My 1997 turbo 850 GLT is due for California smog test but it had P0172. It always cranks 2 or more times before starting. It runs good but exhaust smells unburnt gas. It gives 17 to 19 mpg city and 25 highway driving.

So I replaced that elbow under the PS pump and replaced most visible vacuum lines, but the code is still there. I tested fuel pressure at the rail and got 25 psi only. The fuel pump and fuel filter are only 3 years old.

The vacuum line from the fuel pressure regulator smells gas and had no vacumm in it. It is hard to reach the fpr so I tested the line from the end near the manifold. That line splits into 2 after the fpr with one thin line going towards the turbo area, I don't know what it connects to? Any ideas?

The maf tests good.

Where do I go from here? Any advise what to test next to narrow it down or shall I start throwing parts?

Thanks

 

You have a leak in your evap system most likely. The main culprits are actually back by the tank. The return line from the charcoal canister should be traced, its a solid line but right after the fuel pump there is a 6" hose that gets brittle and cracks. Check this area, its prone for problems. Also, there is a vent hose on top of the tank that gets brittle and cracks, you have to drop the tank for this fix. Its not that bad of a job. These two hoses are the leading cause of evap failure.

 

Should have about 43 psi at idle on the rail, a bit more when you blip the throttle. Did you try pinching off the return fuel line from the rail (temporarily!)? Should be able to bump it up to about 80 psi or so. If it does, you need a fuel pressure regulator.

 

Thanks boxpin.
I did PCV, timing belt, shocks but not droping a tank. How hard is it in comparison?

 

Dropping it shouldn't be hard. I've looked into it myself. Seems to me that there are really only the straps in the way. Obviously you'll have to disconnect the wires and hoses from the pump and sender through the access panels but other than that, I don't see any reason you should have any real trouble. Just disconnect the filler neck from the body, then it's three bolts on the straps I believe, two in the rear and one to the front. It shouldn't be anymore difficult than the PCV. It'll help to have two jacks and probably an extra set of hands.

 

gdog,
From the fpr I see only one fuel line going to the fuel rail and one vacuum line that split into two right after the fpr with one going to the intake manifold, and a thin one going to the turbo area. I will take a second look may be am missing something.

 

Update, thanks all for your help it was great.
Problem solved and here is what I did:
Checked fuel pressure with borrowed fpr from a 2001 S80, no change still low.
Dropped the tank and checked all hoses. All looked good.
While there pulled the fuel pump and yes it was falling apart. The clamp on the rubber hose was loose, and the insert dropped a little inside the plastic housing. I had the fuel pump replaced 2 years ago by a mechanic.
Reset the cel and drove about 100 miles, so far no problems.

 

That's great koko but I'm afraid I gave you a bum spec in post #3. That spec of 43 psi at idle is valid for MY up through 95 (both N/A and turbo).

I have discovered recently that they changed the fuel pressure regulator in MY 1996 and kept same one (on LPT/HPT models) through 1998. The correct pressure spec is a range of 30.5 to 55 psi and what the fuel pressure should be at any given point in time is a result of the absolute pressure at the vacuum line to the rail. At idle both my cars are at 35-36 psi for a reference.

Given that, 25 psi is still way low. For grins ck your fuel pressure now and let us know what you find.

BTW: I would go back to that mechanic that replaced the pump before you and ask for a refund; at minimum he should get a good talking to...!

 

With the FPR an easy test is just to pull off the vacuum line and check it for raw fuel or the smell of raw fuel. If any is present the diaphragm is ruptured and the FPR is junk, no gauge needed !!

Glad your wheels are back rolling.