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

[wonkipop]

f-en weird.

i did not try repeated cranks on mine cold - test 1.
might redo test 1.

though starbears is very similar to mine on the first time it started - about 10 seconds.
sb's would have taken those six cranks to build fuel pressure from cranking as it had been sitting a while? the running for 10 seconds bit is exactly like mine.
i just didn't do the repeated cranks after 30 seconds - so who knows, mine might do that from cold. wouldn't do it warm though.

i was going to ask you van if your fuel pump had been moved.

steve - has your fuel pump been moved up front.

mine is in original spot.
but is a new fuel pump - turbine two port.
but i don't believe we rewired anything.

Yes, moved mine to the front a few years ago. A trusted mechanic so doubt it was wired differently.

yeah the six cranks at the start make sense with the f p up the front.
takes a lot longer to build the pressure in that long circuit than mine.
mine is pretty instant. not suprising with original f p location.

i could not believe how it started yesterday.
bang. i honestly did not even hear the starter motor it was so instant.

[Van B]

I honestly can’t understand the point of the OE three port fuel pump. It was such a chore to sort out the mess of lines that the PO left for me to deal with. I can’t believe a couple of them hadn’t rubbed through between the pressure against a sharp metal edge and the broken mounts for the fuel pump.

[wonkipop]

I honestly can’t understand the point of the OE three port fuel pump. It was such a chore to sort out the mess of lines that the PO left for me to deal with. I can’t believe a couple of them hadn’t rubbed through between the pressure against a sharp metal edge and the broken mounts for the fuel pump.

they make sense in the original location.
all the fuel lines come into one end of it and don't do any vicious curves.

i had to put an inline turbine pump in. which is
a) longer
b) has a line in each end.
i have that pump in the original location.

thats why i am having that little hunting problem on real hot days and the low fuel tank.
the curve i had to do with the hose into the top (inlet) is just tight enough despite the care i tried to take getting it all in, that the fuel after a while is heating enough to boil at that curve before the pump causing the pump to cavitate. also the fuel has to travel about 4-6 inches higher up in the air than it does with the 3 ports down at the bottom of the pump. given its gravity feed from the tank it all adds up enough to disturb things on warm enough days. whereas the old pump never suffered from vapor lock despite the rep. the pump in 74 was jammed right up in the furthest right hand corner of engine bay.

[Van B]

Yeah the mounting location is still there on mine. First time I saw it I was confused. I plan to ditch the three port and put the Bosch pump you have. Then I can run the return line straight from the firewall to the tank. A pump with a little more gusto would be good considering it’s up front now.

[wonkipop]

re having three ports.

the mercs had the same thing but the pressure relief port was internalised.
and so it was hidden.
from the same era they look like two ports but the pressure relief valve is inside as part of the housing under the other end of motor. so it just reliefs backwards into the supply line.

vw and others used the three port to pressure relief back into the tank return line.
i think this was a alternative for a design engineering situation where you wanted all your lines coming in at one end of pump in a tighter space. made the pump itself more compact in terms of the motor housing length and grouped all lines at one end.

i managed to rebuild two of these pumps.
my original one and one out of a 74 saab.
both have barely any wear on the motor brushes bits.
they were just leaking from all the dried out o ring seals.
mine's going back in when i tackle all this business you have been investigating van.

[Van B]

Well… I’m not out of the woods yet fellas. I just tried another cold start after letting it chill in the garage for several hours. It took 5-6 cranks and then it fired up. But this time it went to a low sort of idle after the 8sec of CSV ended. Stable but low. Definitely improved but not like it was earlier today. I touched the TTS and engine case to make sure they were cold enough to activate that cycle and I’m confident they were. So, I’ll think about it tonight and try again in the morning.

[wonkipop]

Yeah the mounting location is still there on mine. First time I saw it I was confused. I plan to ditch the three port and put the Bosch pump you have. Then I can run the return line straight from the firewall to the tank. A pump with a little more gusto would be good considering it’s up front now.

something to be aware of is you are/will be running high pressure line through the cabin.
is it still the original clear plastic line?
if it is its pretty old by now.
you would want the steel lines in.

thats part of the reason i decided to stay with the fuel pump in original location.
i don't have high pressure through the cabin.
but i did renew the plastic lines and made my own out of mild steel tube.
the ss kits won't work for right hand drive at the top end near the front firewall.

when the factory went to front fuel pump in 75 they changed the plastic lines through the cabin to a different type of plastic. for high pressure.

back in the cowboy days of front fuel pump updates it always was on my mind that folks were running high pressure through a clear plastic line that was originally designed for low pressure gravity feed.

they seemed to get away with it. but.............

