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New CPS, Still no start

S

sdigs

NAXJA Forum User
Location
Albuquerque, New Mexico
94 4.0L HO AW4. i drove to a friends house yesterday, parked the Heep, turned it off and 45 minujtes later came back out to leave. Just as the engine was starting to catch i let off the key. After that It cranks but no spark. The coil ohms out good. The CPS tested bad across B+C. Thought i had it figured out so i replaced the CPS. Still no spark. Do i have to disconnect the battery to "Reset" something. or do you think i am looking at another issue.

How can i prove the coil is getting 12 volt. The primary plug on the coil is "sealed" and i cant se a way to attach a multimeter without disconnecting it.
 
You can get a cheap ignition tester from Harbor Freight. It plugs inline between the dist cap and the plug wire and the bulb should flash every time the spark is sent to that cylinder.
I picked up one to put in my truck in case I have another bout of crank but no start. It happens about once every 45 days and is a PITA to troubleshoot. I'm coming up on 30 days now...
 
I would think you could watch the tach to see if it bounces around while cranking. The tach feed is an output from the module so no power=no tach signal.
You could also unplug the connectors and jumper each prong with a piece of wire. I did this to adjust my TPS and it works ok provided you leave enough bare wire and have a little patience. Sometimes it takes some trial and error to get the wire to stay in both the male &female end of the connectors. Then it's very easy to probe with a multimeter.
 
sdigs said:
One more question, is it possible to install the CPS backwards? in other words with the wrong side of the sensor towards the flywheel?
Click to expand...

I don't think so, but the ingenuity of mankind never ceases to surprise me.

On your 94, across B and C is supposed to be infinite resistance with the meter set on 1k to 10k scale, so is it safe to a**ume that is what you found?

The coil gets its 12 volts from the ASD relay in the PDC, that is where you could test for voltage and then disconnect the lead on the coil and check continuity on the wire.

Just for grins and giggles try swapping around the relays--after you first mark them so you can put them back--and see if that gives you spark.
 
Make sure you have the CPS seated properly against the flywheel. I have had that problem in the past. I didnt get it all the way down.
 
bigalpha said:
Why do this?
Click to expand...

Why swap around the relays or why mark them?

Swap around the relays to see if the no spark is due to a bad ASD relay.

Mark the relays so IF the spark problem is fixed by swapping the relays he can hopefully determine which relay is the bad one.
 
Sorry - to mark them. would you move them around more than once? I kind of figured that if you swapped the relays and then you got spark/start then you'd know which one was bad.
 
bigalpha said:
Sorry - to mark them. would you move them around more than once? I kind of figured that if you swapped the relays and then you got spark/start then you'd know which one was bad.
Click to expand...

I'm either annal retentive or a pessimist. Worse case, more than one bad relay. As I don't know the relay arrangement in his model/year, I can't tell him which is the ASD, the fuel pump, the oxygen heater, the a/c.
 
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