Car will not start

[Gary944T]

After reading some old threads I believe I need to test and/or replace the DME temperature sensor. I took out the spark plugs and they are completely fouled, so I think the DME control is too rich. Replaced them and sill won't start. After searching the entire internet, I can't find where a 1986 944 turbo DME temperature sensor is located. Anyone know where this is located?

As an aside I took out the temperature sensor that feeds the dash gauge, cleaned it and reinstalled and now the dash gauge doesn't read hot anymore. I have the older sensor with only one terminal so cleaning it was my best option. The newer ones have 2 terminals, but I can't find a connector to replace mine. Even if I could, what would the DME do with 2 signals instead of 1 ?

[Gary944T]

Thanks to 944online I found it! That sucker is hiding from view behind a coolant pipe at the front of the engine. I was able to get to it by taking the filter box and MAF off. Then it's tight but you can remove and replace. In removing my 38 year old sensor it broke in half and was completely deteriorated inside. I doubt it was sending any signal to the DME.

This is the new one installed:

[walfreyydo]

Originally Posted by Gary944T

After reading some old threads I believe I need to test and/or replace the DME temperature sensor. I took out the spark plugs and they are completely fouled, so I think the DME control is too rich. Replaced them and sill won't start. After searching the entire internet, I can't find where a 1986 944 turbo DME temperature sensor is located. Anyone know where this is located?

As an aside I took out the temperature sensor that feeds the dash gauge, cleaned it and reinstalled and now the dash gauge doesn't read hot anymore. I have the older sensor with only one terminal so cleaning it was my best option. The newer ones have 2 terminals, but I can't find a connector to replace mine. Even if I could, what would the DME do with 2 signals instead of 1 ?

Sounds like lack of spark.

A no start condition always starts with two basic steps: checking for spark, checking for fuel/fuel pressure measurement. Depending on which you lack will then take you down different paths of diagnosis. The process and steps (and methods of testing) have been thoroughly documented here on Clarks Garage so I would recommend this as your starting point: https://www.clarks-garage.com/shop-manual/ts-01.htm Note that you should really test components before replacing, due to the cost of parts, thankfully Clarks, for the most part, outlines how to test each component and system.

Typically a bad DME temp sensor will not be the cause of a no-start condition (rough running yes), so I think it would be best to start at the beginning. The DME temp sensor is located at the front of the engine on the head, its a blue top temp sensor. The gauge sensor is under the intake and much harder to access. If you searched far and wide for this info but couldnt find it, I would again point you to Clarks Garage and strongly encourage you to read through the entirety of the shop manual section as well as download a copy of the FSM pdf's and the PET parts catalog (which gives you parts diagrams and numbers for everything on the car). You will find that Clarks is an incredible resource for every 944 owner, but note that there is some turbo specific info that isnt fully covered

DME temp sensor location info from Clarks:
https://www.clarks-garage.com/shop-manual/elect-19.htm

[huskerick1]

Agree with Tyler above - do check the two reference sensors on the back side (near the fire wall) of the motor. They are also known for failure and create ignition issues. Check more for 'tach bounce' threads which will give you more info on if they are working.

The coils are usually bullet-proof, but have also seem them fail. Also check the cap and rotor and remove a plug wire to check for spark.

[Dolly P]

The DME temperature sensor for your '86 944 Turbo is located on the coolant line, usually near the thermostat housing or cylinder head. It’s a critical sensor for the DME to adjust the fuel mixture, so if it’s faulty, it can definitely cause the engine to run rich and foul plugs.

[kdjones2000]

Originally Posted by Dolly P

The DME temperature sensor for your '86 944 Turbo is located on the coolant line, usually near the thermostat housing or cylinder head. It’s a critical sensor for the DME to adjust the fuel mixture, so if it’s faulty, it can definitely cause the engine to run rich and foul plugs.

Bot?

[Gary944T]

Originally Posted by huskerick1

Agree with Tyler above - do check the two reference sensors on the back side (near the fire wall) of the motor. They are also known for failure and create ignition issues. Check more for 'tach bounce' threads which will give you more info on if they are working.

The coils are usually bullet-proof, but have also seem them fail. Also check the cap and rotor and remove a plug wire to check for spark.

Both reference sensors have been replaced. Today I am testing the fuel pressure, it took me weeks to find a 12x1.5 coupling to fit the pressure gauge I bought. Something weird just happened, when I jumpered the DME the fuel pump started but I forgot to turn on my camera to record the gauge. Now I am trying it again and the fuel pump is not starting (it was recently replaced).

Next I bought a noid light and will be testing the fuel injectors.

Last week I got back my DME and KLR from ECUDoctors, both needed repair, bad capacitors and solder joints. Still won't start though.

[Gary944T]

Originally Posted by walfreyydo

Sounds like lack of spark.

A no start condition always starts with two basic steps: checking for spark, checking for fuel/fuel pressure measurement. Depending on which you lack will then take you down different paths of diagnosis. The process and steps (and methods of testing) have been thoroughly documented here on Clarks Garage so I would recommend this as your starting point: https://www.clarks-garage.com/shop-manual/ts-01.htm Note that you should really test components before replacing, due to the cost of parts, thankfully Clarks, for the most part, outlines how to test each component and system.

