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924 starts, idles very rough, won't accelerate? What to try
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hepkat63  



Joined: 25 Jan 2018
Posts: 15
Location: Narrandera

PostPosted: Sun Jan 28, 2018 12:20 pm    Post subject: 924 starts, idles very rough, won't accelerate? What to try Reply with quote

Hi all
just picked up an old 924 which needs renovations - first thing is to get it going.
The car has been sitting for a long time, so first thing was to drain out the fuel tank and flush it out - cleaned the internal filter, replaced and then swapped out the fuel filter under the hood for a new one.
Now, i can at least start it.
The car runs rough as guts and won't accelerate at all. I left it idleing for about five minutes, but it won't get any further.
What is next to try please? I can't see any vacuum leaks at this stage.
Only new to 924 - first one I've ever owned, so please be gentle ! Any pictures would help too as I'm not that familiar with the porsche part names. I have had a 911 a few years back and worked on that a fair bit, so do know my way around some.
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Fasteddie313  



Joined: 29 Sep 2013
Posts: 1445
Location: Not Detriot - NMI

PostPosted: Sun Jan 28, 2018 4:30 pm    Post subject: Reply with quote

Start with putting techron fuel system cleaner in the tank..

First I'd take the fuel line off the fuel distributor, rig it into a catch can, jump the fuelpump, and see what comes out.. Prolly change the fuel filter no matter what but especially if your fuel is slow but hopefully it should be filter clean up here still..

Once you have good fuel there you can try running it again or try an injector flow test as outlined in the hanes manual or can be searched for here..

If that fails or it still runs like crap then you will need to do a CIS pressure test with a guage setup that you can find at specialTauto or build one yourself.. Search "how to install and operate a hoffman test" something like that.. Also outlined in the haynes, buy a cheap haynes..

Aslo you should check the plugs and see what sort of story they have to tell by their look, and check for spark on all 4 while your at it..

Check your cam timing if you don't have a guard in the way..


This is assuming you have a 77-82 porsche 924 with the 2.0 not the later 924S with a 2.5...

You should tell us more about your car than just "an old 924".. They aren't all the same..
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1980 931S LSD FMIC hobby - 01 RS25 coupe - 95 M3 coupe - 06 X5
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hepkat63  



Joined: 25 Jan 2018
Posts: 15
Location: Narrandera

PostPosted: Sun Jan 28, 2018 5:38 pm    Post subject: Reply with quote

thanks for the reply.
When I drained the tank, I took the filter off, hooked up a fuel line to the end and put it in a bucket - turned on the ignition and pumped it out that way. It was pretty foul and full of crap. About 15 litres of fuel came out.
Once that was done, I disconnected the battery and fuel pump hose at the tank and unscrewed the filter. The filter was full of crap too. I washed out the filter in fuel, and flushed out the tank a few times with fuel - just left the bung out and had a bucket underneath. I used a brush to scrape out any rust etc from the bottom of the tank. Did this about 10 times and in the end, good fuel came out.
Now that i've had a good look around the engine bay, looksl ike some hoses missing and broken - please see these pictures and let me know what you think.
https://photos.app.goo.gl/hIqYraPMLUJJx4De2
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Fasteddie313  



Joined: 29 Sep 2013
Posts: 1445
Location: Not Detriot - NMI

PostPosted: Mon Jan 29, 2018 6:55 am    Post subject: Reply with quote

Aw that's a right hand drive euro NA.. What year?

I'm not intimately familiar with the NA under the hood as far as knowing by picture what hose goes where so hopefully someone else will chime in on that..
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Stunter  



Joined: 09 Jan 2018
Posts: 7
Location: Hot Springs, AR

PostPosted: Tue Jan 30, 2018 1:47 am    Post subject: Reply with quote

That timing belt tensioner looks awfully rusty. I personally would replace the belt and tensioner before I worried about getting it running correctly. It would totally suck to get it running good only to have that seize up and take your engine out.
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Eric P  



Joined: 21 Jun 2017
Posts: 123
Location: NY, USA

PostPosted: Tue Jan 30, 2018 2:06 am    Post subject: Reply with quote

Stunter wrote:
That timing belt tensioner looks awfully rusty. I personally would replace the belt and tensioner before I worried about getting it running correctly. It would totally suck to get it running good only to have that seize up and take your engine out.


I wouldn't worry too much about the belt until you get it running. Being the 2.0L non-turbo, your engine is non-interference. The worst thing that would happen if the belt breaks would be that you would need a new belt and maybe tensioner. You should probably replace the water pump when you do get to the belt job but a broken belt doesn't mean a top end job on that engine.

