Hard Cold and Warm Starting Issues - Need Help Troubleshooting
 

Okay. I have a 1986 944 na. About 18 months ago, I noticed it starting to have a hard warm start issue. Every morning she would fire up no problem. However, if I drove to a gas station, stopped and fueled up, I would run into a hard warm re-start issue. Happened maybe once every 2 months. Then every month and then about every week. Now it has evolved into a hard cold start as well. I am getting the problem both on cold and hard starts. Here is what I have done so far trying to troubleshoot the problem:

1. Replaced both the cross reference/speed sensors (new parts)
2. Replaced both the fuel pressure regulator and damper (new parts)
3. Replaced the fuel filter (new parts)
4. Replaced the fuel pump check valve and fuel pump (new parts)
5. Replaced the fuel pump/dme relay (but that was in early 2010) (new parts)
6. Refurbished all fuel injectors (re-seal kit) and replaced one faulty leaking injector recently (new parts)
7. Replaced throttle position sensor in 2011 (new parts)

When I run into the problem, I have to pop the hood. Usually, if I jiggle the cross reference sensors up top near the fire wall, she will fire up. However, even that is getting hit or miss now. I am guessing I have a DME box on the fritz or something I haven't thought of yet. Any other suggestions? Is it possible to do a bench test on the DME box or some other way to narrow down the problem? This is driving me nuts.
http://forums.pelicanparts.com/uploa...1374510405.jpg

If possible, swap out the DME. I had a similar problem and a replacement did the trick.

I have one on order. Anyone care to post step by step instructions on how to remove and replace?

uvachief,

Clarks has a basic text;
DME Control Unit Removal and Installation

Have a fully charged battery.

There is no easy way to "bench test" a DME
You can consult the WSM for ideas and testing or send it to a shop to test --$50 and up + sh

The Porsche 944 Motronic DME

J_AZ

uvachief,

If you a bit familiar with electronics and the new DME cures the problem, try the following:

1. With the old DME removed, carefully inspect the connector for any damaged pins;
2. Remove the cover and look for any corrosion on the printed circuit boards as well as on any jumpers;
3. Carefully inspect all solder points for "cold solder" connections. You'll see a funky solder point as shown with attached pics.
4. I also would inspect each component (resistor, capacitor, diode, etc.) for burn marks; a clear sign of component failure; and
5. If you still have the patience, look at all the circuit traces for damage including breaks or burns (possibly due to a failed component.

Good luck with the project.

Oops, I forgot the pics...http://forums.pelicanparts.com/uploa...1374546104.jpg
http://forums.pelicanparts.com/uploa...1374546115.jpg
http://forums.pelicanparts.com/uploa...1374546127.jpg

It might not be your problem but I would also check out the DME engine coolant temp sensor. When mine went bad it would have trouble starting when the engine was warm. It would have to cool off a bit before it would restart. It's an easy part to check. You never know, you might have more that one problem. I would probably put my money on the DME though.

I also had a DME go bad. Car just shut off while driving one day and never started again. I swapped the DME and the car came back to life.(after trying many other things) I looked over my bad DME a few times and never found a bad solder.(even with a multimeter) Maybe I will check it out again someday. Never know when it could come in handy.

Here is a clarks-garge write up on checking the DME temp sensor if you want to check yours.
DME temp sensor

Okay. It is allegedly placed in the passenger footwell under the variety near the seat correct? Towards the firewall I see someone had installed and amp and nearly hid it under the carpet and covered it with a door and four screws. How do you post pictures in a reply message?

Okay. It is allegedly placed in the passenger footwell under the carpet near the seat correct? Towards the firewall I see someone had installed and amp and nearly hid it under the carpet and covered it with a door and four screws. How do you post pictures in a reply message?

Very easy, simply "Go Advanced" then "Click here to Upload a Photo", then :Choose file", Browse your computer for your picture file (jpeg) then hit "Open", then hit "Upload now". It gets much easier once you do it a few times..

Okay. I bought a replacement DME/ECU unit from a Pelican Parts patron and swapped it out tonight. I had a heck of a time starting it just to move it into the garage. Swapped the old unit for the replacement unit and voila! Started right up. Cut it off and on about 5x with about 60 seconds or more between shut off and restart. Worked every time. Hoping that has solved my problem. I think I am going to ship my old unit off to Specialized ECU Repair in Florida, let them repair it and install a Rasant performance chip. It is $350 to complete repair and restore your DME/ECU unit back to factory specs and another $100 to add the Rasant performance chip. Supposed to increase horsepower by 15% and torque by 20%.

