FRustration! PLEASE HELP!!!!

fty · 11-23-2003, 01:49 PM

Ok so I still cant get the car running, replaced DME relay and fuel pump, tested valtage to fuel pump...is 11mv and goes up to .43 Mv when engine is cranking.....what could it be? Would a bad dme do it or a bad Maf? Im so frustrated.....any ides Im at my wits end-chris

fty · 11-23-2003, 01:53 PM

would the engine crack witha bad DME?

CT944 · 11-23-2003, 02:30 PM

I went through the same *****. Just replace the DME and go from there. The DME causes 98% of all "no start" problems. Get one off EBAY for under $200.

CT944 · 11-23-2003, 02:33 PM

Yes the car will crank with a bad DME. It just won't ground the coil and generate a spark.

Makis · 11-23-2003, 02:50 PM

Quote:

Originally posted by fty
Ok so I still cant get the car running, replaced DME relay and fuel pump, tested valtage to fuel pump...is 11mv and goes up to .43 Mv when engine is cranking.....what could it be? Would a bad dme do it or a bad Maf? Im so frustrated.....any ides Im at my wits end-chris

Voltage to fuel pump should be 12V when cranking and 0V when the engine is stopped. Not sure what you measure. Suggest you try again and get the correct figures.

fty · 11-29-2003, 07:54 PM

Ok I just bought a DME for 100 bucks....i switched out coils today and still no GO...I hope this works..any tips would be much appreciated THX!!!

MrPants · 11-30-2003, 12:13 AM

maybe some of us missed out on a an earlier thread. what is it doing? starter motor turns but the engine wont start?
have you checked for fuel and spark?

Dark Skies · 03:17 AM

I feel your frustration!!!

I haven't checked the whole thread elsewhere but have you had a look at the reference sensor over the flywheel? What you're describing sounds very much like a problem I experienced last summer. I'd bought a decent second hand sensor (to replace one damaged by a privateer who bailed on replacing my auto donut) and adjusted it as per the Haynes manual (using a washer as a temp shim to set the gap). Car still wouldn't start. I threw a *****load of money at it. New plugs, new coil, new leads, news rotor, new cap. Still couldn't get a spark. I was starting to look at DME related issues when it occured to me to recheck the sensor gap. Turns out that I'd got the gap wrong and the starter ring had chewed out the bottom of the sensor (for reasons posted elsewhere). Might be worth your revisiting this line of thought. Check you've got good / correctly made connections at the sensor plugs too. The sensor can be tested without removing it to see if it's functioning. I seem to remember I posted instructions for making a sensor gap adjusting tool somewhere. I'll go see if I can find the link.

Dark Skies · 03:32 AM

Okay, found it plus some related sensor checking bumf I'd posted on the same subject:

"Check the resistance across two of the three pins of the speed and reference sensors. About 900 - 1040 ohms. Nothing at all means it's bad. It's the easiest test to do without getting bent out of shape or getting greasy and I wish I'd done that on my own car which recently displayed ALL your symptoms and checks."

"You should use it to make a simple adjusting tool for when you need to replace / adjust the speed sensor.

Here's how:"

DIY speed sensor adjustment tool

Hope that's of some use chap.

fty · 11-30-2003, 07:49 AM

Cool well im gonna check that after the new dme goes in....if the dme doesnt work....it all started after I replaced a ton of vacuum lines and replaced the coil resistor....I think it may have been the wrong resistor the guy gave me and maybe blew the dme from the coil...does that make sense? Im using a MSD coil..it was the last thing I touched before it died...ARRRGGG -chris

gobogie · 12-01-2003, 08:19 PM

I hope you figure this out. I had a guy give me a wrong relay for a prevous Porsche but surprisingly it fit. I had blind faith that it worked and did what another guy recommended, replaced all of the fuses assumint that you can't trust any of them only to end up 3 months of on and off trying to find that the relay wasn't working!

