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

[wonkipop]

Where can I get a proper fuel filter for my car? I ordered the round Mahle filter from FCP Euro, but it looks pretty small. I haven’t pulled the tank yet so, I’m only guessing right now. But I figured I’d trust my instinct and ask you guys.

you mean the little plastic cube ones?
i don't think you can get them any more.
also, i think the small mahle cylinder ones you get now might be better?

i've got one left in my box of ones i stockpiled 2 decades ago.
think i got them from Tweeks on west coast, out of business these days.

if you really want one a cube type (they do fit well into the clips off the body) you might be able to get them from a VW online parts shop. quality might be suss. chinese? look for old stock good stuff.

---

i fitted a high pressure cylindrical fuel filter after the pump in the engine bay.
main reason being i had to put a new pump in (for the moment).
original bosch roller cell pumps = a robust design. modern turbine pumps a different matter. i'm looking after the injectors i got given they are n l a.

my set up is the small cube in the gravity line near the pump under the engine bay.
and a much bigger high pressure filter in the engine bay mounted off the decel valve mounting plate. pretty sure it is a RAYCO. brand is hidden under the mounting clip.

this bosch one is very similar in size.
https://www.efihardware.com/products/291/fu...njection-filter


edit
i took a look on cipi vw. they do have old style plastic cubes.
but no brand! have the advantage of going into the retaining clips.
if you still have your fuel pump under the engine bay.

my set up is probably overkill.
the old style one theoretically stops shit going in the pump.
and the big one stops the pump shitting itself into the injectors.

[Van B]

I like the two filter idea. As long as I don’t restrict the pump, I think a pre and post filter would be good insurance. Like I said, I cleaned out eBay on original Bosch injectors so, just like you, want to make sure they last.

[Van B]

Here’s an update on what I’ve got cooking:
I cleaned out eBay for original Bosch injectors. I’ve bought seven NOS 0280150112 injectors. I’ll send all of them out to get dynamic flow testing and see if I have four that can make a matched set. The other three I will sell on here. @StarBear I see that you bought a couple recently so, if you want to complete a set let me know.
Also, I bought a new thermo time switch for a 924/944. The research I’ve done confirms that this part number also traces to the 912E. Not sure why nothing connects back to our 914, but I will compare them with a multimeter at various temps and see what we get.

Reasons for these endeavors are that I noticed a miss for a couple minutes after start on one of my recent attempts. My hypothesis is that if an injector is firing all Wonkipop (lol) then fuel could just be jetting onto the cylinder and not firing until temps get high enough to vaporize the fuel.

Further, I only get a couple of seconds of high idle when the engine starts which is almost certainly thanks to the CSV. So, maybe the thermo switch is not behaving correctly and telling the CSV to run for it’s max time of 20sec.

The test procedure for the 914 is closed below 68F or open above. However, the 912E manual gives varying levels of resistance at progressively warmer temps.

We’ll see if any of this bears fruit, but like I said before, I have no clear direction so it’s all trial and error from here.

Van

Sorry folks, but this thread still lives.
I thought this would be a good time to post some updates:
The temp switch for a 944 is the wrong size and also, apparently is configured differently as a switch. After much searching, I ended up buying a thermo time switch for a Nissan/Datsun 280ZX. I thought to try this experiment as these parts are still in production and are cheaper than the superseded option on the Bosch/Porsche option. My next post will be about what I’ve learned on part numbers and options us lonesome L-Jet owners have.

Injectors all showed up, but one came with a broken tip. So, I’m working to get that resolved. Then I’ll be able to send them off for matching. I have high hopes for these injectors as I’m more convinced that something is up with fueling when cold.

Today I put the new thermo switch in the freezer for a bit, tested it, and then plugged it in the car for a test start. Before I forget to mention, my old switch tested bad. So, new switch checked out ok and when I went to start the car, it was hard to start (cranked for a bit). Once it fired, it came up for a solid 8 sec. but then it started to stumble and drag back down. I gave it some revs for several seconds, to about 1500 and the let it settle. When I did that, the car was running at a normal idle, not high idle, but a normal idle.

