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



Joined: 09 May 2007
Posts: 435
Location: West Hartford, CT

PostPosted: Sat Feb 03, 2018 11:24 am    Post subject: Reply with quote

Have you done any measurements of the volume of fuel delivered by the pump too the engine bay? To the injectors? I believe there are procedures for doing this here on the board and in Haynes.
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RC  



Joined: 25 Mar 2007
Posts: 2624
Location: Australia

PostPosted: Sat Feb 03, 2018 12:20 pm    Post subject: Reply with quote

Green wire & connector is shielded cable that would have pluged into the original VR (pick up coil) dizzy.
The pic of dizzy with capacitor on side is probably points, hence why I said post pic of dizzy WITHOUT CAP. And again, WHAT YEAR???

Seems to idle not too bad anyway. Besides all the dodgy wiring and changed dizzy & etc, your main problem now appears to be VACUUM LEAKS in intake tract and/ or the fuel distributor. You will need to do some flow tests, check the metering plate / AFM, and other tasks that will require much research on this board and/or a proper manual to understand.

I`ve PM you regarding a factory manual.
If any other board members don`t yet have a factory workshop manual then PM me too.
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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: 17
Location: Narrandera

PostPosted: Mon Feb 05, 2018 10:49 am    Post subject: Reply with quote

thanks for the reply. Sorry, it is a 1980 model i believe. Going to check the vacuum hoses best I can. Is there a clear diagram showing where they all should be and what they are connected too floating around on the net and/or forum please?
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RC  



Joined: 25 Mar 2007
Posts: 2624
Location: Australia

PostPosted: Thu Feb 08, 2018 12:18 am    Post subject: Reply with quote

Sure there were some pics or diagrams floating around here somewhere, if photofuket hasn`t killed them. Maybe from Smoothie or Ozzy .... try search. Oh, USA models will be somewhat different from ROW/ Au/ UK/ Euro.

It is the large rubber boots between TB and AFM that are critical. CIS relies on engine vacuum to lift the AFM plate to "measure" airflow and increase fuel proportionally. Perhaps just plug any open lines/ nipples you`re not sure about while troubleshooting it.
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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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agfisher  



Joined: 09 May 2007
Posts: 435
Location: West Hartford, CT

PostPosted: Thu Feb 08, 2018 12:47 am    Post subject: Reply with quote

Here's an image I did several years ago. It might not have everything on it but should give you a start. This is for a '77.


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hepkat63  



Joined: 25 Jan 2018
Posts: 17
Location: Narrandera

PostPosted: Thu Feb 08, 2018 9:20 am    Post subject: Reply with quote

thank you.
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hepkat63  



Joined: 25 Jan 2018
Posts: 17
Location: Narrandera

PostPosted: Sat Feb 10, 2018 10:07 pm    Post subject: Reply with quote

ok, still going with this and getting no where fast. I have had it suggested to me that it could be the throttle position switch sensor. I have had a look under the hood, but can't find anything that looks like (link below for picture) this? I also searched the .pdf manual I have and they don't list one? Perhaps my 1980 model doesn't have one?
So, I'm still stuck - car starts, but won't rev !

https://www.ebay.com/itm/Porsche-944-924-throttle-position-switch-sensor-0-280-120-301-Bosch-ref-B3-1/322937697445?hash=item4b309634a5:g:fzEAAOSwm3paMp-y&vxp=mtr
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agfisher  



Joined: 09 May 2007
Posts: 435
Location: West Hartford, CT

PostPosted: Sat Feb 10, 2018 11:53 pm    Post subject: Reply with quote

Did you ever run the fuel delivery tests? Measure the volume delivered to the fuel distributor and then measure the volume delivered to each injectors? The procedure is mentioned in Haynes and should also be in several places here on the board.
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scm924s  



Joined: 22 Oct 2010
Posts: 214
Location: Gloucester UK

PostPosted: Sun Feb 11, 2018 2:23 am    Post subject: Reply with quote

The strange red cap on the AAV (in front of the coil) is not right, that should be connected to the rubber air trunking to the throttle body
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Fasteddie313  



Joined: 29 Sep 2013
Posts: 1496
Location: Not Detriot - NMI

PostPosted: Sun Feb 11, 2018 5:21 am    Post subject: Reply with quote

hepkat63 wrote:
ok, still going with this and getting no where fast. I have had it suggested to me that it could be the throttle position switch sensor. I have had a look under the hood, but can't find anything that looks like (link below for picture) this? I also searched the .pdf manual I have and they don't list one? Perhaps my 1980 model doesn't have one?
So, I'm still stuck - car starts, but won't rev !

https://www.ebay.com/itm/Porsche-944-924-throttle-position-switch-sensor-0-280-120-301-Bosch-ref-B3-1/322937697445?hash=item4b309634a5:g:fzEAAOSwm3paMp-y&vxp=mtr


