1974 1.8L engine fast idle then stalls, Fuel injection issues Options

[wonkipop]

mangled air filter makes no difference to this scenario.
air filter is before the AFM!!!!
your problems are after it.
in airleaks. in the electronics. or the cuckoo clock analogue devices that mate with the electronics. its actually pretty dumb and quite accessible if you are methodical.
it will turn out to be simple. you just have to find it by careful searching.

you can suck in dirt for sure through a screwed air filter.
but....makes no difference to the current crisis.

read the stuff and get a grasp of L jet.
just a basic grasp.
you are an american. thats what americans do.
aussies just try and emulate. (IMG:style_emoticons/default/smile.gif)

then we can get cracking.
Van's your man to guide you through.

don't do anything random or think random thoughts. (IMG:style_emoticons/default/beerchug.gif)

if you are going to do this yourself you have to know what each element does.
its not that hard. if you ask me its more simple than a carb.
just work out what you think each thing does.
and ask questions.
get a grip on each part in the system.
just be an idiot (iggy pop claimed he was and look at him) and ask like an idiot if you have to.
no shame. (IMG:style_emoticons/default/beer.gif)

[Van B]

Thanks for the vote of confidence @wonkipop . I was definitely in that boat in Oct 21 when I got this car and you were one of my mentors then.

I know his AAV needs a good cleaning, but since it’s metered air, I still remain more perplexed by why it won’t take throttle?

[Van B]

@tshih914 . You should post a video so we can see and hear for ourselves.

Also, as a reminder, what do the plugs looks like? For each cylinder?

[tshih914]

When you pinch the AAV hose, and the rpm drops to 1200, does the car take throttle? Or does it still stall?
Also, when you’re doing all this have you ever let the car warm up to operating temp?

Car does not take throttle it stalls

Tried it before and after warming to operating temp. same result.

[tshih914]

@tshih914 . You should post a video so we can see and hear for ourselves.

Also, as a reminder, what do the plugs looks like? For each cylinder?

I only looked at plug under the snorkel it was running rich as I was cranking and cranking initially to get the engine to start (probably flooded until repeated cranking gave way to correct starting mixture.

I did not check for fuel pump running when AFM gate is depressed

[wonkipop]

Thanks for the vote of confidence @wonkipop . I was definitely in that boat in Oct 21 when I got this car and you were one of my mentors then.

I know his AAV needs a good cleaning, but since it’s metered air, I still remain more perplexed by why it won’t take throttle?

so am i.

coud be the throttle position switch?
could be the distributor. not advancing? clagged points. etc
could even be some kind of ignition system / EFI harness gremlin?
could be further undetected air leaks he has not found yet.


@tshih914 needs to progressively eliminate items on the checklist but also take known items out of the system we have already detected that are defective and don't need to be there for now.

1. fuel pressure has been confirmed as in spec and good.

2. decel is defective. eliminate it from system for now. plug hoses.

3. AAV may not be closing. but is useful to start the engine when its cold.
as tshih notes its hard to start. start it. let it get warm for 5 minutes.
clamp the hose.

4. use the idle screw on the t/b to see if he can establish a low idle.
get it down to 1000 or slightly less if he can.
see if it will do it.

i've been doing a bit of reading up on this as you do when its a fault like this to see if owners of other early L jet systems installed in other cars have had this problem.

turns out its a problem in 928s.
Alfa Romeos. and BWMs.
but its not entirely clear, as is often the case, how its been solved.

i also haven't asked mike yet. and i will. he might have an insight.
wasn't much point until some diagnosis had been done.
which at least a little bit has been done now.

[tshih914]

Thanks for the vote of confidence @wonkipop . I was definitely in that boat in Oct 21 when I got this car and you were one of my mentors then.

I know his AAV needs a good cleaning, but since it’s metered air, I still remain more perplexed by why it won’t take throttle?

so am i.

coud be the throttle position switch?
could be the distributor. not advancing?


@tshih914 needs to progressively eliminate items on the checklist but also take known items out of the system we have already detected that are defective and don't need to be there for now.

1. fuel pressure has been confirmed as in spec and good.

2. decel is defective. eliminate it from system for now. plug hoses.

3. AAV may not be closing. but is useful to start the engine when its cold.
as tshih notes its hard to start. start it. let it get warm for 5 minutes.
clamp the hose.