Check the hose from the crankcase breather (left rear of the engine) to the underside of the intake boot. This hose is difficult to see and is usually dry rotted if it hasn't been replaced. Any vacuum leak will cause poor running until you fix it.
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1980 924 NA, US model
1987 924S, US model
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Stunter  



Joined: 09 Jan 2018
Posts: 7
Location: Hot Springs, AR

PostPosted: Tue Jan 30, 2018 2:21 am    Post subject: Reply with quote

Thanks Eric for pointing that out. I didn't realize the NA engine was built non-interference. I see Ideola and few others have come up with modifications during a rebuild to make the 931 non interference as well. Forgive my ignorance OP and carry on with your testing.
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Fasteddie313  



Joined: 29 Sep 2013
Posts: 1445
Location: Not Detriot - NMI

PostPosted: Tue Jan 30, 2018 4:59 am    Post subject: Reply with quote

[quote="Eric P"]
Stunter wrote:

Check the hose from the crankcase breather (left rear of the engine) to the underside of the intake boot. This hose is difficult to see and is usually dry rotted if it hasn't been replaced. Any vacuum leak will cause poor running until you fix it.


If you are serious about the car just replace every last vacuum line/hose on the entire engine, really.. Especially any cloth covered looking ones...
It's really not worth the headache..

Stunter wrote:
snip


Happens to the best of us..
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Eric P  



Joined: 21 Jun 2017
Posts: 123
Location: NY, USA

PostPosted: Tue Jan 30, 2018 7:51 am    Post subject: Reply with quote

As long as you're in there, take the time to replace the fuel injector o-rings. It takes 10 minutes and costs about $5. It could save you from having to call the fire department.

Inspect your fuel lines too. They're probably almost 40 years old.
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1980 924 NA, US model
1987 924S, US model
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RC  



Joined: 25 Mar 2007
Posts: 2624
Location: Australia

PostPosted: Wed Jan 31, 2018 12:57 am    Post subject: Re: 924 starts, idles very rough, won't accelerate? What to Reply with quote

hepkat63 wrote:
Hi all
just picked up an old 924 which needs renovations - first thing is to get it going.
The car has been sitting for a long time, so first thing was to drain out the fuel tank and flush it out - cleaned the internal filter, replaced and then swapped out the fuel filter under the hood for a new one.

The car runs rough as guts and won't accelerate at all. I left it idleing for about five minutes, but it won't get any further.
What is next to try please? I can't see any vacuum leaks at this stage.


Replied in your other thread before reading this one.
Presume you first have a manual, Haynes or one of those (pirated) FSM PDFs.
Good cleaning the tank & replacing filter. Try an open fuel flow test and test fuel pressure if you can rig up a gauge to the pressure line after the filter. Good pump should flow >2L/min open and >120PSI.

Vac leaks in intake boots can be nearly impossible to see without removing every piece and holding to light while flexing and twisting. Why is there all the silicone?

Then could try pulling all injectors and doing flow test into empty stubbies. With intake rubbers removed, jumper FP relay to power pump, then lift up on Air Flow Meter plate. Refer to manual...
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Allan @ DTA wrote:
I have no issue with superchargers, they are for guys who want to drive a car rather than talk about horsepower with their baseball cap on backwards
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hepkat63  



Joined: 25 Jan 2018
Posts: 15
Location: Narrandera

PostPosted: Fri Feb 02, 2018 1:58 pm    Post subject: Reply with quote

thanks for the replies guys - got back on to it today.
I put a new fuel filter on, removed all the fuel injectors, inspected and cleaned them (they were not too bad anyway. I removed all the plugs , cleaned and regapped them to 0.28, checked all the plug leads, they are all good and in spec. removed the dizzy cap, checked/cleaned, removed rotor button, checked cleaned. All looked good there.
Put the motor on TDC (by leaving out no.1 plug, putting finger over hole, feeling compression on my finger) - checked timing mark notch on back of flywheel aligned with marker and then checked rotor was pointing at no.1 - and it was. Checked firing order 1, 4, 3, 2 as per what was on the rocker cover.
Tried starting it - same as before. Won't start unless you hold in the 'cold start' button and then it just won't run at all now (previously, it kind of kept running, but ran like a dog and would not accelerate one bit).
So, I am pretty confident it is not electrical or timing - which leaves fuel and air.
Yes, the vacuum hoses look all over the place and no, I don't have a manual yet, but have ordered one. Pretty sure I have an air leak somewhere? I have found a vacuum diagram on the net, but it is hard to make sense of. I don't suppose any of you might have a real photo of under a bonnet of a 924 NA engine bay showing where all the hoses are supposed to be and hooked up. I am feeling that the PO was a fiddler and almost certainly bits are missing or plugged into the wrong area.
Also, at the back of the distributor there is a THICK GREEN wire with a black plug with two holes in it which is not plugged into anything and certainly looks like it should be. Any ideas on that too please?
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RC  



Joined: 25 Mar 2007
Posts: 2624
Location: Australia

PostPosted: Sat Feb 03, 2018 12:18 am    Post subject: Reply with quote

hepkat63 wrote:
Checked firing order 1, 4, 3, 2 as per what was on the rocker cover.

