Engine Swap Forum

So, ill probably sum up a story about my swap later on, but first i want to get this thing running nicely.

When i start the engine, it idles from 1 to 5 seconds, very smooth and all cylinders are working. Then it just dies, its like someone would cut the injection.
This is a fuel related problem, the plugs are fireing all the way when the revs drop when the engine dies.

Here are a few things that should describe the setup at this point.
- Stock ecu, stock harness, only made an adapter to adapt the maxima engine harness to the 200sx engine room harness.
- The fuelpump is currently hardwired, so it runs all the time. It is also wired the right way.
- There is no fuelfilter or any other possible causes for problems in the lines now.
- Stock fpr is used, it also works. When i suck or blow into the vac line for the fpr, i hear the pumps sound rising or falling -> pressure changes.
- I am using the stock tb and iacv/aac.
- Tried adjusting the aac/iacv, no change.
- Tried disconnecting the tps, iacv/aac and knck, no change at all.
- The maf is currently disconnected, would a maf cause this? At least the CA18DET has a very similar ecu and it has a limb mode that wont allow you to rev over ~2000rpm, but you can still drive...
- There are some minor vacum leaks, but they would just cause bad idle instead of the engine just stalling after a while?
- The lambdas are disconnected since i dont have exhaust manifold on it yet.
- Obviously, the injectors work when they get a signal because the engine idles for 1 to 5 sec.

Currently im thinking the ecu cuts the power to the injectors because something is not working, i dont have a pressure gauge for the fuel pressure, but i dont really know what would cause the walbro to not make enough pressure. I tested it and the spray from the pressure tube was about 2m long, this indicates that the pump generates some pressure.

Some pointers would be appreciated, thanks in advance for anyone who cares to contribute =)

Well, i put the maf on, and now it responds to the throttle and might just run a little longer - alltough it might just be the mental thing like "I did a waxjob on my car, not it has 10hp more", based on pure feeling.

Ill try to bypass some of my wireing in case i have just used the wrong relay in the bay, it just cuts off like i would flip the key. Could be my wireing too because that is about all thats left to inspect.

My initial reaction would be to say that the cranking is getting the engine firing but the fuel correction isn't working properly. If you say it's a stock ECU, does it need the lambda feedback or else it thinks something isn't working & shuts down? Or alternatively a water temperature sensor isn't plugged-in/isn't working and it doesn't know how much extra fuel needs to go in to keep the engine going. I had a similar problem when initially mapping a PowerFC to run on E85 for an SR20DET on cold-start.

Hmm, i have the ecu water temp sensor plugged in, the lambdas are not plugged since i dont even have an exhaust.
I tried replacing the front crank sensor, but no luck with that either. It just stalls after a few seconds like someone would cut the power. I am very sure its not about the fuelpressure since i have to turn the key to completely off in order to get it fire again. Normally it would just need an other turn from on to start without first waiting for the ecu relay to flip again?

Check with a multimetre if the connections to water temp sensor are correct and working. After that, why not wire up the fuel-pump the way it was originally wired just for testing purposes? Do you have an in-line fuel-pressure guage you can put in temporarily? I think they cost about €80 each or thereabouts to buy but at least you'll have it for future reference.

As for the turning from on to start again, I always turn the key to off if it cuts out but that could be habit more than anything else.

Hmm, would the watertemp cause that? Ill need to check that one just to be sure, ill chime back in a minute to get results =)

I checked the watertemp sensor and the wires. The total resistance seen by the ecu was like 1,4kOhms so it was in range (about 30 to 40 celsius was the temp).

So now there are two possible problems:
1.) The fuel pressure just drops and the ecu wont let me start a second time.
2.) The front crank sensor is toasted, i have tried two different sensors and have tried gaps from 0.1mm to 0.5mm and no luck, always does the same thing.
3.) I have a faulty ecu.

I am also starting to think this might just be pressure related after all - IF the actual ecu phorbits spark or injection after the first run.

Ill need to hook up a pressure gauge to see whats really happening...

Let us know what happens when the fuel pressure guage has been hooked up.

If it was a crank or cam-angle sensor I think the ECU doesn't let the sparks fire at all cause it's potentially dangerous if the cams/crank is out of alignment.

What happens when you crank her & give it a bit of throttle?

Well i can throttle the engine like it was new, no problems in that. The only thing is that it just shuts down with no warning. This *** is starting to really annoy me, its the only thing phrobiting me from driving it!

So, i have a question that i would VERY muck like to be answered now, actually three questions:

What does your vq do if you pull out the front crank sensor?

What does your vq do if you pull out the rear crank sensor?

What voltage does your rear crank sensor give out when the engine is running? (Measured from body ground and the ecu input pin 48 or 49 iirc). Mine gives out 2,5v, but it should read 5v? Ofcourse it oscillates fron 0 to something, but it requires an oscilloscope or a VERY fast multimeter to measure.

What voltage does your front crank sensor give out when the engine is runnin? (This also oscillates, im looking for a peak/regular value).

Im trying to decide which sensor needs my attention because i dont have a clue what the engine is supposed to act like when a certains sensor is missing. Fred, Broaner, Jpo, anyone?

I noticed an intresting addition to our problems.

The engine actually shuts down after a set time counting from the instance i turn the key to ON. So its probably not a sensor failing, rather it could be a short in the harness i think.

Ill need to start measuring things and see if that will help out.

Has anyone else had similar problems, like the ecu preventing damage by shutting itsself down?

If it's a set time from when you turn the key to "on", then possibly a NATS system or similar is immobilising the car? Just a thought if it's a set time regardless of action...

As for the sensors & what they do, I posted above that I believe if a crank or cam-angle sensor isn't doing what it should the engine generally won't start - can't give 100% certainty on this but I've yet to hear of one that does if either are gone.

Might be an immobilizer, but since its a 95 ecu i doubt it, i havent heard of any security related systems phrobiting startup on these older vq's. The 350z has one, and the newer maximas have similar security.
The car its self doesnt have a nats (-93 hatch CA18DET), and constantly puts power to all the neccessary pins on the ecu. The ecu its self is shitting down.

I discovered a burnt eng control fuse and replaced it, no use - the problem presists.

I dont have any lambdas hooked up, could that cause this?

So, it seems that i simply have an immobilizer on the ecu. The european versions came with a nats immoblilizer so its simply preventing me from running the car longer, nothing is really broken or malfunctioning. Im just missing the rest of the things and im very close to buying a VQ30de from a friend.

I would still need a non-immobilized ecu for that one and preferably also the harness for the vq30de just to be sure.
If someone has a suitable ecu laying around (manual). I would be intrested in buying it from someone. I can pay via wiretransfer, and possibly also paypal. No creditcards or cheques.
I can possibly also arrange a local pickup if you like.

So, if you have one laying around, please contact me at wille@race.fi ***SUBSITUTE 'w' WITH 'v'***