4. use the idle screw on the t/b to see if he can establish a low idle.
get it down to 1000 or slightly less if he can.
see if it will do it.

it showed faint promise of something improving when he did manage to lower the idle by taking the decel out of the equation.

i've been doing a bit of reading up on this as you do when its a fault like this to see if owners of other early L jet systems installed in other cars have had this problem.

turns out its a problem in 928s.
Alfa Romeos. and BWMs.
but its not entirely clear, as is often the case, how its been solved.

i also haven't asked mike yet. and i will. he might have an insight.

While I am trying to sort this issue out I am also in the process of rebuilding a 1975 2.0L engine with D-Jet to upgrade my 1.8L currently in my 1974 914. I am at the stage of doing the valve train and was looking for my engine tins #4 and 5. I found also the decel valve still attached to the end piece engine tin. So can that decel valve be used to replace the bad one in the 1.8L

[wonkipop]

@tshih914 . You should post a video so we can see and hear for ourselves.

Also, as a reminder, what do the plugs looks like? For each cylinder?

I only looked at plug under the snorkel it was running rich as I was cranking and cranking initially to get the engine to start (probably flooded until repeated cranking gave way to correct starting mixture.

I did not check for fuel pump running when AFM gate is depressed

i think its safe to say your fuel pump has been wired to run off the ignition as a result of its modification to location at front of car.

the afm plug out test we got you to do indicated that.

if your fuel pump was wired to run off the afm it would maybe have started and run for about 10 seconds at most. and after that it would not have started.

yours did start and duplicated the behaviour of starbear and van's car.
both of them had the f p wired off the ignition circuit and f p ran all the time.

it will be a little hard to do the AFM test the workshop manual way if the fuel pump is already running. AFM flap won't make a difference. i hope that makes sense.

a better test for you to do is turn the ignition on but don't crank and see if you can hear f p running.

do the test anyway. see if with ignition on and pushing flap does anything.
like switching the fuel pump off? i mean who knows. (IMG:style_emoticons/default/smile.gif)

with those high idle revs you were getting as a result of the AAV and the decel valve,
and assuming the boot was ok between the throttle body and the AFM the flap would have already been being pulled well past its idle position. both those devices feed into the section of air intake above the throttle body which is closed at idle. so the only place they can obtain air is from the AFM intake. (or a leak in the boot).

onward. one item at a time.

EDIT
actually do the flapper test.
just to make sure the flapper is moving freely through its full arc and is not binding or catching anywhere. worth doing just for that check.

[wonkipop]

Thanks for the vote of confidence @wonkipop . I was definitely in that boat in Oct 21 when I got this car and you were one of my mentors then.

I know his AAV needs a good cleaning, but since it’s metered air, I still remain more perplexed by why it won’t take throttle?

so am i.

coud be the throttle position switch?
could be the distributor. not advancing?


@tshih914 needs to progressively eliminate items on the checklist but also take known items out of the system we have already detected that are defective and don't need to be there for now.

1. fuel pressure has been confirmed as in spec and good.

2. decel is defective. eliminate it from system for now. plug hoses.

3. AAV may not be closing. but is useful to start the engine when its cold.
as tshih notes its hard to start. start it. let it get warm for 5 minutes.
clamp the hose.

4. use the idle screw on the t/b to see if he can establish a low idle.
get it down to 1000 or slightly less if he can.
see if it will do it.

it showed faint promise of something improving when he did manage to lower the idle by taking the decel out of the equation.

i've been doing a bit of reading up on this as you do when its a fault like this to see if owners of other early L jet systems installed in other cars have had this problem.

turns out its a problem in 928s.
Alfa Romeos. and BWMs.
but its not entirely clear, as is often the case, how its been solved.

i also haven't asked mike yet. and i will. he might have an insight.

While I am trying to sort this issue out I am also in the process of rebuilding a 1975 2.0L engine with D-Jet to upgrade my 1.8L currently in my 1974 914. I am at the stage of doing the valve train and was looking for my engine tins #4 and 5. I found also the decel valve still attached to the end piece engine tin. So can that decel valve be used to replace the bad one in the 1.8L

yes.
its the same decel valve in the 74 L jet.

may need adjustment though.

you can try it.
but for now i would just take the decel out of the equation and leave it out while we stay on the hunt.

i don't think your problem is a decel valve if you know what i mean.
thats not going to solve the issues.

whats going on with your car are several distinct problems over the top of each other.

we got rid of one of them. a faulty decel.

eventually when everything is sorted you can put a properly adjusted decel back on.
to me its the last item you would reinstall back on at the end of this.

as i have said. i don't even have one on mine and haven't for all the time i have owned and driven it. 34 years. (IMG:style_emoticons/default/smile.gif)

