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944 No Start?

Gruppe:

My 1987 944 5-sp had been having an intermittent start issue for a while. I replaced the DME relay (no effect). I found some frayed wires on the crank position sensor and replaced the sensor which fixed it 90%.

The car then sputtered for 20-30s on the highway one day and died. No start now. The car has been doing 100mi/day for at least the previous month w/o issues. Also, it has covered some 30k miles in the past year.

I removed the DME and resoldered the dry solder (cracked) joints on the coil driver (transistor). This is a typical failure point on the mid-80s DMEs from Bosch and the BMWs have this problem as well. Mark D'Sylva pointed me to this.

That did not help. :-(

The car has:
1. New coil
2. New cap and rotor
3. New plugs
4. New wires
5. New sensor - crank speed and position
6. New battery

The engine is getting fuel, but no spark.

Any ideas? Thanks!

Neil Deshpande
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Old 09-24-2005, 12:28 PM
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Maybe a silly question, but when you turn on the key, are you getting 12V all the way to the coil?
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Gene
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Old 09-24-2005, 05:37 PM
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You have been thru all "Clark's Garage" no start diagnoses procedure?. And IF not........you NEED to. EVEN, if it means buying new tools to diagnose with...........within reason.......of course! How commited, and dedicated are you, to working on your own cars/porsche?

good luck!
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1985/1 944 Granite Red (wife's car. Iceshark is lighting her way)
1983 944 Platinum (my daily)
1985/1 Guards Red (project)
Old 09-24-2005, 05:52 PM
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Try your ignition control box-located in the drivers side headlight well
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Old 09-25-2005, 12:54 AM
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944 No Start?

Gene:

Yes, I get 12.49V at the coil (both terminals) when the key is in start. Yes, the ignition key does have some connectivity issues (I have to jiggle it to get wipers and window motors to work), but this is apparently not one of them. Perhaps it stops the 12V supply when cranking even though it is OK when in "ON"? I'll try and check that.

Neil Deshpande

***

Quote:
Originally posted by Gene Alvarez
Maybe a silly question, but when you turn on the key, are you getting 12V all the way to the coil?
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Old 09-25-2005, 11:23 AM
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944 No Start?

Granite 944:

Thanks! I went to Clark's Garage and performed the diagnostics. I didn't check the sensor outputs (no o-scope at home), but one is brand new (1mo) and the other is 1yr old so I'm sure they are OK. Resistance checks are fine.

Unfortunately, it points to the DME. I ordered a DME from Parts Heaven. Hopefully, that'll fix it.

As for tools, I have a good complement. I do all my own work - clutch, engine rebuild, etc. No shortage of enthusiasm, just shortage of time.

***

Quote:
Originally posted by Granite 944
You have been thru all "Clark's Garage" no start diagnoses procedure?. And IF not........you NEED to. EVEN, if it means buying new tools to diagnose with...........within reason.......of course! How commited, and dedicated are you, to working on your own cars/porsche?

good luck!
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Old 09-25-2005, 12:19 PM
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944 No Start?

Jeff:

Tell me more about this. I don't think I have any modules there. Thanks!

Neil Deshpande

***

Quote:
Originally posted by Jeff Laurence
Try your ignition control box-located in the drivers side headlight well
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Old 09-25-2005, 12:21 PM
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Not sure about the 8 valves, but the "S" has an ignition cotrol module that fires the coil; located in the driver 's headlight well.
When mine went bad, it went intermittent, cost at Porsche CDN$ 160.00
Jeff
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Old 09-25-2005, 05:22 PM
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Re: 944 No Start?

Gene:

I checked it in "START" as well and it does get around 11.35V, which is to be expected during the cranking current draw, I think, even if "ON" voltage is 12.49V.

The used DME (90-day warranty) ships UPS Ground on Mon from CA to GA. I'll put it in the minute I have it.

Co-incidentally, my old M5 is also suffering from a dead DME. I may have both cars functional in the next week or so, which would be great. I'm currently driving a BMW cabrio, on which I helped fix the DME(!). Luckily my brain isn't a DME or I'd be really worried.

Neil Deshpande

***

Quote:
Originally posted by neildeshpande
Gene:

Yes, I get 12.49V at the coil (both terminals) when the key is in start. Yes, the ignition key does have some connectivity issues (I have to jiggle it to get wipers and window motors to work), but this is apparently not one of them. Perhaps it stops the 12V supply when cranking even though it is OK when in "ON"? I'll try and check that.

