Fuel pressure

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Intelliduner
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Fuel pressure

Post by Intelliduner »

Gang,
The other thread about the fuel pump is bordering on my own issue, but rather than co-opt that thread, I thought I'd start another :)

My buggy (2332cc VW, 44 IDF Webers) has had some issues with loading up and stumbling when going through bumpier terrain.

Now, keep in mind that it didn't do this the first several trips I had it. Ok, so I thought I'd replace the needles & seats. I also set the closed setting for the needle valve a little lower (11.25mm) than the stock specs (10mm). The problem persisted, though.

Tonight I took the carbs back apart and didn't note anything unusual. I blew on the fuel inlets with the needles closed (just the weight of the floats holding it) and they were absolutely airtight. So I think the needle valves are fine.

So I lowered the closed setting a little more to a bit over 12mm this time.

However, one thing I'm wondering about now is my pressure regulator. I have an electric pump, and one of the chromie 1-to-3 PSI dial regulators. A few trips ago, the little sticker on the dial came off to reaveal a little hole under it. Chances are it might have gotten some sand down in it. I put some duct tape over it and forgot about it.

Now I'm wondering if maybe the pressure regulator is flaking out. If it's letting too much pressure to the carbs, wouldn't that affect performance pretty much all the time, though? Can a regulator (maybe with some sand in it) malfunction intermittently? The engine runs just fine all the time except when it gets jostled good.

Remember, it used to run just fine even under such bumpy conditions, so *something* had to have changed... I dunno what to do except put a fuel pressure gauge in and see what it says. But if it's intermittent, I won't see the problem sitting in the garage, and I won't be able to see the pressure gauge while driving it (unless I run a lot of fuel line :wink: )

Any suggestions welcomed. If the Weber EFI weren't so expensive, I'd be seriously tempted, but I *know* these carbs have and can run better than this.

Thx,
_dennis

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Post by Sandemon »

Dennis, Are you sure that it is not the carbs out of sync? I had a problem with my 44's they would idle just fine and would run fine wide open but low to mid range they sounded like rice krispys. The way I fixed it was to take all the linkage apart and start over pay close attention to the ark that the rods from the crossbar to the carbs take they must be the same not just close. also before you start check the other stuff like plugs, wires, and timeing. There is nothing more frustrating than chasing 2 problems thinking that its just 1 :twisted: 8) :)
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Post by NOSJunkie »

Webers are very sensitive to pressure, those chrome pressure regs. are not worth the money, I'd use one from holley I think they sell for about $20. Joe
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Post by OVERTIME »

I dont know if they make them for 44s but I have emulsion tube extensions on our 48 IDAs. These were specifically designed for bumpy terrain. Dont know if that helps.

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Post by Intelliduner »

Sandemon wrote:Dennis, Are you sure that it is not the carbs out of sync?
Pretty sure. It runs great all the time except when it gets particularly bumpy for more than a couple seconds. If they were out of sync, I'd likely have more consistent problems.

thanks,
_d

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Post by Intelliduner »

jnjburns wrote:Webers are very sensitive to pressure, those chrome pressure regs. are not worth the money, I'd use one from holley I think they sell for about $20. Joe
I see the plain 804 model is about $24 and chrome 500 model is $47 at Summit:

http://store.summitracing.com/product.a ... htype=ecat

These the ones you're suggesting?

Is there a pressure calibration on the body to set it or does it require a fuel pressure gauge in line to set it up? I also can't tell from their info whether it has two exit ports--if just one, I'd have to plumb in a pressure guage downstream, but it looks like most pressure gauges are designed to attach to NPT fittings--are there any that you can just splice in to the fuel line directly, with their own 3/8" flared or barbed inlet and outlet tubes?

thanks,
_d
Last edited by Intelliduner on Thu Feb 05, 2004 1:03 pm, edited 1 time in total.

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Post by Intelliduner »

OVERTIME wrote:I dont know if they make them for 44s but I have emulsion tube extensions on our 48 IDAs. These were specifically designed for bumpy terrain. Dont know if that helps.
If they're what I'm thinking of, I already have 'em. They stick up, oh, about an inch or so out of the top of the body, about halfway up the velocity stacks?

thanks,
_dennis (should have just copied all 3 replies into one message :idea: )

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Post by NOSJunkie »

Yes those are the one I'm talking about. It only has one inlet and one outlet. You can get a russel 3/8" mip to whatever you want with a 1/8" pipe thread in it. I have one on my boat for a water pressure guage. The 1/8 in. hole is on the flats where you put the wrench. I dont know how to post pic. Buy a fuel pressure guage that is liquid filled it will last longer....... Joe
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In-line fuel pressure guage.

Post by Kronikenergy »

I just purchased an in line fuel pressure guage and fitting from a place that if I remember correctly is called performance products and is right up the street (west) of fibertech on prospect. I cut the fuel line, inserted the fitting and used hose clamps to tighten it up. Unfortunately it wasn't a fluid filled guage but I will switch it out with one from fibertech for like 30 bucks or so. I'vegot some pretty trick 48 IDA's with a fuel return system. Anything that the carbs don't want goes right back into the fuel tank. It shows 2psi. I wasn't having any problems but for a few bucks I though I'd have one more thing to look at.

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Re: In-line fuel pressure guage.

Post by Intelliduner »

Kronikenergy wrote:I just purchased an in line fuel pressure guage and fitting from a place that if I remember correctly is called performance products and is right up the street (west) of fibertech on prospect.
Ah, Total Performance Racing? My parents friend owns that shop...I forgot about it! I'll swing by there and see what he can do for me :D

thanks,
_dennis

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Post by Intelliduner »

I never did make it by Total Performance. They've moved from their location across the street from the Dyno Shop--my folks said they moved just up the street, but I ended up just going to FiberTech.

