Help with no spark 924

Lance924 · 02-24-2007, 10:45 AM

Hi,first i like to say im new to the forum so hello to everybody on here.I hope i can give some advice to others on hereaswell as ask for it.

My problem is one of my 924's.It was running one day then not the next.I did some checking and the there is no spark coming from the coil.I removed the coil of my other 924 and tried that but still there is no spark.Also i noticed that the fuel pump doesnt make the familer buzz when you turm the Key.I removed the pump reley from the other vehicle but still the same.I have checked the ground sites behind the fuse box and cleaned the contacts but still i have no spark.I also swaped the unit (silver box)from behind the head light as i have read that these are a common fault,but sadly still the same.
If anybody has any thoughts i would be very grateful.
Cheers

Lance

Lance924 · 02-24-2007, 10:58 AM

Sorry also forgot to add that i do have live going to the coil with the ignition on.

Razorback1980 · Razorback1980's Garage

Welcome Lance. There are a few 924 owners here but also check out 924.org ...there are many there as well. It would help us to help you if you would put the year and model car in your signature line. One other source that might provide some help for you from time to time is clarks-garage.com.

Can you tell us what year and model you are referencing here?

If your car has a DME relay, you may try swapping that first. DME relays (if applicable) control both spark and fuel pump operations on certain models and since yours has both those symptoms, that might be a place to start. I assume you also checked all fuses and the easy stuff.

Lance924 · 11:47 AM

Many thanks for the reply,it is a 1984 standard not the s or turbo.
I am a regular visitor to 924.org but nothing relating to my problem.
I have checked all the fuses and changed fuel pump relay to eliminate it from being the fault.
Not sure about the DME relay.Not sure if the 924 has one.

toolboy62 · 02-24-2007, 12:00 PM

at a guess, I would say that it is the pickup in the distributor, or the wiring associated with same. If you have power to coil, but no spark, and changing the coil for a known good one didn't work, that says to me that it's not getting a signal.

I think the fuel pump only runs when it gets a signal from the ignition (I'm assuming that a 924 has the same CIS as the VW's that I know and love) so that might be part of the same problem. It should run for a second or two when you first turn the key on, then shut off, then start again when you start getting ignition pulses.

hope this helps,

nate

Lance924 · 12:18 PM

Quote:

Originally posted by toolboy62
at a guess, I would say that it is the pickup in the distributor, or the wiring associated with same. If you have power to coil, but no spark, and changing the coil for a known good one didn't work, that says to me that it's not getting a signal.

I think the fuel pump only runs when it gets a signal from the ignition (I'm assuming that a 924 has the same CIS as the VW's that I know and love) so that might be part of the same problem. It should run for a second or two when you first turn the key on, then shut off, then start again when you start getting ignition pulses.

hope this helps,

nate

Thanks for the reply. I did try a known good coil and i was getting voltage to one side.But no spark from the coil itself,therefore nothing getting to the distributor.When talking about the DME as on the others replies,is this the Brain unit in the inner wing behind headlight.If so i have tried the unit out of my othere car and still no spark from the coil.
I have aslo tried the fuel pump relay out of the other car ,just the same results.
And you are correct.it is the cis system. lol
If for some reason the fuel pump had stopped working would this affect any signal to the brain stopping it from sparking?

JonA · 02-24-2007, 04:19 PM

When you turn the key to "on" the fuel pump will run for 2-3 sec and then shut off and wait for the engine to crank. Check to see that you have voltage at the fuel pump during that 2-3 sec. If you do the fuel pump is bad.....
It has been a while since I worked on the 924. I still have some of the schematics, get back if you are still stuck and I will take a stroll down memory lane.......

Jon

Razorback1980 · Razorback1980's Garage

I am not a 924 expert but PM a guy called Slam...he is really good at the 924 and I'm sure he will have no trouble telling you exactly what the problem is.

Lance924 · 04:54 AM

Many thanks for all your replies,sorry i havnt got back straight away,that due to the time differance here in Uk.
In am going to check the voltage at the pump today,and Jona anybody willing to take the trip down memory lane would be a great Help.The more help the better.
Thankyou Razorbackand toolboy62,and i will post back as soon as i have checked the pump.

Lance924 · 02-25-2007, 03:22 AM

Hi again,i have checked the pump and i have no voltage going to it at all.

