240sx died - timing? ecu?

[aradapilot]

So I have a 1990 hatchback, KA24E. Was driving a steady 55mph in 4th down the highway, lost throttle response completely (cable still opens the throttle though), took her out of gear so she stalled out and pulled off the road. Try to start her back up, starter cranks but the motor doesn't start.Got a tow back home, a few miles away, and took a look. Note that it was raining hard at the time this happened and there was some flooding on the roads so consider possible water damage:

-spark is sent to the plugs without fail.

-fuel pressure is fine to the rail, but my guess is it's not being injected due to an ecu issue or grouding failure, likely from the rain (it was raining so hard the cabin was leaking a little, which may have shorted something in the wiring around the ecu).

-I have the ecu sitting in two pieces on a table, there is some light rust and corrosion just from age but no major burns. there is slight water damage on the outside of the case but no evidence it penetrated to the board. the ecu does power up but returns a 55-No Malfunction when checked for codes.

-timing chain is intact, as the camshaft spins and the valves open and shut...it is theoretically possible it jumped a cog, but I'm hoping to rule this out as the engine was under no real stress at the time (cruising at 2500rpm, no accel) so I don't see how it would happen.

Any ideas on what I can test or work on to get her back on the roads where she belongs? I don't have a full garage to work in but I've built this car up from where I found her in a parking lot not running at all so I have plenty of tools and know my way around.

update: I finally got her to start up and idle at about 500 under her own power for about 30 seconds...tps disconnected, throttle full open (died shortly after releasing it), shaking like crazy as if only one or two cyls were firing...gotta pull all the plugs again when I get home tonight and retest everything. Any new ideas on this? plug wires are all on right...1342. can't get her up on her own power today. pulled the plugs again and held them all side by side against a ground and cranked it, they all sparked in the right order.

When I pulled #3 some white gasoline vapor came out of the cylinder, if that's a hint at anything other than that it didnt fire properly and built up a bit from all this testing.

I read voltage on the injectors and they all drop from 12 to about 10 when cranking, im guessing that means they're working and the voltmeter (digital) just cant keep up with the rapid drops to 0.

I'm trying to find someone local with an ecu to plug in and test...but I'm worried this may be more serious. Still, the fact that it coincides with a lot of water just points to electrical.

[MaximA32]

Sounds like you've covered just about everything except possible air flow problems.

As for the vapor in the cylinder, I'd check the timing because the valve may not be opening at the appropriate time to let all the exhaust out of the cylinder. Also, check compression and make sure it's where it needs to be.

[desiman76]

Have you fix the problem. If not..ECU. Check open cover look for rusted transitor leads.

Had problems...it was all fine 55 code means anll intrumentation is functioning. IF you dont have anything to detect pulse from injector power then it hard to tell.

Open cover of ecu...check forf rusted leads ...usuall UPA1456 the bottom one.If leads are rusted...try cleaning rust off and reconnect leads with solder.

If it does not work its something else. Check distributor...it sends a signal to the ecu as well.

When handling ECU...make sure you gound yourself as not to damage it,

[aradapilot]

Well, it wasn't what I expected at all...I was glaring at my timing chain trying to find out if there was any way it could've jumped, but the tensioner was fine and it looked lined up, and then I noticed something odd as i looked up - one intake valve for cyl 2 was open and the other was closed."That can't be right..."So I climb up above the engine and look down, and sure enough, right by the exhaust valve lobe for the second cylinder, the camshaft is snapped in two. That explains pretty much everything, including how it would run on one cylinder as the timing was fine and it still worked for cylinder 1.

So, I have to find a new camshaft. I'll start looking around junkyards for one...Is there anything else I need for this swap? never done one before. I figure the rocker arms and cam gear should be fine and i'll just need to take everything apart and put in the new one. I can't find any tutorials on this though - so any advice is appreciated.

And I have to hope and pray that the one valve thats stuck open didn't get bent by the piston. Anyone have experience with SOHC KA's losing timing? Is the clearance on the intake valves so tight that they get hit or should I be alright?

[desiman76]

Try a new engine ! The double ovehead cam design should be more efficient. I would do that. That is so strange how did you manage to get that to break. Im assuming the other part was free to move and the valves would not be jam like when you make an error with the relative position of piston and valve opening...You might have gotten lucky if the valves move freely, the pistons would just push it up out off the way. At least that how i would imagin it.. By the way the ECU problem i was talking about happend to at least three of my 240sx. Not rich two was given to me one i bought for parts but decided to fix...you know.. cant stand to see a car in pieces.

[aradapilot]

Try a new engine ! The double ovehead cam design should be more efficient. I would do that.

I'd love to, but the $120 for a camshaft is already stretching my budget and sadly rent comes before horsepower. I'd love to eventually get a DE or an SR but that's just not in the picture now.

No idea how the camshaft broke. Best guess so far is that there was a lot of water vapor in the mixture due to the conditions and water doesnt compress...could've held a valve closed when the lobe hit the rocker...but still i'd think the valve or rocker would break before the camshaft did.

Or it could've just worn out? They can say "not a wear item" all they want but, well, I'm stuck with two halves of a camshaft.