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$10 Fuel Pressure Tester


Dangerous_Dr._Dave
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Well I finally got around to checking my fuel pressure... 35psi stable and rises with increased manifold pressure... so my fuel pump and regualtor are not the source of my rough idle gremlin :(

 

But I only spent $10 to find out that I don't need a $100 fuel pump or a $50 regulator!

 

Parts:

 

1 Nylon 1/4" Male Pipe Thread to 1/4" nipple adaptor(<$1),

1 Brass 1/4" Female Pipe Thread to 1/4" nipple adaptor(<$2),

1' 1/4" ID fuel line(<$1),

2 hose clamps for fuel line(<$1),

1 cheap 0-100psi pressure guage with 1/4" Male Pipe Thread fitting(<$5).

 

Assembly:

 

Use the Brass adaptor, a little teflon thread tape, and a hose clamp to attach the Guage to the fuel line.

Attach the Nylon adaptor to the other end of the hose using the other hose clamp.

 

Hook Up:

 

Stop engine. At the back of the top of the Throttle Body, facing the firewall, is a little threaded plug with a 6mm allen wrench drive. Use a 6mm allen wrench and a hammer to "gently" persuade it to turn. The Plug is actually a METRIC tapered pipe thread! This is why you must use a NYLON 1/4" Male Pipe Thread adaptor. The plug is close to 1/4" Male Pipe Thread in size, but not exactly, so the NYLON adaptor will work without tearing up the threads in the Throttle Body, and will seal quite well!

 

Carefully screw the Nylon adaptor into the Throttle Body. Be carefull not to cross-thread it. Gently tighten with an open end wrench of the apropriate size.

 

Testing:

 

Start your engine and read the fuel pressure! Rev your engine and see the fuel pressure go up! CAREFULLY kink the return line to see if the pump can supply about 50psi; be carefull not to go much above 50psi! Stop your engine and check for leak down; the pressure should NOT go down with the engine off!

 

Closing:

 

Stop Engine, remove Pressure Tester from Throttle Body, replace original plug.

 

You just tested about $800 dollars worth of parts for under $10: Fuel Pump, Fuel Pressure Regulator, Fuel Filter, Injectors.

 

Saving Money... It's a GOOD THING!

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  • 1 year later...

hey Dave,or anyone else can you reccomend a place to get a cheapo pressure guage?

 

edit :  i built this guage and it worked out to just under $15.00. i recommend thightening the nylon peice into the t/b before assemby with a six point wrench.

mine stripped the hex shape off trying to tighten it in so i had to crank in in with a vise grip.i used two feet of hose so the guaege had enough slack to sit on the windsheild under a wiper arm for a drive test. see virtual mechanic for results.

thanks Dave.

 

 

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how do you get the fuel line past the hood for the gauge to sit on the windshield? fender well????

 

-chris

 

 

loosen the hood bolts on the driver side. i will allow the fuel line to go straight back through the gap and not be crimped.

oh crap i forgot to tighten mine back down!!!

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  • 2 weeks later...
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http://www.overboost.com/obs/product.asp?pid=2628

 

This is used in conjunction with the stock FPR, so if your stock one isn't gaining 1psi of fuel pressure per 1 pound of boost..You'll need to get a new stock unit as well...You should be able to pick it up at any local auto parts store...

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My stock FPR started to leak out of the nipple on the bottom of the can so I carefully ground down the edge between the two halves of the can until it came apart, gutted it, soldered it back together and pluged the nipple. I now use nothing but the MSD 2222. It works fine and I can bump up the pressure for racing or back it back down to stock for day to day use.
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40 PSI, pull vaccuum hose..... 40 PSI, Rev.... 40 PSI.  Hmmmm, anyone know where to get a cheap FPR? :-[

 

Try the test again while on the road under boost...Tape the gauge to the windshield, or get an in-car meter...You won't go into boost while in neutral...You need a load on the wheels.

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Ok...

 

Since this is my thread, I want to put to everyone who is watching  this thread a challenge:

 

Find a source for a fitting that actually fits the back of the TB to replace the nylon jury rigged idea I came up with.

 

Near as I can figure, its some kind of metric tapered pipe thread.

 

Somebody out there somewhere knows someone who knows what this fitting is and where we can get adaptors so that we can plumb in all kinds of cool stuff!

 

Now go forth and search!

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You can find adaptors for metric pipe threads to NPT.  I bought some at O'Rileys... I think.

But, it didn't work well.  I had a small leak and could never get it to seal.  I ended up having it retapped to 1/4".  I reccomend that over a metric adaptor.

 

I have tried to remove two of the plugs myself.  One came with 6mm allen and the other hasn't budged.  I'm able to apply enough force with the little allen wrench that the socket is deforming.  I get the feeling that some of those plugs just WONT come out without perhaps a torch.

 

Heres a question, what do you do if you have leakdown?  My pressure will bleed off in about two hours.

 

My recent post in Engine Mods about a TBI mounted guage (w/pic)

http://www.starquestclub.com/index.pl?boar...;num=1079664674

 

mm

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There are lots of places you could be having leakdown.

 

By or through the injectors: new seals and a trip to RC Engineering for cleaning should stop this leak,

 

By or through your FPR: new FPR,

 

Back through your pump: new pump,

 

leak in your fuel line between pump and TB: replace or tighten leaky fittings/seals.

 

If you are taking 2 hrs to leak down, I wouldn't worry about it. Instant leak down is another matter.

 

The first thing to do is find out where it's leaking down. Most common is leaky injector(s).

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  • 2 months later...
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