haynes page 177. It’s located UNDER the cold start valve which I must remove first (or just the blue CSV connector?)? I tested a sensor with a green/brown wire, near CSV next to distributor.

@Van Removed blue connector. Noid light shows connectivity b/n the two prongs. Good to go. (IMG:style_emoticons/default/biggrin.gif) Might (?) still get that backup if your Nissan part test proves it works. I think (?) it should. (IMG:style_emoticons/default/biggrin.gif)

[Van B]

@StarBear the blue connector is the CSV. I don’t think you’ll be able to test the TTS without removing it. It’s buried in there.

[StarBear]

@StarBear the blue connector is the CSV. I don’t think you’ll be able to test the TTS without removing it. It’s buried in there.

We’ll, then the CSV has continuity at least. Yes, Haynes instructs to remove the CSV to get/remove the TTS. As cold start seems ok per last week’s test, maybe I’ll leave well enough alone. May order a spare once your Nissan part test checks out. Onward!

[Van B]

I had to unplug the CSV and the TTS and then I was able to finagle a 24mm deep socket on the TTS.
But yeah, I agree with you unless your friends call you whiskers… ‘cause you’re curious like a cat lol!

[wonkipop]

heres a new bit of esoteric trivia for you L jet die hards.

as mentioned previously and likely completely forgotten i hope -
mine suffers a peculiar little quirk in high summer here,
purely as a result of the modern fuel pump replacement i had to to do on recommission.

it hunts. the fuel is boiling and heating. cavitating in the pump.

well it was giving me this treatment sunday while i was trying to enjoy myself while being UV irradiated. at the lights up and down. up and down.
even threatening to die a couple of times. but valiantly coming back to life only to gasp again.
i had less than a quarter tank of juice left (in my reduced and amputated rhd fuel tank).
off to the petrol station to enjoy the pleasure of post lock down $2.00 a litre gas.
pumped in 20 bucks and got to half a tank.
drove out, got to first set of lights, still hunting.
gave it a bit and thought i'll just keep driving.
after 5 minutes the hunting was gone.

kept driving, kept grinning.
kept going for 1/2 an hour.
hunting gone.

got primitive brain into thinking mode and figured this out.
i've got a minimum volume of fuel, to keep fuel cool problem in high summer?
cause its circulating.
the whole fuel temp is rising as its pumped around through the pump and back to the tank.
below a certain volume of fuel the temp of the fuel rises to the point where its boiling just before and probably in the pump.
but get enough fuel going around and around and the fuel cools itself.

i need half a tank min in the car in summer to avoid the problem.

at least until i can get my rebuilt original pump back in which i think handles hot fuel and engine heat better.

[Van B]

That is very interesting.
So return line dumps hot fuel into the tank and after a while fuel becomes hot enough that the low pressure moment within the pump causes boiling inside the pump or do you think it happens inside the fuel line?
Think about basic science class here, but I would think the 30psi system should effectively raise the boiling temp of the fuel.

[wonkipop]

That is very interesting.
So return line dumps hot fuel into the tank and after a while fuel becomes hot enough that the low pressure moment within the pump causes boiling inside the pump or do you think it happens inside the fuel line?
Think about basic science class here, but I would think the 30psi system should effectively raise the boiling temp of the fuel.

boiling in the line just before the pump.
(that runs across from tunnel to pump along rear cabin bulkhead)
and in the intake part of pump itself.
that fuel is gravity feed/pump suction - not much pressure.

not boiling in engine lines after pump.
but i'm getting fuel pressure drops as the pump fights to get fuel.

i also have a bend in the small section of hose line into the pump which i look at always and think - marginal.
works ok when its cooler.
that is probably the point where it boils.
won't solve that until i take the pump off and get the small original one back on.

with enough fuel in the tank i have discovered it seems to be able to cope.
volume of fuel in tank acts a bit like a heat exchanger and lowers temp of fuel enough that it does not boil at the critical section of line pre pump.

