240sx 12v engine help

I really need some advice on getting my car up and running again. I swaped the head on what was a perfectly running car and now have a car that barely runs. I have about 50 hours into trying to diagnos/fix this myself with no luck.

So here's the story, the old head ran fine and a compression check showed about 155-175.
I swapped in the spare head that I had sitting around for a few years. It got a valve job and port matched by the local machine shop. I swaped the new head in with all sensors, vacum lines, intake exhaust and everything installed. After correcting the cam timming (off 1 tooth) it started up but did not run well blowing white smoke out the tail pipe. Timing was set at 15 degrees and compression was now an even 185 across all 4. I hoped it would just burn off and loaded it up and took it home. It drove on the trailer under its own power no problem. Since I got it home it will barely run, it seems to be flooding itself, the white smoke has cleared but it is spitting a bit of oily/gas out the tail pipe. If left alone it stall within 30 seconds. Sometime I can keep it running with a lot of pedal but it does not run well.

Then the part swapping started. I have a parts car that runs well so I have a spare everything. Changed:
Rockers (some lifters were sticking)
TPS, ECU, MAF, fuel rail, regualtor and ijectors, Air flow regulator, BPT, temp sensor.
New parts: O2 sensor, plugs wires, cap, rotor. Change the oil several times since it seemed to have quite a bit of gas in it.

I am not getting any trouble codes in the ecu, I have a FSM and have check most circits, all grounds, most sensors.

By the way it is running I would suspect the timing was off but it checks out ok. The cam gear punch mark is on the right when at TDC. It is at a pefect 3 o'clock relative to the head which actually sits in the engine bay and a bit of an angle.

Anyways, sorry for the short story, but feel free to make suggestions, I will check them out and report back. I have a huge amount of time into this and I'm getting frustrated. More so since I missed a race. I have a FSM and multimeter so I can check the electrical stuff as needed.

Corey

Cold start injector?

Corey,
Have you checked for vacuum leaks? It is easy to miss one around the "choke" mechanism shaft in the intake. Was the compression checked at 185 before or after the cam timing was corrected. If it was before, check it again. If you revved it much with the timing out, you could have bent an exhaust valve(intake also, but the exhaust valves usually are the ones to bend).

Let me know what you find, if this isn't it, we come up with more ideas.

Jim

Not sure what a Cold start injector is. More details?


Jim, I can't remeber when I did the compression check since I have gone through this thing so many times now. I will do it again and report back.

As for vacum leaks, I have looked visually A LOT http://Forums.ImprovedTouring.com/it/smile.gif Its hard to check for them while its running since it is nearly improssible to keep it running. I tried putting compressed air to the intake with the engine off to check for leaks, it all came out the B.P.T (sorry I don't know what that stands for, I think it lets air into the intake). When I took that off and connected the vacum lines to each other I had no leaks and could see the motor rotate when I gave is shots or air.

Is there a better way to check for exhaust leaks with a non-running motor?

Corey

A new ecu from a known good source and all is well with the world again.

What was your source for the ecu

Just a newly aquired parts car (bought for the transmission) but it worked great when I brought it home so I knew the ecu was good.

Turns out #2 injector was firing almost contantly and the rest were barley working. This was the reason I swapped the whole fuel rail earlier. To give you an idea how long I stuggled with this, I put $10 of fuel in the car after changing the head. Without even driving the car I used it all just trouble shooting and had to add more when the new ecu was installed. During the last few weeks I change the oil several times since it was severly deluted with fuel.

Anyways, very frustrating but I learned a bunch more about my car after reading the FSM from cover to cover a few times and spending a few nights in the driveway with a multi-meter.

Thanks for the help

First time out with the new head on was this weekend. The car seems to be struggling for are above 5400rpm and would barely climb to the stock rev limiter in 3rd. I played with the distributer timing until it became aparent that the timing chain was probably off a tooth. We moved it back one link to were it was when I originially assembled it (if you read the whole post you'll see I changed during my original trouble shooting session when I was just trying to get it running).