[wonkipop]

Well… I’m not out of the woods yet fellas. I just tried another cold start after letting it chill in the garage for several hours. It took 5-6 cranks and then it fired up. But this time it went to a low sort of idle after the 8sec of CSV ended. Stable but low. Definitely improved but not like it was earlier today. I touched the TTS and engine case to make sure they were cold enough to activate that cycle and I’m confident they were. So, I’ll think about it tonight and try again in the morning.

damn.

i want you to crack this ---for purely selfish reasons i admit. (IMG:style_emoticons/default/smile.gif) (IMG:style_emoticons/default/beerchug.gif)

[Van B]

I haven’t pulled up the carpet, but I know I have flexible plastic tubes coming our the rear firewall and stainless steel lines, coming out the front under the tank.
Don’t know if that’s stock or not.

[emerygt350]

Yeah, stock.

[wonkipop]

Yeah, stock.

......and ready to burn with 35lbs of healthy pressure testing them out.

[wonkipop]

[wonkipop]

oh yeah.

just been for a nice drive in mine.
pulling out afm plugs didn't re-arrange any electrons in the jurassic brain box.
same old stumble into a hole cold start.
but if did do the bam start thing.

drove fine after warm. still grinning.

[wonkipop]

@Van B

i sat down with mike today at lunchtime and asked him to explain to me exactly how its working at cold idle and warm idle and how do you diagnose the cause of the weak cold start.


first thing to do.

this is a cold start test.

disassemble air cleaner - prop up or hold the afm section so you can see into it and operate it.

you will need someone to sit in the car and start it.

after it uses up the cold start injector fuel, push on the stator flap in. gently but a bit more and a bit more.

if revs increase, say to 1200 or a more.
there is enough air, but its too lean under warm up. (ie you just gave it some more fuel for the same amount of air) it can only pull it through the aav.

if revs decrease or it dies.
its got enough fuel but its not getting enough air under warm up. the aav is no good.

thats step one.


i asked him about the stator flap being open at warm idle.
he told me to do the same thing and look inside it with a torch and see for myself.
(IMG:style_emoticons/default/blink.gif)

[wonkipop]

........and he had a view on why your cars ran.

steve. you better check yours. its 99% sure to be set up like vans.
they would have just found a source off the ignition circuit.

its not that big a deal. but it does mean your fuel pump won't switch off after an accident with the engine stopped but the ignition still on.

[StarBear]

........and he had a view on why your cars ran.

steve. you better check yours. its 99% sure to be set up like vans.
they would have just found a source off the ignition circuit.

its not that big a deal. but it does mean your fuel pump won't switch off after an accident with the engine stopped but the ignition still on.

Thanks for the tip. I’ll check it out.

[Van B]

So, I do not hear my fuel pump running when the ignition is switched on. But I have located the 12v wire as being routed to the bottom of the relay board. Next I need to determine what it's plugging into.

I've also decided to replace my alternator. Even with the improvements made, I'm still getting a "G" light on startup and have to give a little dab of throttle for it to go out. yesterday I put a multimeter on the battery after a cold start and gave it throttle from the engine bay so I could see what was happening.
Keep in mind I spent $200 on a fancy and near impossible to find Bosch Solid State regulator in a previous attempt to solve the issue. What the multimeter revealed is that I'm lingering at 12-ish volts after start (raw batt voltage), when I give a light dab of throttle, it slowly starts to build voltage over about a minute; 13.1, 13.5, and then settles at 13.98v.

I don't think I can confidently assess ignition health on cold start with an issue like this in the background so, I have a Bosch reman alternator on the way.