[Van B]

For a time. As you describe, the longer you drive at temp, then the entire system would become heat soaked again and the problem would return. You either need to raise the boiling point of the fuel or you need to increase pressure on the low pressure/suction side so that you don’t induce low atmosphere boiling.

Luckily all this occurs well below flash point of the fuel; however, should a leak develop and the vapors find a spark, you will kaboom all the same.

I don’t think this is something I’d be comfortable managing. I’d want to solve this all permanent like.
But keep in mind this thread is all about a guy who can’t accept a mild inconvenience of poor cold start performance…

Van

[rhodyguy]

It doesn't dump, it goes right back to the tank adjacent to the outlet spigot.

[wonkipop]

For a time. As you describe, the longer you drive at temp, then the entire system would become heat soaked again and the problem would return. You either need to raise the boiling point of the fuel or you need to increase pressure on the low pressure/suction side so that you don’t induce low atmosphere boiling.

Luckily all this occurs well below flash point of the fuel; however, should a leak develop and the vapors find a spark, you will kaboom all the same.

I don’t think this is something I’d be comfortable managing. I’d want to solve this all permanent like.
But keep in mind this thread is all about a guy who can’t accept a mild inconvenience of poor cold start performance…

Van

the heat builds up in stop start driving.
don't know if you have noticed with yours how if the car is standing still hot air expelled from the engine collects in the right conditions up under the rear fender wells and also in the flank areas just in front of engine.

(this was the old fuel vaporization problem that 914s were famous for before they shifted the fuel pump to the front in 75).

summer down here is real hot. days are often still. no wind or breeze.
thats when i start to get the problem. no breeze to flush that bubble of hot air out.

winter is a different game.

i have carried a fire extinguisher in my 914 for 30 years.

you are obsessed with cold starts.
i have waking nightmares about fuel leaks.
check fuel lines like a kook with obsession syndrome before i go out for a drive.

its interesting, if the car stays on the move the problem never developes.
its just minor enough in stop start to cause the hunting, but never stops the car.

i think the mods to fuel tank come into play in my case as well.
a 1/4 of a tank is not the 1/4 of a tank that a lhd car has.
to do right hand drive you have to slice the bulb at the bottom of the tank in half and reduce the part that faces towards the cabin to get space for firewall mods for pedals.
once the fuel gets down to being in the bottom part of the tank there is not much in there.

sometimes i can starve it for fuel with a low tank and a bit of hard cornering in a long enough roundabout. but only when the tank is right down. (IMG:style_emoticons/default/driving.gif)
but its been a while since i could find an uncrowded roundabout without an SUV kook tiptoeing in front of me trying not to tip over.

I'm going to get into a bit of reflective insulation work on the metal fuel lines i installed as well when i put the rebuilt original fuel pump back in.
that may be part of the problem. the run of steel line across the back of the firewall to the pump.

they used to be plastic until two years ago.

it was pretty hot here on sunday. around 34C. but its hotter than that in the inner city where i am. asphalt and concrete. was easily over 100 in your F scale. it stood up to half an hour of good driving around with the tank more than half full.

[wonkipop]

It doesn't dump, it goes right back to the tank adjacent to the outlet spigot.

i know.

you just described the problem.
its a pretty small volume of fuel when my tank gets down (1/2 what you guys have in that bulb area). so i am circulating a volume thats just small enough to not lose enough heat on the way back there and in the tank.

but Van is right. it is dumping. the return line is being pushed by the pump.
pressure regulators and all. its returning under some pressure.
whereas the feed is a mixture of gravity and much weaker suction.
pumps push way stronger than they pull.
thats why the feed line is 2mm larger diam than return.
doesn't sound like much but it means the cross sectional area is at least twice as big as the cross section of the return. its done like that because of the physics of pumps.

