Itinerant Air-Cooled

First VW, 79 Super Beetle, FI!!! Towed it home, put injectors and fuel filter in, started right up and wife drove it all around!! About 1/2 hour test drive!!! Got home, shut it off, hasn’t ran right sence!!! I’ve checked FI according to Bentley manual!!! While trying to figure it out the fuel pump quit, so replaced it!! Got really mixed fuel pressure readings, so replaced FPR!!! The AFM has a broken lid, so replaced it!! Replaced head temp senor, distributor, points, plugs, cap, condenser, wires, coil!! Tore down and replaced plenum gaskets, intake gaskets, all vacuum lines are new and clamped!!! And here it is, starts right up, but falls over really bad when I push throttle!! I’m running out of ideas!!! Not any kind of certified mechanic, but kept my trucks running for about 40 years, so have had a wrench in my hand a few times!!! I’m just lost here!!! Any help would be awesome!!!!

Just a little more info!!! I went to basics, started by doing compression test!! Well inside recommended!! Adjusted valves!! Had a bad reading on double relay, so replaced!! When I brought it home it wouldn’t start very well, but once started it ran great!! Now it starts right up, but won’t accelerate at all!! Starts to rev up, then just falls off!!!

T Bell wrote: ↑

Mon Nov 11, 2019 10:31 am

First VW, 79 Super Beetle, FI!!!
injectors
fuel filter
fuel pump replaced
replaced FPR
Replaced head temp sensor
distributor
points
plugs
cap
condenser
wires
coil
plenum, intake gaskets, vacuum lines
compression test
adjusted valves
double relay replaced

starts right up, but falls over really bad when I push throttle

T Bell, that is an impressive list. And yet ...

Let's work a diagnostic program where we do not throw parts at it.

Starts right up? Does it idle nicely? Then every damn thing is working.
But, it does not respond to accelerator? The only system that is responsible for adding fuel to an engine that has just ingested a big gulp of air (courtesy, accelerator) is the AFM.
Check the little fingers in the AFM connector. See if any are pushed back inside the molex. They should all be at the same installed height.
Report back.
Colin

Idles great, but a little rich, plug on AFM looks good, all terminals centered in plug!!!
All the same distance out of plug also

Personal stuff probably not important but here we go!!! Always loved these bugs, but didn’t have time to play till now!!! Was owner/operator for many years, then lost leg in loading accident, so now have the time!! Brought this thing home, pulled the injectors, witch looked really used up, and replaced them and fuel filter!! Started right up, so wife drove me around a bit, got back to my shop, and wouldn’t start again, so while still pretty warm, took quick compression test!!! If memory serves me right, all holes were around 115 give or take 1 or 2 pounds!! Next morning I adjusted the valves(006) and as I normally do when I get something new in shop, did a major Tune up!! Bought a Bentley VW manual, and began trouble shooting as per!! Found dead terminal in double relay, so replaced!! Fuel pump just gave up, although had 11.9 volts to wire at pump. Replaced it, then the FPR must have lost diaphragm, cause the vacuum line was full of fuel and it loaded oil up with fuel!! Replaced FPR!! Changed oil again!! AFM had broken cover on bottom, so replaced with Fuel Injection Corp reman!!! Also had readings on Temp sensor 2 all over the place, so replaced it!!! This brings me to where I am now, starts, and idles fine, but a bit rich!! No acceleration!!! Pins in plug all look normal, plug seems ok also!!

T Bell wrote: ↑

Tue Nov 12, 2019 12:48 am

readings on Temp sensor 2 all over the place, so replaced it.
starts, and idles fine, but a bit rich. No acceleration.
Pins in plug all look normal, plug seems ok also.

(First, my condolences for the loss of your "." period dot on your keyboard.
Unless!! You just drink really good coffee!! Like I do!!)

Okay, you have determined that the engine is running rich, yes?

I would like to do a verification of this. With a warm engine (usually 20 minutes of actual drive time), please remove the vacuum hose that goes to the fuel pressure regulator and decel valve. Do not remove it from the fuel pressure regulator end, remove it from the intake manifold end.
a) idle goes up noticeably
b) idle goes up as you remove the hose, then it goes down when the hose is fully off
c) idle sort of breaks up and maybe drops a little
d) engine stalls
Report back.
Colin!!

C

Stumbles and almost dies.

Now that it’s really warm, pulling that line does nothing at all!! Can feel vacuum in line.

T Bell wrote: ↑

Tue Nov 12, 2019 2:05 pm

Now that it’s really warm, pulling that line does nothing at all!! Can feel vacuum in line.

You are shooting our diagnosis in the foot. I have two answers above that I might have interpreted to be "with engine fully warm", but then your last response says, "now that its really warm".

OK, I will assume that with a fully warm engine, pulling off the hose gives barely any change in idle, yes?

That would suggest too rich. Verify by bringing engine to stumble point, and checking for black smoke out the exhaust. We need to verify TS2 sensor in left head has 2,500 ohms at 65-68* ambient.

Too bad your AFM has the adjustments we want to perform upside down, in contrast to the buses.

READ:
viewtopic.php?f=50&t=7761

Amskeptic wrote: ↑

Tue Nov 12, 2019 10:40 pm

Too bad your AFM has the adjustments we want to perform upside down, in contrast to the buses.

The bug AFM can be temporarily mounted "fun side up" if:
The alternator + post is well-insulated.
The work environment is clean enough to run the engine without the air filter for a minute or two.


Robbie

asiab3 wrote: ↑

Wed Nov 13, 2019 9:10 am

Amskeptic wrote: ↑

Tue Nov 12, 2019 10:40 pm

Too bad your AFM has the adjustments we want to perform upside down, in contrast to the buses.

The bug AFM can be temporarily mounted "fun side up" if:
The alternator + post is well-insulated.
The work environment is clean enough to run the engine without the air filter for a minute or two.


Robbie

Yes! That was going to be our next step, if I did not alienate our poor guest!!
Colin!!