dimwittedmoose51

Just shoot me if these questions get too out in left field, but I want to monitor the engine a little better than Audi wants me to, so here's what I'd like to do.
I'd like to have Oil press. fuel press, Water temp, and either vacuum or ammeter. Since the 87 4kq has oil temp already, I thought I'd pass on that one.



I'm hoping to rig the oil press and fuel press into one gauge(0-100psi gauge, obviously) by having a switch flip the sender unit signals.

1.Will the VDO 0-100 psi pressure sending unit withstand the 75-90psi the pump(much less the gas vs. oil issue) is delivering and if so, where would I tap into the fuel lines to get a meaningful reading and what would be the best way to secure the sender in the line? I've had sucess with this installation on my Vanagon, but it only runs maybe 35-40 PSI max, and a solid FI hose clap is taking care of that connection.

2. Would I need a separate sending unit for the water temp gauge or is the resistance value of one of the existing coolant temp sending units the same as the aftermarket VDO temp. gauge?

3. How heavy a wire would I need for the ammeter if I wired it directly between the alternator and the battery and how small a wire could I use if I add a vdo shunt in the line?

4. Where does the "E" light on the dash get it's vacuum reading from? Or is it strictly rpm related? Wondering if this is going to be a little redundant to have vacuum gauge and E light both functioning simultaneously.

Prolly find a couple 2 gauge pods to atttach to the top of the existing dash console. The pods on the A pillar are pretty pricey, for this car anyway. Bottom line is li'd like to monitor the engine functions and maybe spot trouble before it bites me in the_____. I don't know the history of this engine as the odo quit at 128k.

thanks.

Max

87 4ks

The following are just my opinions...

Item 1.
How important is it to have an in cockpit fuel pressure gauge? Even my friends who build supercharged Pro-street cars with 14-71 blowers just rely on the little gauge at the pressure regulator under the hood. Granted, they don't run that much pressure using carbuerators. If you do want to monitor fuel pressure in the cabin, the best way to do it is get a remote isolator. You run your fuel line into the isolator outside the cabin and it changes it into a signal (I can't remember if it changes it to an air pressure line or electrical signal) that then goes to a gauge in the car. That way there are no fuel lines in the cabin. Looks like Autometer has some electric gauges as well.
http://www.autometer.com/tech_faq_answer.aspx?sid=1&qid=1

Item 2.
I would think the aftermarket gauge comes with it's own sending unit. I don't know if the VDOs come with new sensors, but the Autometer gauges do. I am of course assuming you want to run an electric gauge and not a cappilary tube mechanical.

Item 3.
Skip the ammeter and just run your voltmeter.
http://www.autometer.com/tech_faq_answer.aspx?sid=1&qid=5

Item 4.
I am assuming you mean an "economy" light...my car does not have one. I think I would still run a vacuum gauge if I was going to add gauges to my car. It would not only show you the economy of your driving, but can also be used to keep an eye on the tune of your engine. I do not know if you would have to run that kind of signal before or after the throttle body, though.

87 4ks

I re-read your post. If you could rig up an electrical sending unit and switch between oil and fuel readings, that would be neat. My thinking is pressure is pressure, but not sure if whatever diaphragm is in the sending unit would be compatible with the fuel. The hose clamp comment threw me off, I was thinking you ran a fuel line with a hose clamp into your Vanagon. That's why I suggested the remote isolater. I would look into the Autometer electrical fuel pressure gauge. The prices I've checked for some of their other full-sweep electrical gauges were pretty salty though. I'm still not sure it is necessary to monitor fuel pressure on a regular basis, though. I'm thinking "if the car is running it's getting enough fuel". No reason for me to check that unless the car has died.

Cdn Blue Coupe

If you want vacuum the sending unit needs to be between the throttle plates and the engine.

Sallad

The center line is the engine vacuum. just add a "tee" off the line right before the check valve and you're set.

dimwittedmoose51

My main reason for adding the fuel pressure gauge is to monitor a fuel pump that is fairly noisy and has has umpteen thousand miles on it. If I see it straining to make 75PSI(or whatever the numbver is spozed to be), then it's prolly time to be ordering a new one in hopes it will arrive before the old one dies.

Guess I'm still wondering where to tie in the electric sending unit for the Fuel Pressure.

I'm adding the oil pressure gauge for a similar reason due to miles unkown on the engine(guessing 150k though)

I've had good luck withthe VDO gauges and they are cheap buying them used on ebay some come with sending units and some don't.

I tested the "Upshift light and putting 12v to the circuit board concectors and it lights up, so it must be a problem somewhere elase.


thanks for the help gentlemen. I hope to return the favor at a future date.

Max