Horrible Mileage - FIXED! 100%

Post by **Sluggo** » Thu Mar 08, 2007 9:43 am

vdubyah73 wrote:Front tire size?

Bill

Front & back are Michelin Rain Force 185-R14 tires.

Post by **Sluggo** » Thu Mar 08, 2007 9:55 am

Replaced the 200 ACs with 175s. Things seemed to smooth out more. Got rid of a lot of the bogging. I tried spraying carb cleaner at my manifold mating surfaces and the idle didn't change one bit. No effect at the vac connections either.

chitwnvw · Post by **chitwnvw** » Thu Mar 08, 2007 12:31 pm

I say go out to the highway. Drain your fuel. Put exactly 1 gallon in. Watch the mile markers and see exactly how far you get.

Post by **Sluggo** » Thu Mar 08, 2007 12:36 pm

chitwnvw wrote:I say go out to the highway. Drain your fuel. Put exactly 1 gallon in. Watch the mile markers and see exactly how far you get.

That was Bottomend's suggestion.

DurocShark · Post by **DurocShark** » Sat Mar 10, 2007 9:35 pm

If you do the run-dry test, I hope you have a VERY clean tank and lots of filters handy!

Post by **Sluggo** » Sat Mar 10, 2007 9:48 pm

DurocShark wrote:If you do the run-dry test, I hope you have a VERY clean tank and lots of filters handy!

Tank was restored when the engine was rebuilt. Less than 1700 miles ago. Why lots of filters?

DurocShark · Post by **DurocShark** » Sat Mar 10, 2007 10:08 pm

Sluggo wrote:
DurocShark wrote:If you do the run-dry test, I hope you have a VERY clean tank and lots of filters handy!
Tank was restored when the engine was rebuilt. Less than 1700 miles ago. Why lots of filters?

Cuz the gas pumped by the gas station has tons of crap in it too. Especially if the underground tanks are old, it rained recently, the tanks were low, etc etc etc.

If you don't have one yet, pick up one of the glass filters with the replaceable elements. Use it for short periods of time, replacing with your good plastic one. It will give you an idea of what your fuel source(s) are giving you. You may find that some of them are pristine while others are putting crap in your bus. And definitely use it in front of your stock filter if you're running your tank dry.

While I ran with one for a long time in the GWB until I got my tank relined, I don't recommend it. A stray rock at just the right angle could shatter it dumping fuel all over your hot exhaust.

Post by **Sluggo** » Tue Mar 20, 2007 11:00 am

FUEL PRESSURE!

It was suggested before. I was going by my gauge which read 2.5 PSI. Apparently it was reading incorrectly because when I tried adjusting the regulator there was no change in the gauge reading. When I opened the regulator up all the way all of a sudden the gauge started reacting. Must have been a clog because now it reads perfectly and in time with regulator adjustment.

I set the regulator back to where I had it before adjustment and my PSI was 1. After adjustment to 2.4 the Bus ran better & about 40* cooler. But I think I may need to reduce my mains to 125 (130 now). Still a slight bog around 3500 - 4500 RPM unless I give it extra pedal. Mixture screws are now at 1 1/2 turns out (were 1 3/4).

I haven't driven enough to truly gauge my mileage yet. But it seems better (going by the gauge).

Could too little fuel pressure cause bad mileage? I realize that was probably why I had to crack the mixture screws an extra 1/4 turn. And I understand why my heads would be cooler. But I don't see how it could cause poor mileage.

Post by **Amskeptic** » Wed Mar 21, 2007 8:37 am

Sluggo wrote: Could too little fuel pressure cause bad mileage?

Not likely.
You don't have to drain the tank and add a gallon and go drive to test mpg. You don't want to be sucking the bottom of the tank, either. Fill it at your chosen pump at your chosen gas station. Each nozzle has its own full-cut-off behavior. Go drive. Come back to same pump, same nozzle. Fill it again. Divide miles driven (124 ex) by gallons taken in (6.5 ex) and see what your mpg is (19.07 mpg bus last week).

