kc92hatch

Hello all,

I had previously posted this problem in another thread, but the title was a little misleading and the symptoms have changed a bit. 1997 LS 115,000 miles.

If you like to trouble-shoot this is the place for you!!!!!!!

1. Initial issue was that this would only happen when trying to start a warm engine that had been sitting (heat soaked) for a while.
2. Symptoms were fine engine cranking, but no start. No codes and confirmed no-spark.
3. If engine was left to cool down (maybe 30 minutes, maybe 90 minutes), then car would start and run fine.
4. Original symptoms were that this would NOT happen while driving. My thought was that there was fresh air coming through engine bay, keeping temps down.
5. Igniter bypass test done, in no-start condition, I could get igniters to fire when simulating signal from the ECU.
6. Crank and cam position sensors resistance checkout OK.
7. Capacitors changed on ECU. They were not leaking, but changed them anyway. Didn't change anything.

This is my father-in-laws car. He was driving it the other day, and while underway, the car surged a couple times and then died. Luckily, he was able to get it to the side of the road. After it shutdown, it displayed the typical no-start condition. After about an hour it started back up and ran fine.

I was driving the car for a few days, troubleshooting. When it's running, it runs strong. I would run it very hard......full throttle acceleration, redline shifts, over 100MPH from time to time. Felt good and strong. It never had a hickup while underway when I had it.

Soooooo........these are the two things that I'm thinking of right now:

A. ECU. Even though I replaced the capacitors, maybe there is just something wrong with it.

B. Fuses. There is the EFI fuse and the Cut-Out fuse (I might have gotten the term wrong on that). Could either of these fuses if malfunctioning cause the symptoms I'm seeing?

C. Fuel pump / fuel pump fuse. Because I'm in a verified no-spark condition when the problem occurs, I don't think it's the fuel pump or fuel pump fuse.

Would very much appreciate any suggestions you guys have.

Thanks!
Confused in KC (Go Royals!!!)

billydpowe

iTrader: (1)

the Royals went and are going again...... clap clap.. NOW as to your problem, go to a wrecking (salvage) yard and buy dist caps, rotors, & coils, take yours off and put these on and see what happens.. if it is the same, you have eliminated a lot for little $$.. I am sure you have checked your cables real good for contact failure.

dicer

In a gen1 that could likely be the fuel pump resistor. If it was a 2002 Mercedes CLK430 those are typical symptoms of the crank shaft position sensor failure. And I'm sure it also checks good for resistance when it goes out, I don't know what the heat does to them to cause em to work when cold and crap out when warm, oh and the car does throw a code for it.
You really can not depend on resistance checks. The good thing is its a 97 so you can hook up a top quality scan tool like a Snap on Verus and moniter the various sensors and other conditions. Its either that or something I don't prefer to do, but is cheaper than a $10,000 scan tool, is to replace a few suspected parts.

kc92hatch

I picked up a 1996 ECU to swap in and see what happens. What happened is lots of cranking and zero starting. :-)

I've been looking for guidance and see where '97 started with an immobilizer. Could there be an issue with the '96 ECU not being compatible with this engine? Do I need to run some kind of sequence to get the ECU to recognize my present key?

Thanks for any help!

dicer

I don't know about the key deal on those cars. You need a good wire diagram too.

kc92hatch

Well *&^%. Replaced the 1996 ECU with an exact part number matching 1997 ECU. Engine started right up.

Drove around for a day & a half and thought the problem was solved. But then as I was buttoning things up, the problem occurred again - just as before. Darn. So, does not appear that the ECU is my problem.

When this happened, I had the chance to move some relays around to see if that made any difference. So I swapped around the EFI fuse, the cut-out fuse, and one other (can't remember).....made no difference.

Here is one new piece of information: When this happens, if I reset the ECU (remove power) and then re-start the engine, the engine will run fine for about 5 seconds and then die. The next time I try to start, it is a no start. But if I then reset the ECU and try a start again, it will start for about 5 seconds, and then die. Then next time I try a start - no start. Hmmmm.....I feel like this is a clue for something, but I have no idea!!!

The only idea I have at the moment is maybe something is going on with one of the igniters. I did test them and confirmed that when they get a signal from the ECU, they will fire. However, there is some kind of a feedback signal from the igniters back to the ECU. Maybe like an "igniter fired" input to the ECU. Even though the igniters can fire, I wonder if one of them is maybe not feeding back the signal to the ECU and then the ECU is stopping all ignition?

