Car died right when I got home...Now it won't start

Enthuzed1 · 05-04-2009, 06:57 AM

Hey guys, so on my way home my exhaust pipe separated at the weld right behind the catalytic converter (LOUD). Drove it home (about 30 min) Pulled up to the curb and right when I hit reverse and gassed it to align the car.....it just shut off. I thought i just didn't gas it enough (im on a 35 degree incline) but when it tried to start it, no go. I tried again this morning and still the same. Engine turns but no go. I'm gonna check the vacuum and sensors and such right now. DME relay is 3 years new. Thanks!

Enthuzed1 · 09:51 PM

So I don't have spark and my plugs smell of gas. There's some black residue on the contacts of the distributor cap. Is it possible that the computer overcompensated for the extra air flow some how? Maybe the oxygen sensor sent the wrong info causing more fuel and ultimately affecting my spark?

John_AZ · 05-05-2009, 04:57 AM

Good to check the sensor gap and the wire connection at the top of the firewall.
The 3 year old DME could be bad and you should get/build the 3 wire jumper DIY at Clarks to check for sure.

Do you have any tach bounce when you turn the key?

Check your belts. Check the top cam gear and make sure the cam bolt did not work loose.

In a previous post you mentioned electrical gremlins. There still could be a problem with the issue that was made worse when the tail pipe cracked.

The black deposit in the cap could just be normal contact spark or the top carbon post inside the cap may be deteriorating and the cap should be replaced. With the cap on the car, when you grab the cap does it feel loose? If it does, the hold down springs (2) have gotten weak. Also make sure the rotor is on tight.

The O2 sensor is very well built. If no signal you would be running rich at idle. This would not cause a no start.

GL
John_AZ
1988 924S + 1987 924S

Enthuzed1 · 05-06-2009, 08:09 PM

Alright so replaced the spark plugs, rotor and cap. I also did the wire bypass of the dme. Still no start.
When you say sensor gap, are you referring to the sensor above the bell housing of the clutch? if so, how do it determine the gap?
I will also check my belts and cam bolt as well. Thank you

Razorback1980 · Razorback1980's Garage

Checking the belts and cam gear bolt is a good idea if you know you have spark to the distributor cap, but before you go to that trouble back up a little further and check for spark in the main wire coming from the coil. You can do this by putting a plug in the coil wire and grounding the plug. If no spark there, then the distributor isn't the problem and it's time to look even further back. If no spark in the coil wire, then check the black wire going to the coil (terminal 15 I think) for 12V. If you don't have 12V there, then look to the switch key but let us know what you find with these tests and we'll give additional things to check. The reference sensor connectors should ohms through the middle pin and one of the two outside ones but I can't remember which outside one at the moment. Just check them both. You should also have power on the injectors, check that and let us know what you see.

John_AZ · 05-07-2009, 04:34 AM

Quote:

Originally Posted by Enthuzed1

Alright so replaced the spark plugs, rotor and cap. I also did the wire bypass of the dme. Still no start.
When you say sensor gap, are you referring to the sensor above the bell housing of the clutch? if so, how do it determine the gap?
I will also check my belts and cam bolt as well. Thank you

Just a repeat question, When you turn the key to start, does your tach bounce a little bit???? Did you clean the reference sensor connectors at the back of the firewall?

To check the sensor gap:

http://www.clarks-garage.com/shop-manual/ign-02.htm

GL
John_AZ

Enthuzed1 · 05-08-2009, 12:17 AM

Just checked today and my rpm tach does bounce a litte when attempting a start. What does that indicate in reference to my sensor?

John_AZ · 05-08-2009, 04:35 AM

Quote:

Originally Posted by Enthuzed1

Just checked today and my rpm tach does bounce a litte when attempting a start. What does that indicate in reference to my sensor?

Good!

It means that the reference sensor-the sensor closest to the firewall- is sending a signal to the DME computer and this will activate the fuel pump.

The gap should still be checked at some time.

Your second post mentioned the plugs smelled of gas. Your problem may be fuel related. The FPR-fuel pressure regulator.

http://www.clarks-garage.com/pdf-manual/fuel-07.pdf

GL
John_AZ

Enthuzed1 · 05-12-2009, 10:44 PM

Alright so I don't have a fuel pressure gauge. But I did try starting the engine with one fuel injector connector unplugged. I did that both with the dme and dme bypass just to eliminate the dme being faulty.

It was still a no start. I guess i'll have to get a gauge. And the journey continues

Razorback1980 · Razorback1980's Garage

Go back to the basics. It takes four things to make an engine run. Spark, Fuel, timing and compression. It seems you don't have spark so start there and fix that. No reason to check the fuel if there is no spark to ignite it. Try these tests.

Check for power at the coil and at the injectors with the key on.

No power at the coil it's the ignition switch or related wiring.

No power at the injectors it's the DME relay. Sometimes the wiring harness breaks and you won't have power to all injectors so test all of them. You can wire around the DME relay by making a "Y" wire and jump across terminals 87 and 87b and then plug it into terminal 30 last.

Power at the coil and injectors points to a bad reference sensor. The connector may be corroded and/or not plugged in all the way or cracked and may have broken the wires inside. Check for tach bouncing here as well. You already checked this somewhat so this probably isn't your issue.

No spark can also be the HV wire from the coil to the dist cap. Can also be a loose or broken rotor. Can be a broken timing belt not turning the rotor. Take the cap off and make sure it's turning. Usually if it's the timing belt you bent a valve and the motor will spin very fast. The ignition switch is also a suspect here as it could provide power to the coil in the on position but not in the start. Clip a test light on the coil and see if it has power while key is in the start position.

In most no start cases it's not the coil or the wires or the dist cap or the rotor. Usually the DME relay, ignition switch, reference sensor(s), broken timing belt then fuel pump. The DME is also a possibility but it's way down the list.

Do those tests and let us know what you find.

Enthuzed1 · 06-17-2009, 07:04 PM

Hello. Does 10.5 volts at the ignition coil sound right? Cuz that's what i'm getting. Resistance readings were no where near .4 to .6 unless I was testing it wrong. But I know that I did the voltage test correctly.

Enthuzed1 · 06-17-2009, 07:19 PM

Also on a side note, I got a fuel damper in addition to the FPR. Is the fuel damper bolt supposed to be difficult to remove? because I'm holding the larger nut and when I rotate the smaller nut, it just rotates the whole damper. Should I try to use some penetrant or something? Or am I missing something?