So, now I have new question. I installed a new Holley Red (1-4 PSI) regulator, and a pressure gauge that FiberTech carries (Bonaco? it's Taiwanese, but they say they are good quality). I plumbed it all in and turned on the fuel pump without the engine running (because I disassembled several parts to install the regulator). The initial pressure, which was supposedly factory set to 2.9 PSI, was showing as about 5.5 PSI on the gauge.

I thought this was strange for a regulator that supposedly has an upper limit of 4 PSI, but I adjusted the screw on the regulator just to see what it would do. I couldn't get the pressure below 3.5 PSI.

Then the adjusting screw came completely out of the regulator--no more adjustment.

With it running at 3.5 PSI, I saw fuel trickling into one of the carburetor throats, so it was enough pressure to overcome the (new) needle valve I have in there. The other carb was fine.

So a guy at Fibertech hooked the gauge up to an air compressor and he said it was accurate at a couple readings, I think 10 PSI and about 5 PSI. He said they never have problems with the Holley regulators, and that the problem might be in that I was testing it without the engine running. I don't know how that could have a bearing...

So I went ahead and swapped out for a new gauge, and will test it out later, but do you guys think that it would make a difference having the engine running? Do you think I just got a faulty regulator instead?

TIA,
_dennis (needs to get this resolved once and for all before next weekend's trip!)

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Post by NOSJunkie »

I dont think it matters whether or not the motor is running because at an idle the fuel consumtion will be minimal. Sounds like a faulty reg. You have to much pressure if its leaking past the needle and seat.....
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Post by jhitesma »

Greg (In Excess) and I are sitting here discussing this since he had fuel pressure issues on his car which will be racing tomorrow.

And the question is - are you sure it's the right regulator?

It sounds almost like you may have gotten the Holley high pressure 4.5-9PSI regulator instead of the 1-4PSI regulator.

Looking at Holleys website (and Summits and a JEGS catalog we have on hand) it looks like they no longer call them by color so it's hard to say for sure by that. Do you have a part number on yours?

Holley 1-4 PSI regulator:
http://store.summitracing.com/partdetai ... 2D12%2D804

Holley 4.5-9 PSI regulator:
http://store.summitracing.com/partdetai ... 2D12%2D803

Greg is also wondering if you're sure you have it plumbed correctly - he things installing it backwards could force the regulator open.

Greg also sais to take the cover off and look at the spring. If it's really a low pressure it should be painted red - or blue if it's a high pressure.

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Post by like2bcrazy »

You may want to check the pressure going INTO the regulator. The low pressure holly regs cant handle more than 10psi on the input.

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Post by Intelliduner »

jhitesma wrote:It sounds almost like you may have gotten the Holley high pressure 4.5-9PSI regulator instead of the 1-4PSI regulator.

Looking at Holleys website (and Summits and a JEGS catalog we have on hand) it looks like they no longer call them by color so it's hard to say for sure by that. Do you have a part number on yours?

Holley 1-4 PSI regulator:
http://store.summitracing.com/partdetai ... 2D12%2D804

Holley 4.5-9 PSI regulator:
http://store.summitracing.com/partdetai ... 2D12%2D803

Greg is also wondering if you're sure you have it plumbed correctly - he things installing it backwards could force the regulator open.

Greg also sais to take the cover off and look at the spring. If it's really a low pressure it should be painted red - or blue if it's a high pressure.
Yeah, it sure acts like a high-pressure model. But while the unit itself does not have a part # on it, the box had the 804 part # and the spring inside it is red. I'll check the plumbing again, but I'm 99% certain that it is correct: in through the bottom port, and out through the side ports.

_dennis

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Post by Intelliduner »

Gah. After today, I'm even more confused. I think I may be chasing a few tails. With the new gauge, and the engine running, I was able to dial in my pressure to a lower level, about 2.5 PSI. Groovy. But then the pressure dropped while it idled longer. I adjusted the pressure back up. Again, another adjustment. Finally it seemed to stabilize.

Turn the engine off, and I notice two things in one of my carbs. The first, it's leaking fuel from, I think, the cross shaft in between the two throats (ie, outside the carb body), and running down the arm for my accelerator pump. Drip drip drip on the ground. I think there are bushings in there that are probably shot.

The other thing? About 30 seconds after shutting the engine down, fuel begins to drip into one carb throat, from the tube that hangs out in the middle of it as you're looking downward (I think this is the main fuel circuit. Drip drip drip.... for minutes. There is a vertitable lake of fuel sitting down at the bottom of that one throat. The other throat is fine. The other carb is fine. The gauge is reading zero fuel pressure.

I changed the needle valve again, re-set it, start the engine, shut it off, and 30 seconds later, drip drip drip down inside the throat. I'm suprised at how well those butterflys seal. There's another lake of fuel sitting down in there.

So, now I have a pressure gauge I'm uncertain of, a regulator I'm still uncertain of, a leaky bushing or something in the cross shaft in one carb, and a mysterious fuel burbling-over into one throat in one carb after the engine has been shut down for half a minute. I'm at my wits end and need a carb specialist to just wipe this slate clean :x

_dennis (rant-o-rama)

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Post by Intelliduner »

After dinner with my parents today, I take my dad out to the garage to show him this funky behavior my carb was giving me, and wouldn't ya know it, the sucker behaved, didn't do either problem (no leakage at the cross shaft, and no burbling fuel into the carb throat). I could throttle--I mean, strangle--this sucker some times! :wink:

In better news, however, I did discover an exhaust leak at the #1 exhaust port while we had it running, so at least now I know what that popping sound was that I've heard the last couple trips :)

_dennis (with a growing list of stuff to fix)

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