Fuel Pressure Conundrum - DW200 Fuel pump/1995 NA w/ Stock Engine
 

Hey guys! My name's Zak and I'm new to the forum here. I currently have a 1995 NA that I'm building for track use and am planning on boosting in the next 6-8 months. I've currently got most of the common handling upgrades done to the car but the engine is stock aside from a Supermiata Crossflow radiator and coolant reroute. I have a roll bar for the car coming in the mail and decided I should replace/upgrade the fuel pump now before the roll bar goes in and blocks the pump entrance. I decided to go with the Deatschwerks DW200 as I'd like to be around 250-300whp once the car is finished. I have already installed a separate electrical circuit with a higher amperage relay to support the higher electrical draw of the pump.

Anyways, I installed the DW200 this morning and checked fuel pressure on the feed line at idle. ~145PSI. Yikes. Replaced the pump with the stock one and got ~60psi at idle. Tried using the same gauge on another car and the fuel pressure showed within spec so I know the gauge is accurate. Obviously the DW200 is overkill while the engine is stock but I thought I would still be able to run it for the time being before boosting the car. Do I need to be running an adjustable fuel pressure regulator as well? Or could my FPR be stuck closed? Any help would be appreciated.

Also, for what it's worth, the car ran completely the same at idle with the DW200 @145psi as it did with the stock fuel pump @60psi. I decided against testing fuel pressure while driving due to the high number I was seeing at idle.

Any help is appreciated. Thanks!
-Zak

You have something wrong in the fuel system, I would look at the fuel pressure regulator and ensure that the return hard line is plumbed correctly and in good shape. I have seen this hard line damaged (pinched) from road debris.

Copy that. I'll start there. Thanks for the reply!

Side note: With an intact return line and working regulator, should I be able to run the uprated pump without issue?

Most likely yes, although you may detect a slight buzzing noise from the stock regulator due to the increased fuel rate.

Make sure that return doesn't have blockage as well.

Sounds good. Seeing that high pressure on the first startup had me second guessing myself haha.

Got the car in a lift last night. Checked the hard lines under the car for any physical damage. No damage found. Disconnected both fuel lines at the tank and engine bay and blew through both. Ruled out a clogged return line, both had relatively the same resistance, didn't feel excessive for the diameter of the lines. Did another fuel pressure test on the car this morning. 65-70psi at idle. Removed the vacuum line to the FPR, no change in pressure. Used a vacuum gauge to apply varying amounts of vacuum to the FPR, still no change. Removed the FPR and blew through it while applying varying amounts of vacuum to the vacuum port, no change in resistance. Looks like the FPR diaphragm is probably stuck. Ordered a new FPR, will update once I get it installed.

Hopefully this thread can help anyone having the same issue in the future!

Have a cat for following up, following advice, and making a sane diagnosis. Not your average noob.

Thanks man! Just trying to help you guys help me.

I popped in the new pressure regulator with the stock pump this morning. Base fuel pressure at idle dropped down to proper spec - 35psi. Pull the vacuum line to the regulator and pressure jumps to 45psi. Seems right. I then dropped in the DW200 and measured pressure again and am getting ~58 psi at idle with that pump. Fuel pressure stays at ~58psi at idle whether the regulator vacuum line is connected or not. I can feel that there is vacuum in the line going to the regulator, so no concerns there. Does this pressure increase seem normal? Or do I possibly still have blockage in one of the lines given the increased pressure?

Thanks again for all the help thus far!
-Zak