Need Expert Advise for Start up issues

Hi All

Im still building my GTIR- Still waiting for welding. Cars been on the drive for 18 months. obvisouly cant get this car to the gargage to put it on a dyno to check as it needs welding before being moved and also brakes need bleeding.

Ive fitted a second hand engine. about a year ago. I start it up every few weeks.

Ever since ive fitted it i have always had an issue with cold start.

Mods to engine
- FMIC
- CATBack Exhaust
- walbro pump
- 1 bar loop
- bleed valve
- charcoal canister delete
- dump valve will be deleted soon
- new water pump
- new water temp sensor
- new oil temp sensor
- new fuel filter, spark plugs, oil, alloy radiator
- HKS inlet filter
- wide band o2

Current Known annonance issue havent sorted out
- 2 pin water temps sensor not connected (fan switch?) Connector broke and cannot replace it due to location, so fans are always on
- Oil temp gauge not working - dont know why, new sensor fitted. most likely the gauge is broken but will investigate further.
- currently dont have rocker breather connected to inlet air pipe. inlet air pipe is sealed and rocker breather has a filter on it.
- ignition timing needs checking, dizzy was fitted back in similiar place to old engine but not exact

Issues with start up when cold.
1st attempt - cranks and tries to start but doesnt
2nd attempt - cranks and starts but immediately cuts out
3rd attempt - cranks, starts but cuts out after 2 seconds
4th attempt - cranks, starts but runs very lumpy and cuts out after 4 seconds
5th attempt - cranks, starts but runs very lumpy, cuts out if accelerator pedal pressed at all
6th attempt - cranks, starts but runs very lumpy, revs drop when accelerator pedal is pressed but recovers
7th attempt - cranks, starts and runs good


Once its started and runs ok you can turn it off and it will start fine every time after that.

I am really scratching my head, if any one can help please shout. I really need someone who understands what the ECU does on start up, what sensors it checks etc and what happens if a reading is incorrect. I have the ABS light on but not the engine light.

I would check your timing first.
Also might be something as simple as the battery having insufficient charge unless the engines ran for a while.
Also check spark plugs, gaps and vac pipes.
Looks like there's a lot of changes you've made and TBH you might just need these tuned in together as a system.

@Cosmic73 wrote:I would check your timing first.
Also might be something as simple as the battery having insufficient charge unless the engines ran for a while.
Also check spark plugs, gaps and vac pipes.
Looks like there's a lot of changes you've made and TBH you might just need these tuned in together as a system.

Battery is fully charged and is a new battery
Spark Plug gaps were all checked prior to install

To me it seems like its a sensor isssue due to the fact it does exactly the same everytime and also when you press you accelerator it cuts out. But i may be wrong

Sounds like afm to me.
Check plug and also wiring.

Have you done a fault code check?

@joetheeskimo wrote:

Current Known annonance issue havent sorted out
- 2 pin water temps sensor not connected (fan switch?) Connector broke and cannot replace it due to location, so fans are always on

IF you referring to the ecu 2pin temp sensor on back of head then this likely a big part of start up issue and certainly something sort out as can't be left as is.
ECU uses this data towards fueling and idle rpm at start etc, also switches fan relay via values it sees, with it faulty/disconnected it runs in a safe mode with fixed value on water temp & fans always running .
You can buy the connector plugs on tails so need get loom in workable space to solder one on or at least make yours usable even if just for a test purpose before secondary full fix .

Is a good thread we done on here somewhere with quite bit of info on water sensors but I can't find it currently .

I didnt read that part that MrB has raised.
Coolant sensor is a major factor in idle control as B has said.

You will need to take the plenum and throttle bodies off to get to it easily.
This is an easier job if the Y bracket is already removed.

I found the connector on the loom, its a bit broken but does fit the sensor. ive attached it.

I let the car become cold again and tried to start it up with the 2 pin themperature sensor connected and still got the same issue.

Question 1) What wires are on the ECU, i would like to tap into them to make sure i am getting the correct reading from the sensor when cold and warm.

Question 2)Also how do i check the fault codes, does any one have a link to the fault code list. Assuming its like most japanese cars put a paperclip across two pins and monitor the engine light for flashing sequence.

Question 3) How do i check the AFM for good and bad readings

Question 4) Could a faulty IACV cause this issue.

Thanks

you connected it and has the fans stopped running (only other thing controlling fans is aircon)

1.
https://drive.google.com/file/d/0B7Ub2apq5-pfVTFuZW1oYVJYQnc/view

2.
https://www.gtir-motorsport-club.com/t81-ecu-fault-code-check

you also could get the obd1 tool and free scan tech nissan software to see live data, well worth it .
https://www.gtir-motorsport-club.com/t4215-obd

3.
meter tests from FSM and looking at live data can help afm diagnosis .