Typically a bad DME temp sensor will not be the cause of a no-start condition (rough running yes), so I think it would be best to start at the beginning. The DME temp sensor is located at the front of the engine on the head, its a blue top temp sensor. The gauge sensor is under the intake and much harder to access. If you searched far and wide for this info but couldnt find it, I would again point you to Clarks Garage and strongly encourage you to read through the entirety of the shop manual section as well as download a copy of the FSM pdf's and the PET parts catalog (which gives you parts diagrams and numbers for everything on the car). You will find that Clarks is an incredible resource for every 944 owner, but note that there is some turbo specific info that isnt fully covered

DME temp sensor location info from Clarks:
https://www.clarks-garage.com/shop-manual/elect-19.htm

I read the Clark's "Engine cranks but does not fire". Fuel or spark. A month ago I replaced the fuel pump and fuel pressure regulator. I tested the fuel pressure today. It took a long time to find a 12mmx1.5 coupling for the rail and my gauge. The picture is attached. Seems ok.

Last week I put in new spark plugs and the DME/KLR were tested and repaired. Both had bad capacitors that leaked and bad solder joints.

I don't have a spark tester so I will get one tomorrow.

7 years ago all the spark plug wires and distributor were changed when I did a comprehensive $11K refurb by a local Porsche shop. I only drove the car for 1 year as the ac broke, so I put it back in the garage, the wife said no more money.

I saw a video where the rotor can come off if the screw was put in without Loctite so I will check that.

I have not checked TDC, could it be timing?

[kdjones2000]

Gary, the gauge you are showing is for non-fuel injected cars, as the fuel pressure only goes to 10 psig. You need something that will measure up to 60 psig.

[mmascari]

My car is at the shop right now for no start/no spark. It is the KLR not passing the ignition signal through it. on the KLR jump pins 9 and 16. (not 100% sure on these so make sure)

[Gary944T]

Originally Posted by kdjones2000

Gary, the gauge you are showing is for non-fuel injected cars, as the fuel pressure only goes to 10 psig. You need something that will measure up to 60 psig.

Thanks, I'll get a new gauge.

[Gary944T]

Originally Posted by mmascari

My car is at the shop right now for no start/no spark. It is the KLR not passing the ignition signal through it. on the KLR jump pins 9 and 16. (not 100% sure on these so make sure)

I did that jump on the KLR connector and it still would not start. That is when I took them to the ECUdoctors and they were fixed. They have a 944 and tested my DME and KLR and they worked fine after they repaired them.

Did they fix your car? What was wrong?

[mmascari]

I got my car back today. They replaced the reference sensors and the KLR was also repaired by Specialized ECU in Florida. This resolved my issues.

[Gary944T]

Originally Posted by kdjones2000

Gary, the gauge you are showing is for non-fuel injected cars, as the fuel pressure only goes to 10 psig. You need something that will measure up to 60 psig.

The fuel pressure is 34 psi.

fuel or spark ?

The DME and KLR were just repaired by ECU doctors and were tested in a 944 they have onsight.

I installed new spark plugs.

Today I will test the spark with a tester I purchased. Given the DME/KLR are working this is a waste of time but I will do it to check off another box.

All the fuel injector connectors have been replaced. One of the fuel injectors is cracked, the plastic, behind the connector. But when I had them out weeks ago all 4 clicked when 12v was applied. I was told the car would start on 3 cylinders even if this one is bad. Can't get any new ones right now.

I saw a video where the rotor was loose on a car because the screw was not inserted with Loctite. Should I check this?

[Gary944T]

Spark test complete. All 4 spark plug wires are getting spark.

[Gary944T]

I took the distributor cap off which doesn't have that many miles on it and the contacts look fine.

The video I referenced above must be for an old design in a 944 as the rotor is not held on by a 8mm screw in the center, but by a hex set screw.

Since the car knocks sometimes when cranking it, does that mean there is a timing problem?

[huskerick1]

Gary - what injectors did you install? The off-shore versions are junk and it appears these turbos really only perform with the OEM Bosch green tops ending in "803".
I can send you an OEM rebuilt set for testing if needed... new ones cost a small fortune, if you can even find them. I may also have a few other items for testing if interested.
Also, you noted you changed the reference sensors... again, these cars only seem to like the original Bosch components...

[Gary944T]

Originally Posted by huskerick1

Gary - what injectors did you install? The off-shore versions are junk and it appears these turbos really only perform with the OEM Bosch green tops ending in "803".
I can send you an OEM rebuilt set for testing if needed... new ones cost a small fortune, if you can even find them. I may also have a few other items for testing if interested.
Also, you noted you changed the reference sensors... again, these cars only seem to like the original Bosch components...

7 years ago a shop replaced 2 of the injectors with Bosch, and they don't have 5K miles on them, they cleaned the other 2. As you stated you can't even get them right now and yes very expensive.

I bought 4 injectors from KSM Motorsports but I haven't put them in yet because I really don't think they are the problem.

The reference sensors I installed are not Bosch. 944online usually tells me when an OEM is needed but most of the time he says the others are better anyway.

[Gary944T]

I surrender. After cussing and fuming at the Germans for 4 months because there isn't a single part in this car that has access.

If I wasn't the original owner with sentimental value via Tourist Delivery, this car would be in a lake or off a short cliff by now.

So, I give up, this car is going back to Foreign Affairs Motorsports.

[kdjones2000]

DME Test Plan is your best option for a no-start. Get the Turbo version. You need an oscilloscope, and should test things at the DME connector, not at the sensor.