hey single cam ka guys got a massive fuel problem!!!!

[icehouse]

You should try checking to MAF voltage going into the ECU, maybe a wire got crossed or somehow 5v is making it's way into the MAF input on the ECU. Do you have the diagram? I do somewhere on my computer..... haha I need to print all the diagrams out!!! I will try and check after work.

[jesusno2]

The only manual I got is the chiltons manual for the 240. It gives me the worst info on testing sensors and what not. I tested the fuel pressure with a inline guage I borrowed from a freind. Jeff if you got voltage readings for sensors that be great! Although I might need ya to coach me on what wires and such to probe.

[icehouse]

Well my computer is being a complete piece of shit (stupid windows....) But I did manage to find this


http://www.240edge.com/manuals/89-90_240sx/l_wiring.pdf

The KA wiring diagram is a close to the bottom. It looks like pin 16 a white wire. I would check the voltage with the maf plugged in and unplugged for the MAF side and ECU side. Just in case there is a break in the wire or something like that. From memory it should be around 1v it should be no where near 5+ volts. Really from everything you have said this has to be it. 5+ volts is max fuel!!! Which is your problem. I actually did have this happen once... don't ask how

[okayfine]

The only manual I got is the chiltons manual for the 240. It gives me the worst info on testing sensors and what not. I tested the fuel pressure with a inline guage I borrowed from a freind. Jeff if you got voltage readings for sensors that be great! Although I might need ya to coach me on what wires and such to probe.

Why, in this age of the internet, you can't be bothered to find the FSM for your engine is mind-boggling. Moreso because all the information you need to troubleshoot problems is in the FSM. TPS voltages, MAF checks, all that stuff is in there, clearly presented, and worthwhile. Heck, it's $5 on eBay if you're too lazy to search.

I'm not saying it'll solve all your problems, but seriously, RTFM.

[cosmo1stgen]

Ive seen this problem twice alone on the 240sx among many other makes and models and a few after market ECUs. Both times on the 240 were related to the water temp sensor for the ECU. What happens is the sensor craps out or the connector gets a lot of corrosion /loose conection/broken wire and the computer gets a false reading usualy causing it to see a -40 deg water temp. The ECU will bump the fuel as much as 80% while cranking because it thinks its ice cold outside causing the extremely rich condition. Check the FSM for the water temp sensor location (I believe its in the thermostat housing on the 12valve) Unplug the connector and check the resistance across it with an ohm/multi meter and see if its within spec if not replace it. Also check that the connection is good. Most water temp sensors are wired the same. One side of the connector should ring out 0 ohms to ground the other will trace back to the connector on the ECU. Hope that helps you out.

[jesusno2]

my coolant temp sensor is brand new and i have swapped it out 2 other times with used ones? not saying the ecu is relizing its not hooked up though lol?

[icehouse]

The 2 wire temp sensor right?

Did you check the MAF voltage?

[fo0manchu]

did you have your motor rebuilt? Hows the timing on the camshaft and distributor timing? All your spark plugs working, wires, distributor, coil?

[jesusno2]

yes 2 wire temp sensor the motor was rebuilt and the timing is fine dizzy is in the right position as well as the oil pump shaft theirs just something elctronically going haywire i have not tested it out yet been on 10 hour shifts and work with saturdays included. this weekend me and a hairfaus are gonna do some testing i think cause hes coming down from portland.

[jesusno2]

did a little trouble shooting today. I tested the maf voltage at the ecu it has 0.06 volts so under 1 volt is good. swapped ecu's now my symptoms changed some the car starts up cold high idles then dies! never did that before lol? i tested my tps and set it to book says between 0.45 and 0.55 volts i set mine a 0.50 volts which is right dead center on the adjustment. i dunno why it dies now could be timining or ignition related or something now. coolant temp sensor checks out fine also. still runs super rich still.

[510Martinez]

my coolant temp sensor is brand new and i have swapped it out 2 other times with used ones? not saying the ecu is relizing its not hooked up though lol?

It's not usually the sensor itself (that is usually pretty robust); it's usually the wiring/connection. I'd check the voltage to the sensor (at it) and from it at the ECU end and make sure it's within spec.

[jesusno2]

i checked have checked the voltage. The fsm says between 1 to 5 volts but it varies with the water temp i got a reading of 3.5 v when i tested mine after it had ran for a minute or 2

[jesusno2]

scratch that voltage on the temp sensor i got 1.5 volts sorry i dunno what # was stuck in my head another thing i just found interesting ive been running the engine for quite a while now, and i have no pressure in the radiator the coolant is stone cold. im thinking either my thromstat is stuck closed or i have a massive air lock somehow i dont think i have much coolant flowing through the engine.

[510Martinez]

Typical systems work like this: there's a base voltage sent from the ECU to the sensor (about 4.5-5 volts). As the engine/coolant warms up, the resistance through the sensor increases. The return voltage back to the ECU then decreases as it warms up.

When the engine reaches operating temp, the return voltage should be pretty close to it's lowest point. There may be a reserve range in case the engine is running hot/overheating. You'd have to find a Nissan manual and see what the voltage is at different temps to have an idea. On some Chrysler and Ford systems I've worked on it should be no more than 2 volts.

If your engine coolant doesn't reach operating temp (~195 F - check the spec), the ECU will leave you in warm up mode. This burns a lot of extra fuel and likely a part of your problem if not the whole thing. You may have already figured it out if the coolant is staying "stone cold". You know where to look.


made edits: overlooked part of your post. Hmm, I wonder if you're engine is actually getting too hot. If the t-stat is stuck closed, you could keep a cool radiator but at the same time really heat up that sensor. You really need to iron out the temp issue.

[jesusno2]

im defenetley gonna look into the coolant but i somehow dont think its all of my problem but im gonna take it a step at a time. the fsm isn't really clear on the voltage it just says 1 to 5 volts depending on water temp. Ive been told also the fsm is not quite correct on the TPS ohm readings either but i havent dug into that yet.