What's up with my fuel system??

nixter · 06-20-2005, 05:42 PM

I can't believe I'm stil having issues but...

My car is now idling a little rough. I've also been having a cold start issue for the last week or so. Basically when I start up, it seems fine then the needle dips for a bit and she fights to stay alive for a few seconds. All seems fine after that. Except now the idle is a little rough sounding and I'm getting a buzzy/whining noise (fuel pump?) I just had a new one installed recently!

Other than this the car runs good and strong.

I had a rusted out gas tank repaired recently. Is there some way that rust is still in the system and putting stress on the pump?? I'm lost.

I can't afford this thing much longer.

Any ideas guy?

THanks,

Nik.

nixter · 06-20-2005, 06:58 PM

Oh, and I'm getting more decel exhaust crackle than normal.

Nik

Paulporsche · 06-20-2005, 07:32 PM

You have to remind me...did you have your AAR checked? It may be shutting down too soon, which would make your revs stay at first, and then start to drop. It could also be your WUR. If you check mystery train's thread on AARs, you will see how he got his to stay open longer.

nixter · 11:59 PM

Wow, it's been off for a good 36 hours and things are worse. I started it up and this time when it struggled, it died. It did this three times before it was able to keep itself alive. Drove it straight to the mechanic. Not about to risk using my last auto-club tow this year. (I've used 3 in the last month)

I'm trying not to lose faith in my wrench, he's highly recommended and is generally a great guy. He often waives some labour. In fact that's why I go to him, the first time I used him he adjusted my clutch cable free of charge. thing is, I've see him about every two weeks for the last couple months! Everytime something gets fixed, something else goes wrong.

Nik

edit: hmm, paul...I thought I had replied to your post yesterday but I guess not. Anyways, WUR is brand new, not sure about the AAR but as I stated above, I'm not risking the car not starting again. Thanks for the input as always!

steand · 06-22-2005, 12:26 AM

Sounds like the fuel mixture is weak. this normally causes rough idle. and low rpm after the AAR closes. Maybe an air leak, or just a bad adjustment. Try have it adjusted without the O2 sensor active. My 79' without O2 sensor, needs readjustment for summer, fall ,winter driving. to avoid hunting or bad low rpm idle.

Paulporsche · 06-22-2005, 04:40 AM

Nixter,
Did the mech check your control pressures? Thay could still be off, even w/ a new WUR. Also, it definitely sounds like he needs to check the AAR operation. Steen could be right. The mixture could simply need to be richened, now that you have a new WUR. I recently "knocked the plug" on my WUR and had to lean the mixture.

Gunter · Gunter's Garage

Was the tank thoroughly flushed after the rust repair? If not, rust could have clogged up the new pump and check valve. Then the rust would also reach the Accumulator which is before the filter; resulting in a clogged gas filter.
There is a small filter inside the tank which can be checked by opening the bottom-plug; if it shows rust, the whole tank needs to be cleaned.
I would ask for a fuel pressure check and make sure that the tank is realy clean; if there is any doubt about the rust issue, the tank, fuel pump, check valve and lines from the tank have to be flushed. I would also have the accumulator removed and flushed/cleaned and finally, install a new gas filter and re-set the mixture.

nixter · 06-22-2005, 09:49 AM

Gunter, the tank was removed, sent out, chemically stripped and refinished. I'll ask if the pump/acc/lines were fluched though.

The WUR is new but has been in there for a couple months and things "WUR" fine up until now.. haha... so I don't think it's an adjustment issue.

This problem occured basically out of nowhere so it's probably something that's happened rather than a result of something that's been done, ie: a leak.

Oh and Steand, I don't have the O2 sensor hooked up because I don't have one

I'm planning on getting one to improve my dismal fuel consumption.

Thanks guys. I'll probably hear from my mechanic later today and I'll let you know what the problem was.

Nik

nixter · 06-23-2005, 02:23 PM

Well I thought I had a new new WUR but I don't. I have a new advance/retard unit. Not sure of the proper name. Anywho, seems the the WUR might be flaky after all. Wrench doesn't suggest I replace it yet as it's still running, (he richened the mix a bit) and it's a pricey part.

Nik.

Gunter · Gunter's Garage

An O2 sensor will not really improve your gas mileage, especially with an old CAT. Gas consumption is directly related to revving, the higher you rev, the more gas goes through.
I assume that the new Advance/Retard unit is the one on your distributor; it's for the red & blue vacuum lines going to the throttle body.
The 1980 SC has a WUR that is specific to that year; yes, it's pricey like everything else on a Porsche. Wait until the Ignition module fails, that is about $1500.-!) Advertise for a used '80 WUR (And a used Bosch CDI module) on PP. That's what I did.

nixter · 06-24-2005, 04:53 PM

Hi Gunter, what's the CDI module? Do I need one?

Yes, that's correct about the Advance/Retard.

There was a guy in another post I read who has the same year/stock SC as I do and has a switch set up to disable his 02 sensor. He claimed a %22 increase in milage with the sensor.

Gunter · Gunter's Garage

They seldom fail but when they do you'll know. I got a spare just in case.