Author |
Message |
Sham Samba Member
Joined: November 24, 2008 Posts: 16 Location: Antibes-Beach
|
Posted: Tue Nov 30, 2021 8:21 am Post subject: '59 rebuilt 36hp idle very high |
|
|
Hello guys,
So, I have fully rebuilt my 36hp (details here : http://shamwerks.com/Beetle-page-2), and it runs great - well, I had a bit of a misadventure due to a fuel pump spring breaking the lever, but that's been fixed be putting back the original spring.
Anyway.
My issue is that I have a pretty high RPM idle, like 1500 rpm. I'm trying to bring it down, sprayed some brake cleaner squirts at the base of the manifold chasing air leaks (there was none), checked that the cable wasn't pulling on the throttle, same for the choke, checked that the butterfly properly closes... And I still fail to bring down the idle RPM.
The 28PCI has been fully rebuilt ; before the engine rebuild it idled fine at around 500-600RPM .
Would you have ideas to help me lower the idle RPMs? Thank you! _________________ ShamWerks.com |
|
Back to top |
|
|
Lingwendil Samba Member
Joined: February 25, 2009 Posts: 3987 Location: Antioch, California, a block from the hood
|
|
Back to top |
|
|
my59 Samba Member
Joined: August 13, 2003 Posts: 3780 Location: connecting the dots
|
Posted: Tue Nov 30, 2021 3:11 pm Post subject: Re: '59 rebuilt 36hp idle very high |
|
|
Have you made sure the accelerator and choke cable are routed correctly and have been lubricated in their housings? _________________ my59: Well son, my grandfather died before I got to drive it, so does that answer your question?
our79: sunroof bus w/camper interior and 2.0 FI
Other:'12 Jetta, '77 Benz 300D, and a 74 MG Midget. |
|
Back to top |
|
|
mukluk Samba Member
Joined: October 18, 2012 Posts: 6985 Location: Clyde, TX
|
Posted: Tue Nov 30, 2021 3:17 pm Post subject: Re: '59 rebuilt 36hp idle very high |
|
|
Since the carburetor was fully disassembled for cleaning, I would try slightly loosening the nuts at either end of the throttle butterfly shaft where the linkages mount. If these are overtightened, they will cause the throttle shaft to stick and prevent full travel. _________________ 1960 Ragtop w/Semaphores "Inga" |
|
Back to top |
|
|
Sham Samba Member
Joined: November 24, 2008 Posts: 16 Location: Antibes-Beach
|
Posted: Wed Dec 01, 2021 3:56 am Post subject: Re: '59 rebuilt 36hp idle very high |
|
|
Lingwendil wrote: |
If you screw the adjuster in does the butterfly close before the engine begins to stall? Or start running funky? |
You're talking about the adjuster screw on the butterfly lever itself?
I'll give it a try this week end and let you know how it behaves.
my59 wrote: |
Have you made sure the accelerator and choke cable are routed correctly and have been lubricated in their housings? |
Yep, cables changed, greased, and properly routed (I had to redo it twice, got it wrong first try).
mukluk wrote: |
Since the carburetor was fully disassembled for cleaning, I would try slightly loosening the nuts at either end of the throttle butterfly shaft where the linkages mount. If these are overtightened, they will cause the throttle shaft to stick and prevent full travel. |
That's a pretty good idea, I'm going to check that, thanks!
Actually, I've just rewatched the video of the very first start of this engine a few months ago, and it looks like back then I could get to a reasonnable idle RPM :
Link
Hmmm. Food for thoughts, I'll look into your inputs and let you know what I find out. _________________ ShamWerks.com |
|
Back to top |
|
|
Airstream65 Samba Member
Joined: January 28, 2019 Posts: 172 Location: Tulsa,Ok
|
Posted: Wed Dec 01, 2021 5:27 am Post subject: Re: '59 rebuilt 36hp idle very high |
|
|
First off, starting fluid should not be needed to start the car. Have you double checked the valve lash, points gap, and timing? Start from the beginning! |
|
Back to top |
|
|
Sham Samba Member
Joined: November 24, 2008 Posts: 16 Location: Antibes-Beach
|
Posted: Wed Dec 01, 2021 6:02 am Post subject: Re: '59 rebuilt 36hp idle very high |
|
|
Airstream65 : Starting fluid was used only this one time, as it was the very first start of the engine. Oil pressure had been primed before by running the starter motor but disconnecting the ignition. I wanted to ensure the very first sparks would start th engine.
As for points gap, valves, timing, yes, of course those had been adjusted before (and timing checked with a stroboscopic lamp after) this first start.