This change is a definite improvement. But now that we’re having some legit snow and ice weather, I’m getting true cold starts. And this stumble that has appeared certainly seems like an injector issue. I already explained my theory so I won’t recycle that topic. But at any rate, the thermo switch was another defective part removed and a step forward. Plus, we now know that a still in production Nissan part will work.

More to come,
Van

[StarBear]

@Van B = Yes, please do keep us updated. Interesting.... (IMG:style_emoticons/default/popcorn[1].gif)

[wonkipop]

" @Van B"

i had to go google washington dc weather.
yep, that is a true cold start.
7-8 deg centrigrade colder in washington than n melbourne mid winter. your daily max = our daily min.

the cold start injector should, according to the manual, still do some squirting for a very brief time after the engine fires when temps are below 50F, not just on cranking.
so if your thermo switch was not working properly the csi might have been only activated while cranking. somewhere in material i have it says the thermo-switch can keep the csi activated for a maximum of 20 seconds (am guessing though that amount of time would be in super cold conditions near arctic levels of cold?).

thanks for the tip on datsun thermo switch. will see if i can get one down here for the box of spares.

[Van B]

" @Van B"

i had to go google washington dc weather.
yep, that is a true cold start.
7-8 deg centrigrade colder in washington than n melbourne mid winter. your daily max = our daily min.

the cold start injector should, according to the manual, still do some squirting for a very brief time after the engine fires when temps are below 50F, not just on cranking.
so if your thermo switch was not working properly the csi might have been only activated while cranking. somewhere in material i have it says the thermo-switch can keep the csi activated for a maximum of 20 seconds (am guessing though that amount of time would be in super cold conditions near arctic levels of cold?).

thanks for the tip on datsun thermo switch. will see if i can get one down here for the box of spares.

There he is!
Brother the weather here got stupid for several weeks and peaked with 30cm of snow over night and then stayed around freezing for a week lol. 8c was real nice after all that.
I’ve been here three years now and it seems like we get one of those a year… I miss Houston.

About the CSV, I looked back at my test video and it was only spraying while cranking. So, I missed that clue. But I also think the switch having continuity below 19.5c/68f is also telling the computer to enrich the mixture.

Anyway, here’s what I’ve learned about thermo switches for the L-Jet:

The ‘74 VW part number is 022906163. Later cars including the 912E got 043906163, which turned into 043906163A according to several online sources.

Abbreviated part number trail:
022906163 (VW) = 0280130202 (Bosch) > end/NLA

043906163 (VW) > 043906163A (VW) = 0280130214 (Bosch) > 92860510102 (Porsche) = F026T03100 (Bosch) = current/avail

The significant difference between the part families is that our original part was 19.5c for 8sec and the other family is a 35c for 8sec. I think Porsche just dropped the original as they evolved the L-Jet system to later emissions requirements; but that’s speculation.

Now, how I got to the Nissan Part was on a hunch thanks to @JeffBowlsby and his info about the licensing agreement from the Datsun days. Turns out Nissan still sells, via VDO license, the unaltered original part for a 280ZX as PN - 22635-N4711. As you can see from the photos, it is still made to the same spec as our now dead Bosch part at 19.5c/8sec. Further, it can be had for around $50-$75 less than the superseded Porsche/Bosch part depending on the sources available to you. As I described in my previous post I tested it and it works/fits just like the original.

The current Bosch is of a different built than the old style but I’m sure it’s still an option if you wanted to go that route as evidenced by the fact that mine had been replaced with a previous version from that family.

Van

[wonkipop]

@Van B

that sure is interesting with those temp numbers.

good old 19.5 celcius = that magic 68F that the EPA drew the line at?

whereas your 35C, man thats getting warm. the temp here today is 33C and its still going up. but out in the garage i would still consider that a "cold" start on the car left overnight. so would the more modern citroen and renault out there.

that datsun switch sounds kind of right.

most of the time the 914 fires up on about the second turn of the starter motor, - like pretty instant. which would be like 2-3 seconds of fuel from the csi while it cranks.
and unless its under 19.5C its not going to get much more is it? with an original thermo switch (and i'm pretty sure mine is original but still working, or was two years ago).
and most of the time down here except for three months of the year its over 19.5C.
so i reckon i'd be lucky to get more than 4-5 seconds of fuel out of the csi from the thermo and cranking in winter down here.

mine is starting fine though at moment. about 30 seconds of 700-750 rpm and then it climbs to steady 850-900. but its pretty warm right now and strangely humid.