Awesome, it feels really good when you fix something like this. When you plug it in and the car starts up is really nice.

That good feeling just turned to POOP. Started this morning. Drove to gas station to get coffee. Came out and grrrrrrrrrrrr...rrrrrr......rrrrrr......grrrrr. Wouldn't catch. Popped the hood and installed a brand new DME/fuel relay just in case. Turned over after a few seconds. Drove to work. Sat for about 6 hours. Just went out to take some packages to Fedex and grrrr....rrrr....rrrr....grrrr. Wouldn't catch again. SO FLIPPEN FRUSTRATED.

Here is another little tidbit I have noticed. The MPG gauge on the tach has been getting stuck. This, like the hard starting issue, was intermittent and occurred only once in a blue moon about a year ago. It has slowly been getting stuck more often. Now it is stuck on almost every drive. Sometimes it is stuck until you warm it up and sit at idle as when you come to a stop light. Sometimes it doesn't come unstuck the entire 30-40 minute drive to work. Sometimes it works fine. Is there a connection between the two? What else can I do to trouble shoot this incredibly annoying issue!:mad:

Bump...Switched out ecu/dme again and still no spark. Any suggestions?

The MPG gauge could have something to do with your problem, or be a separate problem. ha ha, I guess that wasn't very helpful. No one mentioned it yet, but it could be a bad ground. Your engine looks very clean, but there could be a problem with a ground somewhere. I don't remember where they all are, but it might be a good idea to check and clean the connections. A bad ground could cause both problems. Or there is just something wrong with the MPG gauge, but I would lean more towards a bad ground.

You said that it seems to help if you wiggle the sensor connections. There might be something wrong with the sensor plugs. They get brittle and crack/break very easy. Maybe the wires are broken close to the plug. It's fairly simple to check resistance of the wires from the DME plug to the sensor plugs. I hope that's not your problem, I believe the wires are shielded and hard to fix.(could be wrong)

A multimeter is a great tool to have and you can get a cheap one for about $10 I think. Harbor Freight tools for a cheap one.

This picture isn't the one I was thinking about, it's a little unclear. Maybe someone else can help out with the correct hole number to check on the DME plug.

http://forums.pelicanparts.com/uploa...1377818928.jpg

Picture of dme ecu boxhttp://forums.pelicanparts.com/uploa...1377958353.jpg
http://forums.pelicanparts.com/uploa...1377958379.jpg

What is the second little disconnected plug suppose to be for or disconnected?

I didn't see anywhere if you replaced the DME relay? That cured my warm start issue.....oops nevermind. Just saw you put a new one in.

Ha ha, I was just looking at that plug 2 days ago when I was trying to fix my own problem. My car has a plug that goes in the other end with a wire that loops back around into the plug. It just connects one wire to the other. It's used in other countries and is listed as a code plug. I'm guessing it's to read codes from the DME for other countries? It shouldn't matter if there is nothing connected or if the plug has a looped wire.

Dme relay is item no. 5 and I switched it out with a new one again about 4 weeks ago.

Turns out my lower reference sensor is frayed at the male plug. See below. I was told the male sensor and female connector should have been bound by a thin gold wire. Mine wasn't and just cam3 apart. It looked like the surrounding bracket for the male plug was cracked and missing. The two were joined. I tried to pull apart at first but it was tight. However, then it just came apart. Maybe the wire was hanging on by a thread? What part number is the female plug and where can I find the gold wire?http://forums.pelicanparts.com/uploa...1379286920.jpg

Okay. Dumb question of the night. To remove the old reference sensor, do I just loosen the nut near the firewall and the pull it out?

Each reference sensor has a bolt on top.

http://forums.pelicanparts.com/uploa...1379464229.jpg

Put a piece of tape over the TDC hole on the bell housing to prevent the bolt/nut tool /// from falling in or you will never get it out of the clutch!!!!

Gently turn the sensor R to L and then UP.

There is an "O" ring in the center of the ref sensor. It gets very brittle.
It may prevent removal.

Then this is what happens...

Photo credit h8ter.

http://forums.pelicanparts.com/uploa...1379463988.jpg

Good Luck
J_AZ

Yep, I've had that happen, a broken sensor like in the picture. In theory they just pull out after removing the one screw. Make sure you put tape over the hole right there. Like John said, stuff will fall into the clutch and it won't come out. If you have trouble pulling it out, maybe use some wd40 and let it soak into the sensor, it might help it slide out. Spinning right and left might help too. But they might just spin easy and not come out. I believe that's from the oring holding it back. As a last resort you can remove the complete bracket like in the last picture from John. You will then need to adjust the bracket when you reinstall it, and then the sensors.

