Fuel Pressure Regulator

[Gonzo]

Hey guys,
What can be some of the side effects of increasing the fuel pressure reg too much or decreasing it too much? This is for an early 71 914.

[Dave at Pelican Parts]

Do you mean in addition to richening or leaning the mixture?

I am told that you can damage the injectors and cause them to leak if you set the pressure too high. I don't know how high "too high" is, or whether the amount of time spent at pressure matters. Jim Pasha once told me that the spec for the Euro 2.0 (D-jet) cars was 32 PSI, rather than 29 for the 1.7 and US 2.0 cars. I haven't seen that documented anywhere else, but Jim is a very knowledgeable guy. I've run mine at 32 PSI (new and fresh-rebuilt injectors) for several months without problems so far.

If the pressure gets too low, the fuel will not atomize correctly when it comes out of the injector valve. This can result in a poor burn, which will give you more emissions, reduced power, and probably uneven running. Again, I don't know how low "too low" is.

I'm sure there are other things that can happen as well, but that's what I can think of off the top of my head.

--DD

[Gonzo]

Thanks Dave,
When I inherited this early 71, the PO had adjusted the fuel regulator without any instruments to read the PSIs, he adjusted it by turning it away from him. I haven't tackled this adjustment yet, but by turning it away from you does'nt that decrease the pressure? The symptoms are rough acceleration, loss of power, poor gas mileage, & bluish smoke coming out randomly on decceleration. Are those signs of a mis-adjusted fuel regulator?

[JP Noonan]

That sounds rich to me. If you were running that lean then it would cause similar problems with the additon of over-heating. I had similar symtoms when I forgot to attach the pressure sensor vaccuum line. The ECU (I think this was DD's theory, and I agree)thought that the motor was at full throttle (no vac signal) so it ran dog rich, except at full throttle it had good power. What I did to adjust fuel pressure was to but an "Accel" 0-60 psi 1" fuel guage for about $20. It is the one that comes in kits for Camaros and Mustangs with aftermarket adjustable fuel presssure regulators, it is disigned to be permantantly attached to the fuel rail on those cars. Beware of "brass" gauges, they are meant to be attached only temporarily, they heat up or something and cause fires. Any way buy a 1/8" NPT to 1/4" barb fitting, and a 2" piece of HIGH PRESSURE fuel line, a couple of clamps, some teflon tape, and attach it at the test port on the fuel rail. I've run my car for 3 monthes this way but when it comes to fuel systems be careful, if it don't sound right...Don't do it. The other option is to buy a expensive guage/fuel injector cleaner. They hook up temporarily, can be used with a can of injector cleaner, and can be used on other fuel injected cars. once your fuel pressure is nailed down, check for a "deceleration valve", it is near the batt. and has two 8mm vac lines (maybe 13mm)and one 4mm.