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Date:         Thu, 7 Oct 2004 09:03:33 -0700
Reply-To:     Craig Oda <craigoda@GMAIL.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Craig Oda <craigoda@GMAIL.COM>
Subject:      Re: VDO Fuel Pressure sender?
Comments: To: Max Wellhouse <maxjoyce@ipa.net>
In-Reply-To:  <6.0.0.22.2.20041007005416.02d7bdd0@pop.ipa.net>
Content-Type: text/plain; charset=US-ASCII

Max, thank you for the information. This is helpful. I found three sites that have a bunch of information on reading a vacuum gauge.

http://www.iwemalpg.com/Vacuum_gauge.htm http://www.centuryperformance.com/vacuum.asp http://www.fordf150.net/howto/diagnoseengine.php

I'm looking forward to putting the vacuum gauge tester onto my system and telling me what it says. Per your setup, I'll probably put the gauge inline with the vacuum line going into the fuel pressure regulator. I suspect that my vacuum is low since I am getting fuel pressure at 31psi instead of 29psi.

This is good timing for this bit of info. I was thinking of buying an air compressor so that I could do a leak-down test on one of my cylinders. However, I may not have to do this if I can use the vacuum gauge to figure out if the misfire problem is due to leaking valves or a problem with the piston rings...

I kind of like these gadgets that monitor the engine. I would like to intall a permanent vacuum gauge. However, I'm leary about running a vacuum line all the way from the engine compartment to the front of the van. I would much rather have an electronic sender tapped into the engine compartment. Though, I guess that this type of sender does not exist.

Well, I'll do some tests with the mechanical gauge. Thanks.

Regards, Craig

On Thu, 07 Oct 2004 01:27:50 -0500, Max Wellhouse <maxjoyce@ipa.net> wrote: > Craig and Listees: > > You're plan on the fuel pressure mounting is pretty much what I had > planned. I was being facetious about doubling up the vacuum gauge and the > voltmeter. there is no sending unit for the vacuum gauge(at least not the > VDO vacuum gauge). I originally used 1/4" soft copper tubing routed under > the vehicle from the engine compartment to the place under the dash where > the heater hoses come up through the body. I have since been told that the > diameter of that line is too big for maximum gauge accuracy, so I went down > to some really skinny black plastic tubing(maybe 1/8" or less) I bought at > NAPA. It's about the same diameter as the extension hoses you get with an > air shock kit. I fished that inside the copper and have had no > troubles. Tied the vacuum line into the fuel pressure regulator line with > a small T connector and then used a plastic adapter to go from the small > plastic hose up front to the threaded 90 degree end of the gauge. . I > think regular vw fuel line braided cloth hose slipped over just fine with a > small hose clamp for security. The closer you tap vacuum to the intake > manifold, the more accurate the information you will get( ie don't tap into > the vacuum line that goes to the charcoal canister) > > A vacuum gauge can accurately tell you many things about the health of your > engine ie. burnt valve, slow or retarded timing, weak valve springs, etc, > but I put it on there to keep my lead foot from putting me into the poor > house! My Boston Bob engine with mild cam on it idles at about 15" of Hg > and the difference between driving right behind a semi trailer(of course I > don't do that anymore) in a stiff headwind and regular driving with no wind > break REALLY shows up on the vacuum gaugeI don't think the VDO gauge came > with the diagnostic details of what the vacuum gauge will and won't tell > you, but Most of the old Clymer VW manuals for Rabbit and Dasher have an > excellent troubleshooting guide. I also think buying a cheapo vacuum gauge > tester from an auto parts store(the big garish looking one) should have the > same info. Maybe that info is on line somewhere also. I was going to use > the water temp gauge sending unit from my Haltech engine management system, > but now I'll check it's resistance readings first. If I have to spring for > another VDO temp sender, I'll do it. Cutting one of the smaller coolant > hose lines in the back of the engine won't be too much of a hassle. As far > as stringing the extra wires, I already have 4 in the loom, so adding 2 > more won't be too much of a hassle. The beauty of the vacuum gauge is that > the only wiring necessary is the wiring for the illumination. thanks for > the reply. > > Max > > > > a 06:06 PM 10/6/2004, Craig Oda wrote: > >I use a VDO pressure sender as my fuel pressure sender. I have it > >permanently mounted in the engine compartment attached to the fuel > >pressure testing tap. It works reliably for me. I like it because I > >can at least rule out low fuel pressure as a source of the numerous > >problems that affect drivability of my Westy. ;-) > > > >FYI, I was originally using a cheap JC Whitney oil pressure gauge and > >it died on me after a few weeks. :-(( Worse, it was giving me > >incorrect readings. :-(((( which made debugging the fuel system much > >more difficult. I identified the problem by running a mechanical > >gauge in parallel to the electronic sender and running repeated tests. > > > >The VDO pressure sender seems to be of a much higher quality. > > > >If you're going to run more wires under the van, you might want to > >consider running a pre-built wiring loom, like the type the sell for > >trailer lights. That way, you can run four wires at once at the wires > >will be of different colors. > > > >What sender are you using to read your vacuum? Do they sell a VDO > >sender for that? I'm intrigued. > > > >If you start putting different senders onto different gauges just be > >aware that there are different types of senders. I think that the VDO > >pressure senders are 0-180 ohms and that needs to match up to the > >proper gauge. > > > >Let me know about the vacuum gauge. I've got two spare wires running > >from my engine compartment to my dash that I could tap into. > > > >Also, does this really help with isolating vacuum leaks? I always > >suspect I have vacuum leaks, but never went through the hassle of > >attaching a vacuum gauge. I've got a mechanical vacuum gauge tucked > >away someplace in the garage. > > > >-- Craig > > > > > >On Wed, 6 Oct 2004 17:46:41 -0500, Max Wellhouse <maxjoyce@ipa.net> wrote: > > > Can I use my spare VDO oil pressure sender as a fuel pressure sending > > > unit? I have used it for this purpose once to check FP diagnostically, but > > > was wondering if it was okay for long term use? I was going to run two > > > extra wires from the engine compartment up to my 3 gauge pod on top of the > > > instrument cluster(op/vacuum, and oil temp). > > > > > > By rigging up two toggle or rocker switches nearby, I was going to have the > > > pressure gauge where I could read either oil or fuel pressure and then have > > > the temp gauge do both water and oil. Now if I can just get a toggle > > > switch to make the vacuum gauge read volts(yes, I'm taking that too far). > > > > > > thanks > > > > > > Max > > > > >


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