Hey Trav, I've got a fuel injection question

[threeputtpar]

If a fuel pressure regulator has failed, will it allow the maximum fuel pressure from the pump to make it to the injectors and force more fuel through them than what the ECU is calling for?

I've got another thread going about my car running way too rich all of the time, and I'm starting to suspect the FPR might not be regulating the pressure. The service manual specs fuel pressure at 3 - 3.5 bar, and that is also what the rating on the stock FPR is. I don't know what the pressure is ahead of the FPR, but if it's greater than the regulator's rating will it force more fuel through the injectors? Thanks.

https://bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=2942812#Post2942812 for reference.

 

[Trav]

Originally Posted By: threeputtpar
If a fuel pressure regulator has failed, will it allow the maximum fuel pressure from the pump to make it to the injectors and force more fuel through them than what the ECU is calling for?

Take a 19lb Bosch injector running at 38 psi in a GM and put it in a Ford at 43.5 PSI and it will flow 21 lb so yes it can deliver more fuel than the ecm is calling for.
All injectors will flow more with higher pressure some more than others.

Usually Pump pressure is anywhere between 4-10 psi higher than the FPR but it varies from make and model.
Does you FPR have a vacuum hose? If so any gas at the vacuum hose?

 

[eljefino]

The main problem when they go is the diaphragm blows letting mega-tons (tm) of fuel into the intake manifold through the vacuum port, separately from the injectors. In fact idle is the worst with the most vacuum and the least air mixing with this fuel. WOT will kinda be okay.

 

[threeputtpar]

Originally Posted By: eljefino
The main problem when they go is the diaphragm blows letting mega-tons (tm) of fuel into the intake manifold through the vacuum port, separately from the injectors. In fact idle is the worst with the most vacuum and the least air mixing with this fuel. WOT will kinda be okay.


This is the scenario that I am seeing. At idle is pushes the LTFT into the negative pretty quickly, while at light throttle is slowly pushes the trims into negative. At half throttle to WOT, I think it's ignoring the fuel trims and running off of a predetermined map because it puts the LTFTs to zeros during hard acceleration and they snap back to the numbers they were before when I let off the gas.

I will pull the vacuum line tonight when I get home from work to see if fuel is present. I wonder if the new mapping of the tune pushed a soon-to-be-failing FPR over the edge and hastened its demise.

 

[mattd]

The ECU will ignore 02 readings at WOT. It uses data from a different fuel map.

 

[Trav]

Originally Posted By: mattd
The ECU will ignore 02 readings at WOT. It uses data from a different fuel map.

Not if it has wide band O2's AKA A/F monitors.

 

[mattd]

OP has not said either way. I was talking about a stock vehicle.

 

[Trav]

AFAIK 03 A6 US spec uses wide bands OEM. Maybe he can confirm this or not.

 

[OVERKILL]

Originally Posted By: Trav
AFAIK 03 A6 US spec uses wide bands OEM. Maybe he can confirm this or not.


So do many BMW's. My sister's '03 330i, which is PZEV has wide-band O2's.

 

[threeputtpar]

Sorry guys, I was very busy with the kids last night and didn't check in. I did get the chance to pull the vac line from the FPR and there's no sign of fuel on the wrong side of the regulator.

As for the O2s being wideband, I really don't know. I do know that the S4 guys with the 2.7t do install widebands when they go stage 3, so I'd assume that they are not a stock item the 2.7 across all lines.

At this point, would I be looking at upgraded injectors or are mine just past their prime and need to be replaced with at least stock?

 

[demarpaint]

Originally Posted By: threeputtpar


At this point, would I be looking at upgraded injectors or are mine just past their prime and need to be replaced with at least stock?



Shoot Trav a PM maybe he can hook you up with a set of new injectors if yours can't be salvaged. He tests the new injectors before shipping them and gives you a set that will be spot on, making installing them worry free. Even if you buy a new set you could have slight variations between injectors, Trav makes sure the set is matched up as best as possible. He can explain it better, he's hooked up a few people I know and they've been very pleased.

 

[threeputtpar]

I'm really hoping that it doesn't come down to having to replace the injectors, I was really just asking if injectors have a finite life and if at 145k miles they are just spent.

I guess at this point I really need to drop the coin to get a stock ECU that I can run and monitor all of the pertinant measuring blocks to see if the tune is really to blame for this or not. Ugh, $150 for an ECU just to test it and then throw it on the shelf in the garage is hard to swallow.

 

[demarpaint]

I hear you. Any chance of talking to a manager at the place you plan on buying it and seeing if they'll let you return it doesn't resolve your issue? My AAP guy let me do that with an ECU about 2 years ago.

 

[Trav]

Originally Posted By: threeputtpar
I'm really hoping that it doesn't come down to having to replace the injectors, I was really just asking if injectors have a finite life and if at 145k miles they are just spent.

I guess at this point I really need to drop the coin to get a stock ECU that I can run and monitor all of the pertinant measuring blocks to see if the tune is really to blame for this or not. Ugh, $150 for an ECU just to test it and then throw it on the shelf in the garage is hard to swallow.

If the injectors performed ok before the tune they didn't all of a sudden get "dirty".
If on the other hand there were any running issues at all before the tune these may have been exaggerated with the ECM tuning.

You could clean the injectors, it will at least discover if there are any electrical issues and make sure they are all flowing the same. It cant hurt at 145K.
The injectors have a long lifespan but like anything else they can get dirty but that does not condemn them to the trash.

Do your front O2 sensors have 5 wires?

 

[threeputtpar]

Originally Posted By: Trav
Do your front O2 sensors have 5 wires?


No, the front O2s are four wire which sounds like they are not wideband.

When you say "clean the injectors", do you mean running a fuel system cleaner through the tank or pulling them out and having a professional cleaning?

 

[Trav]

Send them out. They need to go on a flow bench, that's the only way to know which ones if any are problematic.
PM me if you need help with this.

I had an 03 here with wide bands which engine is this some wide bands have 4 wires. I can check out the O2 model.