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have microswitch for full enrichment - but don't use it?
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airkooledchris
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PostPosted: Mon Jan 10, 2011 6:25 pm    Post subject: have microswitch for full enrichment - but don't use it? Reply with quote

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:
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it failed the Bentley test, which is when I then read on and noted the following:

Image may have been reduced in size. Click image to view fullscreen.



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
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PostPosted: Mon Jan 10, 2011 6:33 pm    Post subject: Reply with quote

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?
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airkooledchris
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PostPosted: Mon Jan 10, 2011 6:39 pm    Post subject: Reply with quote

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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PostPosted: Mon Jan 10, 2011 6:46 pm    Post subject: Reply with quote

My ? is if it is causing the enrichment at al times. Read your plugs. Do a fuel pressure test.
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PostPosted: Mon Jan 10, 2011 6:55 pm    Post subject: Reply with quote

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.
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PostPosted: Mon Jan 10, 2011 8:49 pm    Post subject: Reply with quote

Sounds like it's time to break out the OHM meter and test the switch.
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airkooledchris
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PostPosted: Mon Jan 10, 2011 9:32 pm    Post subject: Reply with quote

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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PostPosted: Mon Jan 10, 2011 9:39 pm    Post subject: Reply with quote

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?
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airkooledchris
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PostPosted: Mon Jan 10, 2011 9:59 pm    Post subject: Reply with quote

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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PostPosted: Mon Jan 10, 2011 10:52 pm    Post subject: Reply with quote

is this thread about the micro-switch or 11 mpg?
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airkooledchris
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PostPosted: Mon Jan 10, 2011 11:04 pm    Post subject: Reply with quote

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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PostPosted: Mon Jan 10, 2011 11:22 pm    Post subject: Reply with quote

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.
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PostPosted: Tue Jan 11, 2011 7:09 am    Post subject: Reply with quote

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?
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PostPosted: Tue Jan 11, 2011 9:42 am    Post subject: Reply with quote

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! Shocked

Also; What method are you using to calculate your fuel mileage?
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PostPosted: Tue Jan 11, 2011 10:29 am    Post subject: Reply with quote

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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PostPosted: Tue Jan 11, 2011 8:05 pm    Post subject: Reply with quote

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.
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PostPosted: Tue Jan 11, 2011 8:40 pm    Post subject: Reply with quote

I too am curious about how you are calculating the mileage, those plugs don't look that bad.
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PostPosted: Tue Jan 11, 2011 9:01 pm    Post subject: Reply with quote

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)
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PostPosted: Tue Jan 11, 2011 9:49 pm    Post subject: Reply with quote

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 )
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PostPosted: Tue Jan 11, 2011 9:50 pm    Post subject: Reply with quote

Do you have two loose wires that should connect to the microswitch. They should be there and not wired together.
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