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Delayed Spark! Help!

Digger87xj said:
Yes. however, you may well see a change, too. In my experience, when a sync sensor has failed, you will have to crank it long enough to the point you think it's really isn't going to start after all, and just then, it fires up and runs 'normal'.

crusier seems a bit cranky tonight.:dunno: I too have credentials to stand on that I won't tout here, but I have been a master tech for too many years.
My first XJ was an 87 and was a basket case when I got it. If there was a tech bulletin out, it had the problem that was outlined.

RENIX do crank longer than the late models, but there are long crank times and then there are loooong crank times.
Click to expand...

Haha yes thank you my friend. I'll pick a sync sensor and check back,
I will say that occasionally while I drive it literally feels like someone's holding on the brakes then it grabs and picks up. And an overall sluggish feel to the engine. Manual transmission. Any suggestions?

Really appreciate all the help guys!
 
cruiser54 said:
Why not TEST the sync sensor? There is a test for it. Or, just unplug it and see if there's a difference.
Click to expand...

Leave the connector to the sync sensor plugged up, back pin the connector and test for voltage, should be 5 volts between the blue wire and the white wire with a stripe. While the engine is cranking the volt meter should fluctuate. Works better with an analog volt meter.

If you still suspect the sync sensor, you have to repeat the test at the ECU connector.

I seriously can't tell any difference between when my Sync sensor is connected and not connected. Except maybe one time when I noticed a significant problem idling and reconnected the sync sensor and the problem disappeared after a couple of starts. I honestly don't know if it was the sync sensor or one of those occasional hiccups my Renix has, I never did get it to repeat.

I once (accidentally) drove mine for months without the sync sensor being connected and never noticed.
 
8Mud said:
Leave the connector to the sync sensor plugged up, back pin the connector and test for voltage, should be 5 volts between the blue wire and the white wire with a stripe. While the engine is cranking the volt meter should fluctuate. Works better with an analog volt meter.

If you still suspect the sync sensor, you have to repeat the test at the ECU connector.

I seriously can't tell any difference between when my Sync sensor is connected and not connected. Except maybe one time when I noticed a significant problem idling and reconnected the sync sensor and the problem disappeared after a couple of starts. I honestly don't know if it was the sync sensor or one of those occasional hiccups my Renix has, I never did get it to repeat.

I once (accidentally) drove mine for months without the sync sensor being connected and never noticed.
Click to expand...

Not surprised.
 
Starts on the fifth turn with the sync plugged in and with the sync unplugged it takes a noticeable amount longer to finally start.
But either way my engine roars when it finally does start, I don't have a tach so I can't talk rpms but it revs up pretty good then settles back down.
 
Starts on the fifth turn with the sync plugged in and with the sync unplugged it takes a noticeable amount longer to finally start.
But either way my engine roars when it finally does start, I don't have a tach so I can't talk rpms but it revs up pretty good then settles back down.
Click to expand...
That is unique to the RENIX also. Flare start is normal, so long as it comes right down to a lower idle right away. It should flare to about 1000-1100 rpm at startup and settle to 650-700 rpm.

The latch relay is responsible for this. It keeps the ECM awake for about 15 seconds after key-off so it can set the IAC motor to off-idle 'start' position. Once it fires up, the ECM closes the IAC to idle.


Sounds like the start time is correct.. you say 5 turns but I wonder if you are hearing 5 or 6 compression strokes and then start-up. If that is the case that is one revolution of the crankshaft, and then start-up occurs. That is normal for the RENIX.
 
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And I will say that there is no red wire in the flat 3 wire connector. There is two red wires in the flat 4 prong connector.
If I unplug the flat 3 wire connector there is no difference whatsoever
 
The "flare" is not unique to the Renix OR my '93 is not doing right. It jumps to ~1500 RPM on start up and immediately settles to 750 RPM. It has done this for the nine years I have had it (as far as I can remember) and I quit worrying about it years ago but still occasionally wondered what the procedure accomplished.

I assume I now have the answer and since this is a Renix thread will bow out with the lingering question as to whether this is indeed normal for the post-Renix years.
 
Obviously doesn't make a piddly damn for this thread but I just ran an errand and it flared on the warm start to 1250 RPM, not 1500. Forgot to look at the cold start.
 
You are saying it isn't firing in the first two cranks of the engine. I think if you get out and watch the crankshaft while someone hits the ignition, what you think are cranks of the engine are actually single cylinders going through their compression stroke. It takes enough turning of the crank to get the cps to pulses to be synchronized with the cam position sensor before it will spark.
 
As soon as I get some time, I'm going to hook my timing light up to the cylinder one spark plug cable and try some test starts. You guys have me curious now.
 
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