(IMG:style_emoticons/default/beerchug.gif)

[Van B]

When my car is 10c or less, it takes several seconds of cranking before it fires… on occasion two attempts.
I have high hopes about this fuel injector swap

[wonkipop]

you don't need to worry about your cold start injector over in western australia at the moment. (its a bit cooler here relatively speaking).

https://www.abc.net.au/news/2022-01-13/onsl...ecord/100754082

[StarBear]

@Van B Thanks ever so much for your search and finding on the thermostat switch part. This thermo switch- where is it located? Is this the part that extends out from the oil sump cap underneath the car? (IMG:style_emoticons/default/confused24.gif)

[wonkipop]

@Van B Thanks ever so much for your search and finding on the thermostat switch part. This thermo switch- where is it located? Is this the part that extends out from the oil sump cap underneath the car? (IMG:style_emoticons/default/confused24.gif)

right near the cold start injector steve. tucked under front intake manifold and vac hoses on rhs. if you want to get it out i think it helps to take the cold start injector off first. van will know for sure.

one on the sump is for your temp gauge in the console.
your special mate having a console.
we just have to guess we are cooking the engine.

[StarBear]

@Van B Thanks ever so much for your search and finding on the thermostat switch part. This thermo switch- where is it located? Is this the part that extends out from the oil sump cap underneath the car? (IMG:style_emoticons/default/confused24.gif)

right near the cold start injector steve. tucked under front intake manifold and vac hoses on rhs. if you want to get it out i think it helps to take the cold start injector off first. van will know for sure.

one on the sump is for your temp gauge in the console.
your special mate having a console.
we just have to guess we are cooking the engine.

Ahhhhh, THAT’S what that thing is. Always wondered. Thanks. Still learning!

[wonkipop]

here you go @StarBear .
i'd have sent this in a pm but i can't seem to do an attachment.

most cars it is screwed through engine block into a coolant passage.
takes on temp of the coolant.
this is where its shown in the diagram of L jet.

in ours, being aircooled its mounted it off a bracket just above engine block under the intake plenum runners. photo (from R Atwell) shows what you see if the plenum off.
screw it out of the bracket with a socket to remove. the c s i might be angled enough to get in the way. you might have to take that off first.

given it does not rest in engine coolant, that probably explains why it has different temp parameters compared to the datsun - a question for @Van B ?

this little thing is one of the babies that controls the c s i. engine cranking is one but this is the other. it either keeps it going for longer than engine cranking and firing or shuts it off immediately, depending on its temp. its basically off completely above a certain temp. there is a bit of conflicting info out there on exactly what that temp is.
my understanding is its got a ideal time on it about 8 seconds at 50F and then gets progressively shorter all the way up to something like 90F but you know there are different versions in the tech lit you read. below 50F it goes the other way - up to around a max time of 20 seconds. (after that you are flooded?). its the time it takes for the electrically heated element in it reach the cut off from the ambient it starts at.

after your engine is hot, its sitting there at cut off so the most the csi does is a quick squirt while the engine cranks.

my experience when i was getting the car going again after its long sleep is that it does signal the c s i to squirt for somwhere between 5 and 10 seconds at around that 50F temp. all of my injectors were SNAFU despite cleaning but the engine fired up and ran for about 5 or so seconds. could only have been firing off the cold start valve. it was late autumn/early winter in melb aus in a cold work shop.

[emerygt350]

That is really interesting! 2.0's have the same thing and i have always wondered what was up with it. It looks just like a coolant sensor on my other waterbuffalos.

Yeah, what the cold start injector actually does is so shrouded in mystery and misinformation I am tempted to pull mine and just watch. I have read in some books it does nothing until you are below 50 and then it is just as the engine cranks, others the 20 second thing. All kinds of stuff. My engine does a really good cold start (even at 10F) so I assume it is working the way it should. I should put one of those current detectors on the wires and see what is doing and for how long. -10F tomorrow, too bad I am not near the garage this weekend.

