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Progress on getting the new car started! And some ?'s

 
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mattaebersold  



Joined: 12 Dec 2018
Posts: 12
Location: Washington, United States

PostPosted: Wed Dec 19, 2018 8:14 am    Post subject: Progress on getting the new car started! And some ?'s Reply with quote

I posted a couple weeks ago about getting the new-to-me 931 started, and I did get it started then, but was dealing with lots of white smoke, and bad idle/dying.

I've made some significant progress, as well as ruled out some things I originally thought were the issues.

I'm able to successfully and predictably get the car started once per day. It will idle around 2K for a minute before settling down to 1/1.1K. There's still some white smoke (not blue) but it seems to be either mild or moderate depending on the day. In addition, when I shut it off, I cannot start it up a second time that day (it needs to sit for a LONG time before it will turn over again). This makes me think that the head gasket is still an issue, because 1) the smoke and 2) I think the plugs are getting wet, and need to sit and have all oil slide off of them before it's clean enough for a spark again.

The car will idle for awhile though, which is good. This rules out the Fuel pump, 16A FP relay, and the overboost switch (currently bypassed as a way to rule it out).

At this point here's the main symptoms that still exist:
- smoke
- can't start again once it's been idling for awhile
- no headlights or interior lights (no headlight motor either)
- oil light is on
- gas light is on even though it reads full
- brake light is on no matter if the ebrake is engaged or not
- when idling, I have to put the gas pedal to the floor for anything to register
- pressing the gas causes the car to sputter/die rather than increase throttle. I'm assuming this is an air/fuel mixture in the carb


Any thoughts on those things that are still outstanding?
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1980 931
2005 Touareg V8
2006 530xi Wagon
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Carrera RSR  



Joined: 08 Jan 2010
Posts: 1880
Location: Somerset, UK

PostPosted: Wed Dec 19, 2018 8:20 am    Post subject: Reply with quote

Assume you have read the two stickied threads above this one??
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1980 931 - forged pistons, Piper cam, K27/26 3257 6.10 hybrid turbo, 951 FMIC, custom intake, Mittelmotor dizzy & cam pulley, H&S exhaust, GAZ Gold, Fuch'ed, Quaife
Now www.924board.org/viewtopic.php?t=34690
Then www.924board.org/viewtopic.php?t=31252
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morghen  



Joined: 21 Jan 2005
Posts: 8111
Location: Romania

PostPosted: Wed Dec 19, 2018 5:09 pm    Post subject: Reply with quote

You could also take a video of the car starting, smoking and then not starting again.
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JamesM  



Joined: 11 Sep 2013
Posts: 6
Location: Utah

PostPosted: Fri Dec 21, 2018 12:39 pm    Post subject: Re: Progress on getting the new car started! And some ?'s Reply with quote

I went through a similar experience when I resurrected an 80 turbo that had sat for 20 years before i picked it up. Quite a saga and was a steep learning curve as I have never messed with a CIS system before. Bottom line, you are going to need to go through "all the things" but as your car sounds like its in a similar state to how mine was ill touch on some of the basics that got me back to a derivable condition at least.

1. Fuel system - probably most of your running issues are going to be related to this. Old gas gums up and mechanical injection systems REALLY don't like things getting sticky. These were the issues i encountered and addressed in order.
a.Fuel Distributor - Pull it off and make sure the plunger moves freely. Mine was frozen solid in the bore which resulted in symptoms similar to what you mention (having to hold the gas to keep it idling and not being able to rev at all)
b. Fuel Pumps (there are two), good chance the in tank pump is gummed up and shot restricting flow to the high pressure pump (mine was) car ran once addressing the fuel distributor but cut out under any load at all. Pull the pump, clean the tank, if the pump is shot get a new on or replace it with the in tank screen from a 928. Replace the engine bay fuel filter
c. Fuel accumulator - Most likely gummed up as well, replace it. This is probably the cause of your hot start issue.
d. WUR - I pulled mine and cleaned it for good measure but all the major running issues I initially encountered were due to a,b, and c. however this could also be playing into your hot start issue.
e. Fuel level sensor - most likely gummed up, pull it and clean it, possibly replace it. there is a small tab at the bottom that can be bent to eliminate the low level light coming on at the wrong time.

2. Timing Belt - REPLACE IT. Given you have no idea why the car was parked, when this was last done, or if it was even done correctly, you need to do this. this was the 2nd major issue I encountered with my car in that the timing belt that was in the car from the PO was off by a couple teeth which caused the car to run like crap.

3. Vacuum leaks - Replace ALL the vacuum elbows. If at least half of them arnt cracked and leaking I would be surprised. Also check the turbo to air flow meter boot, mine had a lcrask there as well. ANY leak causes fuel metering issues.

4. Cooling system - Flush it, then flush it again, and then flush it again. and then a couple months down the road flush it again. Seriously two years into driving mine and im still breaking random gunk loose inside the cooling system. Check/replace the thermostat and might as well replace the water pump while you are in doing the timing belt.


Now to respond to the specific points you mentioned


- smoke
This could be a lot of things but my first guess would be your turbo is leaking oil into the exhaust that starts burning off as soon as the exhaust heats up, though it could also be bad mixture or a blown head gasket. wont know until you dig deeper, or until you can let the car run longer to see if it burns off.

- can't start again once it's been idling for awhile
Probably the fuel accumulator, mine was doing the exact same thing. the operation of the priming pulse from the fuel pump relay is "odd" on these cars. If the car has been running you wont get the prime with key on and if your accumulator is bad you wont have the necessary line pressure to start easily. When mine was doing this I could occasionally get it to start by some or all of the following
1. Pull and reinstall the fuel pump relay.
2. Manually depressing the air flow meter plate prior to cranking. (throws extra gas in the intake to help with starting)
3. Cranking for a really long time.
In the end though replacing the accumulator took care of all my hot starting issues.

- no headlights or interior lights (no headlight motor either)
I was lucky and didnt have any electrical issues, but most likely either grounds or fuses.

- oil light is on
Is it on all the time with the engine running, and at all RPMs? Do you have a oil pressure gauge? have you changed the oil? The OP light seems very sensitive in mine. If the engine RPMs drop to low when idling it will come on generally anytime my gauge falls under 2 bar pressure. should go away when the RPMs come up. I have heard the oil light flickering on at idle is not uncommon for these cars but if yours is on all the time there is another issue.

- gas light is on even though it reads full
Check the sending unit in the tank

- brake light is on no matter if the ebrake is engaged or not
possible bad grounds?

- when idling, I have to put the gas pedal to the floor for anything to register
Fuel system or vacuum leak

- pressing the gas causes the car to sputter/die rather than increase throttle. I'm assuming this is an air/fuel mixture in the carb
931s dont have carbs, but again this is most likely going to be related to your fuel system or vacuum leaks.
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