Wont RUN this year

[ice-hot]

Finally got time to actually drive my "79" US 117K today and NO GO!!
Well not quite, car idles but sputters on throttle, with and without load.
Here is some background, don't drive it in the winter but is parked inside unheated portion of shop. Started once a month and ran up to OP temp.
Half tank of new fuel w/sta-Bel and 104 Oct. boost added.
Went through all grounds and relays, new cap, points, plugs, wires, vac. lines and all filters 2 years ago about 300 miles (don't get time to drive it much).
Here's the symptoms;
At OP temp. open throttle slowly can get to red line.
At OP temp. open throttle hard hear lots of vac. but no rev. sputter, backfire.
Acts like fuel pump or filter? No miles on filter but have not R&R pump yet.
Whats got me is it ran great when started in May!!
Any ideas?
Thanks,
John

[Danglerb]

When you started it once a month, did you run up the rpm, or just let it idle til up to temp?

Check the timing and vacuum advance/retard stuff.

[rhjames]

first item >>>> junk fuel or fuel filter

next item >>>> CIS injection

next item >>>> not enough fuel pressure from fuel pump

.......the list goes on, not necessarily in this order.


octane booster is unnecessary. problem is most likely in the CIS system, probably the WUR or fuel distributor.


you can spend thousands hunting this one.....when you don't drive it regularly.

--Russ

[DPW928]

The CIS fuel system doesn't like not being driven. My first guess is the piston in the fuel distributor is crudded and not reacting to the movement of air sensor plate. This would explain the OK operation at low rpm's. Try running a concentrated portion of Techron or Gumout. If that doesn't help, the fuel distributor should be removed and the piston/cylinder cleaned. BTW when you start it in the winter, make sure you run it up to temp and run it up to WOT a few times. Also, expect a once a year cleanup of fuses, relay contacts and grounds.

Dennis

[ice-hot]

Originally Posted by Danglerb

When you started it once a month, did you run up the rpm, or just let it idle til up to temp?

Check the timing and vacuum advance/retard stuff.

Thanks D- Do both, idle and WOT when when run up to OP. Checked timing, looks good maybe a little advanced.

Originally Posted by rhjames

first item >>>> junk fuel or fuel filter

next item >>>> CIS injection

next item >>>> not enough fuel pressure from fuel pump

.......the list goes on, not necessarily in this order.


octane booster is unnecessary. problem is most likely in the CIS system, probably the WUR or fuel distributor.


you can spend thousands hunting this one.....when you don't drive it regularly.

--Russ

Thanks Russ- New fuel, didnt check fuel press. yet. (need to find right fittings) Does WUR function as fuel press. reg. also? Some contaminants at fuel filter, cleaned out, but acts the same.

Originally Posted by DPW928

The CIS fuel system doesn't like not being driven. My first guess is the piston in the fuel distributor is crudded and not reacting to the movement of air sensor plate. This would explain the OK operation at low rpm's. Try running a concentrated portion of Techron or Gumout. If that doesn't help, the fuel distributor should be removed and the piston/cylinder cleaned. BTW when you start it in the winter, make sure you run it up to temp and run it up to WOT a few times. Also, expect a once a year cleanup of fuses, relay contacts and grounds.

Dennis

Thanks Dennis-I agree prob. is in fuel circut. Put in Gumout and it cleared up some.
Is now driveable enough to get around the block but still sputters at hard WOT.
Found corrsion on electircal con. at WUR. and some relays. Does WUR have two funct. warm-up and acts as fuel press. reg? Dont want to mess w/ fuel dist. if I dont have to. Have read about compounding probs. if not R&R'ed correctly.
Have owned three and all have sat the winters in storage w/ no prob!
Guess I've gotten lucky till now. If you play with the Sharks your going to get bit!

Will keep you posted.
Thanks,
John

[DPW928]

John,

The WUR is in actual fact a control pressure regulator. It sets the control pressure based upon temp and is adjusted b counter pressure from the piston in the fuel distributor. That's why the piston can't have any obstructions. Also, you may want to check for debris that could be affecting the movement of the air sensor plate. Mice have been known to nest in that area over the winter months.

[lfausty]

Could it still be a hose (under the volt reg) mine was doing same just found a bigger rubber hose down under volt reg about half foot or so long , is crap, thought got them all and was only considering my problem was fuel still not running right enough but... leak vac hose does bad things , on idle car jumping/rough, op temp, and throttle response.

[ice-hot]

Thanks Dennis,
Air sensor plate moves freely, no mice...lol. Have not touched fuel dist. yet.
Engine is clearing up the more I run it. I noticed a bigger problem while working on it though,
the flex fuel lines at the engine bay are no longer flex, feel more like steel! Not going to run it again till they are R&R'd! Do you know who has these, 928'srus? Maybe have them made locally if the $$ is right.

Thanks lfausty,
Going to go through all lines again.
I saw your other post w/ the pic. The hose looks like one from air pump to diverter valve
or diverter to check valve. Take another pic. from a little farther away so we can see other component's to reference.

Thanks,
John

[DPW928]

John,

The factory fuel lines for the CIS system are plastic lined with a rubber outer layer. I have seen the rubber portion crack and fall off with no leaks or degradation. If you replace them, make sure you go with the OEM CIS lines as the solid rubber high pressure fuel lines don't like the 6 to 6.5 bar pulsing pressures your shark will see.

[lizard928s]

Very sound advice.

As I told you on the other board, Dennis is the fellow to listen to.
His advice on the fuel lines is good too.

Make sure that any fuel hose is rated to a minimum of 100PSI for use on the CIS system. The pump will stall at 92 PSI, so 100PSI should be OK.

[ice-hot]

Thanks Dennis,
Will look them over closely tonight, maybe not as bad as I thought. Didn't know they had plastic liners. Never had any problem w/ them on previous cars.
Found adapters for press. gauge so will check that also. WSM indicates control press. "warm"
2.8-3.2bar, system press. 5.2-5.8bar, nothing at 6 or higher? maybe I'm looking at wrong system chart? Will read again before testing.

Thanks lizard...I am listening.
I am a mechanic by trade, but got smart years ago (my back was killing me) and went back to school (while I could still walk) and now have my own shop. Although I don't physically do the work any more I'd like to believe I still can....lol I think I can! I think I can!
Thanks again,
John

[DPW928]

John,

Do you have a CIS test gauge? They are equipped with a cutoff valve that lets you test both control and system pressure. A good on line primer is at the following link.

http://www.porsche928forums.com/download/manuals/CISRebuild.pdf .

Dennis

[ice-hot]

Thanks Dennis,
Great write-up! Printed and put in WSM. Hope to do more on car this weekend, this will help. I have the CIS gauge you're referring to, have to read up on how to use it correctly.

Thanks again,
John