[wonkipop]

That is really interesting! 2.0's have the same thing and i have always wondered what was up with it. It looks just like a coolant sensor on my other waterbuffalos.

Yeah, what the cold start injector actually does is so shrouded in mystery and misinformation I am tempted to pull mine and just watch. I have read in some books it does nothing until you are below 50 and then it is just as the engine cranks, others the 20 second thing. All kinds of stuff. My engine does a really good cold start (even at 10F) so I assume it is working the way it should. I should put one of those current detectors on the wires and see what is doing and for how long. -10F tomorrow, too bad I am not near the garage this weekend.

yeah, lots of different stories on it.

i take the factory manual to be reasonably accurate. it asks you to test it at 50F.
it should switch off after 11 seconds max. any longer and throw it away. obviously all a bit approximate as a rough test for workshop technicians, you know as if you are going to be standing around waiting for the shop temp to be 50.

lots of other stuff on L jets is for water cooled cars and have different cut off temps.
hence lots of differing info.

but the gist is the same with all.
its a graduating scale all about the time it takes to go from ambient up to the temp the internals heat to and ground the circuit. and if the little fella is already sitting there at that internal temp due to ambient engine heat its already grounded anyway.
but it doesn't necessarily stop the c s i giving a squirt during the cranking.
just like your old school carby car it still needs a little pump of the gas to start even in summer when its been left overnight.

and it is as dumb as being just a water cooled engine sensor.
bosch were running a component supermarket.
just tweaked the internal heated element.
all the rest of it stays the same for whatever car it was going on.
so the vw ones might be super tweaked. which is why i thought all of a sudden to ask van that question.

[Van B]

Went and tested my new switch again since I haven’t permanently installed it yet.
21c/70f, nothing. Open circuit.
18c/65f, continuity.

The part that was in my car, 0280130214; and also broken, is not the correct part. It was a 35c switched used in all sorts of liquid cooled cars; BMW, DeLorean, SAAB, Porsche, etc.

Emery,
Many pages back, I took out the CSV and left it plugged in. I videoed it and it only sprayed while cranking. I didn’t think about it until recently, but it should have kept spraying for 8 sec after start. When I tried the new switch, guess what, 8 sec after start, then off.
I think the computer tells the CSV to spark when cranking just to help start, but only sprays for 8 sec when the switch says so. I’m also speculating that same signal may also tell the computer to richen the fuel mixture for warm up. The AAV circuit always activates for a set time to warm the heating element. But even if the element fails, the engine heat will heat the AAV and make the valve close.

Van

[Van B]

Also, it’s so annoying that my name seems impossible to tag!
@Van B
@“Van B”
“@Van B”
@Van_B

Ugh….

[StarBear]

Ok, maybe an interesting test this morning. Now 10F, “feels like” 0. (IMG:style_emoticons/default/beer.gif)

@Van Yes, the tagging is quirky. Since no other “Van” users it picks that up and stops. Since other “Big” names I’ve not yet figured how to tag @Big Len or @Dr914_AutomobileAtlanta. (IMG:style_emoticons/default/confused24.gif)

[emerygt350]

That always while cranking and 8 seconds when cold is what I suspected was the reality. I think Chilton says a much lower temperature than 65 but I can't remember exactly.

I can detect the enrichment with my afr gauge but it has been cold since I installed it...

[StarBear]

Ok; here’s my morning test:
14F, “feels like” 3F. Sunny.
Used tach for rpm data.
Cranks to start: 7
Secs to start: 3
Initial idle 1100 rpm
1:30 idle 1300 rpm
2:00 idle 1050 rpm
3:00 idle. 950 rpm
4:30 idle. 900 rpm
5:30 idle. 950 rpm
6:30 idle. 1000 rpm
9:30 idle. 1000 rpm
10:30 idle. 1025 rpm
Steady at 1025-1050 after that.
All seems well in New Jersey…. (IMG:style_emoticons/default/biggrin.gif)