Help! 3.2L Conversion in '73 911T wont run!

[Tspringer]

So after being up on jack stands and in various stages of either sitting waiting on me to work on it or being worked on, my '73 911T with a Euro '85 3.2 engine failed to fire up and run for my test drive. I just put her back together after doing tons of work - new front suspension pan, rust repairs, electrical repair and other stuff for the past 2 years.

Maddeningly frustrating. Yesterday, while still up on jack stands right after I had the exhaust all bolted back up, on a whim - just to see what would happen - I turned the key. The starter turned for 3-4 seconds and WHAMMY - she fired right up! I let her run for about 30 seconds and then shut down as the new exhaust was gassing out (new ceramic coatings ) and I did not want it in the garage. So I am pretty happy, she fired right up so easy after 2 years in the garage.

So I re-install the carpet and seats, bleed brakes, tidy up some wiring with zip ties and get her all ready for the first test ride. Nothing. All set and ready to go - not even a peep of firing up. She turns over on the key just fine, but does not fire.

I did not do the 3.2 conversion on the car. I honestly don't know really where to start to track down what is wrong. I have gone back over the wiring that I tidied up and cannot find anything wrong. There are fair number of dead and loose wires in the engine bay, but most I have identified as things no longer necessary with the conversion.

With the ignition key ON - I have no voltage showing at the coil. Should I? Seems I should.

I have been reading a number of threads on the 3.2 conversion into an early car - '73 included. I have tried to review all the details and compare to my car but it seems to be causing more questions rather than leading to any answers. I really don't want to have to completely re-do the entire conversion.

Any guidance or suggestions on what to try and how to be diagnose and correct this would be greatly appreciated.

[JJ 911SC]

First thing to do on a non starting 3.2, is to replace the DME Relay.

[Tspringer]

That sounds like an expensive guess. Just pop for a new DME Relay and hope for the best?

Surely there must be a means of diagnosing a bad DME Relay?


Terry

[JJ 911SC]

I hope that you are confusing DME Relay with the DME itself... Because a DME relay is about $30 and is the least money you will spend on your car

A DME relay is about $30 to $40 depending which one you buy and $90 if you want a Porsche one .

You should not ride a 3.2 without a spare one in the glove box.

Pelican Parts - Product Information: 911-618-154-01-M252

[tpweiss9953]

Help this man please!

[sundevil64]

Originally Posted by JJ 911SC

First thing to do on a non starting 3.2, is to replace the DME Relay.

I would test the relay first with a multimeter and jump it out. I thought I had dme relay problem on my targa that sat for years with the PO and had several people in it. The dme tested out fine. Spend the 15-20 jumping out the relay and testing it and save the money. Did you mess with the cht wiring? What about the reference sensors. The easy test was to flip flop them. It fired up right after that. Check the fuel pump relay just in case. Start with the easy stuff first.

I understand your frustration. I am planning a very similar project putting a 3.2 into a 71. it will be a 1-2 year project.

[fasterlaster]

I have a similar transplant in a '74 with a 3.2 with all the ECU goodies on it. I don't have my Bentley handy to check if there should be voltage on the coil like traditional kettering ignitions, but the troubleshooting section is great, and may apply to your installation. One thing I can suggest is to not assume anything, and start with the basics.

• Is there spark at all? Perhaps try checking for spark while having a helper crank the engine over.
• Is there any fuel? Pull a plug and check for any dampness or fuel small.

If I remember when I get off work I'll take a look in the bentley and see if I can answer the coil voltage question.

[Arne2]

Try to jumper the DME relay. On a real 3.2, the relay is under the driver's seat. Don't know where it might be on your swap.

Start at post #23:

DME Relay - carry the spare.

[Tippy]

Will it run if you jumper power to coil?

[mreid]

Don't fool around. Carry a spare DME relay. Order it and while waiting for it to arrive, hook a timing light to the coil wire and see if it flashes while cranking (there is no voltage at the coil with the ignition on).

[MConn]

Originally Posted by Tspringer

So I re-install the carpet and seats...

She turns over on the key just fine, but does not fire.

