1978 FI Super won't idle

[rjwitt15]

I have a 1978 fuel injected Super Beetle and my dad and I have recently rebuilt the engine. I am a 22 year old female who just graduated college and I'm excited to finally have more time to dedicate to get my Beetle running properly.

The car starts and runs only when the accelerator pedal is being pushed down. The engine has run for approximately 30 minutes when someone is constantly pushing down on the accelerator pedal. However, when the accelerator pedal is released, the engine stalls. It took awhile for my dad and I to get the engine started, I had connected some electrical wires improperly and our fuel injectors were not working correctly. So we have completed a lot of tests on this car to first determine why it was not starting and now to figure out why it is not idling. Below is a list of the many tests we have completed to troubleshoot the issues we have had and a list of the parts that were replaced during the rebuild.

- We bought a brand new battery and new positive/negative battery leads. We also thoroughly cleaned where the battery leads connect to the car
- We got new spark plugs (and gapped them according to the specifications in the Bentley), new spark plug wires, distributor points, distributor rotor, distributor cap and fuel injectors
- We replaced all of the rubber fuel hoses with brand new ones
- We checked the fuel pressure with a fuel pressure gauge that we borrowed from a local auto parts store (our fuel pressure was measured to be 38 psi, according to the Bentley it should be 35 psi)
- we removed the fuel tank and inspected the interior (which appeared to be in great shape)
The fuel system seems to be in good shape and working properly.

- We checked the double relay and ended up replacing it
- We bought an additional ECU in order to verify that ours was working properly
- We replaced the EGR valve with a different used EGR valve
- We tested the cold start valve and the thermo time switch according to the procedure in the Bentley, both are fine
- We adjusted the values (and have double checked them)
- We thought the intake air sensor resistance value readings were suspicious so we tried to find a new one but ended up finding someone who was able to rebuild our current one instead
- We statically timed the engine but have not been able to time it with a timing light because the engine is not idling
- We tried to adjust the idle speed by adjusting the idle adjustment screw on the throttle body which did not seem to make a difference in the idle speed

Most of our troubleshooting has been done using the Bentley but we have also consulted the Robert Bosch Volkswagen Workshop Manual (specifically the flow chart for 'engine runs but then dies'). My dad and I believe that we have checked all of the items that the Bosch manual indicates to check and we just do not know where to go from here. Does anyone have any troubleshooting suggestions? Thank you so much in advance!

[busdaddy]

Welcome!
Thanks for the impressive first post, nicely detailed.

Sounds like you've covered many of the potential issues already, I'm left wondering if there's any black smoke when the engine is running?, if not then you may want to read this thread and see if there's any vacuum leaks you may have missed: http://www.thesamba.com/vw/forum/viewtopic.php?t=620083&highlight=smoke+tester
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[joey1320]

Hello amd welcome to The Samba. I'll be honest and say I'm not fully versed with the FI system in these VW's (D jeftronic?) but your issue sounds like a vacuum leak and/or an issue with your idle screw.

Can you please post pics of your engine?

What exactly happens when you played with the idle screw?

Have you tried spraying carb cleaner around your intake system to check for leaks?

There's an extremely knowledgeable member that frequents the Type3 forum who is an encyclopedia regarding the FI systems on these cars, I recommend maybe asking there if we can't help you here. His name is Tram.
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[garyt]

Ok, if you have done all those things properly, as the others have said it sounds like a vacuum leak in the air hoses, and you need to make sure they are connected correctly.

Otherwise could be the electrical connection from the air flow meter, check each contact for proper continuity, a loss of contact on one can switch off the fuel pump while running. Use a multimeter.

For me it was the pump contact in the potentiometer that was not contacting fully that caused the problem.

[unclewede]

It was the third mechanic who finally found all my vacuum leak(s) and got my son's 77 FI running well. The first mechanic would directly ground the fuel pump, and the engine would race like a greyhound.

Even recently, when I was checking for oil blowback and pulled the dipstick out, that little bit of vacuum leak caused the engine to die. . .

[rjwitt15]

A full view of the engine

The airflow meter

Distributor and coil

Here are a few pictures I took earlier today. I also had my dad take a video of the car running and I uploaded it to YouTube. https://www.youtube.com/watch?v=TGuME2maVgY
In the video I am pumping the accelerator pedal to keep the car running. There is no black smoke while the engine is running.
The FI system in my car is L-Jetronic. We tried using carb cleaner today to check for vacuum leaks around the joints of the intake system. It's very difficult to keep the car at a steady rpm so it's hard to tell if an increase in engine speed occurs due to pushing down more on the accelerator pedal to prevent the engine from stalling or from carb cleaner entering the intake system. It's also difficult to reach some of the junctions in the intake system due to the compactness of the engine. There are a few vacuum hoses that we did not replace. They are the thick braided hoses that attach to the bottom of the S boot (seen in the second picture). We sprayed those hoses with carb cleaner as well but no clear result emerged from that.

