Crank Sensor Location on a 94

[___Brandon]

Where is the crank sensor located on a TBI 454? On a 350?

[jdl]

No crank sensor. The rpm signal should come from the distributor. Purple wire with white tracer carries rpm signal from distributor to computer.

What's the problem?

[___Brandon]

No spark is the problem. I had the Ignition Module tested and it showed good. I swapped in a different working ignition module and coil. No spark no matter what.

A friend was telling me that there isn't a crank sensor also. I got confused because autozone's website actually shows a part # for a crank sensor for that motor. That sent me right down the wrong path! My friennd was saying there is a magnetic pickup in the bottom of the distributor that I need to check into.

If I put a test light on that purple wire and roll the engine over should I see a pulse?

Can the pickup be replaced or do I need to repace the whole distributor?

Thanks

[brcidd]

Do you have spark on the coil wire? if so distributor cap is highly suspect.

[j cAT]

Originally Posted by ___Brandon

Where is the crank sensor located on a TBI 454? On a 350?

get a voltmeter and check for power at the coil. and other components ignition on..

[Schurkey]

My '88 K1500 had an intermittent spark problem that was only resolved with a replacement distributor shaft.

A replacement distributor would accomplish the same thing, provided it's in usable condition.

As said, your first step is to verify power to the coil. Since the power connectors are all sealed, you'll have to remove them to test for power. It's not a great way to do it, but you probably don't want to buy the proper test adapters; or to pierce the wire and potentially introduce a corrosion-point.

The distributor is powered by a pass-through from the coil.

If this were in MY driveway, I'd
1. Remove the coil wire from the DISTRIBUTOR CAP, put a spark-tester on the coil wire,
2. pull the distributor cap and rotor,
3. unplug the pickup coil,
4. turn on the ignition, and
5. use a test light to activate the module.

Connect the test light wire to battery + or the alternator output terminal (whichever is more convenient) so the point of the test light is "hot". Test light lights-up when you touch the point to GROUND. Then, touch the point of the test light to the terminal of the module that the green pickup-coil wire was attached to. You should get a spark every time you REMOVE the test light from the terminal. If you do get a spark when you remove the test-light, the pickup coil is faulty. If you do NOT get a spark when you remove the test-light from the module terminal, the fault is in the module, coil, or power supply.

This photo is from an older version of the HEI, yours won't look like this--but you get the idea. Your module will have eight terminals, but you're only concerned with the two little ones on the back side that the pickup coil plugs into.


HEI diagnosis is the second part of this article:
http://www.chevelles.com/techref/ftecref5.html
The article is primarily focused on the older-style HEI.

[___Brandon]

Thanks! I hooked up the test light like you said and the coil sparked everytime I touched the pin that the green wire goes to on the ignition module. It must be the pickup.


I'll make sure to make another post once I get the distributor swapped and let you know how it turns out.

[___Brandon]

It was the distributor pickup. I dropped a new distributor in and it started right up like it never had a problem. I set the timing and it seems good to go.