A Different Fuel Pump Relay Experience & Education (Long) (1 Viewer)

[turbocruiser]

I applied 8psi to the diaphragm at idle and watched little change in the FT%. If the system was setup up for a constant pressure differential that 8Psi should have increased the fuel pressure by 8psi which would mean about an 18% increase in differential.

There was a methodology. I'm trained to use on board components to evaluate system performance. It comes from being a field technician and not being able to carry a complete lab with you on a service call.

Rick, adding 8psi at idle isn't going to tell us the story through all the rpm ranges we're worried about. I read what was written way back then as adding 8psi through all the rpm ranges and assumed relationships that weren't there apparently. It maybe my bad but I'm just saying what was interpreted. That 8psi at idle ignores the contributing factors from the fuel pump fast mode, the return line restrictions, etc. I still say we're only halfway to having an understanding about this and "concluding" apparently isn't the same thing as "calculating". A full range fuel rail pressure study is still important here and we must strictly stick to the data delivered not to the thesis that's desired.

 

[landtank]

adding the 8psi was only to evaluate if while in boost if the FPR would maintain a constant fuel pressure differential as asserted by Slee as a requirement of the ECU and designed in by Toyota. That was his argument for not capping off the FPR. Completely different from this thread.

As far as this thread goes, evaluating how the high side of the pump influences fuel pressure can't be as easily checked through the use of OBDII because it comes in during open loop and the injectors are flowing a substantial amount of fuel. That is why I'll have to plumb in a gauge.

The gauge will be needed to confirm what we suspect here and if correct it will be necessary to determine the appropriate resistor to trim the pumps output so it doesn't influence rail pressure when first becoming active.

I'm actually hoping we are onto something because if this is the case even stock NA trucks would benefit from a better AFR at WOT.

 

[sleeoffroad]

adding the 8psi was only to evaluate if while in boost if the FPR would maintain a constant fuel pressure differential as asserted by Slee as a requirement of the ECU and designed in by Toyota. That was his argument for not capping off the FPR. Completely different from this thread.

Rick, you chose to argue my points on fuel pressure by stating that in your testing (to which anyone would conclude you actually tested fuel pressure) uyou got a 1.5 psi increase in fuel rail pressure for 8 psi increase on the port on the FPR. Now it seems the case this was a calculation or assumption based on monitoring fuel trim while adding pressure to the FPR. How you got to the 1.5 PSI value and stated it as fact absolutely amazes me as a calculation derived from changes in fuel trim percentages. There is simply no way that it can be done. You chose to remove the control on the fuel pressure regulator without actually measuring fuel pressure, yet you stated facts about fuel pressure that was never even verified.

Did you by any chance notice an increase in RPM when you applied the pressure?

Also, it is not me that stated the system is a constant fuel pressure differential system but Toyota.

As far as this thread goes, evaluating how the high side of the pump influences fuel pressure can't be as easily checked through the use of OBDII because it comes in during open loop and the injectors are flowing a substantial amount of fuel. That is why I'll have to plumb in a gauge.

I don't see how you can use fuel trim at all to calculate fuel pressure.

 

[turbocruiser]

As my completely conflictedly Catholic Physical Education teacher in High School told us many moons ago, "There are always two sides to the diaphragm issue!"

Seriously though without assuming a direct, inverse or linear relationship regarding FT adjustments made by the computer I cannot figure out formulas to convert the FT to psi. Doesn't mean that there isn't one, just means that I cannot figure out formulas to convert this and something must be mathed out of assumption which we don't do to follow the proper scientific process. Since it is so incredibly important to answering all the questions we have here I suggest that someone (Rick) put a proper gauge on and start graphing through all the rpm ranges and all the load ranges while actually driving around. Until we've done that we've taken literally only one side of this issue and assumed an awful lot.

 

[sleeoffroad]

Shaun, please see
https://forum.ih8mud.com/80-series-...-vs-intake-manifold-pressure-here-skinny.html

 

[turbocruiser]

Sean, please see
https://forum.ih8mud.com/80-series-...-vs-intake-manifold-pressure-here-skinny.html

Yes I already saw, already posted and already congratulated you for proving your point simply and scientifically. Well done very well done. Now I know that to start with the end in mind, I gotta get that regulator reference back on before I boost the boost. Again congrats. Signed, Shaun.

 

[sleeoffroad]

Sorry about the name

 

[turbocruiser]

Sorry about the name

Chris, please, no worries whatsoever.

 

[Kenso]

You need a double banjo bolt if you want to do it right after the filter, or a special fitting underneath the fuel regulator.

This thread came up in a search I did recently regarding how to check the fuel pressure on an 80. In looking around for a fitting that would work, I found that Actron sells a banjo bolt with a schrader valve on the end that can be installed in place of the stock banjo bolt on the inlet end of the fuel rail. Most any standard fuel pressure gauge will screw onto the new bolt once you install it. If you already have a fuel pressure gauge, the Actron banjo bolt is about $3. Or you can buy the whole gauge setup with various adapters for about $60. Might come in handy for anyone who wants to see what their fuel pressure is doing under load, etc.

 

[turbocruiser]

This thread came up in a search I did recently regarding how to check the fuel pressure on an 80. In looking around for a fitting that would work, I found that Actron sells a banjo bolt with a schrader valve on the end that can be installed in place of the stock banjo bolt on the inlet end of the fuel rail. Most any standard fuel pressure gauge will screw onto the new bolt once you install it. If you already have a fuel pressure gauge, the Actron banjo bolt is about $3. Or you can buy the whole gauge setup with various adapters for about $60. Might come in handy for anyone who wants to see what their fuel pressure is doing under load, etc.

Wow, thanks for the follow up! Would you happen to have the part number? Thanks Again!

 

[Kenso]

This is the banjo bolt with the schrader valve fitting on the end.

Actron®

This is the whole kit if you need the gauge etc. You can buy it cheaper elsewhere, lists at $66 here. The fitting in the pic with the red cap is the one we can use.

Actron®

Edit: Something else I thought to mention. The inlet holes on the sides of the Actron bolt are slightly smaller than the holes in the OEM bolt. I drilled them out to match with a 15/64 drill bit. Probably not necessary, but my rig is running the S/C and I wanted to be sure I wasn't going to be restricting fuel flow by installing the Actron bolt. I doubt it would've mattered but figured I would mention it.

 

[alia176]

This is the banjo bolt with the schrader valve fitting on the end.

Actron®

This is the whole kit if you need the gauge etc. You can buy it cheaper elsewhere, lists at $66 here. The fitting in the pic with the red cap is the one we can use.

Actron®

EXCELLENT info, thanks dude!