[StarBear]

Hmmmm…. I always keep my tank at half full or more anyway as I think it handles better and lessens chance of plugging the strainer sock. Another reason. Moved pump to the front a few years ago. (IMG:style_emoticons/default/biggrin.gif)

[Van B]

Well friends, this weekend has been another weekend of trying to do a simple task only to discover another PO nightmare. So much on this car is all original, but more and more, I find that the work that has been performed was done half-ass and by idiots. So, imagine the work an idiot does at best and then divide by 2. What was meant to be a simple fuel filter change turned into a complete reorganization of the relocated fuel pump and filter to remove all the areas of pinched, twisted, and abrading hose. And replacing the vibration isolation bolts that were sheared because the cross clamping bolt was not installed in the fuel pump bracket.

But now that is all behind me, tomorrow I will be installing the TTS and injectors. Of the 7 NOS injectors purchased, 4 were fully fit for service. The other three flowed great, but had a terminal case of slanted spray pattern. Of the four good ones, they are perfectly matched. Ironically, tomorrow will be fantastic weather so, no cold start test. But I remain convinced, until proved a fool, that the injectors are the primary cause of the struggles on cold start. The secondary cause would be the failed TTS.

Hoping for success so I can close this thread and move on to more conventional 914 projects… like oil leaks and worn out suspension.

Stay tuned! (IMG:style_emoticons/default/yellow914.JPG)

[StarBear]

Best wishes, Van, and keeping my Fuchs crossed for you..... (IMG:style_emoticons/default/biggrin.gif) (IMG:style_emoticons/default/drunk.gif)

[Van B]

Thanks Steve!
@JeffBowlsby would you know where I can find the gasket or clip for the Bosch 2 pin connector?

[JeffBowlsby]

Thanks Steve!
@JeffBowlsby would you know where I can find the gasket or clip for the Bosch 2 pin connector?

Only available with a new connector housing.

[Van B]

Thanks Steve!
@JeffBowlsby would you know where I can find the gasket or clip for the Bosch 2 pin connector?

Only available with a new connector housing.

Copy, I suspected that might be the case. Thanks for the confirmation!

[Van B]

Injectors are installed and have made a noticeable improvement to driving/running quality. Engine was out of time slightly again. I think my distributor clamp is not up to the task when I really wind the engine to redline.
Initial start up was obviously rough since the car had not run in a while and the fuel was drained. I’m concerned that I may not have solved the cold start as the engine reaily struggled until warm just like it has been. Once I got everything warm, starts are not problem, even when it was heat soaked from sitting there idling forever while adjusting the timing, it only cranked a couple seconds longer than a normal start.

It will get down to 9c tonight so, I’ll let the car sit outside and chill out lol… and then try a cold start again. This will be about the most ideal conditions I can give so, if it struggles again, I am completely out of ideas.

[emerygt350]

You should write a summary of what you did for each part of the cold start circuit and how you know each is up to snuff. Just for future folk with this issue.

[wonkipop]

Injectors are installed and have made a noticeable improvement to driving/running quality. Engine was out of time slightly again. I think my distributor clamp is not up to the task when I really wind the engine to redline.
Initial start up was obviously rough since the car had not run in a while and the fuel was drained. I’m concerned that I may not have solved the cold start as the engine reaily struggled until warm just like it has been. Once I got everything warm, starts are not problem, even when it was heat soaked from sitting there idling forever while adjusting the timing, it only cranked a couple seconds longer than a normal start.

It will get down to 9c tonight so, I’ll let the car sit outside and chill out lol… and then try a cold start again. This will be about the most ideal conditions I can give so, if it struggles again, I am completely out of ideas.

ah well.

wait and see.

still have not got to mine. nearing the end with the falcon but as usual i was over optimistic re time to finish it.

stacking up all my 914 components to hit it.
meanwhile, really enjoying driving it at the moment. weather is fine and sunny without being insanely hot and projecting death ray UV.

its running real nice apart from --------the same warm up weak knees as yours van.
but the good thing is while i have its arse stuck out of my roller door in the lane lots of old guys walk past on their way to the super market and i make their day --- apart from the old lady with her poodle that has a bow tie who makes a big scene every time holding her nose. its got me beat why she keeps taking the same short cut to do her shopping.
the poodle barks at the car like an extension of her personality.

look forward to your report.