I have my gauges hooked up and today thought I would test to see how my fuel pressure holds. I have been having fouling problems on 2 cylinders.


I turned the key to ON and left it like that for 10 mins and took readings every minute.

36.5 PSI Initially

2 min later = 35.5 PSI
3min later = 34.5 PSI
4min later = 32 PSI
5min later = 30 PSI
6min later = 29 PSI
7min later = 27.5 PSI
8 min later = 27 PSI
7min later = 25 PSI
8 min later = 24 PSI


Now does that look about normal or is the pressure drop too much in that 10 minutes?

 

It shouldnt drop that much. Was that with the feed and return lines clamped? Because those are two other places of possible pressure loss.

 

Also make sure you don't have a Holley AFPR, they are designed to leak down the pressure.....

 

How did it start after the fp dropped that low? If it was injectors you would have a ruff time starting your car. Here are my fp readings when I had some leaky injectors.




After the 30 min mark the car would take multiple cranks to start. and when it did, it would chug for a bit.

 

be sure to check the diaphragm on your fp regulator. I had some leaky injectors as well, and replacing them didn't help the fuel pressure loss. I pulled the regulator apart and the diaphragm had a large tear in it, problem solved.

 

Iroc5.7L your results look very similar to mine. I don't have a Holley AFPR.

I did not try and start the car when the pressure got to 24PSI I just turned the car off.

If someone can refresh my memory what test do I do on the return lines when I crimp them? And what do I look for?

I am just trying to figure out why I have a rich gas smell and 2 fouled cylinders all the time. Everything else has been checked just not the injectors.

 

Presurize the fuel system and pinch both the feed and return fuel lines. If the pressure continues to drop you have leaky injectors or a leaking diaphram in the regulator. The regulator is pretty easy to spot because youll have fuel in the vacuum line going to it. Otherwise you have leaky injectors.

 

Thanks man will try that out