EDIT
the decel valve will not be attached to engine tin.
its in all cases mounted off the inner engine bay bodywork on rhs of car.
whats mounted off the engine tin is the fuel pressure regulator.
thats probably what you are looking at.
looks very similar to a decel valve.
esp the f p regulator on a D jet. it has an adjusting nut on it i believe that can make you think its a decel. the f p regulator on the L jet has no adjustment nut but is mounted on same place off engine tin on lhs like a d jet. its just a mounting nut on a L Jet.
(IMG:style_emoticons/default/beerchug.gif)

[wonkipop]

@tshih914

where i would want you to go next is the throttle body and throttle body switch.

you have a new intake boot and a t/b gasket.
so to install those the t/b needs to come off anyway.

you can give it a good clean.
check the idle passage is clear.
and take the t/b switch off.
see how clean or dirty that is.
test it as per workshop manual.

lets make sure that is all tip top and working right.

[Geezer914]

The AFM could be bad. Send it to Fuel Injection Corp in CA to get it checked out.

[wonkipop]

The AFM could be bad. Send it to Fuel Injection Corp in CA to get it checked out.

he has a brand spanking AFM from fuel injection corp.
so unlikely its that.

but i would not discount it as a dud rebuild.
but doubtful.

[wonkipop]

if this is what you are talking about @tshih914 then its a fuel pressure regulator for a D jet not a decel.

[wonkipop]

@tshih914

i had done some snooping about with google searches.
(anything about L jet problems, including your car, interests me for purely selfish reasons (IMG:style_emoticons/default/smile.gif) )
i was going to ask my mechanic mike about this too.

read this article.
its specifically about Alfa Romeos fitted with L-Jet.
but it does not matter.
the systems are very similar across cars early L jet was fitted to.
go to section about electrical grounds.
i think he calls it step 2 in this article.
he specifically mentions the "starts and stalls syndrome".
not sure that is the problem you have, but perhaps it is.
others on 928 forums also refer to the "starts and stall syndrom" and lack of power when accelerating problem. which this kind of is. esp if we can get the high idle behaviour out of the picture and stop it masking what will be the pure behaviour of lack of throttle response/dies problem.

https://hpsimotorsports.com/blogs/tech-arti...nd-tune-up-page

i did notice in one of your earlier posts that the ECU in your car seems no longer to be bolted to the factory fixing off the battery tray and is instead floating about in the corner of the engine bay above the hell hole region. and its plug is oriented upwards which i don't think is ideal in terms of moisture entry. not sure how long its been that way in your car or whether you have it temporarily in that state while you have been doing this work.

i'd want to check that connection plug to the ECU.

have a read of the article for some guidance. (IMG:style_emoticons/default/beerchug.gif)

[nihil44]

I have removed and replaced the AFM many times for various reasons - 3 operations. Undo hose clamp onto the intake boot, undo clips on air filter, disconnect AFM connector. On numerous occasions on starting the car up again I have found the car would start but dies when the throttle opens - WTF I have forgotten to replace the AFM connector again.

Your symptoms seem to be similar. This test could be worthwhile. I may be barking up the wrong tree but indulge me for a moment.

Will the car start and run with the AFM unplugged? If not, don't bother with reading further.
If so, how about starting the car and running the car with AFM connector unplugged and adding the gas and see if the motor dies. This may disclose that the problem is in the AFM to harness interface ie connector interface

If it dies, then start the car with AFM plug connected and (2 persons required) have one person open the throttle while the other jiggles the AFM connector plug and the AFM connector wires . The purpose is to possibly reveal a broken wire in the harness making intermittent connection or poor contact or corrosion in one or several of the 6 pins in the connection

Simple test and I may be way off the mark but worth a go. I feel yuor pain!

[wonkipop]

I have removed and replaced the AFM many times for various reasons - 3 operations. Undo hose clamp onto the intake boot, undo clips on air filter, disconnect AFM connector. On numerous occasions on starting the car up again I have found the car would start but dies when the throttle opens - WTF I have forgotten to replace the AFM connector again.

Your symptoms seem to be similar. This test could be worthwhile. I may be barking up the wrong tree but indulge me for a moment.

Will the car start and run with the AFM unplugged? If not, don't bother with reading further.
If so, how about starting the car and running the car with AFM connector unplugged and adding the gas and see if the motor dies. This may disclose that the problem is in the AFM to harness interface ie connector interface

If it dies, then start the car with AFM plug connected and (2 persons required) have one person open the throttle while the other jiggles the AFM connector plug and the AFM connector wires . The purpose is to possibly reveal a broken wire in the harness making intermittent connection or poor contact or corrosion in one or several of the 6 pins in the connection

Simple test and I may be way off the mark but worth a go. I feel yuor pain!

