FieroGTFan Posted September 13, 2023 Report Share Posted September 13, 2023 Hello all! Had the car out today (not driving nearly as much as I would like) and on the way to work, about 5 miles, the car ran great and felt strong. On the way home I noticed pulling out of the office that it felt a bit sluggish. Checking my gauges it appeared that fuel pressure was low (~35psi), normally the car is set to run 43psi. Thought it might have been a bad reading until I saw the air/fuel was also reading lean. I kept the car out of boost to get it home, but when on the throttle the fuel pressure would only drop lower. Car has a 17C turbo, 650/950CC injectors, trilogy turbos fuel pressure regulator, and a roughly 4 year old Walbro 255 pump in it. Any help would be greatly appreciated! Fuel is from May as I haven't been driving it much but I find it hard to believe that would be dropping my fuel pressure instead of just decreasing combustion, but I am not an expert. Link to comment Share on other sites More sharing options...
GoldStar Posted September 14, 2023 Report Share Posted September 14, 2023 Yeah old fuel isn't going to affect fuel pressure. It's either that fuel pump dying or the fuel pressure regulator going out. I believe those Trilogy FPRs are adjustable. See if the adjusting nut at the bottom is loose; it could be "adjusting" itself when the engine is running. Link to comment Share on other sites More sharing options...
obsolete Posted September 14, 2023 Report Share Posted September 14, 2023 Might try changing the fuel filter also, just to rule that out. Link to comment Share on other sites More sharing options...
psu_Crash Posted September 14, 2023 Report Share Posted September 14, 2023 2 hours ago, GoldStar said: Yeah old fuel isn't going to affect fuel pressure. It's either that fuel pump dying or the fuel pressure regulator going out. I believe those Trilogy FPRs are adjustable. See if the adjusting nut at the bottom is loose; it could be "adjusting" itself when the engine is running. That's what I was thinking too. Also not sure how rugged those trilogy regulators are. Could be an internal problem with the regulator. Link to comment Share on other sites More sharing options...
techboy Posted September 15, 2023 Report Share Posted September 15, 2023 I previously had a Trilogy fpr that wouldn't hold pressure. I took it apart and it looked fine, but it wouldn't hold. I ended getting a Spa Turbos fpr and it's been working great so far. I wouldn't be surprised if it's that. Do you have a stock one you could put back on? Link to comment Share on other sites More sharing options...
FieroGTFan Posted September 15, 2023 Author Report Share Posted September 15, 2023 Thanks for the input everyone! I am going to check a few things this weekend and get back to you. Going to start with ensuring the FPR nut isn't loose and readjusting if necessary. I will also look to see if any of the local parts stores have a fuel filter in stock to replace the engine bay mounted one. I will also be sure to check the voltage at the pump and make sure this is not an issue with supply voltage. Has anyone ever taken the fuel pump off of the main relay and wired it to it's own separate relay? I am thinking about possibly going this route over the winter and running a larger gauge wire to help with any type of voltage drop there might be. Link to comment Share on other sites More sharing options...
psu_Crash Posted September 15, 2023 Report Share Posted September 15, 2023 Running fresh wire to the pump is always a good idea. We have seen a lot of issues over the years due to a bad ground or bad connection. I did add a separate relay for the fuel pump. The main reason for me was to have it controlled by my stand alone instead. No reason you couldn't use the stock relay output to trigger another relay of your choice though. Link to comment Share on other sites More sharing options...
FieroGTFan Posted September 19, 2023 Author Report Share Posted September 19, 2023 So the issue was the fuel pressure regulator, I had another used but good Trilogy Turbos FPR I dropped in, set to the correct pressure, and it worked great. The other one was acting strange, with no intake reference connected it would just right back to the 43PSI I had set it at, but as soon as I attached the reference it would drop to ~35PSI. I don't fully understand how this happens because I thought they were supposed to be somehow spring controlled so that a vacuum wouldn't effect it, only positive pressure. Question is, TechBoy mentioned he had a Trilogy Turbo FPR fail and now it seems I had one fail as well. Is there another FPR I should look at? It appears the one on MKS is sold out as well as the one from SPA Turbos. I can try to wait for them to come back, but just looking for other recommendations as well. Thanks Crash, I am going to do that as a winter project. I will take the output from the main relay and wire it to the coil of another relay, then run a 12AWG wire directly to power the pump. Link to comment Share on other sites More sharing options...
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