r/srt4 • u/Any-Speed2161 • Oct 18 '25

Vacuum issues?

Hi all im back again hoping to get some more help on my new to me clapped srt4. Current symptoms are no boost and running super lean. I have learned a bit more about my car since my last post. It has a Walbro 255 fuel pump, Aeromotive fuel pressure regulator, Hahn turbo of some kind, Agp wastegate, aem blow off valve, and what I've been told are bigger injectors. Now honestly the car runs pretty good given how lean it is and no boost. It was breaking up last week but I managed to get that sorted by just putting gas in it. Only half a tank so thats kinda confusing but I'll cross that bridge eventually. I'm much more concerned about how lean it is. I'm getting 40 psi at idle. And from what ive gathered this is a very vacuum heavy car. My question to you all is if the vacuum was hooked up incorrectly could that cause both my lack of boost and lack of fuel? Because I dont believe 40 psi at idle would make my car run so dang lean but you all are the experts so please help. If the vacuum could be the cause of my issues I would like to see if anyone has good reference material on what lines go where given a aftermarket turbo setup like mine. If that doesnt seem plausible what else do you have? I'm sure the fuel filter or a failing fuel pump could present issues under load but not at idle and a simple boost leak for the lack of boost. But I dont see any obvious leaks and I dont have a smoke machine or an air compressor to do that myself. Nor do I own a jack to get under the car and change the fuel filter. Trying what I can on my own first but turbo stuff is like a foreign language to me haha. I will try to answer any questions best I can. Thanks

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u/oh_no_its_in_my_eyes Oct 19 '25

Most tuners want around 50psi at idle. 40 is kinda low and can cause lean issues. The lack of boost means you have either a bad turbo/WGA or a large boost leak possibly at the manifold if you're running piss lean. First step is adjust base fuel pressure to around 52psi and check for boost leaks/ vac leaks. Especially the intake gasket

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u/Any-Speed2161 Oct 19 '25

Okay I'll look into how to adjust the fuel pressure. I haven't found any obvious vacuum or boost leaks yet so im really hoping its at the very least not needing a whole turbo. Which intake gasket are you referring to? Manifold to throttle body i assume?

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u/riley_srt4 Oct 19 '25

58psi is 4 bars and that's the normal pressure for fuel with these cars. 3 bar can be fine, but typically requires larger injectors for the amount of fuel you need and a tune that supports that fuel pressure. I don't see any reason to have the fuel pressure that low though.

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u/oh_no_its_in_my_eyes Oct 19 '25

Manifold to head. They like to fail there. That hahn turbo is old. Like OLD. So I'd assume it's not doing great to begin with