Carrera No Start; Motivated by Greed to Not Throw in The Towel--Yet

[MOMO3.2]

I am starting over fresh and with new resolve to solve the "No Start" problem on my 1987 Carrera that left me stranded a few weeks ago. If I can get this problem solved DIY, I will be able to justify a much needed re-upholsterey of my manual Sport seats with fancy tartan inserts...

So, I am pleading to all Carrera Motronic experts to kindly help me in my quest.

I will first Recapitulate what has transpired: I was waiting at a light after driving for about 1/2 hour when my car suddenly sputtered as if it were gasping for spark or fuel. I pumped the pedal and it died after 3-5 seconds. It turned over normally as I tried to re-start, but never even hinted that it might fire. I towed the car home and bought a new DME Relay from Pelican Parts. That did nothing for me. I fumbled through a few checks, but I feel I need to start over at this point from square 1.

Here is where things stand today:

(1) I have a 12.48 V at my battery terminals.

(2) I have a 12.18 V at the wires that lead to the coil when the coil is not connected and the ignition is in the "on" position.

(3) I have a 1.0 V reading with the wires connected to the coil and the ignition in the "on" position.

(4) I have a 0.0 V reading with the wires connected to the coil and the ignition in the "off" position.

I have a new multimeter (to cross check the $5.00 unit I bought at HFT). My battery is an 8 month old Odyssey PC 680 that has worked flawlessly. My coil is brand new.

I genuinely appreciate the help of anyone willing to guide me on this journey through electrical hell!

Sincerely.

Mike

[tonythetarga]

two things come to mind. Hopefully things you haven't already eliminated.
The AFM sensor on the intake OR the DME itself, not just the relay. Both will give you crank but no start symptoms.

[nineoneone]

Reference sensor

or (new)bad relay
I had to fold a piece of paper (matchbook cover) to fit inside the dme relay and close back up...

Looks like this V-----] v is paper dotted line circuit bd.


I have not had any issues since then. But , probably reference sensor..

[ischmitz]

Mike,

I might have missed that but first you need to find out whether you are missing spark or fuel or both to start the engine. That will decide your further course of action:

The cheapo way for spark is to disconnect one spark plug cable and hook it to an old used spark plug that is grounded to the engine or chasis. When your assistant cranks you should see a spark. Don't touch it in the process. There also little gadgets that you clamp to the ignition wire. These light up with each spark.

Next you need to find out whether the DME is no comanding fuel or spark or both. Then you can go on to find out why that is the case (sensors, DME, etc.)

If you don't do this methodically, you could overlook a simple thing like a clogged fuel filter or burned fuse for the fuel pump while throwing expensive parts at the problem.....

Good luck,
Ingo

[Carl_Boehme]

First I would check for spark. If spark then:
2nd cold start injector should inject fuel into manifold. Disconnect and allow it to inject into a cup or appropriate container.
3rd or 2nd you should be able to hear the fuel pump running. If not remove fuel pump relay and jumper 30 to 87 on the socket of the fuel pump (red) relay. 12ga stranded wire works well. This will cause the fuel pump to run as soon as the ignition is turned on.

Good Luck

[MOMO3.2]

Ingo:

I am pretty certain it is not a fuel problem. I get a strong fuel smell after cranking the motor over for a few seconds. I also previously connected the fuel pump fuse to 12V and I can hear the pump spin smooth and strong.

I did check for spark and have none. I am not even getting 12V to the coil. At this point, I have to deduce that there is something wrong between the battery and the coil.

Could it be ground wires, DME Relay, or ECU unit?

How do I proceed from here? Where/How do I check for ground. Can I check the new DME Relay with my meter? Can I check my ECU with a meter?

Mike

[Zeke]

Originally posted by Carl_Boehme

2nd cold start injector should inject fuel into manifold.

Good Luck

Motronics have a cold start injector?

[ischmitz]

Originally posted by milt
Motronics have a cold start injector?

NO

[tonythetarga]

Is there anyone near you with a similar year car? You could unplg your DME and see if it starts in another car. relacing a $400 part for no reason is no fun!

[SMC]

My 88 has a issue turned out to be a bad coil.

it check out OK on OHM meeter but was bad.

[jester911]

Very well could be a ground issue. Having no spark at all I would check this since you believe the coil and dme to be good.

[MOMO3.2]

Tony:

I would love to be able to hook an ECU that is known to be working up to my car. That would help me eliminate a bad ECU as the possible problem.

