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airkooledchris Samba Member
Joined: January 25, 2005 Posts: 2710
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Posted: Mon Jan 10, 2011 6:25 pm Post subject: have microswitch for full enrichment - but don't use it? |
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the bus is a California model 79
I am doing a bunch of random testing trying to hunt down why im getting barely 11 MPG and in doing so, I tested the 'microswitch'
this thing:
it failed the Bentley test, which is when I then read on and noted the following:
If this was eliminated from 1977 models onward, why do I have one?
Did they leave it there and it just doesn't do anything?
Or did the PO hack it in during a previous rebuild and it just shouldn't be there?
Im not sure if I should bother testing it further or replacing it, if it's not supposed to be there in the first place. |
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Westfabulous Samba Member
Joined: January 07, 2007 Posts: 4207 Location: The tropic of Canada, dodging the giant flying moose of Surrey!
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Posted: Mon Jan 10, 2011 6:33 pm Post subject: |
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That wasn't there on later models. Do you have the original engine? Perhaps a throttle body replacement at some point? It does not belong on your bus as original 1979 equipment, unless it was part of the Cali package? _________________ *****************
"I will gladly pay you Tuesday for a hamburger today." |
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airkooledchris Samba Member
Joined: January 25, 2005 Posts: 2710
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Posted: Mon Jan 10, 2011 6:39 pm Post subject: |
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Westfabulous wrote: |
That wasn't there on later models. Do you have the original engine? Perhaps a throttle body replacement at some point? It does not belong on your bus as original 1979 equipment, unless it was part of the Cali package? |
I have all the rest of the Cali specific bits, coil, electronic ignition, AFM, o2 sensor, CAT, etc.
what has me stumped is that the Cali wiring harness is unique, so if it was eliminated at some point, why would it have the wiring for it? |
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RocketRod Samba Member
Joined: July 19, 2007 Posts: 641 Location: Colorado Springs, CO
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Posted: Mon Jan 10, 2011 6:46 pm Post subject: |
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My ? is if it is causing the enrichment at al times. Read your plugs. Do a fuel pressure test. _________________ Why Yes it is a Magic bus!
Common Sense isn't so common. |
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germansupplyscott Samba Member
Joined: May 22, 2004 Posts: 7093 Location: toronto
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Posted: Mon Jan 10, 2011 6:55 pm Post subject: |
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the full throttle enrichment switch should be on your '79 CA engine, it was a feature of this model. highly unlikely to me that the switch or wiring could malfunction and cause 11mpg but you never know. on my engine i odn't use the switch at all because my bus is '79 federal injection components, not CA. the CA system is quite skittish to tune in my experience so i federalized my bus.
fyi, the switch almost never comes in play even on a CA bus, the throttle must be almost 100% open and you seldom drive this way. _________________ SL |
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busdaddy Samba Member
Joined: February 12, 2004 Posts: 51130 Location: Surrey B.C. Canada, but thinking of Ukraine
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Posted: Mon Jan 10, 2011 8:49 pm Post subject: |
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Sounds like it's time to break out the OHM meter and test the switch. _________________ 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
Stop dead photo links! Post your photos to The Samba Gallery!
Слава Україні! |
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airkooledchris Samba Member
Joined: January 25, 2005 Posts: 2710
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Posted: Mon Jan 10, 2011 9:32 pm Post subject: |
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thanks for the reply. im glad to know its at least supposed to be there, even if it isn't working (or rarely used even when working.)
I have a working one from my aircooled Vanagon I can swap in....
did a fuel pressure test
I disconnected the vacuum hose from the pressure regulator and plugged the hose
fuel pressure at idle (1000 RPM) was 40 PSI, which is 5 higher than spec and 3 higher than the tolerance listed
With vacuum hose connected, at idle (1000 RPM), fuel pressure was 32 PSI, which is 4 higher than spec and 2 PSI higher than the tolerance listed
At full throttle and with the vacuum hose connected, I saw exactly 30 PSI
what im wondering is, how much is too much? could these slightly higher numbers give me poor fuel economy?
is it more likely that the Fuel Pressure Regulator is failing or just that something is blocking the return line?
here are the plugs, which look OK to me.
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busdaddy Samba Member
Joined: February 12, 2004 Posts: 51130 Location: Surrey B.C. Canada, but thinking of Ukraine
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Posted: Mon Jan 10, 2011 9:39 pm Post subject: |
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That's a pretty consistant error, sure it isn't just the gauge?
How old are those plugs and where have they been? on the highway or idling in the driveway? _________________ 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
Stop dead photo links! Post your photos to The Samba Gallery!
Слава Україні! |
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airkooledchris Samba Member
Joined: January 25, 2005 Posts: 2710
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Posted: Mon Jan 10, 2011 9:59 pm Post subject: |
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busdaddy wrote: |
That's a pretty consistant error, sure it isn't just the gauge?