Wrong, look again. It`s 1342

hepkat63 wrote:
Tried starting it - same as before. Won't start unless you hold in the 'cold start' button and then it just won't run at all now (previously, it kind of kept running, but ran like a dog and would not accelerate one bit).

These never came with a factory 'cold start' button! That is a PO hack and somewhat explains the dodgy mess of wiring. Also an excellent indication of a previous problem like faulty CIS metering unit/ leaking injectors.

hepkat63 wrote:
So, I am pretty confident it is not electrical or timing - which leaves fuel and air.

Possibly your ignition timing is NOW incorrect, at least. Have you checked initial cranking timing with timing light?

hepkat63 wrote:
I am feeling that the PO was a fiddler and almost certainly bits are missing or plugged into the wrong area.

Indeed!

hepkat63 wrote:
Also, at the back of the distributor there is a THICK GREEN wire with a black plug with two holes in it which is not plugged into anything and certainly looks like it should be. Any ideas on that too please?

Sounds like the original wire that was plugged into the distributor. Since the "green wire" is a notorious problem, perhaps it has been bypassed/ hacked/ or dizzy changed to points? FIIK without pictures or more detail. As previously asked, what year? It does make a difference.

Perhaps post a photo of dizzy without cap and the associated wiring while you are waiting for a manual rather that probably further compounding your problems without proper knowledge.
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World`s quickest 924 2L slushbox

Allan @ DTA wrote:
I have no issue with superchargers, they are for guys who want to drive a car rather than talk about horsepower with their baseball cap on backwards
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hepkat63  



Joined: 25 Jan 2018
Posts: 15
Location: Narrandera

PostPosted: Sat Feb 03, 2018 7:29 am    Post subject: Reply with quote

RC wrote:
hepkat63 wrote:
Checked firing order 1, 4, 3, 2 as per what was on the rocker cover.

Wrong, look again. It`s 1342

hepkat63 wrote:
Tried starting it - same as before. Won't start unless you hold in the 'cold start' button and then it just won't run at all now (previously, it kind of kept running, but ran like a dog and would not accelerate one bit).

These never came with a factory 'cold start' button! That is a PO hack and somewhat explains the dodgy mess of wiring. Also an excellent indication of a previous problem like faulty CIS metering unit/ leaking injectors.

hepkat63 wrote:
So, I am pretty confident it is not electrical or timing - which leaves fuel and air.

Possibly your ignition timing is NOW incorrect, at least. Have you checked initial cranking timing with timing light?

hepkat63 wrote:
I am feeling that the PO was a fiddler and almost certainly bits are missing or plugged into the wrong area.

Indeed!

hepkat63 wrote:
Also, at the back of the distributor there is a THICK GREEN wire with a black plug with two holes in it which is not plugged into anything and certainly looks like it should be. Any ideas on that too please?

Sounds like the original wire that was plugged into the distributor. Since the "green wire" is a notorious problem, perhaps it has been bypassed/ hacked/ or dizzy changed to points? FIIK without pictures or more detail. As previously asked, what year? It does make a difference.

Perhaps post a photo of dizzy without cap and the associated wiring while you are waiting for a manual rather that probably further compounding your problems without proper knowledge.


thanks for your help Alan - yes, the firing order is correct, it was my typo.
I will go and get some photos and post in a hour or so.
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hepkat63  



Joined: 25 Jan 2018
Posts: 15
Location: Narrandera

PostPosted: Sat Feb 03, 2018 9:05 am    Post subject: Reply with quote

Ok, here are some photos as it stands now. So, i have got the car started - again, but pressing cold start button - which I can only assume triggers the cold start valve somehow. It idles, but won't rev at all when i try to accelerate. I found that a small hose just under the fuel filter was missing entirely.
Can you please have a look at the following photos and advise . Note too the green wire I was talking about next to the distributor.





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hepkat63  



Joined: 25 Jan 2018
Posts: 15
Location: Narrandera

PostPosted: Sat Feb 03, 2018 9:59 am    Post subject: Reply with quote

Ok, so I have now set the timing (with vacuum advance disconnected) to +10 as per specs.
Here is a video of it running. So, it starts ok, but won't accelerate. In the video, I show this using throttle on the carbie and then from inside car. Any comments please?
https://photos.app.goo.gl/0cYgD6M4J1dIhg8O2
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