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> 1974 1.8L engine fast idle then stalls, Fuel injection issues
wonkipop
post Feb 20 2023, 06:52 PM
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QUOTE(Van B @ Feb 20 2023, 06:45 PM) *

@wonkipop . What he described is exactly what happened when I started the car and forgot to plug in the AFM. Steve tried it and the same thing happened for him. You tried it and it didn’t work. That’s when I realized my fuel pump wiring was wrong as yours was OE and Steve and I had a different setup from the relocation to the front.


yeah -
see my post above where i edited it. memory recall was coming back.
i'm getting old and my ECU is a bit hard to fire up.
but i was remembering you did something exactly like this.

i'm thinking his pump wiring is letting the engine run because it does not need the AFM contacts operating at idle to do it.

and i'm thinking that maybe his EFI plug and harness from AFM to ECU is possibly kaput.
like despite being plugged in its not actually connecting.
so as you gas it its all over. all air and suddenly no fuel.
the ECU is not opening the injectors. no signal?

would pull those plugs out at both ECU and AFM and given them a good clean first of all.
checking for corrosion. then i guess test it all as per factory manual.
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wonkipop
post Feb 20 2023, 06:56 PM
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@Van B

which is to say as i suspected that high idle at start is not directly connected to his other problem. yeah its running at idle and weird but if it was factory set up it would not run at all. which is his real problem. if i recall correctly what mine did with plug out was fire up into life and then die immediately. as you would expect with original wiring of fuel pump to only run on crank and then hand off to AFM as soon as it fires and moves the flap, just that little bit that opens the fuel pump contacts.

which is why i think its not a vac leak that is his problem. (though never say never completely).

the real symptom to investigate in a trouble shooting manual is --->starts, then immediately dies and will not idle. as is noted in original post as the first sign of trouble some time back--------> before undertaking additional work? on fuel system? etc.

question for @tshih914 did you do anything to fuel pump in your work doing fuel lines after the problem initially presented with difficult start?
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Geezer914
post Feb 20 2023, 07:13 PM
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Go to Jeff Bowlsby's web site
and get the Ljet fuel injection wire harness diagrams. Get a test light and check the continuity of the wire harnesses.
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porschetub
post Feb 20 2023, 08:34 PM
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QUOTE(wonkipop @ Feb 21 2023, 11:39 AM) *

QUOTE(Van B @ Feb 20 2023, 04:24 PM) *

Boy does that all sound familiar.

I’d still like to know what changed from when it ran normal.


it does sound a bit familiar, but not completely the same.

he said he left it to sit in storage for a few years.
something in there gave up the ghost during rip van winkle period.

they don't like sitting around.

(IMG:style_emoticons/default/agree.gif) reckon the only thing that will cause that is a sticking air gate in the AFM,most normal air leaks will cause a high idle of say 1500 but generally not more but not 3000.
I had this with one of my old BMW's after top overhaul and found the AFM was full of crap,run great after a good clean,same system but the 914 AFM is known to suffer issues after backfire of I'am thinking that's happened.
Cheers.
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JeffBowlsby
post Feb 20 2023, 11:58 PM
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You might also check the quality of the contacts in the harness connector to the AFM. Bent? Gapped? Corroded/dirty? It’s very common for the old original contacts to be worn out by now, negatively affecting connectivity . The contacts are two cantilever springs that separate due to 50 years of metal fatigue, in addition to dirt, corrosion and others contamination causing deteriorated connectivity.
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wonkipop
post Feb 21 2023, 02:57 AM
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QUOTE(porschetub @ Feb 20 2023, 08:34 PM) *

QUOTE(wonkipop @ Feb 21 2023, 11:39 AM) *

QUOTE(Van B @ Feb 20 2023, 04:24 PM) *

Boy does that all sound familiar.

I’d still like to know what changed from when it ran normal.


it does sound a bit familiar, but not completely the same.

he said he left it to sit in storage for a few years.
something in there gave up the ghost during rip van winkle period.

they don't like sitting around.

(IMG:style_emoticons/default/agree.gif) reckon the only thing that will cause that is a sticking air gate in the AFM,most normal air leaks will cause a high idle of say 1500 but generally not more but not 3000.
I had this with one of my old BMW's after top overhaul and found the AFM was full of crap,run great after a good clean,same system but the 914 AFM is known to suffer issues after backfire of I'am thinking that's happened.
Cheers.


yeah though this is even weirder and its something @Van B discovered.

it could be internal to the AFM like dirt, corrosion.wear on contacts etc.
but @tshih914 does have a new/rebuilt AFM now. i would think its probably pretty ok in those terms.

