4horseman

Hi,

Just had a quick question. I have a ls1 with a boost a pump and lingenfelter 255 with racetronix harness.
Just recently after 22000 miles of perfect performance, I noticed that my afr is 11.0-11.8 but as soon as I hit about 4-5 PSI my afr creeps up to 12.8-13.4. I have methanol injection, but after reflashing my tune , changing o2 sensors and fuel filter it did it again.My fuel pressure stays dead on 60lbs without moving of course that doesnt mean the flow is keeping up.
If I connect the two wires going to my hobbs switch and turn on the ignition can I check that my kenne bell boost a pump is working if I take a voltage reading at the pump?
I suspect its either the fuel pump or the booster.
Any help would be greatly appreciated.

Rkreigh

usually if the fuel pressure isn't dropping too bad you are producing volume. If the volts drop though the pump won't be keeping up with the demand

one thing is to try and measure the actual volume the system is putting out as you mentioned and check the filter, lines, ect to make sure their isn't a kink or something restricting flow (pressure will be good as you say)

that's too lean!

4horseman

Thanks for replying. Yes I know its too lean.The fact the pressure doesnt budge off 58-60 lbs leads me to believe the Boost a pump crapped out.Do you know how the easiest way to check the boost a pump while still in the car hooked up?
Anyone?

Shoaf85

Have you checked your meth kit?

4horseman

Yes it is performing great.By passed the relay and gave it 12volts and works fine. That and the fact my tank level is dropping. The cars methanol was installed only as a fail safe . The tune was created using the current fuel pump and boost a pump without methanol.

SBCGENII

If your fuel pressure stays at 60# the flow is keeping up. Either your injectors are not flowing the same amount of fuel or you have an exhaust leak.

4horseman

Exhaust leak huh? Didnt think about that one.Thanks.

I have HP tuners and my injector duty does not touch 50%. I guess I would need to do a flow test on them wouldnt I?

Shoaf85

Maybe try another sensor if the wideband is a little old. For the most part sounds like you've checked everything pretty well. Are you logging with a tuning software or just watching afr gauge?

4horseman

I have two logs right now with Hp Tuners and I have a wide band. I am getting no more than 2-3 degrees of knock and sometimes no knock at all when it goes 13 ish but I am dumping a lot of methanol.....so.....

SBCGENII

You did check fuel pressure at WOT and not just idle correct? I was assuming you did earlier. You have to have volume to make pressure so you know the fuel is available to the injectors. We don't know if the injectors are being commanded to open the proper amount of time or if they are clogged and not flowing the right amount of fuel. Then it could also be an exhaust leak or a bad sensor like someone stated above.

4horseman

Yes Sir I did. The Fuel pump pressure was minimum 58 maximum 60 from Idle to 6140 rpm.

I was assuming it might be the Boost a pump because the boost a pump just raises flow at around 4-5 PSI by triggering the 17.5 volt surge to the pump.
I am putting the car up and taking off the header to check for a crack in the pipes right now because the gaskets look fine. I can see no abrasions on any of the exposed exhaust parts

SBCGENII

Look for leaks from the head to 2 feet behind your o2 sensors. If you injectors have been in the car for a few years I would send them out to be cleaned aswell. If your boost a pump raises pressure by only 5 psi I wouldn't expect it to have that big of a difference on your afr.

4horseman

Ok. The boost a pump comes on using a hobbs switch at 3-5 psi of boost. When it comes on it increases the walbros headroom to flow more fuel not the fuel pressure though. Sorry for the confusion
Still going to check the exhaust though from heads to sensors. Thats one place I have not looked

Shoaf85

If you have exhaust leaks you should see some pretty erratic afr fluctuation at light loads and low rpm.

4horseman

My afr starts lean around 13.6 at idle then levels to 14.4-14.9 @ 900rpm once the o2 sensors are hot.
Runs right at stoich under 97 map unless decelerating then its rich at around 12.5.
When I first get on boost it drops to 11.3 at 100- around 127 so low boost is right on it, 11.6 at 134, 12.0 at 139, 12.4 at 144, 12.8 at 150 13 at 154, then I let off .

As I have said it only goes up when hitting high boost after about 5 lbs. keep in mind this car ran 11.7 AFR from 2 psi to 14 psi for a year

4horseman

No leaks. Looks like new. No cracks, no dents. Nothing

Shoaf85

Verify with another wideband.

4horseman

I dont have an extra one.Just the LC1 that's hooked up right now. Do you think if I change to a new bosch sensor and recalibrate it would be ok?

Shoaf85

Yea as long as it's a compatible sensor.

4horseman

Ok so I put in a new sensor and calibrated it in free air. I installed brand new siemens 80lbs injectors. I installed a new honeywell pressure switch. Still the same. lean after 5 lbs of boost OR going too deep into RPMs

I checked voltage at pump and it was battery output 12.47 volts. I then connected the wires of the hobb switch to act as a closed circuit and the voltage went down. Isnt it supposed to go up to like 17 volts?
Resistance between a and d contacts on fuel pump itself was 1.7 ohms which is good.

I am concerned that my boost a pump is out. The voltage bleed down from 12.47 to 7.8 volts seemed wrong to me.