Poor Fuel Mileage on 1973 Super - 1600 DP

[spectre1995]

Lately I've been noticing the fuel economy on my 1973 Super has gradually been worsening. The engine is a 1600cc dual port, using a H30/31 carburetor and a DVDA distributor. Lately, I've been getting about 11-15 MPG

Last week, I pulled the tank to check for leaks and noticed that there was some fuel residue underneath the tank, but I figured this could be due to when my filler neck hose broke, and the residue was just left over. I replaced the gasket for the sender as well as the hoses for the breather, but I am still noticing a very slight fuel smell in the trunk, which could be due to one of the hoses coming off of the expansion chamber being open ended (not sure where it leads but I'll cap it off at some point today).

The Bentley book mentions a few possible problems & solutions. The ones I've already done (besides rebuilding the carb);

-Tested the float for leaks
-Installed new needle valve and function tested it
-Tested automatic choke
-New spark plugs / wires / distributor cap & rotor

What I still need to do;

-Check jets (have two new idle jets, need to check accelerator)
-Check fuel pressure at float needle valve
-Check / adjust points




So my question is, if the fuel pressure at the needle valve is excessive, will it have a serious effect on my fuel economy? Also, what other problems / solutions should I consider to improve my fuel economy?

I'm also considering swapping the DVDA for a 009 distributor, or even an SVDA. Which would be the best paired with the H30/31 carb, and why?


Thank you all in advance

[67rustavenger]

[Tim Donahoe]

When I first bought my ‘74 Super Beetle, it got about 13 mpg. I had the stock Bosch 034 SVDA, coupled with an H 30/31. The engine ran very rich.

My solution was to replace it with a Solex 34 pict 3. The reason? That’s what the car came with when new.

The difference was amazing. Five years and no issues.

Some people do well with an 09 distributor and an H30/31. But the SVDA distributor doesn’t go well with your carburetor. Not enough vacuum.

Tim
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Let's do the Time Warp again!

Richard O'Brien

[Cusser]

[docdanracy]

I have 009 with Petronix and H30/31 carb.
Good throttle response and 23-25MPG
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Doc
1970 Sunroof Bug Yukon Yellow (L19K)
Custom 6.5x15” 914 Sport Wheels wrapped in 185x65x15 Contis
Empi shifter, full compliment of gauges, 1679 with mild cam, stock induction

SOLD: 1974 Marina Blue Standard Beetle undergoing restoration/preservation
1679 with Kadrons and header/QP
914 sport wheels 5.5" ET40 wrapped in 195x65x15 Kumhos

[spectre1995]

I spent the day cleaning and rebuilding the carburetor once again, this time installing a larger main jet (125 vs. the 120 that was in it), then checked the fuel pressure. It seems to be holding steady at +/- 3 PSI at varying RPM's (Up to about 3400 it goes just beyond 3 PSI).

I tried setting the idle RPM but it was fluctuating between 600 and 900, and would not hold steady. I also discovered the timing was improperly set.

I brought the distributor to the local VW place, and we determined that the DVDA distributor may not have been the best option for the H30/31 carburetor. So, I picked up a brand new Kuhltek SVDA and installed it, and not only does the idle RPM seem more stable, the engine itself seems "happier" with the new distributor setup.

At some point I plan to "upgrade" to a 34 PICT-3 so vacuum should be less of an issue in the future.



In any case, I'd assume having the timing improperly set (5 degrees ATDC) would be my #1 cause for poor fuel economy, as everything else checked out okay, save for some corrosion on the spark plug wire connectors which I had not seen before.

[Lingwendil]

With the h30/31, make sure you are using the vacuum port facing the rear of the car, that is angled upwards/diagonally From the flange of the carb. The port facing the drivers side of the car (above the cutoff solenoid) is meant for use with vacuum-only distributors, and will over advance the timing if used.

[Frank Bassman]

Just to be clear, use D for advance and B for retard.

-Frank

[jinx758]

Please verify you have no vacuum leaks ... anywhere. Check ALL OVER : anywhere on the carb that has a shaft or gasket, intake runner boots, and manifold intake. It's a little concerning to me your statement of a fluctuating idle.

You won't be able to correctly tune your carb with any vacuum leak.

My experience after rebuilding my stock carb was no less than 4 places that I had idle changes when sprayed with carb cleaner. I replaced the intake boots, carb & also put a Kuhltek 034. Car has been very well behaved ever since. I also found a cheap RPM/dwell meter & found out my El Cheapo dizzy prefers a "loose" point gap. The dwell was @ 65 so my points were too close together. Once this was corrected ... What a difference in drivability !

I used to be able to tune by ear but because of my degraded hearing from surfing and installing way too many stupidly loud audio systems over 3 decades I have to rely on tuning tools.

Just trying to help ... good luck ... jinx
_________________
" It's not valuable unless you learn something from an experience. " Henry Ford

It's not unlike the same difference

You can't push a rope


VALVES (cold)
POINTS
TIMING
CARB (fully warmed engine)

SCRAPE ALL GROUNDS

My Craigslist rescued 100 footer :
1971 Standard Bug
1776cc dual port
034 distributor
38mm EGAS Carburetor

[vamram]

Have you checked your oil level and smell? Is there gas in it? I had a fuel pump go bad allowing gas to leak into the crankcase and was getting like 10-14 mpg. I "figured it out" once the engine hydrolocked from so much gas in the block.
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'74 Super 9/16 - present, in refurb process.
'73 Super - 6/18 - Present - Daily Driver!
'75 Super Le Grande...waiting it's turn in line behind '74.
Click to view image
Save the Supers!!

