Any L98 350 People Here? I have a fuel pressure question

[Midnightmoon]

Has anyone ever experienced this with a L98 350 (Corvette, Firebird, Camaro)? Overall pressure is low. But check out the fluttering, both gauge and engine. I need to finish the diagnostic later in the week to determine if this is a pump or pressure regulator issue. But, I find this very odd.

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[bucket]

I had gauge flutter like that once, it was defective right out of the package.

Are you having any driveability issues?

 

[Midnightmoon]

Yes. Hard starts when warm, part throttle hesitation around 2200-2300 RPM, rough idle, and will not hold a steady RPM under throttle. I had it out in the heat on Sunday and it ran fine at first. After I shut it down, it wouldn't restart until it cooled back down. Once it restarted, the other issues started.

According to the test procedure in the service manual, the benchmark for the flow chart is 40.5 psi. So, it is definitely low. It points to either the pressure regulator or the pump. I need to try and narrow that down later in the week. That gauge never acted like that for me before. It could have failed I guess. But, it seems to bounce around with the stumble of the engine (hard to hear in the video)

Just to eliminate the possibility, I also did a quick resistance test on all 8 injectors this evening. All came back from 16.2-16.6, well within spec. I'm gong to do a pulse test tomorrow evening just to make sure.

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[bucket]

I've never had a FPR fail on one. Just pumps and injectors. Pinch off the return hose and see if the pump can muster any more pressure.

 

[Midnightmoon]

I've never had a FPR fail on one. Just pumps and injectors. Pinch off the return hose and see if the pump can muster any more pressure.

Thanks, will do that tomorrow.

 

[Midnightmoon]

Just ordered a new Delphi pump and related components. Should be here Friday. I can't get the old pump to build pressure even blocking the return line and bypassing the relay as described in the service manual. Hopefully this will fix this issue. But if not, I know it is weak and needs replacement anyway.

 

[Bextreme04]

Just ordered a new Delphi pump and related components. Should be here Friday. I can't get the old pump to build pressure even blocking the return line and bypassing the relay as described in the service manual. Hopefully this will fix this issue. But if not, I know it is weak and needs replacement anyway.

If you can hear the pump, but aren't building pressure, your problem could be the short piece of rubber hose inside the tank that connects the sending unit to the outlet. I'm 2 for 2 with this being the issue for this fault this week

I'd pull the sender and see what it looks like. You'll have to do that anyways to install the new pump, so might as well do it now and see if you don't even need the new pump.

 

[Midnightmoon]

If you can hear the pump, but aren't building pressure, your problem could be the short piece of rubber hose inside the tank that connects the sending unit to the outlet. I'm 2 for 2 with this being the issue for this fault this week

I'd pull the sender and see what it looks like. You'll have to do that anyways to install the new pump, so might as well do it now and see if you don't even need the new pump.

Thanks, you are the second person today that told me the same thing. I will definitely take a look at what is going on in there when I pull it out (hopefully Friday).

I have a shop account that I order through. So, it will be no problem to send the pump back if I don't need it. I just don't want to not have it when I open it up.

 

[Bextreme04]

Thanks, you are the second person today that told me the same thing. I will definitely take a look at what is going on in there when I pull it out (hopefully Friday).

I have a shop account that I order through. So, it will be no problem to send the pump back if I don't need it. I just don't want to not have it when I open it up.

Make sure you get your own short section of SAE j30R9 fuel injection hose and metal hose clamps. The plastic ratchet clamps and china knockoff hose is hot garbage

 

[Midnightmoon]

New Delphi pump in. Great steady fuel pressure. Starts and runs great.

Thanks for the help.

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[Rusty Nail]

Y U NO Corvette pix?

 

[bucket]

Just for future reference if you have anymore issues...

If you have good fuel pressure but have driveability issues as if there's a lack of fuel pressure, also pinch off the return hose. If the car then runs great, the injectors likely need replaced, even if they ohm good.

 

[Midnightmoon]

Y U NO Corvette pix?

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[Rusty Nail]

Dang. That's really good lookin. No need to hold out on pix of thaq ones yo!

 

[Midnightmoon]

Dang. That's really good lookin. No need to hold out on pix of thaq ones yo!

I've had it since 1997. 46K miles on it as we speak. I'll get a few more pics later in the weekend when I have it out.