Obviously starting fluid isn't needed any longer, and the engine happily starts right when the key is turned. _________________ ShamWerks.com |
|
Back to top |
|
|
KTPhil Samba Member
Joined: April 06, 2006 Posts: 33875 Location: Conejo Valley, CA
|
Posted: Wed Dec 01, 2021 11:38 am Post subject: Re: '59 rebuilt 36hp idle very high |
|
|
Many are not familiar with the somewhat picky throttle return spring/cone/washer arrangement of the early cars, and it often binds when not cleaned, deburred, straightened, and assembled correctly. |
|
Back to top |
|
|
Erik G Samba Member
Joined: October 16, 2002 Posts: 13247 Location: Tejas!
|
Posted: Wed Dec 01, 2021 1:34 pm Post subject: Re: '59 rebuilt 36hp idle very high |
|
|
KTPhil wrote: |
Many are not familiar with the somewhat picky throttle return spring/cone/washer arrangement of the early cars, and it often binds when not cleaned, deburred, straightened, and assembled correctly. |
right. I would start by disconnecting the cable altogether and work backwards from there |
|
Back to top |
|
|
KTPhil Samba Member
Joined: April 06, 2006 Posts: 33875 Location: Conejo Valley, CA
|
Posted: Wed Dec 01, 2021 1:50 pm Post subject: Re: '59 rebuilt 36hp idle very high |
|
|
A more far out possibility is that the heat riser has burned through to the intake manifold pipe and you are getting extra air through that path. Rare, but it's been reported here.
Yes, take the cable off completely to eliminate/confirm it's a contributor! Easy things first! |
|
Back to top |
|
|
motofly196 Samba Member
Joined: June 01, 2008 Posts: 1467 Location: Eastern WA
|
Posted: Thu Dec 02, 2021 12:10 am Post subject: Re: '59 rebuilt 36hp idle very high |
|
|
Check that your manifold to head nuts are tight too. Could of loosened up over a few heat/ cool down cycles. |
|
Back to top |
|
|
Sham Samba Member
Joined: November 24, 2008 Posts: 16 Location: Antibes-Beach
|
Posted: Thu Dec 02, 2021 1:40 am Post subject: Re: '59 rebuilt 36hp idle very high |
|
|
KTPhil wrote: |
Many are not familiar with the somewhat picky throttle return spring/cone/washer arrangement of the early cars, and it often binds when not cleaned, deburred, straightened, and assembled correctly. |
Erik G wrote: |
I would start by disconnecting the cable altogether and work backwards from there |
I've had that car for over 26 years now, I'm very familiar with the spring setup. But you're right, I'll take it off completely, give it another check, and see how disconnecting the cable affects the idle.
KTPhil wrote: |
A more far out possibility is that the heat riser has burned through to the intake manifold pipe and you are getting extra air through that path. Rare, but it's been reported here. |
No, I think I can strike out that option. I've modified the manifold to shorten it (in the process of increasing compression ratio - details here), and doing so I've pressure tested it for leaks.
motofly196 wrote: |
Check that your manifold to head nuts are tight too. Could of loosened up over a few heat/ cool down cycles. |
Good point. I have squirted brake fluid at the manifold bottom looking for leaks, but I'll check the nuts are tight too. _________________ ShamWerks.com |
|
Back to top |
|
|
KTPhil Samba Member
Joined: April 06, 2006 Posts: 33875 Location: Conejo Valley, CA
|
Posted: Thu Dec 02, 2021 10:11 am Post subject: Re: '59 rebuilt 36hp idle very high |
|
|
Another common source is NOT removing the old manifold sealing rings (easy to do since it gets squashed and looks like part of the head), and putting an "extra" one on when installing the manifold. You really have to look carefully at the inlet port to tell the difference! |
|
Back to top |
|
|
motofly196 Samba Member
Joined: June 01, 2008 Posts: 1467 Location: Eastern WA
|
Posted: Thu Dec 02, 2021 10:18 am Post subject: Re: '59 rebuilt 36hp idle very high |
|
|
I was actually going to mention the same thing! But I didn't want to "mechanic shame" anybody Sometimes the crush washer on the intake can blend right in with the color of the head. You've gotta get a pick in there and lift up. |
|
Back to top |
|
|
KTPhil Samba Member
Joined: April 06, 2006 Posts: 33875 Location: Conejo Valley, CA
|
Posted: Thu Dec 02, 2021 10:23 am Post subject: Re: '59 rebuilt 36hp idle very high |
|
|
Sounds like the OP has a thick skin and at least a few brain cells between the ears, so I wouldn't worry!
He's covered all the easy sources, so we need to think outside the box and consider rarer options, so keep 'em comin'! |
|
Back to top |
|
|
Sham Samba Member
Joined: November 24, 2008 Posts: 16 Location: Antibes-Beach
|
Posted: Mon Dec 06, 2021 7:43 am Post subject: Re: '59 rebuilt 36hp idle very high |
|
|
No worries about mechanic shaming, I'm not taking anything personally, and even though I've been into VWs for about 3 decades, I can will make dumb mistakes just like the next guy.
Crush washer, you know what, since I bead blasted the heads I inspected them veeeeeeery closely. Yet, digging into my pictures library, I found one where... Well, I have the tiniest doubt now. Damn. One more thing to check, though I wouln't put that on top of the list as 1/ no RPM change when squirting brake fluid at the base of the manifold 2/ I did have a correct idle when I first started the engine.
Back to the workshop it is! _________________ ShamWerks.com |
|
Back to top |
|
|
|