fuel pressure adjustment

[InfinitiTech351]

I am trying to dial in my Ty, i have red top injectors part# 171 150756. I un plugged my fuel pressure regulator and warmed up at idle its reading around 60psi... does anyone know what size the injectors are and what my fuel pressure should be at idle? It has a mild cam in it.unknown specs

 

[Quickstop [UK]]

Re: fuel pressure adjustment

60 psi is too high. What chip have you got? Those seem to correspond to 37 lb injectors. You should be at 43 psi with the engine off.

What else have you done to the truck and how does it behave?

 

[InfinitiTech351]

Re: fuel pressure adjustment

60 psi is too high. What chip have you got? Those seem to correspond to 37 lb injectors. You should be at 43 psi with the engine off.

What elese have you done to the truck and how does it behave?

i just bought it a month ago, its a 3 prong chip burned by RPM motorsports but i have been unable to get in contact with mike lea who was the one that just rebuilt and tuned the engine 20,000miles ago... stock turbo with aftermarket turbine. it has a 3 bar map sensor i believe, but only a three wire o2 sensor. so with the regulator unplugged, turn off the engine and it needs to be sitting around 43psi? what about @ idle? or @ 2,000 rpm?

 

[InfinitiTech351]

Re: fuel pressure adjustment

60 psi is too high. What chip have you got? Those seem to correspond to 37 lb injectors. You should be at 43 psi with the engine off.

What elese have you done to the truck and how does it behave?

i feel loss of power after second gear, overboost issues at times, loong crank stumble to start, surging idle at times, smells like it is running rich, im still waiting to get a scanmaster soon, but i still want to try to dial in what i can mechanicly

 

[Quickstop [UK]]

Re: fuel pressure adjustment

What diagnostics do you have? Datamaster?

Your FP should be set with the engine off then it will move up/down depending on the fuel pressure regulator. 1 psi increase will move the diaphragm up by 1 psi so in 15 psi of boost, your pump would need to make 75psi which most would struggle with.

The idle fuel pressure will depend on your cam.

As for tuning it, you need to know what you have first. Can you take pics of the chip? An 02 sensor is normally 3 wires for stock and two wires for a wideband. If you plan to tune it, you'll need a wideband. Again, a pic will help. Any gauges in the truck? Boxes? PLX is a popular brand for wideband sensors.

Without a scan tool, you'll be throwing a lot of parts at it and not really knowing what the problem is. I would suggest you go over all your vac lines in the meantime, check you have a cat or if you have a delete pipe (CA - presumably they are hot on emissions).

When were the plugs/wires/cap/rotor last changed? Lots of basics to be covered first.

 

[InfinitiTech351]

Re: fuel pressure adjustment

What diagnostics do you have? Datamaster?

Your FP should be set with the engine off then it will move up/down depending on the fuel pressure regulator. 1 psi increase will move the diaphragm up by 1 psi so in 15 psi of boost, your pump would need to make 75psi which most would struggle with.

The idle fuel pressure will depend on your cam.

As for tuning it, you need to know what you have first. Can you take pics of the chip? An 02 sensor is normally 3 wires for stock and two wires for a wideband. If you plan to tune it, you'll need a wideband. Again, a pic will help. Any gauges in the truck? Boxes? PLX is a popular brand for wideband sensors.

Without a scan tool, you'll be throwing a lot of parts at it and not really knowing what the problem is. I would suggest you go over all your vac lines in the meantime, check you have a cat or if you have a delete pipe (CA - presumably they are hot on emissions).

When were the plugs/wires/cap/rotor last changed? Lots of basics to be covered first.

i agree, thank you for your advice, i will take some pictures next time i have it apart and the ecu out. it has a high flow cat, plugs and wires were changed recently by previous owner... so if im set to 15psi boost, it should be @ 43psi fuel press. key on engine off? or key off engine off? and close to 75psi while at max boost? what is the delete pipe? sorry im new to this turbo game

 

[Quickstop [UK]]

Re: fuel pressure adjustment

No need for the key - you can jump the fuel pump using the grey terminal that hangs loose below the power block on the pass side. Set it to 43 psi and leave it. The AFPR should do the rest. BUT..

In the unlikely event that your chip is set to use those injectors at 60 psi idle, it will affect it. I certainly wouldn't be thinking about getting into boost until you know what you have.

As I explained, 1 psi boost will add to base pressure and without knowing what your chip is, it may go to 15 psi, it may go to 25 psi. Base of 43 + 15 = 58 psi fuel pressure, 43 + 25 = 68 psi. MAX.

The delete pipe is a pipe that people use to replace the catalytic converter to free up the exhaust but it can lead to boost spikes. Also, if it is blocked then it will not run right. That IS a mechanical check you can do without a scan tool, as is checking over the vacuum lines.

You need Datamaster or something to look over the other parameters first.

No problem re: the help. There is a lot of info on here so search freely! :tup:

Oh yeah, congrats! Welcome to the group.

 

[InfinitiTech351]

Re: fuel pressure adjustment

Thank you

 

[autoaddictions]

Re: fuel pressure adjustment

I check mine with the engine running. Vacuumed removed or pinched from the regulator. This way the fuel pump will see operating voltage 14+ volts. If engine is off you will only have 12volts thus the pump will spin slower and your pressure will be off. 60 psi is too high.
Think of it this way. If your base is 60 and you run 20 pounds of boost. You will require your pump to flow enough volume for your horse power level at 80 psi. Most in tank pumps won't flow well at that high a pressure. Fuel pressure regulator will add one psi per pound of boost. So 60 will be 80. 43 will be 63. Get it.

 

[Quickstop [UK]]

Re: fuel pressure adjustment

The whole point of the regulator is that the pump makes no difference - if you set it at 43 psi, it doesn't matter if the pump has 14v or 12v. The regulator will only let 43 psi through or whatever. Only if your battery was so low as to be unable to get 43 psi would you worry about battery voltage.

 

[dgoodhue]

Re: fuel pressure adjustment

You really should get a scan tool before you do anything else. 60psi is very likely too way too high if everything is working fine. However, the previous owner could have jack up the fuel pressure to compensate for a weak fuel pump.

 

[TYTILIDIE]

Re: fuel pressure adjustment

I think you're always better off setting things like fuel pressure when the vehicle is running, thats a real world adjustment you want to make.

I thought Widebands had 6 wires???

 

[TYTILIDIE]

Re: fuel pressure adjustment

Red tops sound like stock injectors. Any pics?

 

[autoaddictions]

Re: fuel pressure adjustment

The whole point of the regulator is that the pump makes no difference - if you set it at 43 psi, it doesn't matter if the pump has 14v or 12v. The regulator will only let 43 psi through or whatever. Only if your battery was so low as to be unable to get 43 psi would you worry about battery voltage.

Your wrong. Voltage plays a part in the fuel pressure. Here's a video showing a 5 psi jump from a 4volt change. Always check your pressure while engine running.
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