I set the timing at 18 degrees. Next session it seemed quicker. No noticable drop in power at a certain rpm but still not as fast as my old junk yard head. And it was running hot. Thinking I had to much advance I set it to 15 degrees for the last session but after a few laps the temp gauage was almost spiked again. It was an hour race so I cruised around, occasionally driving hard for a few laps but the temps would go up right away.

So, I'm at a lose as to what to try next. I am probably going to park it for the rest of the season regardless but I'd love to sort it out before I do so I don't have to worry about it. The only way I can know if I have the cam timed correctly is to tear down the whole front of the motor and start from scratch using the silver links on the chain.

Any suggestions?

BTW I do not run the stock clutch fan, I do run an electric fan which I used to only use in the pits. This weekend I has it on all the time but it didn't help.

Corey,
Wow, that thing must really be trying your patience.
You can check the cam timing without removing the timing cover and doing that chain stuff. Set it at TDC on the crank pulley. take off the valve cover. The keyway on the cam gear should line up with the arrow on the front cam bearing journal. When doing it this way, make sure that the chain is tight. (sometimes the chain will be a little slack depending on where in the rotation the engine was when it stopped running or which direction you turn it to line the marks up)

Still scratching my head on the rest of your problems..

Jim

Quote:

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Originally posted by crs240sx:
It was an hour race so I cruised around, occasionally driving hard for a few laps but the temps would go up right away.

---

This may be a longshot, but in April, I took to the track with a new KA24DE in my '97... In putting the motor together, I found that the spade on the temp sender was "jiggly", so I pulled one out of a spare intake I had. When I'd run the engine for ANY length of time, the temps would ROCKET up on the guage... The engine, otherwise, showed no signs of any overheating problems...

Turns out that there is a difference in resistance values between the ealier KA24DE sending units and the '95-'97 units... even though the sending units look identcal.

Put back in my "jiggly" '97 sending unit and the problem went away...

Than all I had left to blame my slow lap times on was the loose nut behind the wheel! http://Forums.ImprovedTouring.com/it/wink.gif

Keep in mind that I'm talking about '91-'94 KA24DEs vs. '95-'98 DEs... don't know about the 12V KA24D's intake system or whether the sending units are the same as the later cars...

If the motor is otherwise not showing any signs of overheating, it might be worth a look... This unit could also effect the FI mixture, if engine temp is one of your inputs to the ECU...

Good Luck... Let us know what you find out...


------------------
Darin E. Jordan
SCCA #273080, OR/NW Regions
Auburn, WA
ITS '97 240SX
http://home.attbi.com/~djjordan/Web/...1203_thumb.jpg

[This message has been edited by Banzai240 (edited July 29, 2003).]

I think there are 2 sensors, 1 for the guage and one for the ecu. The engine did not seem to be affected by the heat.

I do have an autometer guage sitting on the shelf that I have been meaning to install. Guess it would be work a shot.

There are lots of improvements I could make to cool the thing down as I currently run the old stock rad and no oil cooler. I also have the stock clutch fan removed. I have run lots of races with the fan with no problems before the head swap and 1 full weekend without the fan (using an electric in the pits) without problems but it was a rain weekend. Should I just put the fan back on? Install a real guage and go again?

May I ask what some of you set your ignition timing at? Mine is currently about 15 at idle 750-800rpm.

Just thinking out loud, where is the thermostat on the 12v?

Corey.
I have my initial timing set at 5 degrees (or maybe it was 6). I know this is very diffenet from convential theory and from the service manual, but when it was on the dyno, this is what it wanted.

The thremostat is located in the housing where the upper hose bolts into the timing cover. FWIW, I do run the thermostat in mine (170).

Jim

"There are lots of improvements I could make to cool the thing down as I currently run the old stock rad and no oil cooler."

Corey,
240's run hot so you need to get a larger capacity/better cooling radiator in the car. The Oil temps will be incredibly high with out a oil cooler also. I'm not sure what region of the country you are in, but here in the southeast, your motor would fry with out the above.

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Tristan Smith
Buffalo's Southwest Cafe
ITA Nissan 240sx #56

Yep........head temp sensor will do exactly that.

The 280zx turbos will do exactly the same thing if the connector is "jiggly".