How old are those plugs and where have they been? on the highway or idling in the driveway? |
I can't be sure it isn't the gauge. it's a nice little VDO, only had it a few years, so unless it is off from the factory, id trust it. I don't have another to compare it to....
the plugs were installed in the bus when I picked it up last summer. when I pulled them it had just been idling in the driveway for a little while earlier in the day, otherwise a few days of short in town trips and last weekend I drove it about 600 miles over the course of the weekend. |
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SGKent Samba Member
Joined: October 30, 2007 Posts: 41031 Location: Citrus Heights CA (Near Sacramento)
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Posted: Mon Jan 10, 2011 10:52 pm Post subject: |
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is this thread about the micro-switch or 11 mpg? _________________ “Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin |
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airkooledchris Samba Member
Joined: January 25, 2005 Posts: 2710
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Posted: Mon Jan 10, 2011 11:04 pm Post subject: |
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SGKent wrote: |
is this thread about the micro-switch or 11 mpg? |
why, do we really need another thread just about MPG?
it's topic is clearly defined as a microswitch question, but I don't think it hurts anything to stray a bit from the main issue along the way. I was testing the micro switch as part of the process of elimination with my MPG issue...
it's still an oddball thing to run into, where it wasn't used in any post-77 models EXCEPT the CA setup - apparently. why wouldn't the "new control unit" in the post 77 models be able to do the same? maybe the control unit had to factor in the o2 sensor and just couldn't do that much math at once.
busdaddy - check the switch for voltage, or is there another reading you'd be looking for? |
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RocketRod Samba Member
Joined: July 19, 2007 Posts: 641 Location: Colorado Springs, CO
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Posted: Mon Jan 10, 2011 11:22 pm Post subject: |
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Switch is a switch. Check for continuity open and closed. Check its wires also. Many other things can be your MPG issue, vacuum, CSV, or any part of the FI system. Take the time and ensure it is all within tolerances. _________________ Why Yes it is a Magic bus!
Common Sense isn't so common. |
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SGKent Samba Member
Joined: October 30, 2007 Posts: 41031 Location: Citrus Heights CA (Near Sacramento)
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Posted: Tue Jan 11, 2011 7:09 am Post subject: |
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chris do you have a thread going about your 11 mpg? My question wasn't about buses mpg - it was asking if this thread is really you trying to figure out why your bus is only geting 11 mpg? We may be answering switch questions for days when you are really working on a problem of only getting 11 mpg. Testing the switch is easy.
Here is why it is probably there. The late 1970 (76 on) models sense that the door swing in the AFM is the bus going WOT and enrich the mixture. On a 1979 with O2 sensor the AFM is leaned and richened by the O2 sensor so it sits at 14.7:1. At WOT it would still be 14.7:1 but it needs to be richer so the switch overrides the O2 sensor.
How old is the catalytic convertor?
What kind of compresson readings are you getting? _________________ “Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin
Last edited by SGKent on Tue Jan 11, 2011 7:58 pm; edited 1 time in total |
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josh Samba Member
Joined: July 13, 2003 Posts: 1773 Location: laid back in the tall grass
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Posted: Tue Jan 11, 2011 9:42 am Post subject: |
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At least your investigating the right way, through process of elimination, doing the tests in the Bentley.
Be sure to check all of your temp sensors. If they aren't functioning your bus could stay in rich warm up mode. Also the thermo time switch controls the amount of time the CSV stays on which would inject extra fuel. A leaking CSV itself or leaking fuel injector would would waste fuel. the only way to check for that is to pull the valve and run the fuel pump.
Also keep in mind that it may not be a FI problem. All the normal tune up stuff is important, valve adjustment, plugs, points/ dwell (if you have them), timing, compression ect.
I would also make sure the distributor advance mechanisms are working both mechanical and vacuum.
I once had a bus that seemed to be driving fine exempt for low mpg. While checking everything over I found that one cylinder had almost no compression. I hadn't noticed any issues even though I had driven through the Santa Cruz mountains the previous day!
Also; What method are you using to calculate your fuel mileage? _________________
modok wrote: |
...If If stoner A takes a hit and then stoner B goes right away(not waiting two seconds), he's trying to suck on it while it's still got a vaccum, doesen't get much of a hit at all! Cause it hasn't filled back up all the way yet.
Stoner A is cylinders #2/4 B is #1/3 The plugged bowl is the throttle, the bong is the manifold |
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airkooledchris Samba Member
Joined: January 25, 2005 Posts: 2710
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Posted: Tue Jan 11, 2011 10:29 am Post subject: |
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SGKent wrote: |
Here is why it is probably there. The late 1970 models sense that the door swing in the AFM is the bus going WOT and enrich the mixture. On a 1979 with O2 sensor the AFM is leaned and richened by the O2 sensor so it sits at 14.7:1. At WOT it would still be 14.7:1 but it needs to be richer so the switch overrides the O2 sensor.
How old is the catalytic convertor?
What kind of compresson readings are you getting? |
I did the continuity test in my spare microswitch and it checks out fine, ill test the one in the bus later today and if it fails that test as well (only did the 'test light' check so far as outlined in Bentley) ill swap in the other one just to cross that off my list. I know the microswitch won't have anything really to do with low MPG, but it was one of the items that didn't pass the Bentley test so it's the first one im tackling.
