My 89's L98 has a hard start problem that's been getting worse of late, so I started troubleshooting it. I was rather confident it wasn't due to the ignition since I recently replaced distributor cap, rotor, wires and plugs, so I started with fuel. Lo and behold, when the ignition is turned to ON, the fuel pressure zips up to about 43 psi, then when the pump turns off, slowly starts to bleed down to zero. The good old service manual tells me the pressure should hold within a few psi.
Now here's where my problem is. The next step in the troubleshooting chart is to pinch the flex hose on the fuel pressure line to see if that stops the pressure drop. That'll determine if it's the check valve in the pressure regulator, or a leak somewhere else. Only thing is, I don't seem to have any flex hose in my fuel lines at all. It's all stainless steel, which is rather difficult to pinch (No, I didn't try). Any other way I can find my problem? Other info: the Vette usually starts up on the second or third try, and occasionally I smell raw fuel from somewhere. Car runs fine once started, though. No idle problems, no trouble running. The fuel smell made me wary, so I've grounded the car until I get this sorted out.
Thoughts?

- Super 89

 

Should have rubber flex lines back at the tank, but you have to remove the fuel filler door and rubber boot, of course gas cap first.

 

I'll give that a try, though I guess I'll have to find a second set of hands for this operation.

 

I had similiar problem with my 93. Check the vacuum hose on your fuel pressure requlator--if fuel is present on this side of your regulator, it is toast and is allowing fuel to be sucked into the intake.

 

I had similiar problem with my 93. Check the vacuum hose on your fuel pressure requlator--if fuel is present on this side of your regulator, it is toast and is allowing fuel to be sucked into the intake.

 

If I am correct in assuming that the vacuum hose is the one leading from the black upper casing of the regulator to the intake plenum, then I guess my regulator is fried. I pulled the little rubber boot on the hose, and it smelled distinctly of fuel. Looks like I have another project... I'm debating whether or not to just go ahead and rebuild the intake while I'm at it. Get some large tube runners, one of those big mouth manifolds.... What a hobby I picked...

 

The test you did tells you there is a fuel leak. It could be in a few different places. Injectors, FPR, check valve, pulsator, or fuel line leaks. The FPR is check by removing the vacuum and looking for signs of wetness or gas. It will smell like gas and not a problem. For the check valve, you pinch off the fuel feed line (largest diameter line going to the right on top of the tank). As stated you will have to remove the fuel lid, rubber boot and gas cap, to get to these (also harder, but you can pinch off the lines where they turn into rubber under the A/C compressor). There is about a foot and a half of rubber line between the metal lines that makes the U shape going backwards to the tank.

For the injectors, prime the system and quickly pinch off the fuel return line and watch the pressure. If it drops there is a good probability that the injectors are at fault. You can also ohm the injector coils to check there resistance. This will need to be done cold and hot. Pull the injector connector off and touch the terminals of the injectors with the ohm meter leads. They should all read around 16 ohms. Report the results. If the leak is as fast as you described then there is a good chance the injectors or lines (you say you smell gas) are leaking. Looks for signs of gas dripping under the passenger side of the car and at the connecton at the fuel rail (o-rings don't last forever). If you have to get new o-rings they need to be fuel o-rings (brown/tan in color).

Also if the fuel filter needs to be changed, it a good time to do so.

https://www.corvetteforum.com/techti...=278&TopicID=2

 

https://www.corvetteforum.com/techti...=192&TopicID=2