Another 3.2 Carrera no-start thread

[dtw]

My Carrera has some kind of battery drain. I was working on diagnosing it today and disconnected the battery a few times while I worked with my multimeter.

When I buttoned everything back up, the car would not start. Starter runs fine, but the engine will not catch. Everything else seems to be fine electrically...stuff like the stereo and the window regulators are working.

The battery is fully charged and the car started up with no issues earlier today.

What did I do? Blow up the DME relay or the DME itself ( ) or something?

[rick-l]

You are supposed to be able to see if the DME is powered by feeling if the Idle Air Control Valve vibrates.

[3.2 CAB]

A question or two:

You state the starter runs fine.

You state that the engine will not catch.

Are you saying the starter motor is running, but does not engage the ring gear to turn the engine over? Or, the starter is working fine, and is turning over the engine, but... the engine does not start? If it is the starter turning but not turning the engine over, it could be a starter problem. If the starter is turning the engine over, but it is not starting, it could be an assortment of problems. Do you know if you are getting fuel? Can you smell gas at the exhaust, after a starting attempt? Have you checked for spark? If no fuel odor, or no spark, it could be the DME relay. Try a known good DME relay. If, with the known good DME relay, the engine still does not start, check for fuel odor again after a starting attempt. If no odor, you might have a fuel pump circuit issue. If you can smell fuel, but engine still does not start, check for spark. If no spark, it could be anything from the DME control unit, to a reference sensor being bad. Hope this helps a little to nail it down. Good luck!! Tony.

[dtw]

Rick - I'm a relative newbie to DME. Am used to CIS and MFI (no expert on those either but I can usually troubleshoot a no-start). Where is the idle air control valve? Under what condition will it vibrate - ignition on, or do I need to be cranking.

3.2Cab - no issues with starter or ring gear. The engine will turn over on the key but will not fire. The only thing I did yesterday was disconnect the battery cables a few times will figuring out where my amp draw was coming from. Reference sensors are both replaced within the last 2k miles.

After about 5 seconds of cranking I did try sniffing the tailpipes and didn't smell any fuel. Didn't have time to check for spark. I'll pick up a spare DME relay this week and try that first.

[Rot 911]

Go with the DME relay first as it is the easiest and cheapest fix. I can't imagine what the problem would be as I disconnect my battery all the time and never have problems.

[dtw]

OK, I swapped out with a new DME relay and still no start. After 10-15 seconds of cranking, I can clearly smell fuel at the exhaust tips.

[ischmitz]

IF you can feel the ICV vibrating with the key to ON and you are positive that you get fuel smell after prolonged cranking at the exhaust you seem to have lost spark. This is not a sensor issue or a DME relay issue since a missing sensor or bad DME relay will prevent fuel AND spark.

Things to check are:
Cap, rotor, coil resistance Bad Coil?.

If all checks out you might have a damaged DME box (the large silver box uinder the driver's seat). Turn your ignition to ON and feel if the coil gets very warm - a sure sign for a broken DME.

Ingo

[ischmitz]

Originally Posted by dtw

Rick - I'm a relative newbie to DME. Am used to CIS and MFI (no expert on those either but I can usually troubleshoot a no-start). Where is the idle air control valve? Under what condition will it vibrate - ignition on, or do I need to be cranking.

The ICV is a silver cannister that sits on the intake in the center of the engine. It has about an inch and a half diameter and two rubber hoses and an electrical connector. It will vibrate as soon as the key is turned to ON (not cranking) and indicates that the computer in the DME is powered (good first stage of the DME relay). With that you can safely exclude the factory alarm or a catastrophic failure of the DME to be the root cause.

Then, once you crank the fuel pump and the O2 sensor will get powered. A test light on the right fuse will confirm that and give the DME relay a clean bill of health.

Next, if the DME receives proper signals from the speed and reference sensors it will produce fuel injector and spark signals. If one is missing while the other is present it is either something downstream (fuel pressure regulator, coil, rotor, cap) or the DME is bad. Sal has posted a nice tutorial to confirm the signals for coil and fuel injectors with an LED test light. Do a search - it was just the other day.

Ingo

[dtw]

Originally Posted by ischmitz

IF you can feel the ICV vibrating with the key to ON and you are positive that you get fuel smell after prolonged cranking at the exhaust you seem to have lost spark. This is not a sensor issue or a DME relay issue since a missing sensor or bad DME relay will prevent fuel AND spark.

Things to check are:
Cap, rotor, coil resistance Bad Coil?.

If all checks out you might have a damaged DME box (the large silver box uinder the driver's seat). Turn your ignition to ON and feel if the coil gets very warm - a sure sign for a broken DME.

Ingo

Thanks for the posts, Ingo, I appreciate it. I get to do work on this in quick little 10 minute bursts as I have time. Tonight I turned the key to 'on' (just before cranking). The ICV did not have any noticeable vibration, and the coil stayed ice cold. I left the key at 'on' for a minute or two.

Guess I'm off to pull up those threads you referenced. One other thing: battery connections. On the positive side, there's the main starter cable, then some lighter gauge ancillary connections on the other side of the positive terminal. With the main starter circuit connected, I did disconnect and reconnect those smaller connections. Would this possibly have fried something?

Oh how I hate electrical work...

[ischmitz]

If the ICV doesn't vibrate you have no power to the DME. I am not terribly familiar with the battery hookup on a 3.2. In essence once you turn the key to ON (oil light comes on, etc) you provide power to the first stage of the DME relay. You should hear it click. When you put your hand on it while you turn the ignition to ON you can feel it switch. The DME relay in fact powers the DME. And once the DME has +12 V on pin 18 and pin 35 it will operate the ICV with an 80 Hz signal.

So when you put your hand onto the ICV and do not feel anything that is a sure sign you have missing power to the DME box (or a bad DME, unlikely but not impossible). What baffles me is that you say you smell fuel when you crank. I don't see how that is happening without the DME being energized.

Ingo

[dtw]

Just to close this up, maybe we should add this to the "Admit your stupidity" thread.

Ingo nailed it with 'no power to the DME'. I doublechecked by grasping the relay while I switched the ignition on and off. Nada. Headed back up to the trunk and checked my connections. All were fine. But wait, they look a little light. Poke around some more. Hmmmm, what's this cable going under my battery? Yep, it is the DME power cable that got stuck under there when I reinstalled the battery. Connected it back to the battery, turned key, fire. Score...still can't find my battery drain, though. That's another thread...

[wolf]