Help car wont start! (84 Carrera)

[dimeified]

I want to give you a history of recent changes and such, and test's i've done to narrow down the possibilities for you guys to help me.

About 3 months ago i replaced my alternator + fan after an accidental "not enough shims" mistake changing a fan belt. Broken alternator cured.

About a month ago i changed my idle valve to hunt down a "hunting idle" issue thats always been there as long as i can remember. Hunting idle cured. However the new valve sticks after a while causing me to have to hold the gas pedal at startup to keep the car from dying the second it fires. Waiting for replacement from pelican.

Recently my tach started jumping. Being i bought a Paris Rhone alternator from Eagle Auto Electric on ebay to hold me over until summer until i could afford a good one from pelican, i figured the Voltage Regulator was the problem. I bought a valeo regulator from pelican and put it on the car. Tach issue did not dissapear. Chalking it up to possible co mixture which i still need to have analyzed per Zonas's recommendation.

This week i installed a new stereo head unit and kenwood subwoofer under the passenger seat of the car. After a couple days driving around to and from work, car almost wouldnt start leaving work. After a couple tries it started. I made it back to my apartment in NY. Went to start this morning, car would not start no matter how hard i tried.

Facts to help you guys help me...

1) Car cranks.

1) Battery reads a lil more than 12 volts across the terminals. I think it was 12.4.

2) From battery neg post to random chassis points volt meter reads 0 volts. So that would mean when i reconnected the ground strap to the battery after the audio work, it has a good connection.

3) After several tries of starting, i can smell fuel in the engine cabin, and i hear a slight pulsing hum from under the dash near the firewall. Fuel pump should be ok.

4) Tried to arch a spark from a plug wire to the intake runners while cranking. No spark. Tried it from the coil wire to the intake runners. No spark. Coil is powered by dme relay.

5) Idle valve does not vibrate. Idle valve is powered by dme relay.

6) Removed distributor cap, rotor and cap look clean. Rotor is in tact.

I am guessing (hoping) that the vibration from the under seat sub rattled the ***** out of the dme relay causing it to fail. But then why would i hear the fuel pump operating? I thought it was controlled by the relay as well?

If you guys have other suggestions to narrow down the problem, feel free.

Oh yes, in between tries at work i wouldn't shut the key completely off so the sub and cd player would still be shaking the cabin. Hence my sub causing the dme relay theory (thinking specifically weak solder joints in the relay shaking around).

[S ECU Repair]

i will check the reference sensors

[rusnak]

I would add a good multimeter and the Bentley manual to your parts order.

Did you try a new DME relay? Also check your grounds (1 in the front trunk next to fuse box, one on intake runner #1, and a third in engine compartment next to fuse board), and clean them with a brass brush if needed. To me, 12.4 volts is low. The Motronic system needs sufficient voltage to operate, but I doubt that is causing the problem.

[dimeified]

I have a good multimeter. I havn't tried a new relay. I wanted to try to be as sure as possible that it is the problem before replacing. I am going outside now to try the Screw Driver Whack TSB. Brb.

[ischmitz]

Originally Posted by dimeified

Recently my tach started jumping. Being i bought a Paris Rhone alternator from Eagle Auto Electric on ebay to hold me over until summer until i could afford a good one from pelican, i figured the Voltage Regulator was the problem.

A DVM would tell you. Why guess?

Originally Posted by dimeified

I bought a valeo regulator from pelican and put it on the car. Tach issue did not disappear. Chalking it up to possible co mixture which i still need to have analyzed per Zonas's recommendation.

This is wired. If the tach only jumps it's electrical. If the engine hunts or stumbles and the tach correctly indicates that it could be a mixture-related problem.

Originally Posted by dimeified

2) From battery neg post to random chassis points volt meter reads 0 volts. So that would mean when i reconnected the ground strap to the battery after the audio work, it has a good connection.

It is very difficult to identify a bad ground with an Ohm meter. Typically corroded ground straps show problems under load. Your Ohm meter test is inconclusive at best. Furthermore, do not understand your test setup. Did you try to measure a voltage while the ground lead was not connected to the battery?

Originally Posted by dimeified

4) Tried to arch a spark from a plug wire to the intake runners while cranking. No spark. Tried it from the coil wire to the intake runners. No spark. Coil is powered by dme relay.

If the DME relay switches on during cranking and powers the fuel pump it is not broken - the reference sensor could be a problem like said earlier since you do not get a spark. Other than that check your ground and the ground strap between the engine and the transmission.

Good luck,
Ingo

[dimeified]

HO LY *****! I tried the Screw Driver Whack TSB as i read about in another forum, and the car fired right up! No this wasn't a joke. Thanks for your help guys! I only just had access to my voltmeter today so i will be sure to check the tach problem out with it after i replace the relay.

[scottb]

Probably not a bad idea to order two new DME relays...one to install now and one for the glove box as an insurance policy.

Congrats on getting it running again.