Euro cars don't have lambda systems therefore have no throttle microswitches, O2 sensor, frequency valve, etc.
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ted von Kampen  



Joined: 14 Oct 2016
Posts: 73
Location: Scottsbluff, Nebraska

PostPosted: Sun Feb 25, 2018 11:28 am    Post subject: Fuel delivery measurements Reply with quote

Agfisher keeps mentioning this. I went through this whole nightmare about a year ago. Car had sat for 15 yrs and all was varnished. Pulled fuel tank and had radiator shop clean it and then put back in. the in-tank pump was varnished and stuck. I just bought one of the bung-hole screens they sell. Put n a new external fuel pump and filter. Had to tear the CIS down partially and used lacquer thinner and Q-tips to clean passages of varnish. Also did injectors, put in new O rings on injectors. I did the flow test using 4 glass that. I bought 4 cheap rain gauges with volume markings on the side. Then pulled injectors after all the cleaning and ran a test and compared the amount of fuel in the glass tube and found one a little shy so did more cleaning. I loaded up the fuel tank partially with about 1/2 tank of 91 octane no-alcohol fuel and put in 2 or 3 cans of the Techron based cleaner. As I continued working on the engine this cleaner moved around with the fuel and did more cleaning as it sat. I too thought I had an ignition problem and bought a new module which did not help. Finally I was going to change the hall-effect pickup coil which I thought might be intermitent. As I tore done the distributor down I found that some one had put in a 5 slot trigger wheel. Surprised it ran at all. I could start it but it would not idle. Would start backfiring through exhaust the intake and then straighten out a few revs and then start all over again. I bought a new 4 slot trigger wheel (for a Bosch VW rabbit ignition) and it started running correctly. It is not good to let these systems set but do measure the injector flow, compare cylinders and keep that fuel system loaded with Techron. It will straighten out the more you run it. My 2-cents worth. Good luck
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hepkat63  



Joined: 25 Jan 2018
Posts: 17
Location: Narrandera

PostPosted: Sun Feb 25, 2018 2:24 pm    Post subject: Re: Fuel delivery measurements Reply with quote

ted von Kampen wrote:
Agfisher keeps mentioning this. I went through this whole nightmare about a year ago. Car had sat for 15 yrs and all was varnished. Pulled fuel tank and had radiator shop clean it and then put back in. the in-tank pump was varnished and stuck. I just bought one of the bung-hole screens they sell. Put n a new external fuel pump and filter. Had to tear the CIS down partially and used lacquer thinner and Q-tips to clean passages of varnish. Also did injectors, put in new O rings on injectors. I did the flow test using 4 glass that. I bought 4 cheap rain gauges with volume markings on the side. Then pulled injectors after all the cleaning and ran a test and compared the amount of fuel in the glass tube and found one a little shy so did more cleaning. I loaded up the fuel tank partially with about 1/2 tank of 91 octane no-alcohol fuel and put in 2 or 3 cans of the Techron based cleaner. As I continued working on the engine this cleaner moved around with the fuel and did more cleaning as it sat. I too thought I had an ignition problem and bought a new module which did not help. Finally I was going to change the hall-effect pickup coil which I thought might be intermitent. As I tore done the distributor down I found that some one had put in a 5 slot trigger wheel. Surprised it ran at all. I could start it but it would not idle. Would start backfiring through exhaust the intake and then straighten out a few revs and then start all over again. I bought a new 4 slot trigger wheel (for a Bosch VW rabbit ignition) and it started running correctly. It is not good to let these systems set but do measure the injector flow, compare cylinders and keep that fuel system loaded with Techron. It will straighten out the more you run it. My 2-cents worth. Good luck


Thanks Ted. Still no luck so far! I have now:
drained tank
cleaned internal filter
replaced fuel pump
replaced fuel filter
replaced plugs
replaced plug leads
replaced coil
replaced points with electronic pickup

Same thing - starts but dies instantly. I rang a porsche shop and they told me it was probably the piston in the distribution block jamming. So, I took it apart and it seems fine, the piston moves in and out freely.

Someone has rigged up the 'cold start' injector to a switch - and you have to press it to start the car, if you don't it won't start at all.

I'm stuck - no idea what to try next. Seems like a pile of junk
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ted von Kampen  



Joined: 14 Oct 2016
Posts: 73
Location: Scottsbluff, Nebraska

PostPosted: Sun Feb 25, 2018 5:51 pm    Post subject: Your problem Reply with quote

It sounds like the cold start switch added is just emulating the normal one that heats electrically at starts and powers that extra injector. The normal electrically heated injector swtich cuts out after a couple minutes anyway. My cold start injector was plugged with varnish. Not being able to clean mine, I ended up getting a used VW one from a junk yard. I tested it on the bench and it does flow fuel so I put it in and it works. The VW has a bit higher flow rate than the Porsche one but works okay for me.