[Van B]

@Van B

i sat down with mike today at lunchtime and asked him to explain to me exactly how its working at cold idle and warm idle and how do you diagnose the cause of the weak cold start.


first thing to do.

this is a cold start test.

disassemble air cleaner - prop up or hold the afm section so you can see into it and operate it.

you will need someone to sit in the car and start it.

after it uses up the cold start injector fuel, push on the stator flap in. gently but a bit more and a bit more.

if revs increase, say to 1200 or a more.
there is enough air, but its too lean under warm up. (ie you just gave it some more fuel for the same amount of air) it can only pull it through the aav.

if revs decrease or it dies.
its got enough fuel but its not getting enough air under warm up. the aav is no good.

thats step one.


i asked him about the stator flap being open at warm idle.
he told me to do the same thing and look inside it with a torch and see for myself.
(IMG:style_emoticons/default/blink.gif)

@wonkipop
I certainly appreciate you recruiting your mechanic into the conversation. After I get the alternator in, and before I do any further experimentation with the distributor/ignition, I'll give this a try. Spring is near so, I'm going to be running out of truly cold mornings in a month or so. Normally, I would be firmly excited about that, but my lack of resolution has me a bit frustrated.

I bought this AFM on the samba:
https://www.thesamba.com/vw/classifieds/det....php?id=2399180
Now that it's sold, the other pictures are gone, but it is a NOS of a Bosch reman; which Bosch doesn't do anymore. Best case, this will help me confirm a temp sensor 1 issue; worst case, it's busted from years in storage and will need another rebuild in order to give me a viable spare.

[wonkipop]

@Van B

this is pretty interesting.





http://www.itinerant-air-cooled.com/viewtopic.php?t=7761

[wonkipop]

@Van B

i sat down with mike today at lunchtime and asked him to explain to me exactly how its working at cold idle and warm idle and how do you diagnose the cause of the weak cold start.


first thing to do.

this is a cold start test.

disassemble air cleaner - prop up or hold the afm section so you can see into it and operate it.

you will need someone to sit in the car and start it.

after it uses up the cold start injector fuel, push on the stator flap in. gently but a bit more and a bit more.

if revs increase, say to 1200 or a more.
there is enough air, but its too lean under warm up. (ie you just gave it some more fuel for the same amount of air) it can only pull it through the aav.

if revs decrease or it dies.
its got enough fuel but its not getting enough air under warm up. the aav is no good.

thats step one.


i asked him about the stator flap being open at warm idle.
he told me to do the same thing and look inside it with a torch and see for myself.
(IMG:style_emoticons/default/blink.gif)

@wonkipop
I certainly appreciate you recruiting your mechanic into the conversation. After I get the alternator in, and before I do any further experimentation with the distributor/ignition, I'll give this a try. Spring is near so, I'm going to be running out of truly cold mornings in a month or so. Normally, I would be firmly excited about that, but my lack of resolution has me a bit frustrated.

I bought this AFM on the samba:
https://www.thesamba.com/vw/classifieds/det....php?id=2399180
Now that it's sold, the other pictures are gone, but it is a NOS of a Bosch reman; which Bosch doesn't do anymore. Best case, this will help me confirm a temp sensor 1 issue; worst case, it's busted from years in storage and will need another rebuild in order to give me a viable spare.

mike was telling me about the AFM on 964s yesterday.
porsche reverted to stator flap AFMs on those cars.
he said that the printed track can get a lot of wear around the idle position from years of doing city traffic. that can upset things with those cars.

again - i have not opened my AFM up. that can wait for time and space in the workshop.
edged the falcon that bit closer yesterday. i'm discovering that finishing the final touches on reassembly takes about 3 times the amount of hours you think it does.
especially when you hit small hitches correcting things broken on the car and cobbled together over its life in the previous 25 years. morning consumed by a tail light lens yesterday.

----

re alternators.
most will struggle with output if engine is below 750/800 rpm.
its a kind of a catch 22 situation? - for the alternator if the engine doesn't jump to a strong start. or is there some other subtlety here you can explain to me so i can go looking for that when the time comes.

------

be interested to hear confirmation on fuel pump running or not with ignition on.
because unless that stator flap is controlling it there is no way it should run and for there to be fuel pressure. depending on the fuel pump they can run pretty quiet. my orig three ports were pretty quiet when i bench tested them running kerosine through them.


.