Checking fuel pressure

Just got off the phone with A.J. Sims, "Mr. Kadron." I called to inquire about getting properly-sized jets for the Wonderbus's carbs. I've been getting poor mileage (14mpg mixed street and highway), the plugs have that tell-tale black sooty look, and even with the mixture screws all the way in, the engine will not lean misfire. According to a couple websites, (lowbuggit.com and aircooled.net) this can be due to improper jetting.

So I called A.J. -- sounds like a nice guy -- and he told me to first check the fuel pressure. "Kadrons do not like pressure," he said. Anything more than 2lbs. If it's more than that I'd be wasting my time jetting and adjusting; the first step is to get that pressure in the acceptable range.

So my questions to the group are:

  1. What's my cheap and easy way to check fuel pressure -- Bentleys tells us to install a "T" fitting after the pump and connect it to a pressure gauge. Is it easy to find a suitable pressure gauge that will be happy with this 1971-sized fuel line?
  2. I have a mechanical pump on my engine. A.J. said to add shims to the pump to lower the pressure. I'd like to make sure I understand the procedure. So students, pull out your Bentleys 68-79 Bus manual and refer to Section 3, Page 9, Figure 4-3. If I understand what A.J. is telling me, I would want to add more of Item 13 -- "Intermediate flange gasket" as needed to lower fuel pressure. Do I understand this correctly?
Reply to
Mike Rocket J. Squirrel Elliot
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John @ aircooled.net recommended a simple sears one for combo vac/pressure to me. If they're the same as the ones you see in NAPA and such they might be in the range of 70psi - 30 vac. How accurate it would be in the

2 psi range is unknown to me. I looked around for a while to find a direct-mount 1/8" NPT 5 psi full scale gauge with good accuracy, but never found one.

Seeing as one would be interested in the 2-3 psi range as nominal (webers, too), this is out-of-range @ 15psi full scale:

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Just googled, and found this:
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AS1497 looks good. And $85 for a NIST certificate of accuracy :)

The kick-ass setup might really be 5 1/2 psi rotary pump with an adjustable regulator with 2 electrical pressure sender units pre and post the regulator (with a switch at the cockpit gauge). At 5 1/2 psi you'd have some good percent of regulation when dropping it to 2-3.

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Can't find a 10-180 Ohm sender unit, nor a VDO gauge in the 5 or 10 psi range, though.

I'm just a quack anyways, just ignore what I said about the sender units ;)

Agreed, though from my Type 1 Bently manual it is section 2, page 6, figure 4-2 that says you are looking for 13 mm of extension of the pushrod tube.

Reply to
David Gravereaux

Aircooled.net has a rental fuel pressure gauge, described as "low pressure." It's not clear if it reads well into the sub-2psi range. John's on vacation right now, I'll send him a letter.

[snip]

The idea of using an add-on pump then downregulating the pressure is appealing but maybe overcomplex? I'm tempted to just find a good regulator and keep the mechanical pump in good shape. Problem with the cbperformance regulator is that it outputs 3.5psi while the Kadrons want less than 2 psi -- A.J. Sims sez 1.25 psi is the target.

Aircooled has a regulator that can be dialed down to 2psi, and Jbugs.com sells one (#1540) that can also be dialed from 1 to 5psi in half-pound increments, though we don't know how accurate it is.

I think that's to achieve the normal 3.0 to 5.0 psi required by the stock carbs. Need to shim it up more to get lower pressure if I don't follow the pump with an appropriate regulator.

I think I might rent that aircooled.net pressure gauge and get one of those Jbugs regulators and see if that works.

Thanks for looking at this, David!

Reply to
Mike Rocket J. Squirrel Elliot

Might be... Given that I don't have an in-cockpit FP gauge, nor a data logger to record it, I can't say FP is an issue that I have for such a weird way to run fuel to get around a problem that I don't know exists.

When I swapped to an electric pump, my car ran more stable.

The CB one has an adjustment screw, but the text doesn't describe the range of adjustment it can do, but assuming (ass-u-me) its a european model, it seems like it could regulate down @ 2 as webers are popular carbs over there and they like 2.5-3 psi.

I know that 1 to 5 in 1/2 pound clicks regulator. Please avoid it. Mine gummed-up in a week. The sprung rubber stop got all mis-shapen in the bore and I had to toss it. Everyone from EMPI to Mr. Gasket re-brands it as their own.

