Mongo

Has anyone made a website on how to replace a fuel pump check valve? I've never done it before since my car has a hard starting issue when warm and usually I have to step on the gas pedal a little to get it started. When cold it fires right up after 1-4 cranks.


If no site on how to do it, how do I go about the replacement, if anyone knows...

worf928

There is (was - haven't checked in a while) a short write-up on the 928 Specialists website that covered fuel filter replacement. The check valve is attached to the pump which is attached to the filter - so it's in the same spot. However, ...

... a faulty check-valve would lead to the opposite behavior you describe.

Essentially, you clamp shut the feed line from the tank/in-tank pump, unscrew the hardline (use a flare wrench and counter-hold with a second wrench) that connects the filter to the pump and then R&R the check-valve at the output side of the pump. You'll need two (or three - I forget) new copper crush rings along with the valve. Oh... and you access the pump/filter after removing the cover plate underneath the tank (between tank and bumper.)

Mongo

Thanks worf, but if its the opposite, I'm sorta at a loss of thought for troubleshooting what it could be? faulty damper and regulator maybe????

worf928

Andy, there are a number of items that could cause a warm-start problem. The likely candidates are the TEMP II sensor and MAS. The idle control valve could also contribute. Beyond those three there are others as well.

Do you have any other symptoms? What's your gas mileage like? Once the car starts when warm does it idle well? Or does it die immediately if you don't give it partial throttle? Any other info will help narrow down the list.

Bad fuel pressure can also cause starting problems. The best way to diagnose would be a fuel pressure guage. However, I'm not immediately able to think of why a fuel pressure problem would cause only a warm start problem.

Mongo

Gas mileage is great!!! Very reliable! I'd say its as good as my 944 if it wasn't an 8 Hence my confusion...

figgen

I've got the same issue...I've replaced the MAF (good deal on an E-bay new item), the temp II sensor...just because it's cheap and the other was old, the fuel distributors and dampers and still sometimes have the problem.....new check valve is on the work bench for next time I'm in there!

The hard to start when hot is typically not a big problem....just annoying and a bit embarrassing when you have to crank the car so many times to get it to fire!

My idle is steady and the car give me no grief when it's started

Mongo

my idle is a little unsteady on a start but will steady out when warmed up. Same thing after driving then parking; then coming out to restart it in 30min- 1 hour.

worf928

Sorry I didn't respond last night. I was watching the SOX own the Yankees...

Mileage for an 87 should be in the 19-21 range on the highway. 16 - 19 for mixed driving. Maybe a bit less if you have a right-foot deformity. If it is consistently 15,14,13, or less then it's too low.

Have you tested (can you test?) the resistance of the TEMP II sensor?


As for other troubleshooting items:
These are the obvious ones:
Fuel Pressure
Fuel Pump Power
Intake/Vacuum leaks
Idle Control

Not so obvious:
O2 Sensor
Tank venting system
Final stage ignition
Fuel Injectors

What does the Fuel Pump sound like? A light buzzing that is constant? Or a loud buzzing? Or a buzzing that gets louder with the throttle? (Kinda like a stereo badly-suppressed?) Does the warm start problem happen at all ambient temps? Have you looked at all of your vacuum lines and checked to make sure that they are correctly attached to the correct gizmos?

Has this condition come on gradually? Or suddenly? If the latter what was the last thing on the car that was touched?