This has been a head scratcher LOL.
If wideband is trending lean, it almost has to be a real reading.

That basically leaves pump/regulator/fuel temps.

 

That's why I've been pulling my hair out. New pump, new reg, new feed hose, new clamps. To me I need to do the following:

1. replace the power wire from the alternator to the pump with something thicker gauge to remove voltage drop as the car/wire heats up. This will keep the pump voltage more stable, which should help with fuel pressure.
2. Reset base fuel pressure with a warm motor/car.
3. Still think freeze spray on the transducer under the hood is a good test just because.

Reassess at that point.

 

How many connections between pump and gnd stud that may contribute to voltage drop?
Remind me, does the reg have vacuum/boost ref connected? If so, have you repeated pressure drop test with it disconnected?
When fp drop occurs and you shutdown and restart, is drop still present?

 

I guess as a low boost setup, and what was my initial expectation for a rear mount FPR....just run it at a fixed 60-70psi base, and see how it copes with that ?

 

1 butt connector from fuel pump ground wire to the actual stud.
I've disconnected vacuum line without a change in FP when it's already dropped.
Once the fuel pressure has dropped and everything is "warmed up" it stays dropped regardless of shutting off and restarting.

 

Im trying to fix this pressure drop so I can turn the boost up lol. I can turn up the base pressure like you said, would just like to understand the drop.

 

I assume, butt connector in tank?
Duplicate drop test with vac line disconnected.
Once pressure drops, why do you think you can turn off and just prime pump and pressure returns? Sounds like reg/internal ref issue.

 

Butt connector is in tank.

I've got the car up on the lift right now running and logging. I can pinch the return line to the input of the FPR and watch the fuel pressure at the rail raise to 75 psi or so.....indicating its working. I can actually hear the pump increase in noise when I deadhead it like this. I also can disconnect the vacuum line and watch fuel pressure increase. I waiting until I saw a drop in pressure and increased base pressure again to 58 psi. Reconnected vacuum line and saw pressure slowly drop again

I'm not ruling out that I got a bad regulator, just don't understand why it happens only at idle/stop and go, but once everything "gets airflow" pressure comes back.

Fuel filter and regulator are all cool to the touch btw.

I do think I'm dropping too much voltage from the hot wire though. That will need to be upgraded.

 

With 70psi fixed base, you could easily run 25psi boost and still have a quite normal 45psi across the injector....if the reg holds 70psi.

 

Fair, I think the engineer in me is just being bugged by the root cause. Time for a thicker gauge hot wire and another log.

 

Pinch test after idling with pressure drop occurring?
Duplicate drop test with ref line disconnected? It's not the same as pulling ref line, etc and disrupting reg function.

 

I agree it should not be happening....but a fixed pressure test is simple and easy to do.

If anything, running it at 70psi will place more strain on the wiring so may highlight if there was a deficiency there easier.

 

Pinch test pre and post pressure drop and pressure increases each time.

If I understood the 2nd questions, the pressure drops regardless of whether or not ref line is connected. I plan to call Racetronix next week as there were some assembly issues with the unit anyways. We'll see what they say.

 

Bolded is a good point. I'm going to see what I get from the wiring upgrade since I should do it either way and then can try this higher base pressure. This is also all OLMAF only tune so I do have the option to go closed loop and have it correct, but I would still be concerned around WOT if pressure is dropping. The benefit of keeping the vacuum/boost ref is that if it does drop it will increase pressure again with boost.

 

Or just try it at 70psi base, and then re-attach vac line for the drive.

it would be interesting to watch or log pump current during this. If pressure drops, current should drop too.

 

Which would indicate an undersized hot wire, knowing ground is 12awg or thicker and short. Logging current would be tough as the oscilloscope current clamp is powered so getting the output into efi live would be a hassle. I could log the voltage drop across the fuse with a simple conversion for current.

 

2nd question - perform the pressure drop test with the line disconnected from the start. Do not disrupt line, reg etc. after the test starts.

 

Ill need to wait until it's cool and pressure comes back but can do it when I swap hot wires early next week.

 

piece of ****.

My current clamp just runs off a 9v battery. ( cheapy Hantek, although have a few handhelds too not for a scope )

Tie clamp ground into sensor ground and the clamps output is 0-5v anyway. No hassle at all. There are only 2 wires at the BNC plug of the current clamp ( if it's even a BNC ). ground and signal.

 

That does give me an idea for a 5V split core transducer we use at work....hmmmm

PS....500th post of the build thread, woot!