@nihil44

yep it could be the afm connector.

but what you need to realise @nihil44 is that you don't have a legit factory connection to how the fuel pump works either.
(and neither does our friend).
and we have done your test./or our test, the same thing.
read back a page or two. (IMG:style_emoticons/default/beerchug.gif) (IMG:style_emoticons/default/beer.gif)
the car should not run period with the afm disconnected if its legit original.
most it should do is run off the cold start injector for about 10 seconds and then quit.

but
"i'll fix vapor lock" etc.....and we are now in that!


so many of you don't have a legit system you can benchmark against the factory manual
50 years of "bogan" departures from the system. (IMG:style_emoticons/default/biggrin.gif)
the thing about it starting and then dying when you go the gas is not legit system,
or it is?, but you have to read it carefully.
its because you have a fuel pump which is not operating off the afm flap that the car runs at all.
if your fuel pump ran off the afm flap in the first place it would not run at all to even be in the space we are in.
see above.
but........that doesn't mean you are not close to the truth. (IMG:style_emoticons/default/beerchug.gif)


i think the problem connection could be in either of the plugs.
either the plug to the afm or the plug to the ECM.
or an earth problem.
or as you say the harness.
but thats not the reason yours quits when you gas it with the afm plug out.
because it should not even go with the afm plug out.
if that makes sense. yours quits whether the harness is good or not. or the connections and plugs. if the afm plug is out. because its artificially going in the first place like our friends. its being run when it shouldn't even run. in a stock L jet the afm runs the fuel pump. period. end of story. so to be accurate what is going on here is that something is not going right when the throttle body switch signs off on "i am finished with telling the ECU i am done with the idle circuit --- its all over to you and the AFM to tell the engine what to do". which is why you are right about the harness. or the plugs? maybe.
because there is still the distrbutor? one thing at a time?!

i must have one of the last fully intact L jet systems left.
i've never shifted the fuel pump.
the only thing out is the decel.
the rest of its factory intact.

so mostly i can do the trouble shoot and i am not getting misinformation from unaccountated for "improvements".

[wonkipop]

i think what i am trying to say @nihil44
is this.

we are on about the same thing.

if it was a legit factory L jet set up it would not even idle.
so lets leave that out of it.

its idleing. sort of. because its getting fuel. illegitmately.

and because it has a non legit L jet fuel pump power scenario it will idle.

-----
but as soon as you crack open the throttle it all goes to hell.
because thats when the ECU wants something more than the whatever the signal is from from the t/b and t.b position switch to idle.

and its not getting it?
because the plugs are dirty, the harness is farked or its not earthed reliably.

amongst other problems
because seriously. its all farked. the decel is farked up. the AAV is maybe farked up.
and why wouldnt they be. its 50 years old. you have to give it a break! (IMG:style_emoticons/default/biggrin.gif)
and help it.

[wonkipop]

further thought @nihil44 and @Van B

i reckon if this baby was OEM wired up it wouldn't even run the fuel pump and idle to even get to the point where it was stumbling when you opened the throttle.

so..........the hot rod set ups of fuel pump actually provides an insight?

i'm thinking back to his plug in/plug out afm test,
it did something.
but regardless the engine would run at idle?
and we know no way, unless either fuel pump gives fuel.
either provided by wiring.
or by AFM flap.
thats the only two scenarios it can run at idle and get fuel.

but once she goes on to throttle off idle stop it has to be AFM.
or its all over?
the fuel pump can be delivering fuel.
but the ECU expects information about how much air is coming in, air fuel ratio sincro etc.

[Geezer914]

Go to Bowlsby's web site and print his wire diagrams for Ljet. Get a test light and do a continuity check of the wire harness from the ECU plug. I had a bunch of cracked wires that I had to replace.

[Van B]

Wonkipop. I agree that the TPS may be an issue or even the ECU, but he’s got to solve the obvious issues first… control the variables. In general, people’s approach trouble shooting cars loke theres an OBDII port and a code to read. But we’re talking about an open loop vacuum system. And computers that are little more than if/then statements as code.

-Fix all potential vacuum leaks
-confirm baseline settings
-confirm fuel, air, spark per cylinder
-confirm timing (difficult to do at this point without a stable idle)

We’re doing a whole lot of talking in thinking without much information at this point. You already said it, @tshih914 has got to get methodical. Four pages into this thread and the airbox lid just now being removed is a SMH moment for sure.