@Van B is on to this one i think.

if there was ever an argument for preserving a car in original condition - and by this i mean technically, not just aesthetically, it was during his relentless program to get his 1.8 running right. he knew i had a pretty unmolested car. so he kept giving me scenarios to try on mine. we didn't get the same outcomes. eventually between us all we cracked the fuel pump wiring trickery.

it sure is weird. but if that fuel pump is wired to the ignition circuit and it stays on, the car will run with the AFM disconnected from the ECU. but only with the TPS closed in idle position. no other position. and however it does it, it runs it at elevated revs.

and if its factory original wiring to fuel pump it won't run. it will fire, but it won't continue to run.
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wonkipop
post Feb 21 2023, 03:05 AM
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QUOTE(JeffBowlsby @ Feb 20 2023, 11:58 PM) *

You might also check the quality of the contacts in the harness connector to the AFM. Bent? Gapped? Corroded/dirty? It’s very common for the old original contacts to be worn out by now, negatively affecting connectivity . The contacts are two cantilever springs that separate due to 50 years of metal fatigue, in addition to dirt, corrosion and others contamination causing deteriorated connectivity.


yes.
and you are the man who would know. (IMG:style_emoticons/default/beerchug.gif)
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tshih914
post Feb 22 2023, 07:36 PM
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QUOTE(wonkipop @ Feb 20 2023, 02:13 PM) *

@Van B

thinking about his problem there are two tests he can do right now without fiddling with anything or altering things as they stand. given the engine starts and fast idles at 3000 rpm. its obviously getting fuel at crank and at idle. and plenty of air.

1. before starting check the operation of the throttle valve. move it around by hand and make sure it is moving freely and resting right back at closed position.

2. start it up and let it settle at its 3000 rpm.

3. clamp off the vac hose tightly shut between decel valve and intake plenum.
note what happens if anything. does idle change. (make sure you clamp the right hose, its the one that comes out of side of decel valve and goes to intake plenum EDIT - sorry it comes out of end of decel and goes to plenum - it operates the valve off vacuum, but thinking about it you can also clamp off the hose that comes off side as its getting the air from the intake boot, so either of those can be clamped off shut).

4. unclamp hose. let engine return to 3000 rpm if it did change.

5. clamp Aux Air Valve hose tightly shut between end of AAV and intake boot.
(clamp it before it gets to the Y junction into boot as you want to isolate the AAV. - the other hose off Y junction is going to the decel valve).
note what happens if anything. does idle change.

Refer excellent video by prof Van B of hoses posted above to know which hoses referred to.

report results of 3 and 5 back here.

------

@wonkipop

When I pinched off either one of the 2 hoses from the decel valve to the intake plenum the idle dropped from 3000 to closer to 1000 rpm. (result of 3)

The idle also dropped when AAV hose was clamped (result of 5.)


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Van B
post Feb 22 2023, 08:19 PM
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Whatever you have back there by the batter near where the decel valve should be is not the correct part. If that thing is opening at idle, it will surely cause a high idle.

Edit: here is a thread of mine about the decel valve.
http://www.914world.com/bbs2/index.php?s=&...t&p=2956383

Leave the Aux Air Regulator/Valve alone for now as it should be open until the engine is warm.
But if what I’m seeing back there on your second picture is the AAV setup, its a hot mess and probably a big part of your problem.
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tshih914
post Feb 23 2023, 04:46 AM
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QUOTE(Van B @ Feb 22 2023, 06:19 PM) *

Whatever you have back there by the batter near where the decel valve should be is not the correct part. If that thing is opening at idle, it will surely cause a high idle.

Edit: here is a thread of mine about the decel valve.
http://www.914world.com/bbs2/index.php?s=&...t&p=2956383

Leave the Aux Air Regulator/Valve alone for now as it should be open until the engine is warm.
But if what I’m seeing back there on your second picture is the AAV setup, its a hot mess and probably a big part of your problem.

@van B
Lol the hot mess near the battery is indeed not stock. When I replaced the fuel lines I used the braided hoses to connect the steel lines in the tunnel to the non-stock metal fuel filter inline to the remnant plastic line feeding the engine fuel rails (temporary hook up since I intend to stick a 2L rebuilt engine when done in place of the 1.8L currently in place). That mess is not any vacuum hose causing/relating to my high idle issue.
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Van B
post Feb 23 2023, 05:54 AM
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Ok. Glad that thing wasn't some decel valve rip off. So, what you can do next is take off the decel valve and adjust it. I went through that in the thread I posted the link to. You just need a vacuum gauge.
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Geezer914
post Feb 23 2023, 08:45 AM
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Got rid of all that shit, the decel valve and the charcoal canister.. Just have a hose from the oil fill neck to the throttle body boot and kept the auxiliary air valve.
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rjames
post Feb 23 2023, 11:50 AM
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QUOTE(Geezer914 @ Feb 23 2023, 06:45 AM) *

Got rid of all that shit, the decel valve and the charcoal canister.. Just have a hose from the oil fill neck to the throttle body boot and kept the auxiliary air valve.