[AlmostHeavenWV_VW]

[spectre1995]

Good morning everyone,

To start out, yes the vacuum advance is using port "D" on the carburetor, and it appears to be advancing properly.

As far as vacuum leaks, the only noticeable one (spraying carb cleaner and watching for RPM changes) is on the throttle shaft of the carburetor. Everything else in the engine compartment is okay.

I recently changed my fuel pump because the diaphragm on the old one was leaking fuel into the oil. I changed the pump, and the oil. My oil level seems to be dropping at a very slow rate over the past couple months, and I have noticed a minor leak coming from around the filler / alternator stand, which I will address sometime soon. It probably just needs to be torqued down a bit further.

My goal for today is to verify the points gap and the timing, and possibly have the time to do a compression test on all four cylinders.

As far as distributor lubrication goes, will a health amount of engine oil suffice? I have some leftover 20W-50 sitting in the trunk that could possibly be used.

[Randy in Maine]

Put a dusting of this on the point rubbing block inside the distributor cap....that is the lube you desire.

http://vwparts.aircooled.net/Distributor-Points-an...-small.htm

[AlmostHeavenWV_VW]

[jinx758]

Almost : thanks for sharing that bit of knowledge. That's what makes this forum so great !

I checked the gap on my new Craptek 034 before installation & it was spot on perfect out of the box. My OCD, PSM, & CRS force me to double & triple check most projects ( lol ). After 2 weeks of 009-like hesitation & head scratchin I researched & found some posts about dwell. I regapped my point dwell while slightly twisting the feeler gauge as it didn't have a .017. Hence the "loose" reference. All was good / better, and I have no pinging - I run premium gas only.

My drivability & miles per gallon did improve.

Just my experience ... your mileage may vary ( 'nother pun ).

Best regards ... jinx
_________________
" It's not valuable unless you learn something from an experience. " Henry Ford

It's not unlike the same difference

You can't push a rope


VALVES (cold)
POINTS
TIMING
CARB (fully warmed engine)

SCRAPE ALL GROUNDS

My Craigslist rescued 100 footer :
1971 Standard Bug
1776cc dual port
034 distributor
38mm EGAS Carburetor

[spectre1995]

Hm, still having some issues here.

So I found out the center intake manifold section was off of a single port engine, so when I went to install this brand new 34 PICT 3 carb on the engine, it didn't fit. I swapped in a DP center intake and then the 34-3, and it seems to run a lot better than it did before.

So here's the issue. Last night I took the car out for a run and it ran really good with the new carb, definitely better than before, the issue is that once again I ran out of fuel at the 130 mile mark on the odometer. I find it nearly impossible to me getting 13 MPG on a car like this.

I suspect my gas may have been stolen (recent string of auto thefts and gas siphoning nearby) but in the event that it wasn't stolen, I'm still scratching my head over this since I have not found any leaking, etc. I still need to do a compression test, which I will likely be doing sometime this week

[Lingwendil]

What is your timing set to?

Definitely check the jetting in the carb, but it should be pretty close. 55 idle, 125-130 main should be ballpark.

Plug gaps? you did check the before installing, right

Don't bother with premium. The car doesn't have high enough compression to need it. Also, try buying gas somewhere different, just in case.

What air filter? restrictive aftermarket stuff can hurt economy.



Any pics of the engine?
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73 super beetle thread http://www.thesamba.com/vw/forum/viewtopic.php?t=649622 Back on the Road!

Modify your Kadrons for SVDA http://www.thesamba.com/vw/forum/viewtopic.php?p=8115884#8115884

Cast iron VJU4BR8 SVDA reference thread- https://www.thesamba.com/vw/forum/viewtopic.php?t=...mp;start=0

Need replacement filters for original Kadron aircleaners? WIX #42087 is a perfect fit, as is Napa Gold #2087!

[spectre1995]

It's set to 7.5 Degrees BTDC

Jetting is 55 idle, 130 main

I checked the plugs prior to install.vif I recall it was 0.028 gap

Air filter is a round aftermarket one from the local VW parts shop

[Lingwendil]

Have you checked that it goes up to a max of ~30° or so at max advance? Some of the new SVDAs that I'v checked out have either excessive advance, or not enough.


Definitely check compression. You could have a poorly sealing valve causing it to run on practically 3 cylinders power wise.
_________________
73 super beetle thread http://www.thesamba.com/vw/forum/viewtopic.php?t=649622 Back on the Road!

Modify your Kadrons for SVDA http://www.thesamba.com/vw/forum/viewtopic.php?p=8115884#8115884

Cast iron VJU4BR8 SVDA reference thread- https://www.thesamba.com/vw/forum/viewtopic.php?t=...mp;start=0

Need replacement filters for original Kadron aircleaners? WIX #42087 is a perfect fit, as is Napa Gold #2087!

[spectre1995]

Without sparking an oil debate like, is the fact I'm using 20W-50 going to have an effect on MPG?