BLM went high, why?

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Gnx6

Member
Joined
Jun 22, 2003
Messages
554
So I ordered a new chip from full throttle a while ago for California 91 octane and Alky. The chip has been awesome, car has run like a champ. BLM is 124 to 126 cruising all day long, power is awesome, no knock, life is good! I took a long drive for the Ride On Molly memorial drive, was 8 hours of driving from San Francsico to Temecula. On the way down I turned on the A/C and BLM went to 133, which I figured who cares, A/C puts more load, needs more fuel.

On the drive I noticed the BLM was going leaner and leaner without the A/C on. Where the car would typically would be 124ish it was 144 ish. The car would start to knock at 6psi right before the alky turned on. If I held the Alky purge button and then stepped on it there would be no knock and I could go over 20 psi. (My norm is 25) The scanmaster read 770 or so when I hit the recall button which confirms I was a bit lean as before it would be 820 or so. I know 780 is OK but I think there is not enough fuel at low boost hence the knock at 6psi which I never experienced previously.

On the drive hom BLM was 142 cruising, I had no fuel pressure gauge with me so I took a shot in the dark and put a half turn on the fuel regulator. Cruising BLM was maybe 136? I figured close enough for the chip to take over When I had time a week later I checked the pressure and it was spot on 45 so it changed at some point. I know I've had issues with a restricted return line in the past, don't know if it has turned into a flapper valve or what.. any ideas?
 
I hate to say it, but I would keep a eye on the pump, every time I had knock at low boost, the pump was on it's way out. Good thing you have alky, to help you out, in a boost situation.

Chuck
 
I did some testing and inspection, finally got to work on the car for a bit.

Starting the car Fuel pressure was 45 psi line off. Took it for a 30 minute drive and blm was constant they way it used to be. Started getting high occasionally 133 which is not a common thing. Crusing was 122 when I left the house. Got back from the drive and fuel pressure was 44 psi.

Interesting thing is a month ago when I put a half a turn on the regulator, I checked with my guage by lowering half a turn and back up again. Half a turn is about 3psi. So the fuel pressure has dropped about 4psi total from initial point regulator was set at 45 psi. (3 psi on long drive and another 1 on this drive)

Clearly my pressure is dropping slowly but does seem to be linear... Pump getting weak? Regulator starting to bleed?
 
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