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efi related questions

Kain

Kain

3/4 ton status
Joined
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Lubbock Texas
I have the fitech installed and have been chasing why afr numbers would spike when shifting.
(falls on its face when shifting have defco turned off)
I changed cap and rotor cause it was bad. checked the pressure regulator and it was bad (dripping fuel out the vacuum connection) checked fuel filter to make sure it wasn't clogged and it was clear.
So I took out pump to check it , have ep381 in tank and the line was bulging and the clamps supplied with pup had came lose so I replaced em both the line and clamps. rechecked fuel pressure and it had barely below 30 psi. wouldn't start and today it has 40 psi and started and ran well even 40 deg weather.

what would cause not to have pressure yesterday and to have today? I didn't do anything but turn they today to show it dint have pressure and it did all of the sudden.
 
Kain said:
I have the fitech installed and have been chasing why afr numbers would spike when shifting.
(falls on its face when shifting have defco turned off)
I changed cap and rotor cause it was bad. checked the pressure regulator and it was bad (dripping fuel out the vacuum connection) checked fuel filter to make sure it wasn't clogged and it was clear.
So I took out pump to check it , have ep381 in tank and the line was bulging and the clamps supplied with pup had came lose so I replaced em both the line and clamps. rechecked fuel pressure and it had barely below 30 psi. wouldn't start and today it has 40 psi and started and ran well even 40 deg weather.

what would cause not to have pressure yesterday and to have today? I didn't do anything but turn they today to show it dint have pressure and it did all of the sudden.
Click to expand...

Make damn sure the attaching hose in the tank is SUBMERSIBLE fuel hose, regular fuel hose cannot be immersed in fuel. Fuel hose must also be EFI rated.
 
went to napa and it was 20 bucks just for the hose
I thought the pump was going out or is toast so i bought a new pump
then today it has pressure and started
 
GROUND to the sender is a big thing also . a good solid ground .

also do a voltage drop test from the batt to the fuel pump conector at tank . if the wire is week and or failing the wire cant hold the load needed and the pump suffers voltage drop and = less power to make less pressure/volume.
 
Checked grounds redid them and no help
I have pump tomorrow and these but have to wait till I install em they are a Xmas present

IMG_20181115_174255.jpg

IMG_20181115_174303.jpg
 
Well with the Blazer running and vacuum source for efi unplugged it drops pressure to 30 psi from 43 psi so I think pump is tost
 
What fuel line and filter(s) are between the pump and fitech?
Do you have the 12v+ off the fitech harness wired to the pump?
How and where are you reading the fuel pressure?
 
Ls from 1999 Chevy truck adapted to fit 6an line metal most of the way at. Braided 6an to throttle body Same from Fuel pump that's in tank to hard line
Fitech. Controls relay gauge
Fuel pressure at throttle body inlet
 
Replaced pressure regulator cause it driped fuel when you unplug vacuum source....
 
Kain said:
Ls from 1999 Chevy truck adapted to fit 6an line metal most of the way at. Braided 6an to throttle body Same from Fuel pump that's in tank to hard line
Fitech. Controls relay gauge
Fuel pressure at throttle body inlet
Click to expand...

So you're running the LS filter/regulator. I would start there or remove it and let fitech regulate the fuel pressure like it was designed.

and I don't understand your response about the 12v source for the pump.
 
The fuel pump is targeted off of a relay Fitech is wired to that orange wire to relay
had painless wiring harness on running electric pump jus used fitech to activate relay
 
Last edited:
Kain said:
No LS filter not regulator
Click to expand...

I'd swap it out before I touched the pump again. And you have a return plumbed in right?

Kain said:
The fuel pump is targeted off of a relay Fitech is wired to that orange wire to relay
Click to expand...

you should not have any relays, the 12V fitech wire goes direct to the pump. Fitech regulates the voltage to the pump.
 
yes, and was reading that it can work both ways,
I am going change filter about 2 it should be warm enough that i wont start shivering
 
It was the fuel pump .ac delco unit i got off ebay is so much quieter than oreillys precision cant here the pump run but no more funky fuel pressure readings
 
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