Incorrect fuel pressure Key on and Engine Running

[Matthew Jeschke]

Welp I've got an aftermarket pump in the truck / sending unit now. Saved all my notes:

NBS 2nd gen Tahoe Fuel Pump Upgrade - Matthew Jeschke

Have you been chasing fuel problems? Bad gas mileage on your Chevy Truck? Then you are in the right place. I built up a 2001 Tahoe with a LQ9 (6.0L LS). Initially Fuel mileage was BETTER than the smaller 5.3L LM7 I replaced. However, somewhere along the line my gas mileage dropped by nearly...

matthewjeschke.com

It didn't solve my fuel pressure problem lol I think what happened is OEM is now selling a single pressure in their regulators. They must have taken pressure from the flex fuel L59 engine and made the gasoline regulator the same. Despite these two regulators & fuel rails are different sizes!

I'm going to buy a regulator that specifically says 55 PSI and see if it raises the pressure. I'm out of ideas and nobody makes a drop in adjustable regulator.

 

[exp500]

Did you ever try an aftermarket big block pump assy for a cheap test

 

[Matthew Jeschke]

I did not. Would be interesting. Pump I installed is 340LPH

I found out Bosch makes a similar pump for 300 LPH at 40$ maybe would have been a better option. Although I have had some troubles with Bosch parts. My starter only lasted 10k miles from them.

 

[exp500]

I did not. Would be interesting. Pump I installed is 340LPH

I found out Bosch makes a similar pump for 300 LPH at 40$ maybe would have been a better option. Although I have had some troubles with Bosch parts. My starter only lasted 10k miles from them.

Parts are getting harder and harder to figure out, with less and less published info. My curious nature has had me quietly following along your upgrade adventures. I never noticed a pressure at the 340 liters/hr at your required spec. And the larger guage wires and connectors are always a pita. Like when you think you are ready for crimping but the larger wires will not fit thru rubber block without drilling, and that leads to making a new block...then material homework..then sealant....because it is gas after all else. Good Luck!
My neighbor bought some $40 Bosch wipers long ago, they worked great for the first month of rain and snow, then were an average wiper and were due for replacement at 6-8 months like all the rest that were at the time$10 or so. He learned a lesson and bought rainx and cheap wipers afterward.

 

[Matthew Jeschke]

Thanks for following along. No surprise with Bosch whipers. Truck idles and has much improved part throttle response with the new pump which was the opposite of what I thought it might do.

340 LPH is good for some insane HP, 800? I think I maybe over 400 HP at crank so the factory pump was too small either way. Even if I am not quite there it maybe soon with a little more tuning.

Fun project. Have made LOTS of mistakes along the way but think build is pretty solid as I have so far.

 

[S33k3r]

Fun project. Have made LOTS of mistakes along the way but think build is pretty solid as I have so far.

I hope the added expense has been minimal, and thanks for sharing things here. Maybe it will help someone else avoid those mistakes.

 

[Matthew Jeschke]

FIXED! I finally figured it out!

It's GM's FAULT. They're selling parts categorized for wrong vehicle! The catalogs have the AC Delco Gold regulator listed for a LM7, LM4, LQ9, etc. However, the part I ordered was for the FLEX FUEL engine NOT the Gasoline engines.

I purchased a regulator that SPECIFICALLY said 57 PSI and I got 57 PSI! The part number 2173299 from AC Delco Gold IS not factory spec for Gasoline Engine. I think it's a 45 PSI regulator.

 

[Matthew Jeschke]

I hope the added expense has been minimal, and thanks for sharing things here. Maybe it will help someone else avoid those mistakes.

I think it's cost me around $400. The first regulator (wrong pressure) was $60. Replacement was $60. Aftermarket fuel pump was around $200. Fuel injection test kit was $100.

The aftermarket pump was probably a good thing regardless. Truck idles much better with the aftermarket pump than the factory one. Regulator just further improved idle performance a bit more.

Will monitor gas mileage and see what happens. That's what originally lead me down this path.