The fact that you can start for a few seconds with pushing your cold start switch tells me that you CIS is not flowing. I think it is vitally important you try to do the injector flow test. You don't have to start the engine to do this just run the fuel pump a few seconds and rig the glass tubes to catch the injector output. I rigged a temporary switch to bypass the fuel pump relay on the fuse block to switch the fuel pump on and off. Now, if you runt the fp for a few seconds (you can hear it) and GET NO FLOW INTO THE TUBES) then something in the CIS furel distributor is indeed plugged or not working. The cold start injector does not use the CIS distributor so that is why it will start a few seconds after you push it. Try to start it while holding that cold start injector switch down and crank the starter. If the engine starts and runs till you let loose of that switch that verifys you are not getting CIS flow at all. Let me know if this gives you any information. I took me 2 months of work to get mine running at all and until I solved the trigger wheel problem so hang in there. These 924's are a real education and lesson in frustration .
Ted
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hepkat63  



Joined: 25 Jan 2018
Posts: 17
Location: Narrandera

PostPosted: Sun Feb 25, 2018 5:53 pm    Post subject: Re: Your problem Reply with quote

ted von Kampen wrote:
It sounds like the cold start switch added is just emulating the normal one that heats electrically at starts and powers that extra injector. The normal electrically heated injector swtich cuts out after a couple minutes anyway. My cold start injector was plugged with varnish. Not being able to clean mine, I ended up getting a used VW one from a junk yard. I tested it on the bench and it does flow fuel so I put it in and it works. The VW has a bit higher flow rate than the Porsche one but works okay for me.

The fact that you can start for a few seconds with pushing your cold start switch tells me that you CIS is not flowing. I think it is vitally important you try to do the injector flow test. You don't have to start the engine to do this just run the fuel pump a few seconds and rig the glass tubes to catch the injector output. I rigged a temporary switch to bypass the fuel pump relay on the fuse block to switch the fuel pump on and off. Now, if you runt the fp for a few seconds (you can hear it) and GET NO FLOW INTO THE TUBES) then something in the CIS furel distributor is indeed plugged or not working. The cold start injector does not use the CIS distributor so that is why it will start a few seconds after you push it. Try to start it while holding that cold start injector switch down and crank the starter. If the engine starts and runs till you let loose of that switch that verifys you are not getting CIS flow at all. Let me know if this gives you any information. I took me 2 months of work to get mine running at all and until I solved the trigger wheel problem so hang in there. These 924's are a real education and lesson in frustration .
Ted


Thanks Ted. I'll give it a go. I have tried to just keep holding in the 'cold start' button, but it still dies after a few seconds.
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ted von Kampen  



Joined: 14 Oct 2016
Posts: 73
Location: Scottsbluff, Nebraska

PostPosted: Mon Feb 26, 2018 11:34 am    Post subject: Starting problems Reply with quote

When you say you have tried holding in the cold start switch but is dies anyway, do you mean it dies a few seconds after you let go of the switch or while you are holding the switch in? If it is after you release the switch then that reinforces my thoughts about not getting fuel from the CIS. If it happens while still holding the switch in that may mean something else.

One of the early tests I did was to start my fuel flow testing by disconnecting the fuel line from the test and using the fuel pump bypass switch, see if the pump does flow fuel. I suspect it does since it does cold start as you described.

The next step is the injector flow test as I outlined previously. If you do get flow there then I would make a pressure testing setup. You can make one a lot cheaper than you can buy one. There is an article that I can find again that shows how to do this cheaply. You have to order a couple special fittings for a few dollars and a pressure gauge. The pressure gauge is nothing special. You can buy one intended for an air pressure setup (Menards store). If you get to that stage then I can get the article and the sources I used. The pressure testing setup can be kept as you might need some other time.

There is a time and heat sensitive regulator that I think is called the WU (warmup) valve that may need cleaning and adjusting. It may be another varnish victum. I am going from memory but I think that is the name. It actually interacts with the CIS distributor to regulate fuel pressure. This unit is expensive if you can find one. I worked out a procedure to recalibrate mine. You can use the pressure testing setup to do this. I will share how I did it if you need it. So let me know if you want a copy.

Only after your get this stuff done can you tune it, get idle straightened out and make it runnable. Hang in there though. I did get some help from the board people and I am grateful for that. Using that information and my own background I was able to solve most of this stuff. Hang in there, you should be able to get this 924 engine going. Porsche parts are expensive. However, remember that this car was co-designed by Audi and VW And Porsche. It does contain a lot of VW parts which are much cheaper. Let me know how these test go and I will see if I can be of further help. Keep the faith...LOL
Ted
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