Crank no start - round 2

[ChrisVCR]

After chasing down a "crank no start" situation over the last few weeks, I thought it was finally resolved after having the DME rebuilt by Pelican. Car is 1984 Carrera Targa, stock.

I had confirmed that fuel pump was working, replaced DME relay, replaced reference sensor, confirmed coil was working yet still had no start and no spark. A local shop confirmed that the DME was at fault. After receiving back the repaired DME, I plugged it in and it started right up. I drove it around later that evening and all was well.

The car sat for about two weeks while I traveled for work and after returning.. no start.. crank.. but no start. I double checked everything and it all seemed to test fine, I even replaced the coil and still no start.

Any thoughts!!??

[Chuck.H]

Well, it could always be the newly repaired DME has failed - can you confirm it's not starting due to no spark?

Chuck.H
'89 TurboLookTarga, 370k miles

[ChrisVCR]

Confirmed there is no spark when I do a test plug.

[Chuck.H]

Another cause for 'crank but no spark' is failed reference or speed sensors, as the DME doesn't know the engine is spinning without these. Not easy to test, but you can check them for resistance; the electrical connections are there on the left side of the engine.

They will also not work if they are too far from the flywheel -- any recent work that may have disturbed these?

Chuck.H
'89 TurboLookTarga, 370k miles

[Joe Bob]

Is the DME RELAY clicking when you turn on the ignition? If it is, the DME box is good. If not, the relay is bad or you are not getting 12v to the box.

Pelican "ischmitz" is a good resource for testing. He helped me when I was toast in Reno at about this time of the year. I learned a LOT trouble shooting. I ended up having an intermittent short in my fuse box, supplied 12v power to the DME.

The relay, clicked....but when the starter engaged it shorted the power to the DME. New wire and fuse solved the problem. The symptoms made the DME relay continuously click while cranking.

[ChrisVCR]

I am not getting any clicks from the new DME relay. Possible it has gone bad already? Other than something being wrong with the new reference sensor that I put in, all things lead back to the DME relay (new) or the DME itself (newly refurbished)??

[Joe Bob]

I would get a wire diagram and start checking power into the DME.

[ischmitz]

The DME relay needs to click once when you turn the key to ON. That powers the DME. In that condition (engine not running) the ICV needs to vibrate.

Once you crank the DME relay needs to click again (powering the fuel pump and the O2 sensor).

Do these checks and report back.
Ingo

[3.2 CAB]

It could be as simple as a bad relay connection. Make sure the tabs on the relay are clean, as well as the socket they connect with. I had a similar no-start/no spark problem a while back. Good luck, Tony.

[ChrisVCR]

The connections on the relay (its a new one) the relay connector (it is as clean as new) and even the DME harness look great.

I am not getting any clicks with this relay, I will try to confirm if the ICV is vibrating today.

[ischmitz]

Does your car have an alarm system? If so check it and make sure it isn't triggered. Next, check that your ignition switch is working fine. You didn't mention it so I ask: Do all the light come on when you turn the key to ON? Then verify ground points.

You seem to have no power to the DME and need to find out why.

Good luck,
Ingo

[ChrisVCR]

Ok, I confirmed that the ICV is getting nothing. No vibration or humming noise.

I don't think it is the ignition switch as everything else powers up and the car cranks.

As for the alarm.... it could be? I have never used it and the PO said he did not either. I have never had it accidentally trigger. The small key does not seem to turn the switch in the door. Am I do the point where I need to take the door panel off and start checking alarm switch connections?

Will the alarm going bad cause a crank-no-start or simply cause the car to not power on as if it had a bad ignition switch?

[kidrock]

You'd be amazed at the problems an aftermarket car alarm will do to these cars. You may want to check to see if you had an aftermarket alarm installed. Check under the front hood, near the brake master cylinder. If so, check the main alarm box, all the wiring connections going into the box, and most importantly, the wiring that is tied in from the box into the ignition switch....especially the yellow (ignition) wire.

[ischmitz]

The factory alarm interrupts the +12V to the DME. So do many aftermarket alarms. Go figure.....