Lance924 · 04:51 AM

Just an update,i have ran a live straight to the pumps and both are spinning fine,so they are working.Also fuel pump rely does activate when the key is turned.
Any other ideas?

Cheers

Lance

toolboy62 · 02-25-2007, 05:35 AM

Sure sounds like the pickup in the distributor has failed. Do you have access to another distributor you could just swap in to test?

nate

Lance924 · 02-25-2007, 05:45 AM

Quote:

Originally posted by toolboy62
Sure sounds like the pickup in the distributor has failed. Do you have access to another distributor you could just swap in to test?

nate

Yes i can take the distributor off my other car to test.
But would that stop my fuel pump from spinning up?
Also would that stop the coil from sparking,i understand that it would stop the plugs from firing?
But sounds like good advice to me,thanks toolboy thats what i will try today.
Update to follow.

toolboy62 · 02-25-2007, 05:57 AM

ASSuming that it uses the same kinds of controls as a 1980's VW; yes, it will indeed keep your fuel pump from running because the fuel pump relay relies on a good signal from the distributor to keep it pulled in. The reason it does this is because you don't want the fuel pump to keep running if the engine has stopped; e.g. in the case of a crash or a ruptured fuel line.

nate

Lance924 · 02-25-2007, 06:00 AM

Quote:

Originally posted by toolboy62
ASSuming that it uses the same kinds of controls as a 1980's VW; yes, it will indeed keep your fuel pump from running because the fuel pump relay relies on a good signal from the distributor to keep it pulled in. The reason it does this is because you don't want the fuel pump to keep running if the engine has stopped; e.g. in the case of a crash or a ruptured fuel line.

nate

Distributor is coming of the other car within the next hour,hope i can post back with some good news.
Thank you again toolboy.

Lance924 · 06:33 AM

Quote:

Originally posted by toolboy62
ASSuming that it uses the same kinds of controls as a 1980's VW; yes, it will indeed keep your fuel pump from running because the fuel pump relay relies on a good signal from the distributor to keep it pulled in. The reason it does this is because you don't want the fuel pump to keep running if the engine has stopped; e.g. in the case of a crash or a ruptured fuel line.

nate

Well i just want to say a big thankyou to all for your input.
Toolboy THANKYOU very much,i decided to clean the wire contacts on the distributor pickup following your advice.I then checked to see if i had spark from the coil,and to my delight there was.
I couldnt get the dissy cap back on fast enough to see if she would come back to life.
Sure enough she did,and today i am a very happy person.
Many thanks again to all that helped,and to you Toolboy i am in your debt.
Great forum,i will be regular visiter to try and help others as much as i can.
Once again a big thankyou from a happy porsche owner in the UK.

EMBPilot · EMBPilot's Garage

Interesting resolution, well done Nate. does the 944 operate under this concept?

what is the distributor pick up? is that where the coil plugs into the distributor cap?

toolboy62 · 02-25-2007, 09:13 AM

I haven't a clue; I actually am more familiar with VW's (my mom has owned an '86 golf since the late 80's, and I've had an '84 GTI, an '84 Scirocco, and an '89 GTI 16V all with CIS, as well as an '02 GTI 1.8T) than Porsches, so this was much easier for me to give advice on than a 944-specific question

I've actually been toying with the idea of using a VW fuel pump relay to provide a safety switch for an electric fuel pump on my old Studebaker because a) the stock mechanical fuel pump is LOUD and b) I don't like the concept of wiring the fuel pump through an oil pressure switch; if you lose oil pressure in the fast lane of a freeway, say, you want to be able to get over to the shoulder, engine damage or no. So I've actually done some research on how the fuel pump relay works on a CIS car...

nate

toolboy62 · 02-25-2007, 09:21 AM

oh, yeah, the pickup is the bit in the distributor that actually tells the coil when to fire, similar to a set of breaker points. I think on a VW it is a Hall sensor, but don't hold me to that.

I think on a 944 it is actually a sensor on the flywheel? which is theoretically more stable than a little chopper in the distributor, which is why high-RPM race cars pretty much universally use crank-triggered ignitions.

nate

Lance924 · 02-25-2007, 09:26 AM

The 944 uses two speed censors on the top of the gear box aswell as the crank censor.These have to be at the right gap for them to read correctly.