No Spark

[hosmerb]

I have an '86 with an '87 engine that has sat for 8 years. I'm going through it and when I try to start it, much like most of my high school dating career, I get nothing.

I jumped the DRM with no luck. I pulled a plug, grounded it and got no spark. I tested the coil with an ohm meter and it met specs. I moved on to testing the RPM and TDC sensors and found the RPM sensor to be bad. When I test pins 8 and 27 the meter starts at 1550 and then just keeps increasing. I assume this is bad though I don't get why the meter doesn't settle on a number. Either way, when I test the voltage coming off the sensor while cranking the engine, I only get .14v which is way low.

I'm trying to confirm the diagnosis. Is there anything other than a bad sensor that would produce those values and is there anything else I should check while I'm pulling things apart. I'm guessing this car has no points or CDI because all that is handled by the ECU. I put the meter on the negative terminal of the battery and the engine block and it read 0 which I think means the grounds are okay. Outside of checking the fuel injectors and fuses anything else?

Regards,

Hosmer

[John_AZ]

How much have you put into parts?
I see you have a $500 budget until you part it out.
Oprv

With this in mind, I think you should begin to part it out.

With "no spark" the cost will climb rapidly if you need a new/used main computer, aka DME.

In addition to reading Clarks Garage information on trouble shooting,
Clark's Garage Home Page

here is a "No Start Checklist"

Let start a NO START checklist

J_AZ

[hosmerb]

I'm at $398 so $102 left... Plenty! Thanks for the links, I will run down the list. One thing though, any reason the ohm meter kept creeping up?

[nynor]

if you have a sensor that is bad, i don't think you are going to get spark.

[John_AZ]

Right ^.

Basic test.

The tach needle will bounce 1/16th of an inch while cranking if the reference sensors are OK.

So with a charged battery, all wires hooked up, crank the engine and watch for the slightest tach needle movement.

J_AZ

[dodger1]

Tach bounce also assumes the DME has battery and ground. Unless the car was parked eight years ago because it didn't run I would not expect a sensor problem - not even the one with the funny reading. I suspect a poor connection somewhere. You need a wiring diagram or at least the pin-out designations for the DME. With the pin-outs in hand disconnect the DME and check the harness end with a 12v test light (not a meter) for battery and ground on all the correct terminals with the ign. in "run" position and in "start" position. The test light helps you see if it is a good ground or battery signal better than the best meter. I used to do electrical testing for a living and have been fooled by my meter more than I wish to admit. It's got something to do with the current draw of the test light I'm sure. Of course one must be careful when testing sensor leads with a light with the DME plugged in. Let us know how you make out.

[911tracker85]

I picked up an 86 951 project car with a rebuilt 87 engine/long block in the bay and all the other parts in boxes.

in my case I got it running, went for first drive and it died.

initial check showed no spark. initial suspicion was something pulled loose or something broke on the wiring harness.

long story, finally figured out the new COIL went bad.

I also replaced my crank/speed sensor as the tach needle would not bounce. that turns out to be someting causing the tach to not work and not the sensors. still need to figure that out.

OHM readings are one thing, but to finally convince myself the crank/speed sensors were sending good signals to the DME I used an O scope at the DME connector end to verify. those signals are low voltage and happen (on/off) so fast the volt meter just cant show them. and had also put my DME in another guy's 951 to confirm it was OK.

did you also check to verify you are getting 'triggering signals' (cant recall correct term) at the coil? that is how I found my bad coil. power to the coil lead and flashing pulses on the triggering lead, but nothing coming off the coil.

so got it running ... again... and putting on break-in miles when the clutch started making noise (thinking TO bearing) and shuddering. so it is back on the jack stands and new SPEC stage III clutch kit and alum flywheel on the shelf waiting for me to start that project.

good luck.

[hosmerb]

The only check I did on the coil was with an ohm meter.

I finally had time to work on it so I pushed the PITA into the garage, again. If I keep this up I will have incredible hulk legs soon. I disconnected the sensor from the harness and put the meter on it directly. I confirmed the readings. Its my understanding that if the sensor is out of perspective, I will get no spark so that is what I'm focusing on.

Now if I can only get the thing out... any hints on that would be much appreciated. I stuffed a 17MM wrench down in there to get it to turn which was a bear. I've been spraying it with PB Blaster in the hopes that she will free up. I don't see how I'm going to get this thing out short of a drill.

[hosmerb]

Was able to replace the sensors with much effort which cured my no spark problem. Thanks to all for your help.