After all of this, it turns out to be a defective after market dme relay. I had yet another spare. 3rd time replacing since may of 2010. Found a frayed mark reference sensor with a cracked male connector. Replaced that and still would not catch. Checked dme fuse box. No power. Swapped out dme relay (uro) with another new dme relay (uro) and voila...fired and catches. So irritated it was this dang relay!

You should make a DME jumper with a paperclip and keep that to test the DME relay. I can't remember where I saw it, I think it's a post on here. I keep a new DME and a paperclip jumper in my car at all times, just in case.

I found out years ago URO DME relays (and every other URO aftermarket part) are junk and never last.

Buy a decent OEM Stribel relay:
Pelican Parts - Product Information: 993-615-227-01-M76

and use the 3 Wire Jumper as an emergency spare.

DME Relay Information and Testing

J_AZ

Thanks John. That's the jumper that I was talking about. Just make sure it touches all the right prongs on the relay and you are good.

Oh I wish I had seen John's post before I removed the sensor. I know I dropped that bolt into the top dead center hole. Cheese and crackers!

Okay. Replaced the frayed sensor and put in a new DME relay and voila! It started. Drove it for about 1,000 miles since 10-9-13. Never had any issues with the clutch but I never ever found the dang bolt. Put in a new Stribel relay. Was running fine until 2 weeks ago. I noticed it cranked funny. Tach bounced to about 5,000 and it barely caught. Had a hard time starting it when going home with the same sort of problem. Sounded like a week battery (battery is 3 years old). I tried to start it yesterday. Bounced to 5,000 rpm and then it didn't catch. I put the charger on the battery. Only took about 20 minutes to get a full charge green light on the battery and it was showing 75% or more capacity when i hooked it up. Switched out the DME relay again just to be sure. Tried to crank it. Nothing. No tach bounce at all. No spark. Tried the paper clip DME relay method. Didn't work. Put back in the recently installed Stribel DME relay. Nothing. You turn the key, you get lights and power but the engine does not turn over at all. Any suggestions?

Just a guess, but it might be worth checking the starter. If the starter is broken then it won't turn over the engine and you wouldn't get any tach bounce.

I don't know why the Tach would jump to 5000 while starting it. If possible, I would try to borrow a DME from a friend and see if that fixes the problem.

The starter is something I have not replaced. That and the alternator. Would a dying starter contribute to frying DME fuel pump relays? That might explain a lot.

This is the part number for the rebuilt Bosch starter correct? 951-604-101-00-M14

Yeah, that looks like the part number for the starter, at least it's not too much money. I would make sure that the starter is bad before buying a new one. The starter is something that's pretty easy to test once it's off the car.

I don't think the starter being bad would make the DME relay fry, but who knows with the 944, anything's possible.

Thinking out loud here. If the DME relay is frying, then that means that it's getting WAY too much power at point. The problem is how/why it's getting so much power.

I really hate electrical problems, mostly because it's something that still confuses me.

Thanks GreenWater! It was the starter. Why that didn't come to mind first, I have no idea. I'll monitor the DME fuel pump relays. I bought the car in May of 2010. It had an existing DME relay. I replaced that within a few months with the URO one that recently died. It now has a brand new Stribel in it so if that goes bad I know I have an electric gremlin somewhere. I think my starting issues were a combination of problems: frayed cross reference sensor, dying URO relay and dying starter. She should be good to go now. Here is crossing my fingers!

Awesome, I hope that's the last of your problems and the car runs great.

I'm sure it was a combination of a few things. That seems to be the M.O. of the 944.

Glad I could help.

Now ain't that the truth! ;);)

It's always good to see a problem resolved here...:cool:

I would have pushed my car over a cliff by now if it wasn't for this site and its members. Nikki would be rusting in a dismantler's yard otherwise. Yeah it has a name. I know that is lame.

It's really not that lame to name your car. There was a post here about who names their cars and what the name is. It seems like most people have names for their 944s. I never named my cars until I got married, my wife does it and now that we have several cars it just makes it easier that way. My 85.5 is called Crusty. It's not in the best shape and has broke down a lot, but now it's running great. My other 944 is just called White car.

Believe me, we have ALL wanted to push our cars off a cliff, set them on fire, or jump them into a lake, but once they are fixed, we all love them again. It's just the relationship that we all have with the 944. Once I was planning on setting Crusty on fire to collect the insurance money, but now I'm glad I didn't.

Okay...fixed the starting issue. My starter had died. Fires and catches just fine now.