As asked earlier. is there a way to check my ECU with a multimeter? What grounds should I be looking at? And, can I check my new DME relay with a meter to verify that it is functioning properly?

Thank you.

Mike

[Early_S_Man]

Mike,

Do you have a Bentley manual?

A couple of important things ...

1. Your battery should be charged, because 12.48 Volts is not a fully-charged reading! Disconnect ground [or hot lead] and charge overnight. A good reading is 12.8 Volts or higher.

2. Your ignition coil should have +12 Volts at terminal # 15 with the ignition switch on ... it comes from a multiple at the luggage compartment fuse block, Black wire on this diagram below.

[MOMO3.2]

Warren:

Thank you.

My battery is charged to 12.89V. It just got a little low from cranking previously.

I do have a Bentley Manual. The reading I just took at the + & - terminals of the coil is 1.1V with the key in the "on" position. What does this mean?

Mike

[Fast951]

Some of things that could cause a no start, you will have to test each till you fix it.

- Speed and Ref sensors on the flywheel. One reads the flywheel teeth, the second reads a single set screw on the flywheel. You will need a scope to verify the proper operation. The DME uses this data to know what to do.
When cranking, does the tach move?

- Make sure engine is dry, no fuel anywhere outside of engine. Take out the fuel pump fuse, we do not need fuel for this test. Unplug one spark plug wire from a plug, install a spare plug, check for ignition. Check & install fuel pump fuse back in place.
* If you have spark, proceed to next step. If you do not have a spark, the coil and/or DME are bad.

- Next you have to figure out if you have fuel, procedure described above. Or simply loosen the cap at the end of the rail. Fuel will be under pressure, so have plenty of rags handy. If you do have fuel in the rail, you have to check to see if the injectors are firing (procedure described above).
* If you do not have fuel in the rail, bypass the DME relay, if still no fuel, pump is bad.
* If you have fuel in the rail, but the injector is not firing, bad DME.

EDIT: If you have spark or the injector is firing, the speed & ref signals are fine. You might want to leave the speed & Ref tests for last.

[Early_S_Man]

Mike,

The reading you are looking for at the coil should be taken between the + terminal of the coil and ground. You want to look at the Voltage available at the coil, not the Voltage across the coil!

[MOMO3.2]

I just realized that Warren--doh! The reading at the + and a ground is fine. I get 12.6V.

I need to check for spark coming out of the coil wire that feeds the distributor. What is the best (safest) method for doing this?


FWIW I checked the rotor in the distributor. It reads 1.15. My manual calls for 1.0. I assume that my reading is fine.

Thank you for sticking with me Warren. I really appreciate it.

You definitely get a big gold star if I can solve this.

Mike

[MOMO3.2]

I also replaced the distributor cap with a new one.

Mike

[Steve W]

Check for spark by with one of the spark plug leads and a spare spark plug, grounding the spark plug against the case. Have someone turn the starter and look for a spark. You should be able to plug one of the spark plugs onto the coil if you want to check for spark out of the coil.

[TroyGT]

I feel your pain Momo

If the spare plug on a plug wire shows no spark, pull the wire off the top of the distributor, roll back the insulation, and then hold it about a 1/2 inch from your intake runner ground point and have someone crank. You should get a really strong spark here. Make sure you don't hold it with your hand... use some insulated pliers. It's not as bad as it sounds. For sanity checks, I occasionally had my wife look at the spark in this manner just to get another opinion on the strength/color/etc of the arc. She had no problems doing this.

Open the distributor, pull the rotor off, clean it and the contact on the inside of the cap. Look for dark streaks inside the cap as an indicator of current running to a ground. Look for cracks in the cap. Re-test with spare plug on an ignition wire. I use #1 for convenience.

Next, check the sensor connectors on the left side of the engine compartment. Pull the retainer clip out so you can unplug the three sensor connectors. Check them for wear, cracks, etc... clean them if necessary. Re-attach and try cranking again. A faulty ref sensor can cause a no spark situation. If you can get your hands on a spare to test... that would be great as these go for $150 a pop.

Unbolt all your major ground points, clean, inspect, and re-attach. Two are on the left side engine compartment, one at the intake runner... easy to see, the other is behind the coil (if yours is mounted on the left inside fender well) toward the hood shock area. You'll see it with a flash light. There's also a main point on the transmission casing. These are all very important ground points to verify.

-Troy