Neil Deshpande

***
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Old 09-25-2005, 05:40 PM
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Re: 944 No Start?

Quote:
Originally posted by neildeshpande
Granite 944:

Thanks! I went to Clark's Garage and performed the diagnostics. I didn't check the sensor outputs (no o-scope at home), but one is brand new (1mo) and the other is 1yr old so I'm sure they are OK. Resistance checks are fine.

Unfortunately, it points to the DME. I ordered a DME from Parts Heaven. Hopefully, that'll fix it.

As for tools, I have a good complement. I do all my own work - clutch, engine rebuild, etc. No shortage of enthusiasm, just shortage of time.

***
You already ordered a used DME, but.......there isn't SOMEONE around you, that could offer a known good test unit? Oh....yeah....I know......I'm the same way!

R checks came out good........thats good......but not always a definative way to know either. Wire harnesses there, have been known to be a source of problems also (heat/deterioration).

"shortage of time".........OH BOY!!........ I can relate!

GOOD LUCK! let us know what it all turns out to be.
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1985/1 Guards Red (project)
Old 09-25-2005, 05:42 PM
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Re: Re: 944 No Start?

Granite 944:

Unfortunately, I am not really part of any of the local Porsche activities. The other problem is that I wouldn't be too happy using another person's DME not knowing what caused the DME in my car to fail. For example, in the BMWs a common cause of failure is failure of the dielectric in the coil sending hi-voltage back through the primary, which is connected to the DME, and frying the coil driver transistor in the DME. Any good DME would suffer the same fate as the fried one. I replaced the coil on the M5 in preparation for the repaired DME install.

More of a BMW person. Saved the 944 from rotting in my brother's backyard (coil quit on him and he just bought a new car and let the car sit with a smashed window in Boston), which is why I have it.

Also, since I've been working on the car for the past 2yr, I'm pretty familiar with the wiring and components. I diagnosed a no-start (coil) 2yr ago when I got the car. As I worked on it, I replaced all the critical parts to make it reliable for my 100mi/day commute. So, I know that aspect of the car pretty well. I think my fixing list runs over 100 items so I'm not jumping the gun too much with getting the DME this early in the game.

Also, I checked on E-Bay and saw that DMEs go for about $200+ so I figured that I could E-Bay the DME if that wasn't it and get back most of my money. Diagnostic at Programa is $80 so buy-E-Bay diagnostic methods would cost about the same, with the added advantage of potentially fixing the problem where at Programa I'd be out of $500 extra to have them repair the DME.

I have put the bad sensor in my car. I'll stop by the BMW dealer tomorrow to get a new harness side plug and wires (they look frayed). The crank pos/speed sensor on the M5 has the exact same connector so I'll get that part (probably use the same supplier as Porsche!) and put it in the 944 to better the harness at that location. Porsche dealer is incoveniently located.

One I get this fixed, I have to address the sometimes-full-on heat in the car - fixed the damper $1.50 thingie and the valve seems to actuate. Being an Indian from the hot plains in that country, I can take the heat with the windows down, but being an engineer its not working bugs me. Then, I have to put in the replacement condensor and get the AC going (new compressor and drier) and it'll be quite comfy.

Don't mind the work at all, but I just have a lot else I also like doing. Most hands-on people I know are exactly the same.

Neil Deshpande

***

Quote:
Originally posted by Granite 944
You already ordered a used DME, but.......there isn't SOMEONE around you, that could offer a known good test unit? Oh....yeah....I know......I'm the same way!

R checks came out good........thats good......but not always a definative way to know either. Wire harnesses there, have been known to be a source of problems also (heat/deterioration).

"shortage of time".........OH BOY!!........ I can relate!

GOOD LUCK! let us know what it all turns out to be.
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Old 09-25-2005, 05:59 PM
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As the engine cranks the DME should be pulling that 12V at the coil to ground momentarily to generate the spark. If you have a steady 12V then the DME is not working right.

I had a similar problem; the DME was not providing a ground for the fuel pump relay coil. F.R. Wilke has the DME schematic on his site. I replaced the IC on the DME ($ .40) and all is well now. The coil appears to connect to pin 1 and to a different IC internally. If you were to succeed in repairing your DME I would be very interested in hearing about it.
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Old 09-26-2005, 08:00 PM
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944 No Start?

