View Full Version : Fuel System: How much fuel pressure is to much?

Ron Dame
09-03-2017, 11:49 AM
The truck has been running pretty rich for some time (way too long, OK?) so it was finally time to investigate.
It's a Carter AS, rebuilt by Daytona Carbs a few years ago from a core I picked up somewhere to replace the RBS. It had no tag, so who knows what it is from, except it did come off of a '62 Lark just before I got it.

Anyway, at idle there is no dripping from the venturi, but once I raise it above idle, I see droplets coming from it. Checked the fuel pressure, and its right at 5, maybe a bit more, even at idle. That seems high, but there are no drips at idle like I'd expect from high FP. On the other hand, if the float level is high, I'd expect dripping all the time as well.


Mike Van Veghten
09-03-2017, 11:53 AM
Actually two things could be at problem.

1. Your pressure should be 3 to 3-1/2.
2. Float height. High float adjustment will richen, low float height will lean.


Ron Dame
09-03-2017, 11:59 AM
What's the best way to drop the pressure? Can I shim the fuel pump by doubling or tripling the gasket? Or use a spacer? Or just buy a regulator? ( OHV6)

t walgamuth
09-03-2017, 12:35 PM
The regulators are simple. If you add a gauge to the line you can monitor it too. I think last time I used a regulator I just put it in and guessed a setting then adjusted until the car ran correctly.

09-03-2017, 04:40 PM
I have owned Stude. Fuel pumps that were older, and had swelling Diaphragms which increased the pressure and caused these issues.