[Evansa22]

So recently, maybe last month or so, have noticed my lowside pressure isn't meeting commanded. I've been working on the tune with my tuner, and only seems to happen WOT pulls high rpms. Didn't have the issue before, tank pump settings are stock as well. Tuner thinks the JMS may be burning up the pump and shouldnt be maxing more than 16.5 volts. Set it up according to a post on here and haven't had an issue until now. Have had the booster on for about 5k miles. Checked the settings and voltages this passed weekend, maxing out at 17.3 volts, ramps in starting just past 50% throttle and maxes out at about 90% pedal. Anyone here have a similar issue or encounter anything like this? Just trying to get it nailed down before I drop the fuel tank. Thanks

[Joshinator99]

Originally Posted by Evansa22

So recently, maybe last month or so, have noticed my lowside pressure isn't meeting commanded. I've been working on the tune with my tuner, and only seems to happen WOT pulls high rpms. Didn't have the issue before, tank pump settings are stock as well. Tuner thinks the JMS may be burning up the pump and shouldnt be maxing more than 16.5 volts. Set it up according to a post on here and haven't had an issue until now. Have had the booster on for about 5k miles. Checked the settings and voltages this passed weekend, maxing out at 17.3 volts, ramps in starting just past 50% throttle and maxes out at about 90% pedal. Anyone here have a similar issue or encounter anything like this? Just trying to get it nailed down before I drop the fuel tank. Thanks

Not sure where you’re located. In colder weather you’ll see the boost numbers rise and your fueling struggle if you were on the edge previously. Not uncommon to see.

[Evansa22]

Originally Posted by Joshinator99

Not sure where you’re located. In colder weather you’ll see the boost numbers rise and your fueling struggle if you were on the edge previously. Not uncommon to see.

Located in socal so not real cold. I've been averaging about 15.5 psi lately with the colder weather so that is definitely a possibility. We're still tuning on 91 so was hoping it would hold up until we got some ethanol in it but maybe that was wishful thinking. On a side not was looking at the dw400 you used from Dixie, how is that holding up? If it is the pump crapping out then would like to use one of those. Gonna run through my logs and see exactly when it started to fall off. Thanks

[SATINSTEEL1LE]

I had the same problem but it was with my MAF. We had been tuning around a bad maf and the car was asking for so much fuel, it was pushing the low side even with the JMS so far past its capability. One new maf and another tuning session later, and mine holds perfect at 76psi+ to redline.

They way you said yours is looking with voltage and how it comes on is perfect operation. You might just have a fuel pump going bad at this point.

[Joshinator99]

Originally Posted by Evansa22

Located in socal so not real cold. I've been averaging about 15.5 psi lately with the colder weather so that is definitely a possibility. We're still tuning on 91 so was hoping it would hold up until we got some ethanol in it but maybe that was wishful thinking. On a side not was looking at the dw400 you used from Dixie, how is that holding up? If it is the pump crapping out then would like to use one of those. Gonna run through my logs and see exactly when it started to fall off. Thanks

So compare logs from earlier in the year. You could have been at 14 psi or so earlier this summer and holding low side pressure fine. Now you’re at 15.5 psi so the fuel strain went up. What are you commanding for lambda? 91 is terrible lol

I have not run the DW400 for a long time now. I have the Fore Innovations Triple in tank system. I found the DW400 only marginally better than the LT4 in tank. The Fore triple rocks and wish I would have done it a long time ago.

[WilliammLesly]

It's most likely the fuel pump, I think. In cold weather, it starts to work worse!!

[radz28]

I probably get bigger swings in temperature a little further North, but I can go from almost 15-lbs in around 100* temps in the Summer, to 16-plus-lbs now, in the 50s (if I can stay to the wood, lol...). That boost weather is a real thing.

[Evansa22]

Originally Posted by Joshinator99

So compare logs from earlier in the year. You could have been at 14 psi or so earlier this summer and holding low side pressure fine. Now you’re at 15.5 psi so the fuel strain went up. What are you commanding for lambda? 91 is terrible lol

I have not run the DW400 for a long time now. I have the Fore Innovations Triple in tank system. I found the DW400 only marginally better than the LT4 in tank. The Fore triple rocks and wish I would have done it a long time ago.

I'm gonna try to go through logs tonight, just got home late yesterday and had no time. Lambda is .82 and yes 91 is crap, can't wait to get ethanol in it and make more power. It's a road course/twistys car which is why I decided not to go with the fore in tank system, heard about issues on track with the bucketless pick up and lower fuel level but for your application I'm sure it does really well.

Originally Posted by SATINSTEEL1LE

I had the same problem but it was with my MAF. We had been tuning around a bad maf and the car was asking for so much fuel, it was pushing the low side even with the JMS so far past its capability. One new maf and another tuning session later, and mine holds perfect at 76psi+ to redline.

They way you said yours is looking with voltage and how it comes on is perfect operation. You might just have a fuel pump going bad at this point.

Funny I actually just put in a new MAF sensor not long ago. Understand how that would screw up your fueling for sure. Highside holds no problem, pulse widths are low 5's, just the dang lowside. You guys are probably right and I'll just have to bite the bullet and drop the tank.

My tuner said their's only 2 possibilities, bad pump or blockage in the line. Wants to get a mechanic gauge on there to verify. I was just hoping it wasn't the issue but back to the garage i guess. Thanks for everyone's feedback, and appreciate your responses.

[Evansa22]

Looking back, found a log on 10/30 where pressure held right at 73 or a tad above. Same boost last weekend, similar rpm run down to about 50 psi. Lambda is a hair richer now at .81. Kind of a bummer if it is the pump crapping out, tune was just about dialed in. Oh well, just money haha

[SOCAL.M6.ZLE]

Glad this is getting worked out Aaron... only money indeed
Have you considered cutting an access hole under the back seat vs. dropping the tank?

[Evansa22]

Originally Posted by SOCAL.M6.ZLE

Glad this is getting worked out Aaron... only money indeed
Have you considered cutting an access hole under the back seat vs. dropping the tank?

Yes, still on the fence about it. Would make future access much easier but have a hard time cutting up the car. Probably gonna get a mechanical gauge on it first just to verify the pressure.