Never assume... I about took a shoot-gun to that car! It was great when it started though and a learning experience to boot!

fty · 12-01-2003, 08:24 PM

Yeah im gonna second the shotgun thing if this NEW DME doesnt fix this problem!!!!!!

SoCal Driver · SoCal Driver's Garage

You would think that with over 1500 posts you could fix your car.

overkill · 12-02-2003, 02:14 PM

You could rebuild the top end of your engine,... LOL.

fty · 12-03-2003, 12:10 AM

Quote:

Originally posted by SoCal Driver
You would think that with over 1500 posts you could fix your car.

Please take in consideration that 1485 of these posts have been based on nonsense replys rather than tech stuff...

SoCal Driver · SoCal Driver's Garage

Quote:

Originally posted by fty
Please take in consideration that 1485 of these posts have been based on nonsense replys rather than tech stuff...

OK.

What was the last thing mechanical that you did that affects the basic running of the car? You messed with the after market coil.

The question is why.

Here is some basics on the ignition.

Stock 944 coils do not have resistors. The 12 vdc comes directly off of the ignition switch. The DME grounds out the coil through the green wire. The other wire is the 12 VDC from the switch.

The signal for the firing of the coil by the DME comes from the reference sensor on the flywheel. This is the one toward the front of the engine.

The DME and the injectors gets their 12 vdc from the DME/fuel pump relay's first set of contacts. These close when you turn on the key. If you don't have 12 vdc to one side of the injectors with the key on and there is 12 vdc at the coil, you have a bad DME/fuel pump relay or a break in the harness to the injectors.

The second set of contacts in the DME/fuel pump relay close under two circumstances; the first is when you crank the car. The solenoid wire to the starter also splits and goes to the DME. This tells the DME to run the fuel pump to charge the system. Once the engine is running over 200 rpms the speed sensor input tells the DME to keep the fuel pump contacts closed. A safety thing.

The fuel pump contacts will not close unless the first set of contacts, DME, are closed.

So this boils down to using a volt meter and checking for 12 VDC at the coil and at the injectors with the key on. If there is 12 vdc both places you know that the ignition switch is good and that the first set of contacts in the DME relay have closed.

On the early 944's you can use a test light off of one side of the idle bypass valve or off of the fuel pump fuse holder to see the fuel pump contacts close.

Other things to check: With a test light go from the battery 12 VDC to the green wire on the coil. You should see the test light flicker when you crank the car. This tells you that the DME is powering up and that it can "see" the reference sensor.

Get a spare spark plug, pull one of the spark plug wires off of the car, stick the plug into it and lay it across the intake. You should see a spark. This tells you all of the above and that the HV circuit from the coil through the dist and rotor is working.

There is nothing wrong with the stock ignition setup including the spark plug cables as long as they are maintained.

fty · 12-03-2003, 11:42 AM

Thanks SOCAl..i replaced the dme relay...would the DME itself cuase any of these problems? I replaced the msd coil with the original one..still no start.....when i get a chance i will check the wires..thx again-chris

SoCal Driver · SoCal Driver's Garage

Quote:

Originally posted by fty
Thanks SOCAl..i replaced the dme relay...would the DME itself cuase any of these problems? I replaced the msd coil with the original one..still no start.....when i get a chance i will check the wires..thx again-chris

You have to check for the voltages at the places I described.

Just replacing things does not do it.

fty · 12-04-2003, 12:22 AM

Ok well the dme i thought i bought fell through..i will check voltages as you specified asap...where are these sensors do you have a picture..thx, apreciate the time-chris

SoCal Driver · SoCal Driver's Garage

These are the electrical diagrams for the early 944's:

http://www.pelicanparts.com/944/electrical/944_electrical_diagrams.htm

These are the parts diagrams:

http://www.pelicanparts.com/944/944_parts/944_83-85.htm

If you are not familar with the 944 injection system then Wilks web site is worth reading:

www.frwilk.com

Another worth reading is:

www.clarks-garage.com

With out you flying me to the east coast so I can point things out this is the best I can do.

I suggest finding someone local that knows these cars and can give you one on one instruction.