Fuel Pressure Regulator – Take 2

While investigating the fuel system to try and address the rough running issue, I noticed that the fuel pressure in the rail would drop off quickly.

The Jaguar workshop manual says “A slow steady drop is permissible; a rapid fall MUST be investigated”…..OK, what defines a “rapid” fall. Luckily, Charles Probst’s book is more helpful. “After 20 minutes, pressure in the system should not have fallen below 1 bar (14.5 psi)”. Well, I definitely have a problem then. My pressure falls completely off in a few minutes. Time to troubleshoot.

First, I ran the fuel pump the get pressure in the rail a few times and let the pressure drop. Then I did the scientific smell test. I couldn’t smell any fuel in the engine bay, trunk around the fuel pump or under the car. It didn’t seem that I had an external fuel leak.

Turned on ignition to build up pressure and then clamped the fuel line coming into the fuel rail with vice grips. Fuel pressure still fell off, so it doesn’t look like a problem with the fuel pump check valve.

I then repeated the test by clamping at the exit from the pressure regulator. Now there was no drop at all in pressure, so that confirms no leaking between the fuel pump and regulator exit and no fuel injector stuck open.

The new regulator is not holding fuel pressure. If you remember from my previous post, this is the second one that I am trying, so its time to look at an alternative.

I could put in my second OEM Bosch regulator, but that seems to be asking for trouble as I have had one fail and my setup requires these regulators to handle double the flow they were designed for.

Some research and reading of reviews led me to this Fuelab 53501 regulator. One of the reviews specifically indicated that this unit held pressure while others didn’t. I’ve placed an order with Jegs and will let you know how this turns out.

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