No start

[89325iturbo]

Hello everyone, new to the forum. Recommend to join here.
Here’s my issue, 86 turbo no start.
Up until this point it has never not started or died when driving or anything.
But I went to start it this weekend, just cranks. Battery is probably a touch weak, volts are in the 12.2-12.3 range. Cold here aswell 20’s in th northeast.
Anyway appears to have no tach bounce, but when turning the key off the needle bounces.
So good chance one of the reference/speed sensors not working.
I did replace the sensor closest to the engine block. ( was crumbling at the plug in connection) that was around a year back so was running fine after that. I was going to change the other but it was seized in the bracket. Looked ok so left it.
Other thing I remember from the last few months is it was hard to start sometimes after warming up. Usually it would be when I was getting gas. Since I was trying to start it a few minutes after shutting it off.
So not sure if that correlates. I assume it was an injector leaking a little or pressure bleeding off at the rail. Maybe dme relay?
What are your thoughts? One of the sensors? How do you check with a multimeter?
Thanks-

[Tom]

Hello everyone, new to the forum. Recommend to join here.
Here’s my issue, 86 turbo no start.
Up until this point it has never not started or died when driving or anything.
But I went to start it this weekend, just cranks. Battery is probably a touch weak, volts are in the 12.2-12.3 range. Cold here aswell 20’s in th northeast.
Anyway appears to have no tach bounce, but when turning the key off the needle bounces.
So good chance one of the reference/speed sensors not working.
I did replace the sensor closest to the engine block. ( was crumbling at the plug in connection) that was around a year back so was running fine after that. I was going to change the other but it was seized in the bracket. Looked ok so left it.
Other thing I remember from the last few months is it was hard to start sometimes after warming up. Usually it would be when I was getting gas. Since I was trying to start it a few minutes after shutting it off.
So not sure if that correlates. I assume it was an injector leaking a little or pressure bleeding off at the rail. Maybe dme relay?
What are your thoughts? One of the sensors? How do you check with a multimeter?
Thanks-

Here is a basic test for the sensors. It's not going to detect every fault, but will find the most likely issue -- i.e., frayed/shorted wires in the harness.

https://www.ecudoctors.com/pages/porsch ... ensor-test

The great majority of the time, no tach bounce means the DME is not getting a good speed and/or ref signal. And when that happens, it's almost always due to frayed wires inside the rubber boots behind the connectors. But here's the thing, when you replace the sensor, you are only replacing one half of the connector. The other half is in the engine harness and is a very common problem. Read all about those connectors here. 944online.com (and others) sell patch cables to repair the factory harness, if needed.

Wiggle the wires when someone cranks the motor -- sometime you can jiggle the frayed wires enough to start the motor. That's not a fix, of course, but is useful to isolate the problem.

When the DME relay goes bad, you don't get any power to the DME/KLR. If your boost gauge goes to about 1 when you turn the ignition on, that's a very strong indicator that your relay is working. If the boost gauge doesn't go to 1 with the ignition on, then focus on that -- typically DME relay, faulty alarm, or bad ignition switch.

[89325iturbo]

^^^Thank you. When I have a moment I’ll check and report back.

[Richey]

What is is the condition of you your plug wires? Mine were breaking a part just by moving them around. Plug wires were on of the few reasons for my crank no start. Even thought my spark plug test light was illuminating it wasn't until I had replaced the cap, rotor and plugs that it finally started.

[89325iturbo]

I got a moment to take a look at my car. I remembered that I had bought a spare dme relay just haven’t had to use. Then I ordered just a dme temp sensor.
Figured I’d try these couple things first since it takes just a few minutes.
It did start right up. So whether it was one of those causing the issue or just coincidence that it happened to start this time.
Some more checking of things will have to be order. But for the moment it was nice to have it fire up.
As far as plug wires, there not new by any means but don’t look bad either.