With the ignition key ON - I have no voltage showing at the coil. Should I? Seems I should.

It sounds like it ran before the seats went in - double check the ECU and DME under the driver's seat.

Do you have spark? pull a plug wire, and connect an extra plug with a jumper wire to ground the case of the extra plug, turn the engine over - the plug should spark.

Do you have fuel pressure with the key on? There is a port at the rear of the left fuel rail, or you may be able to disconnect a fuel line and route it to a bucket.

It's hard to read the voltage pulse on the input side of the coil, unless you have an oscilloscope to see the pulse waveform from the ECU.

I never touch the gas pedal when starting mine, because I have flooded mine, and it would turn over but not start. The next day it would start OK.

Mike

[E Sully]

The coil should have power when the key is in run and start position. You cannot check it across the 2 coil leads. The green lead on the coil is the DME trigger ground. It works like the points opening and closing to trigger the spark. You have to check the black lead to a good chassis ground.
Without knowing how the conversion wiring was done or any pictures makes it very difficult. Which fuel pump was used, where is the fuel pump located and how was it wired. If using the original pump feed it would run when the key is turned on. If the R/Gr wire from the DME relay was used it will only run when the key is turned to start, and then the DME keeps it running when its sensors see rotation. Removing the DME relay and putting in a jumper wire will make the pump run if the relay is bad. Even if it isn't, a spare relay is a must. The relay can be opened and resoldered to eliminate one of the main problems that cause the relay to fail.

[Tspringer]

Ok - THANK YOU for all the replies and help so far, lots of good info.

I have done some more testing and fiddling with it. No obvious problem discovered. It is baffling that it fired up first thing - really surprising me - when I still had it up on jack stands and not tidied up. Then next go - nothing. Still nothing.

Here is what I have learned so far -

1. Using a spare spark plug, I attached a spark plug lead to it and then grounded the plug body to the chassis and attempted to start. Engine turns over normally but no spark shown at the spark plug at all. So I assume the issue is spark and not fuel.

2. The fuel pump comes on with the key. It turns on and off immediately with the key and does not appear to be associated with the DME relay at all. I jumped #30 and #87 on the relay plug and it did not cause the fuel pump to run. The fuel pump runs continuously if the ignition key is on. So it seems the fuel pump is still wired as per original 1973 and not tied into the DME Relay.

3. I am getting 12V at the coil. I attached the positive lead from my multimeter to the black wire on the coil and the negative lead to ground. With the ignition key on I get 11.9V at the black coil terminal.

4. DME Relay - testing here... Relay plug terminal 30 is always hot. That would seem correct. Relay plug 86 shows 12V when the ignition key is on which also seems correct. Relay plug 85 is grounded. When the ignition key is switched on, I can feel two distinct relay actions taking place inside the relay - one when the key is turned on and another when the starter is engaged. The car does not fire.

I am shooting some pictures of the wiring and some question areas, will post those in just a bit. I am at a loss as to what to test or try next. Seems very strange to have run and then quit.

[kodioneill]

Reference and position sensors hooked up with good connections? Did you knock off a wire when installing seats?

[E Sully]

It sounds like the fuel pump is definitely using the CIS connection still, so the fuel supply should be good.
I have read in the past where the electrical connector for the injectors on the drivers side by the rear shock tower came apart. Check to see all the harness connections are good.

[Tspringer]

Still working to try and track this down. Below are some photos to wiring questions and possible issues.


















Thanks for the help, this one is baffling!

[Tspringer]

Here is a diagram of the wiring that goes to the coil. Most of it is not used. IS this correct?

[E Sully]

I don't have time right now, and will look over it later.
The 2 brown wires by the DME should be left disconnected. It is only for emmissions in California.
Last picture of Cylinder head temp sensor, it is the old single wire. Newer type is 2 wire and performs better. Would still run, but mixture would be off.

[E Sully]

A quick reference diagram for you.

[Tspringer]

E Sully - really appreciate your help and thoughts on this. I can replace the cylinder head temp sensor. I can also order a DME Relay but I dont think that is the problem.