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Bob51
Samba Member
Joined: September 11, 2022
Posts: 21
Location: MI
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 Posted: Mon Sep 26, 2022 2:50 pm Post subject: Starting problem |
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I have a 1979 FI Super Beetle. Just finished an engine rebuild. It purrs like a kitten when it runs - Problem; the only way to get it started is by holding the Air Flow Sensor paddle open manually with a dowel !!
All the continuity and voltage tests seem to be normal. Has a new double relay.
Any Ideas?? |
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busdaddy
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Joined: February 12, 2004
Posts: 51116
Location: Surrey B.C. Canada, but thinking of Ukraine
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| Posted: Mon Sep 26, 2022 4:01 pm Post subject: Re: Starting problem |
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Unless the AFM flap has a backfire valve in it that's stuck or broken (spring loaded disc) it's gotta be a vacuum leak. And a biggish one too, had a close look at the S boot while holding it up to the sun and bending it?
Even if there was a leak it should at least try to cough though, have you confirmed 86a on the DR plug (usually red/black) gets power from the starter's #50 circuit when cranking?, is the fuel pressure bleeding off when shut down?
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Bob51
Samba Member
Joined: September 11, 2022
Posts: 21
Location: MI
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| Posted: Tue Sep 27, 2022 5:02 am Post subject: Re: Starting problem |
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| Thanks for the ideas. I will check for vac leaks. Also, is there any way to check the backfire valve or is it just a process of elimination? |
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busdaddy
Samba Member
Joined: February 12, 2004
Posts: 51116
Location: Surrey B.C. Canada, but thinking of Ukraine
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| Posted: Tue Sep 27, 2022 7:41 am Post subject: Re: Starting problem |
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| Bob51 wrote: |
| ... is there any way to check the backfire valve or is it just a process of elimination? |
Look down the throat of the AFM, better yet if it's off the car and up to the light, any daylight showing through?
Not all AFM flaps have the valve in them, some are solid.
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Bob51
Samba Member
Joined: September 11, 2022
Posts: 21
Location: MI
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| Posted: Tue Sep 27, 2022 12:56 pm Post subject: Re: Starting problem |
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update: Found two possible vac leaks. DR 86a volts good. AFM flap is one piece. Didn't have much time today, but also decided to check out the Air Assist valve. Manual recommended 30ohms and I got 20.
Planning on trying to start it again tomorrow. If I have to do it manually again, will check to see if I have vacuum out of the air assist valve.
Question: Do you know if 20ohms is tolerable for the air assist? |
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busdaddy
Samba Member
Joined: February 12, 2004
Posts: 51116
Location: Surrey B.C. Canada, but thinking of Ukraine
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| Posted: Tue Sep 27, 2022 4:08 pm Post subject: Re: Starting problem |
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That doesn't sound like a big deal, it's better than infinite ohms...
Once it's running and warmed up pinch the hose on the AAR (I'm assuming you mean auxiliary air regulator by "air assist valve"), if the idle doesn't change it's OK, if the idle drops it could need attention.
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Rust NEVER sleeps and stock never goes out of style.
Please don't PM technical questions, ask your problem in public so everyone can play along. If you think it's too stupid post it here
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Bob51
Samba Member
Joined: September 11, 2022
Posts: 21
Location: MI
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| Posted: Wed Sep 28, 2022 6:13 am Post subject: Re: Starting problem |
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Latest: Had to manually start up. Got it warmed up. Used adjustable plyers to pinch and had no detectable change. However, wasn't sure I was getting enough "pinch" so pulled the hose from the S Boot. The engine stopped immediately.
What do you think? |
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busdaddy
Samba Member
Joined: February 12, 2004
Posts: 51116
Location: Surrey B.C. Canada, but thinking of Ukraine
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| Posted: Wed Sep 28, 2022 6:26 am Post subject: Re: Starting problem |
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It's not surprising it quit, you created a sudden huge vacuum leak. You could cap the nipple and plug the end of the hose to see if it idles lower for a temporary test, those hoses to the AAR are a little hard to find so it may not be worth the risk of screwing one up with pliers if it's stiff.
Out of curiosity have you ever done a fuel pressure test?, how about Ohm readings from the TS2 cold as well as warm?
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Please don't PM technical questions, ask your problem in public so everyone can play along. If you think it's too stupid post it here
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Bob51
Samba Member
Joined: September 11, 2022
Posts: 21
Location: MI
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| Posted: Wed Sep 28, 2022 8:05 am Post subject: Re: Starting problem |
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fyi: Took your advice and "capped & plugged". I can now confidently say that the AAR is working fine. TS2 is new from the rebuild. Last fuel pressure test was during turn-overs. If memory serves, it was at around 30psi.
Since everything we have talked about looks good, I decided to redo continuity checks on the air intake sensor. There is no continuity between 6 & 9 !! |
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VW_Jimbo 
Samba Member
Joined: May 22, 2016
Posts: 9946
Location: Huntington Beach, CA
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| Posted: Wed Sep 28, 2022 8:17 am Post subject: Re: Starting problem |
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| Bob51 wrote: |
I have a 1979 FI Super Beetle. Just finished an engine rebuild. It purrs like a kitten when it runs - Problem; the only way to get it started is by holding the Air Flow Sensor paddle open manually with a dowel !!
All the continuity and voltage tests seem to be normal. Has a new double relay.
Any Ideas?? |
This is a vacum leak, 9 out of ten times.
If not, you are chasing a overly lean condition. Lack of fuel OR too much unmetered air. Spark is most likely good. You did a test for vacum leaks and got no where. How about the fuel filter? What is the voltage to the fuel pump when running?
My money is on plugged or carboned up injectors. Might want to take them out and get them cleaned up, but check them first.
Got a picture of the spark plugs? They tell a lot!
And as always, valve adjustment last done? Oil change last done?
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