I'm tempted to pick up one igniter and see if I can get the problem to re-occur and then swap out the new igniter with the old ones, one at a time, and see if that might solve the no-spark no-start condition.

Aside from this igniter possibility, I am just about out of ideas!

Open to any suggestions or feedback!

Thanks!

brybo86

when the key is turn to the on position do you hear the fuel pump running before starting?

konax

My 1993 does the same. Already learned not to shut her down after a while of driving if I plan to continue my journey
Although mine won't event crank, all I hear is a dull click. Disconnecting the battery does nothing, also it does not have an immobilizer so it's not the case.
I'll be watching this thread for any ideas, good luck.

dicer

Now re look at my above post. No spark? I lean towards cam and crank sensors. Or circuit opening relay. Need a scan tool. Did you read codes?

kc92hatch

Hi guys,

Thanks for feedback. To answer your questions:

-On this car, I cannot hear the fuel pump prime ever. So I can't tell if it primes or not. However, my problem is a no-spark condition.....so I think fuel pump is OK.

- The crank sensor is new. The one it replaced was only about 2 years old.

- Would a problem with the fuel pump resistor cause a no-spark condition? Can the computer become aware of a fuel pump problem and then kill ignition?

- When this problem happened last, I did swap around the main relays (I said fuses in earlier post, but I meant relays) including EFI & circuit opening. When swapped, it didn't help starting.

- Codes are a little strange. Here is the typical sequence of what happens:
* The first time car does a no-start (no-spark), it will run for about 5 seconds and then quickly die...just like you turned off via key. When this happens code 335 is normally thrown. (crank position sensor trouble).
* After this, all the next start attempts will only crank and the engine will not start. If I clear the 335 code right after it happens, that code will NOT re-appear during any of the following crank / no-start events.
* So I was thinking that the initial 335 was perhaps an anomaly associated with the first engine dying event. It seems odd that the code does not reappear any other time than after the first event. So if I'm trying to start the car over a 30 minute period (let's say 5 start attempts during that period) the car will not throw any other codes during that period.

The present crank position sensor is a Denso unit. Maybe I'm making a mistake by discounting the crank position sensor circuit. But with the new unit in there already I'm not sure where else to go. I have inspected the connector near the sensor and it looks fine.

Keep the ideas coming.

Thanks!

Yamae

Sounds like your engine goes into the inhibiting mode. In that mode, the circuit opening relay is forced to stop the DC supply to the fuel pump in 3 or 5 seconds depending on following conditions.

1, No signal from the MAF for more than 3 seconds.
2, No signal from the crank position sensor for more than 5 seconds.
3, No signal from the cam position sensor for more than 5 seconds.
4, No IGF signal from the igniter for more than 3 seconds although the IGT signal is sent.

I have experienced the inhibiting mode several times at shops where I sometimes visit requested by local shop owners. Many of those failures were caused by just the mistake of mechanics. They just forgot to insert the connector or they didn't insert it well enough. Sometimes the connector, the wire or the sensor itself was dead though.

dicer

Its a 97 ? I don't think they have a fuel pump resistor. And I would swap out all the position sensors, it would be nice to have known good ones. I think 97's have a crank and 2 cam position sensors. And like Yamae says connectors, they need good connections.

Yamae

You'd better not to inform others incorrect or uncertain information. I know you are kind enough to try to help others but your uncertainty sometimes confuses others.
All LS400 90-00 have a fuel pump resistor.

dicer

Your right I shouldn't help the newer stuff, I need to stick to the below 92 stuff at least for the electrics.

kc92hatch

Thank you both. Yes - 1997.

Yamae - the interesting thing is that the problem almost all the time happens after the car is parked after a drive. It seems that as the heat builds up in the engine compartment, that is part of the cause.

When the car is driving, or after being parked the hood/bonnet is raised, then the problem does not occur. (Note: it has happened while driving two times, but 99 times out of 100, the problem only happens after parked heat soak.) Seems to me that when there is airflow in the engine compartment, the problem does not occur.

Based on your experience, would the igniters be likely suspect where even though the igniter is triggering the coils correctly, the IGF feedback is not working correctly?

Thank you!