Keep the decel valve as long as it's functional and you can set it properly. It should help extend the life of the MPS diaphragm.
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wonkipop
post Feb 23 2023, 11:54 AM
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QUOTE(rjames @ Feb 23 2023, 11:50 AM) *

QUOTE(Geezer914 @ Feb 23 2023, 06:45 AM) *

Got rid of all that shit, the decel valve and the charcoal canister.. Just have a hose from the oil fill neck to the throttle body boot and kept the auxiliary air valve.


Keep the decel valve as long as it's functional and you can set it properly. It should help extend the life of the MPS diaphragm.


no mps in a L-jet. so decel is not as critical as it is in D jet.

however agree with you, there is no need to get rid of the decel valve.
@Van B has successfully adjusted one to the correct level.

but this is not his real problem?
his problem is the car only starts and runs at this idle level and dies as soon as he gases it.

the decel valve is elevating the idle level for sure.
if it was adjusted correctly idle would drop.
but.......it would still have the problem of not running once the tps switch comes off idle.

test would appear to indicate that the AAV is working as it should. maybe.
i imagine the engine was still cold when he did this test for us.
eventually it would probably have closed and the 3000 rpm would have dropped slightly. later on he can test his AAV to make sure its closing properly.
but not critical at this stage.
its not his real problem.

he can now move on to the next test which i have described in further post.
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rhodyguy
post Feb 23 2023, 11:58 AM
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Curious. What kind of condition are the oil fill tower gaskets in? Replaced?
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wonkipop
post Feb 23 2023, 12:00 PM
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ok @tshih914

@Van B (i'm sure) and i would like you to do one more test.

pull the AFM plug out (you can pull it out up at the AFM unit on the aircleaner) and see it if starts and runs at this 3000 rpm. don't touch the gas pedal. just let it start on its own.

if it does start and run do a second thing.

turn if off, restart it without touching the gas pedal or throttle and then once its running again at this steady 3000 open the throttle to give it the gas and see what happens. again with AFM plug out.

report back on the result.
-------


thanks for including the photos.
i am studying them trying to look at area between battery and firewall.
it looks like your ECU is not securely fixed but floating around in there.
its been rotated 90 degrees.
not that its necessarily the cause of your problem,
but @Van B (and i) are thinking of your ECU to AFM connection.
the test i have asked you to do is going to see if this is the problem.


-------

i can see from photos how you have rigged up the fuel lines.
looks fine. i can see most of your vacuum lines and they look right and looks like you have gone over them. i can even see the intake runners appear to have new or good condition woven seals. so all that looks pretty good for being tight and leak free.

its a good idea inserting a full flow high pressure fuel filter in the line like you have.
i have one too which i have installed in almost the same spot.
will save your injectors if you have a newer type fuel pump and it detonates internally.

which leads to the next question.

when this problem of more and more difficult starting first was happening, where was the fuel pump and what was it. original type pump under engine bay on rhs? with original electrical connection?

and did you install a new fuel pump with all your work on the fuel lines.
if you did, where is it, what type and how is it wired in to run?
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Van B
post Feb 23 2023, 02:50 PM
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@wonkipop if the decel valve is full flow, it could still make the car stall as soon as he touches the gas because you're just introducing even more air into an already excessively lean scenario.

that said, I agree that this symptom is way to similar to what we learned about how the engine acts when the AFM is unplugged/dead and the fuel pump is DAPO wired.
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wonkipop
post Feb 23 2023, 03:58 PM
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QUOTE(Van B @ Feb 23 2023, 02:50 PM) *

@wonkipop if the decel valve is full flow, it could still make the car stall as soon as he touches the gas because you're just introducing even more air into an already excessively lean scenario.

that said, I agree that this symptom is way to similar to what we learned about how the engine acts when the AFM is unplugged/dead and the fuel pump is DAPO wired.


yes agree re the decel valve/lean scenario.

test i have suggested is another easy one to do without jiggling or mucking about with anything much.

just methodically ticking it off.

he should definitely go and adjust the decel valve following your instructions in thread you linked to. but before he takes if off and does that, just to run this test.

and tell us how the fuel pump is wired.

it won't exactly nail it down to the ECU connection.
but i'm thinking about how he reported the problem initially arising.
progressively more difficult starting.
then it dying when he gassed it.
to me this is the real problem he has?
that could point to either poor contacts in the AFM unit itself or a dodgy ECU/AFM connection. progressive degeneration of an electrical contact? he has a new AFM now, so its unlikely to be internal to that.
but the other two parts could still be the issue.

he has subsequently done more work on the fuel system.
so now it appears to start ok, but run only at idle.
so something did change.
we both know how that can happen if the fuel pump is not wired OE.
it can and will start easily. with that plug out. when it should not.
but it won't do much else.
i guess i am interested in whether his work in between has resulted in this easier start.
but thats all its resulted in. and its a bit of a smokescreen.

and perhaps most importantly in between these two states of affairs it seems it ran fine for a while!!!

lets see.

i'm also looking at that ECU which is very evident in photos to be in a less than desirable state of affairs. perhaps he has just disconnected its mounting as he undertakes this work. but its not great.