Gene:

I was using a regular multimeter and getting 11.35V during cranking and 12.49V in "ON". I don't think the meter (an el cheap Radio Shack) would be able to see the pulsing from the DME grounding the coil. It may see it as a slightly reduced DC voltage or something, which may be what the 11.35V I saw was.

I will certainly work on the defective DME. I've resoldered the coil driver transistor's connections. I'll check out the ones that connect the ribbon cable tomorrow and solder them as well.

How did you decide to replace the IC (I'm assuming this is the 14-pin S400 on the schematic)? I looked at the schematic on F R Wilk's site and it doesn't seem to show pin 1 on the DME connector going to the IC. I do know that pin 1 is connected to the coil because the factory diagnositc to check the coil involves intermittently putting 12V to this pin.

I'm definitely up for giving the DME repair a go and I'd love to understand more about the DME.

Thanks for you efforts.

Neil Deshpande

***

Quote:
Originally posted by Gene Alvarez
As the engine cranks the DME should be pulling that 12V at the coil to ground momentarily to generate the spark. If you have a steady 12V then the DME is not working right.

I had a similar problem; the DME was not providing a ground for the fuel pump relay coil. F.R. Wilke has the DME schematic on his site. I replaced the IC on the DME ($ .40) and all is well now. The coil appears to connect to pin 1 and to a different IC internally. If you were to succeed in repairing your DME I would be very interested in hearing about it.
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Old 09-26-2005, 08:26 PM
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Gene:

OK, my mistake. I didn't see that you were talking about the fuel relay coil being grounded, not the DME coil. So, which pin 1 are you talking about and which IC internally? There is only 1 IC on the analog half of the board, right? Thanks for any comments.

Neil Deshpande
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Old 09-26-2005, 08:27 PM
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Gruppe:

Well, the used DME from Parts Heaven arrived today and it didn't fix the car. Darn!

So, I'm going to have to start the diagnostic again. I'll probably bring an o-scope back home from work to properly diagnose the systems and see what is going on.

Neil Deshpande
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Old 10-03-2005, 06:17 PM
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Sorry I've been away from the board a while.
I agree that 11.35V is probably the average as the DME cycles the coil. A 12V light wired in place of the coil should blink on-off, if you want proof.
One horrible thought: does the cam rotate when you crank? Check the belt.
The IC I replaced is the CD4049UBEX. Used a CD4049UBE. This is the one that controls the fuel pump relay
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Old 10-03-2005, 07:04 PM
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Gene:

The first thing I checked was the belt and it is fine. I had to remove the distributor cap and look inside and it was OK. Also, I can tell the feel of and engine rotating w/ and w/o compression and it feels fine in that regard.

I'll give it some more thought and work with the o-scope. I'll let the board know what I find.

As an aside, I have sold the car to a friend who'll take delivery once I get it running. I replaced it with a 99 BMW 328i. So, I've replaced my Porsche with a BMW and will replace my BMW (92 M5) with a Porsche (911) shortly.

Neil Deshpande
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Old 10-03-2005, 07:08 PM
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Hope I'm not repeating something already offered. But when my '87 started having an intermittent start problem it turned out to be "grounds". If your car had been sitting dead for a couple of years and perhaps even a broken window you could have the same problem. This journey, if you choose to accept it, will be quite a treasure hunt. I got the best result when I cleaned the grounds that are under the fuse/relay box, inside the car, reachable above where your left foot would normally be when driving. It will help if you are about 12 inches tall when trying to reach them. You will see two bolts with brown wires going to them. Remove the bolts, shine everything up, maybe put a little dielectric grease on to help in the future, and turn the key. Maybe it will start and maybe it won't. But its a cheap fix if it works. Good luck and let us know how the journey ends.
Old 10-08-2005, 10:30 AM
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This may be waaaaaay to simple, but it got me home one night

On older model 944 cars, just reach under with left hand, tap the fuse relay box sharply, and turn the ign key with the other hand.

http://www.network54.com/Forum/message-426130-1128643557

In the event you have a loose ground or relay that's about to give it up, this just might get you home, it saved my a$$ one day, and it may save yours too!

Good luck
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Old 10-08-2005, 12:17 PM
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Have you checked the fuel pump?
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Old 10-08-2005, 05:33 PM
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