I don't know how old the CAT is. It *looks* good, but ive only had the bus for about 8 months now, so I only know that this setup passed CA smog just last year. I doubt much has changed since then, so chances are it passed smog even with these poor MPG figures.
compression:
#3 = 120
#4 = 115
#1 = 114
#2 = 120
so far, out of the items I have tested so far, the only ones that haven't been in spec is the fuel pressure (noted in above post, high by a few PSI), my temp 2 sensor (swapping now) and this microswitch |
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SGKent Samba Member
Joined: October 30, 2007 Posts: 41031 Location: Citrus Heights CA (Near Sacramento)
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Posted: Tue Jan 11, 2011 8:05 pm Post subject: |
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hmmmn. If it passed smog for you one year ago - odds are that the cat is good. Sometimes they can go bad and start to plug up. That will really mess with fuel efficiency. A bad O2 sensor can do the same thing as can a bad TSII sensor if 1979 has them. Another thing in California that can mess with your mileage is the new gas fillers. If you don't check over 6 or 7 tanks, the new nozzles will really throw you as they fill a bus terrible and cut off early after dumping a gallon on the ground. I would be satified with your compression. Since it is a 1979 the lifters are hydraulic so it is harder to get a good compression test as they collapse without oil pressure from running. But it could be your switch too shorted. You are going the right way about this. _________________ “Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin |
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busdaddy Samba Member
Joined: February 12, 2004 Posts: 51130 Location: Surrey B.C. Canada, but thinking of Ukraine
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Posted: Tue Jan 11, 2011 8:40 pm Post subject: |
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I too am curious about how you are calculating the mileage, those plugs don't look that bad. _________________ 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
Stop dead photo links! Post your photos to The Samba Gallery!
Слава Україні! |
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Amskeptic Samba Member
Joined: October 18, 2002 Posts: 8568 Location: All Across The Country
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Posted: Tue Jan 11, 2011 9:01 pm Post subject: |
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Tire inflation
Brake adjustment (no drag)
Chronic headwind
Tons o crap stashed in the car
Fuel leak
Your plugs look quite fine, almost leanish.
Colin
(fuel pressure gauge is VDO?? Casual at best) _________________ www.itinerant-air-cooled.com |
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airkooledchris Samba Member
Joined: January 25, 2005 Posts: 2710
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Posted: Tue Jan 11, 2011 9:49 pm Post subject: |
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First, the Microswitch since that's where this topic started.
I tested my spare switch and it worked fine, so that was swapped in.
The 'light' test in the Bentley still doesn't work, but I can see 12 volts on one side of the switch (passenger side spade) so im not sure why the light doesn't turn on.
I then adjusted the switch position so it comes on ever so slightly before WOT (because I rarely floor it, it's adjusted for MY top end throttle position.)
The lean-ish look to the plugs might be a side effect of running the last 600ish miles using an NOS AFM. Even though both my old and new AFM checked out on all of the Bentley tests, I swapped the 'old' one back in for now so if I want to mess with anything, im not doing it on the NOS unit
is there a more trusted fuel pressure gauge to consider? I still have a few xmas gift certificates left I might be able to burn through...
my 'next up' list of stuff to check:
[ ] Re-check odometer accuracy
[ ] O2 sensor
[ ] Brake dragging
[ ] Thermo time switch
[ ] Injectors, leaks/clogged/volume/spray (and send my spare set out to be cleaned)
Im assuming that I calculate MPG the same as everyone else.
fill up, note amount of fuel required to fill up completely, note number of miles since last fillup. do math.
Now I 'have an app for that' and track my MPG numbers using it, which is nice as it gives you an overall number in addition to your per tank numbers (and your average price paid per gallon.)
I only wish I had been getting these numbers all along, but id been hesitant to fill the bus completely because I thought the PO had done something odd to the way the tank seals or something
- with how you can't pull the fuel hose trigger all the way anymore or it runs down the side of the bus.
It wasn't until Colin posted his trick about flipping the seal around that I realized I wasn't the only one (though when I tried that, that pump wouldn't work and I had to move on to the next one. myfault? not sure )
Last edited by airkooledchris on Tue Jan 11, 2011 9:55 pm; edited 1 time in total |
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1975 Kombi Samba Member
Joined: August 12, 2007 Posts: 2452 Location: Acton, Ontario, Canada
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Posted: Tue Jan 11, 2011 9:50 pm Post subject: |
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Do you have two loose wires that should connect to the microswitch. They should be there and not wired together. _________________ Brett
“He’s decieving you boy! Reach into his pocket and take what he’s got.” Mr. Crabbs.
75 Westy auto
03 Jetta TDI
71 SB
74 Westy
Licensed pilot (single engine land VFR)
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Rust In Pieces: 72 Bug, 73 Bug, 81 Rabbit LS D 2D, 83 Rabbit D 2D, 84 Jetta TD GL, 85 Jetta D, 68 Z28 RS 302, 91 Passat 16v |
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