Post by **Sluggo** » Wed Mar 21, 2007 11:13 am

Amskeptic wrote:
Sluggo wrote: Could too little fuel pressure cause bad mileage?
Not likely.

I was hoping I had found it. I've had several other respected people say yes but not to the degree that I was experiencing.

You don't have to drain the tank and add a gallon and go drive to test mpg. You don't want to be sucking the bottom of the tank, either.

That's my theory too. I know it's not good to run your tank dry. That's why I didn't do it even though it was suggested a few times.

Fill it at your chosen pump at your chosen gas station. Each nozzle has its own full-cut-off behavior. Go drive. Come back to same pump, same nozzle. Fill it again. Divide miles driven (124 ex) by gallons taken in (6.5 ex) and see what your mpg is (19.07 mpg bus last week).

That's how I've been doing it. Miles driven divided by fuel consumption = MPG

Post by **Sluggo** » Mon Apr 02, 2007 10:58 am

Finally got my jets and got to work. Pulled out the 175 A/Cs, 130 mains & 55idles and put in some 145 A/Cs, 120 mains and 45 idles. With this combo it idled very rough and would peter out at 2800 RPM until I gunned it up to 4500. Put the 175 A/C back in, no change. Change back to 145 A/C and put the 130 mains back, still peters out at 2800 RPM. Got to 145 A/C, 120 main & 55 idle. Mixture screws at 1 1/2 turns. Now we're getting somewhere.

This is the best it's been so far. Averaged 16.5 MPG with very spirited freeway driving between 65 & 75 MPH. Barely have to touch the pedal to start accelerating. But (there's always a but...), When I give it just a little gas I'm good. I accelerate moderately. If I give it just a little more I get a bog. Give it a little more past that and I'm accelerating faster but giving it too much gas.

Could this be pump jets? If so, how do you adjust pump jets on Weber 36s? Should I try 50 idles?

dingo · Post by **dingo** » Mon Apr 02, 2007 3:19 pm

pump jets have different sizes...50 for instance

main jets affect throughout the entire range, while A/C is mostly influential as rpms rise

idle jets also affect the progression up to maybe 2k

im no expert, but just somethings i read

Post by **Amskeptic** » Tue Apr 03, 2007 7:17 am

dingo wrote:pump jets have different sizes...50 for instance

main jets affect throughout the entire range, while A/C is mostly influential as rpms rise

idle jets also affect the progression up to maybe 2k

im no expert, but just somethings i read

Randy, you need to distinguish where and how this "bog" is occurring.
Does it occur only at the moment you hit the gas, or does it occur slightly after? The accelerator pumps only squirt for a 1/2 second. A rich bog feels so similar to a lean bog that it can be the devil to figure out which one you are experiencing. Clue, no symptoms with a cold engine but more symptoms as it gets hot is a rich bog.
Colin

Post by **Sluggo** » Tue Apr 03, 2007 10:16 am

Amskeptic wrote:Randy, you need to distinguish where and how this "bog" is occurring.
Does it occur only at the moment you hit the gas, or does it occur slightly after? The accelerator pumps only squirt for a 1/2 second. A rich bog feels so similar to a lean bog that it can be the devil to figure out which one you are experiencing. Clue, no symptoms with a cold engine but more symptoms as it gets hot is a rich bog.
Colin

It was only when I hit the gas just a little while accelerating. Meaning I'm already accelerating but I'd like to accelerate faster so I give it just a little more and it bogs. Happens more when cold. I changed out the E-Tube from F-11 to F-7 and it seemed to help.

dingo · Post by **dingo** » Tue Apr 03, 2007 3:59 pm

also...Adjusting the spring in the injection pump for tension or length can give 'short,sharp burst of fuel' or 'long,smooth'.....if you think that might help your scenario

Itinerant Air-Cooled

Itinerant Air-Cooled

Horrible Mileage - FIXED! 100%