IMHO, I think your best way to maintain proper FP is to use a regulator between the pump output and the carb(s). But which model, I can't say for sure. But first, please verify that FP is a problem in your current setup. I know I need to get a nice accurate in-cockpit gauge for myself...

Reply to
David Gravereaux

Your HO is welcomed.

Thanks for the caveat about the 1-to-5 psi click regulator. I'll avoid it. I sent CB Performance a note about what they suggest for < 2psi fuel pressure regulation. If that European regulator can be turned down that far, I bet they'll let me know.

I'm asking around to find someone with a pressure gauge and as soon as I get one -- maybe rent John C.'s unit -- I'll have a way to determine what I need to do.

I'd think that whether one runs an electric pump or follows his mechanical one with a regulator, it should give the same effect that you noted -- greater stability. The goal is to give the carbs constant pressure to work with.

Reply to
Mike Rocket J. Squirrel Elliot

Any large auto parts chain carries Holley. The 12-804 regulator is for

1 to 4 psi and a similar style (non-restrictive) to what Berg recommends in his writings.

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They also make gauges. I have a small 1 1/2" 15 psi gauge, p/n 26-500 that works fine. A shop might opt for something more larger/expensive.

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RT

Reply to
Raymond Lowe

I'll look for it at my FLAPS . . . but I note on that page that the regulator is "Not legal for sale or use in California on any pollution controlled motor vehicles."

I wonder if CB Performance, a California company, sells their "Petrol King" regulator to Californians?

0 to 15psi is a bit larger a range than I need for dialing in 1.25psi, but in a pinch . . .

Thanks, Richard!

Reply to
Mike Rocket J. Squirrel Elliot

On Thu, 20 May 2004 19:24:20 -0700, "Mike Rocket J. Squirrel Elliott" ran around screaming and yelling:

you bet....they have a disclaimer on everything that says their parts are for racing and offroad applications.... JT

Reply to
Joey Tribiani

Ah -- lawyer stuff. Of course.

Found a local shop with stock on the Holley fuel pressure regulators. A friend turned up a 0 - 10 psi gauge. Even talked my youngest brother, who knows quite a lot about engines and cars, to pop over on Sunday.

We're gonna park the bus under a big ol' shade tree to work on it. We'll black out a few front teeth, put on some overalls, find a big lout with a low forehead to stand around and just grin, get some hound dawgs, and drink whiskey out of glass jars. There may be some firearms present.

That ought to go over big in our quiet middle-class southern California suburban neighborhood.

Reply to
Mike Rocket J. Squirrel Elliot

Hey now, wait a minute here... :-) psst- Can I get directions?

They all love me in my neighborhood. Every time I walk up to a couple of neighbors that are talking, they change the subject just as I get there as if though they know I don't want to talk about whatever nonsense it was they were talking about when I walked up. :-D

Reply to
Shaggie

heh heh, lovely picture you painted there ;)

Jan

Reply to
Jan Andersson

Neighbor woman -- of the tense short-haired brunette breed -- said to me when I was delving (again) into the engine compartment, "You sure must like driving that bus." I picked up a bit of sarcasm there.

I smiled, "Yep, I do." (Get used to it, lady.)

Reply to
Mike Rocket J. Squirrel Elliot

That's not how it's done?

Reply to
Mike Rocket J. Squirrel Elliot

Sometime, just sometimes, the "racing only" designation is for your own good. Like lightweight wheels that bend up when you nudge a curb or hit a pothole. On a raceway you have allowances for certain failures such as run-off room.

Why don't you dig a big hole and bury that sorry POS?

Reply to
jjs

Probably against the local zoning laws.

No sir -- I'm gonna see this thing through. I will be a friggin' VW /HERO/ when I am done.

Reply to
Mike Rocket J. Squirrel Elliot

I've also seen a similar sticker on this empi glove-box enclosure.

http://63.230.74.177/cruises/2000_04_08/1/mvc-018f.jpg Think it'll make my car go faster?

Max

Reply to
Max Welton

Here, too. The locals are afraid that planting a Bug could lead to some kind of horticultural horror, maybe Frederic and the Bug Stalk.

Reply to
jjs

LOL!

Reply to
Mike Rocket J. Squirrel Elliot

Maybe it will go even faster with TEN of them!

Reply to
Mike Rocket J. Squirrel Elliot

Reply to
ilambert

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