---------

after he reports back we could also get him to run an easy test on the decel to explore your suggestion. even before he adjusts it he could take it out of the equation by pulling the hoses out of it. and plugging the hoses. it should still start i think, even without all that air its getting from the decel - but start and idle lower.
he can then give the throttle a tweak and see what happens. ie does it die once it comes off TPS or will it respond to throttle and not die.

but i am thinking one step at a time.

do test i suggest above in previous post first.

then do the decel valve delete test second.
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wonkipop
post Feb 23 2023, 06:50 PM
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ok
@Van B and @tshih914

i found Van's topic regarding the way the car will run with the AFM plug out.

link to the page.
goes over next 3 pages.

http://www.914world.com/bbs2/index.php?sho...6678&st=320


mine with OE wiring of fuel pump (runs when cranking and then runs off AFM flap which moves enough at idle to open the fuel pump contacts) would crank and fire and run for about 10 seconds from a cold start. conclusion was it was running off cold start injector.
after that on repeated starts it would crank, fire for a second and die.


starbear's with non OE wiring of fuel pump (pump on whenever ignition on).
good condition AAV. good condition decel.
would crank, fire and run but die after a longer period of time than mine.
repeated starts led to repeat of cycle except it ran at idle on its own for longer each time with revs gradually rising.
eventually getting out to running for 40 seconds.


van's with non OE wiring of fuel pump similar to starbear.
started with high idle (1400). slowly rose to 2000 rpm this was when the car was still suffering from a poor low idle at cold due to the non functioning AAV. but after a non functioning decel valve had been corrected. ran happily at high idle. van blipped throttle and it died. started it a second time and it repeated the effort.
van noticed the next day his AFM plug was out. plugged it back in and car started normally with its usual poor/low idle from cold.

as a result of this accident, wonki and starbear were asked to see if they could repeat what van's car did. see results above.

from this we worked out that if the ignition circuit was running the fuel pump an L jet would start and run in a strange way without the AFM plug. but only if the ignition circuit was running the fuel pump. wonki car with OEM wiring needed the hand off between the cranking circuit running the f p to the AFM flap which kicked forward and opened the contacts to run the fuel pump. no hand off with the plug out. so it dies instantly.

none of them would run once you kicked the throttle open as all of them were looking for the AFM signal once the throttle comes off the throttle position switch at idle.

this is the condition we want to try and tick off the list for @tshih914 .
to do this we have to work out what is running the fuel pump at start up.
is it ignition circuit modification or is it still stock.
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tshih914
post Feb 23 2023, 07:58 PM
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QUOTE(wonkipop @ Feb 23 2023, 10:00 AM) *

ok @tshih914

@Van B (i'm sure) and i would like you to do one more test.

pull the AFM plug out (you can pull it out up at the AFM unit on the aircleaner) and see it if starts and runs at this 3000 rpm. don't touch the gas pedal. just let it start on its own.

if it does start and run do a second thing.

turn if off, restart it without touching the gas pedal or throttle and then once its running again at this steady 3000 open the throttle to give it the gas and see what happens. again with AFM plug out.

report back on the result.
-------
@wonkipop The fuel pump was left as OEM stock just replaced the old fuel hoses to tank and line to engine.

I unplugged the AFM and the engine started after several attempts and started to idle around 1200 rpm initially then rose to 2000 rpm. Shut it off and upon restart while at 2000rpm try to give it gas it immediately stall. All the while unplugged so no AFM inputs

thanks for including the photos.
i am studying them trying to look at area between battery and firewall.
it looks like your ECU is not securely fixed but floating around in there.
its been rotated 90 degrees.
not that its necessarily the cause of your problem,
but @Van B (and i) are thinking of your ECU to AFM connection.
the test i have asked you to do is going to see if this is the problem.


-------

i can see from photos how you have rigged up the fuel lines.
looks fine. i can see most of your vacuum lines and they look right and looks like you have gone over them. i can even see the intake runners appear to have new or good condition woven seals. so all that looks pretty good for being tight and leak free.

its a good idea inserting a full flow high pressure fuel filter in the line like you have.
i have one too which i have installed in almost the same spot.
will save your injectors if you have a newer type fuel pump and it detonates internally.

which leads to the next question.

when this problem of more and more difficult starting first was happening, where was the fuel pump and what was it. original type pump under engine bay on rhs? with original electrical connection?

and did you install a new fuel pump with all your work on the fuel lines.
if you did, where is it, what type and how is it wired in to run?

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