User 41221

Its your DME (assuming you didn't also wreck your speed sensor while shaking it... thats really not the best thing to do, tsk tsk...), most likely you did one of two things:

1) didn't seat the connector on the DME when you were plugging it back in

or

2) cracked one of the wire traces or a solder connection when you were separating the boards

If it isn't #1, then plan on spending an evening with your DME and a magnifying glass. Kind of a pain, but relatively easy to fix, assuming you have some rudimentary soldering skills. If you have a friend with a DME you can borrow, it will be easy to verify it, as all you have to do is swap his in and try starting the car.

Regards,

Bri Bro

Will the sensors be responsible for no spark?
You bet you, a bad reference or speed sensor will cause a no spark condition. The sensors that tells the DME when to generate the spark. If you don't have a scope to measure the sensors, take Dannos advice and swap out the DME. If the condition persists, change out the sensors.

BTW. I had both of my connectors just fall apart on the sensor side. Might what to check that you have a good connection

TonyG

sh944 hit the "nail on the head"....

When you seperate the boards, they will flex to a degree. It's this flex that will crack the wire traces or cold solder joints.

It's pretty common.

Shaking the DME win't do a thing.


And you pretty much answered the question yourself...

If you touch something, and it doesn't start after you have touched it, then it's a 99.9% chance that you screwed up the thing you touched!

Get a known good DME to replace your with and I'm sure the problem will go away.

MHT

when you pulled the control unit, did you remove the chip? There is a notch on the chip and a notch on the socket, if you installed the chip in reverse, then it is fried and you will need a new one.

W88951

If you have a bad solder joint, it may look something like this.



Remeber, there are two boards on your DME and the bad joint may be on the bottom board. I recently had the same problem with my 88 951 and was finally able to trace it to this joint. Also make sure that if you did remove the chip, that you inserted it back correctly.

Below are full pictures of the inside of a DME from a Turbo car.

Bottom of the Top Board.


Top of the Top Board


Bottom of Bottom Board
This also shows where the bad solder joint on my board was located.


Top of Bottom Board.


Hope these Help

Cyrus951

Wow, this is what I had been waiting for. Thanks, any idea on what part of the DME is responsible for producing spark? Danno? Thanks.

W88951

Now, I am not an expert on these computers, but can relay my expierence. You should have ~12 volts across pins 1 and 19 with the ignition in the Run position. It will maintain ~12 volts with the car running. I know that pin 1 is responsible for sending a signal to the coil. If you have a bad coil then you will not have ~12 volts on those pins. If you don't then your coil should be good and there is something else wrong in the computer. Again, look for bad solder joints. Below is another picture of the bottom board with the Pins 1 and 19 listed. To view this board you will have to remove Six screws and the two black pins on the end. You can then remove the rest of the cover.

Danno

I vote for something wrong with the DME since that's the only component you touched. Although wiggling the speed/ref. sensors whiel cranking may not have been the best idea due to how fragile the connectors are. One thing you can do to verify the harness-side connectors are good by checking for continuity between the connector end out in the engine-bay and the DME connector. This was how Dan87951 found his not-starting problems (broken connector at speed/ref. connector).

To check the DME, I don't know if troubleshooting specific parts would do any good as any one part can cause problems. The speed/ref. sensor signals are processed at the custom-IC S700. And the spark is initiated at S800, but bad components before and after it will result in no spark as well. One guy mentioned he was able to fix his DME by resoldering every connection on the DME boards.

Cyrus951

I'm heading out right now to a TV/VCR repair shop, so I can have one of those guys resolder the joints. I just don't trust myself anymore.

Cyrus951

Ok, I'm back from the shop, and he said everything looks fine, without doing any work. He just glanced at it at an angle several times, checked both boards, and said it's all okay. I'm totally confused now, I'm heading out to look for a 951 in the Los Angeles area, can anybody let me borrow theirs to plug my DME in to check if it's working? Thanks.

Water944t

I still say it couldnt hurt to keep an open mind about possible other things, like even the rotor or something simple. You stated at first it hadnt run in 10 days or so, and these cars are known for gremlins.

Cyrus951

Sorry, I ment it hasn't been running for the past 10 days. It was running perfectley prior to me pulling out the DME. Anybody in Los Angeles area have a turbo DME I could plug into my car? Thanks a lot.

944Fest (aka Dan P)

Andrew, those were some fine, helpful post and pics. Well done!

Cyrus951

bump