We played around with the idle adjustment screw today as well and there was no difference in engine performance whether the screw was almost all the way out, almost all the way in or somewhere in between.

We also did some testing with the fuel pump today. I used a test light to determine when there was voltage on the positive terminal on the fuel pump while my dad started and kept the car running. The fuel pump was on when the key was in the start position, which as I understand it, means that the double relay is turning on the fuel pump. When the key is in the on position and my dad is pushing down on the accelerator pedal, the fuel pump is still turned on, which I believe indicates that the switch in the air flow meter is supplying voltage to the fuel pump. When my dad took his foot off the accelerator to let the engine try to idle, there was still voltage at the fuel pump. Within a few seconds, the engine stalled and the test light at the fuel pump simultaneously went out. It seems like the fuel pump is working properly along with the switch in the air flow meter.

[racoguy]

I've not read through the whole thread but my cylinder head temp sensor stopped mine idling.
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[joey1320]

While watching the video, I couldn't help but notice how loud your engine is. Out of curiosity, are your ignition wires properly routed and is your engine not misfiring?
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[wcfvw69]

[sawed off]

Is the big hose behind the rubber elbow hooked up to oil fill breather? I cant tell in pics.

[KKiley]

Ok, if you watch the video, you do have bursts of black smoke puffing. From your notes above, you said you have 38 psi of fuel pressure. That is too much. Mine runs 30-32 when running. Having it that high would make it rich.
I think you have a bad fuel pressure regulator or the vacuum line is bad.
And that S tube looks like a leak waiting to happen.
Just my 1st thoughts...
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1978 Super Beetle convertible

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[garyt]

The air bypass screw not having any affect on idle speed signifies an air leak on a vacuum line, or a problem with the fuel pressure regulator. You can take the latter out and if there is black liquid gunk coming from the small air hose it needs replacing.

Although you have fuel pressure, fuel volume may still be an issue and can cause this (it happened to me due to bits in the tank clogging the line, I still had correct fuel pressure at idle).

Also do a check for kinks in the fuel feed lines, has the same effect.

[bug1000000000]

Have the same car and engine. Where are the paper tubes from the fan to the holes (empty in the photo) that would cool the engine?

On another note, best thing I ever did was replace points with Pertronix ignition.

[rjwitt15]

Okay we finally had time to recheck the fuel pressure regulator and you guys were right - fuel pressure is too high. 38 psi without the vacuum hose attached and 32 psi with the vacuum hose attached. According to the Bently, it should be 35 psi without vacuum and 26 psi with vacuum. We are currently ordering a new regulator.

Thank you so much for all the responses. I will keep you all posted on what happens when the new fuel pressure regulator arrives!

[sawed off]

Ok the fuel pressure a little high. I watched the video its still not going to run right, something else still not right.

[garyt]

I changed to an adjustable rising rate fuel pressure regulator and it works fine and the car runs and idles well even with far higher fuel pressure than you state (although I don't leave it like that of course). It has a useful guage. Did you take out the old FPR to check it? I also suspect it is not the only problem. You may need to clean the tank and lines, which is not too difficult. Also, check the line from the oil funnel to the S boot is present and attached properly (it is hard to attach at the bottom).

[garyt]

Watching the video, the timing seems a little slow as well, try turning the dizzy just a bit anticlockwise, then try starting again.

[rjwitt15]

I have an exciting update about our progress! I replaced the fuel pressure regulator, found and fixed the exhaust leak and the car is idling!!! I have posted another video on youtube: https://www.youtube.com/watch?v=DuX2MGqIo5M.

We are now going to check the point gap with a dwell meter, set the timing with a timing light and set the idle speed. Hopefully these things will help achieve a normal idle.

Thanks again for all the replies on this post. I am so excited that my beloved beetle is finally idling and I couldn't have done it without you guys!

[joey1320]

Congrats . That sounds a lot better. Keep picking away at it and post some pics of it. We like pics!!!
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[51astro456]

We just got a 1978 convertible super beetle as well...and we are in the middle of rebuilding the engine...

One we get it all back together, this thread will probably be very useful!!

In fact, the pictures have already been useful in seeing what we were missing in the engine bay...like the intake snorkel! Luckily we found a used one....

Someone had inverted the flow meter, and if you do that...the snorkel doesn't fit under the lid!! So I guess one of the previous owners just left it off!