If not got pdf FSM manual you can find it here (has useful data on ecu temp sensor)
https://www.gtir-motorsport-club.com/t5301-useful-pdf-files-software-info-on-the-gtir-easy-download-from-google-drive


4.
What is the cold start idle rpm speed like and idle speed in general ?
issues here certainly won't help.
*do note cold start idle needs correct reading from coolant sensor so if cold start rpm off be sure ecu seeing correct temp data before moving on to other areas

>
Personally i'm still inclined to think it not seeing true engine temp thus not fueling enough when cold but after several attempts it got enough fuel and bit of cylinder heat get going .

highly likely you got more than 1 issue creating this but covering the obvious first should help pin down anything else.
coolant temp reading/sensor needs checking further then expand to other basics such as fuel supply/pressure, vacuum hoses etc .
from experience temp sensor can cause poor/odd start issues from cold and from hot too pending exactly how faulty ...
more testing needed and hopefully results from it will help pin down areas of fault .

If it's sitting outside plugs get cold damp as dose maf etc. Battery voltage drops to sensors. I would be checking that timing.is it priming ok etc

thanks for all the help. i will see what i can find out this week and report back in a week or so.

Can be quite an anoying situation to be in with a car not running right and no MOT as its difficult to get it anywere etc.

When was the fuel filter last changed?

It was changed about 3 weeks ago.

How old is the fuel?

Old. About 19 months old to be honest. That's my next worry. But my thought is if the fuel was bad why would run ok once it gets going

Get some fresh fuel in there. That won't be helping things!
Do the fault code check and see what codes it throws up.
If any make a note of them. Then clear the codes and try starting the car again.

I've started cars on 3yr+ old fuel.
wouldn't do a dyno run on it or drive hard on it before changing or adding some fresh to it but 19month old fuel should run car ok but indeed not technically ideal .
You really need confirm water temp signal to ecu due to wiring plug issue & test temp sender for values (procedure in FSM) as not uncommon have wrong ones fitted with values out of spec (other model sensors fit but resistance values differ slightly) .
Basic ecu fault code reading would be good but if you intending stick with car I would invest in obd1 reader cable (20 bucks) as makes things easier and far better/useful data can be seen .
fuel pump priming, does it prime on ignition key, what pressure etc, injectors ok (no nozzle leaks)
All breathers, vacuum lines and idle valves need looking at (more so if ecu has right coolant signal and idle rpms off) as errors here can cause issues.
If does eventually run and idle good enough, checking timing would be good .

Questions:
Are fans still running with temp sensor connected ?
when does start what rpm it run at hot and cold ?
Does it rev freely or got lot of hesitation etc ?

As B said really but only other thing i would check is your plugs (go back to basic testing) they tell you so much as to whats likely to be wrong.

So after 2-3 attempts at starting and wont fire remove the plugs and check to see if they are flooded with fuel or relatively dry, this will tell you if theres too little or too much fuel.
Next (Assuming they are flooded) means you could possibly have an ignition fault as you need a far greater spark especially on initial cold start which will always be more apparent as winter approaches.
Then i would be checking ignition timing, plug gaps, (infact condition of the whole ign system) because if you have high or low kv's i.e 'not a big enough spark' then cold starts will always be a pain in butt.

One last thing, the lambda sensor is another major culprit as readings are used at start and low load / rpm until around 1800rpm when the ecu then takes its reading from maf as opposed to lambda.

Once again as B said its worth investing in some kind of datascan to monitor readings as that can help massively with diagnosis times

Like bobs says looking at plugs can tell a lot and doing all basics is a must before going further.

3 things that stand out to me from points you made is >
1. water temp sender
2. air breathers/vacuums
3. ignition timing

a lot of changes to breather system don't work well so that could be area run through .

obd1 cable and scan tech nissan (link in post 8, software now free, I use it, version 1.29 as newer ones tend screen freeze) is a must from any owner who likes get hands on and it cheap at like £17 .
you can also simply put in a false signal for water temp using a resistor to get required cold voltage range, i've done this before and similar to bypass knock sensor for quick cheap diagnosis .

As car starts eventually & idles and starts again as long as warm it can't be much at fault besides cold start fueling, idle air control or odd ignition issue .

So the fan is always on even when the engine is cold..

I got the ecu to a place where I can probe it. Put the probes across pin 18 and pin 21. Temperate sensor and 0v. With ignition on it read 0.3V across the temperature sensor. It should be reading 3V. Need to check connections.
I will see if I can read the codes tomorrow.
It doesn't hesitate when revving when warm. Only hesitates and cut ours during 1st - 6th cold start attempt after that it's fine.

@joetheeskimo wrote:So the fan is always on even when the engine is cold..

I got the ecu to a place where I can probe it. Put the probes across pin 18 and pin 21. Temperate sensor and 0v. With ignition on it read 0.3V across the temperature sensor. It should be reading 3V.  Need to check connections.
I will see if I can read the codes tomorrow.
It doesn't hesitate when revving when warm. Only hesitates and cut ours during 1st - 6th cold start attempt after that it's fine.

Looks very much like your problem.
If you read the ecu error codes I suspect you got code 13 for temp signal and thus ecu in safe run mode and fan constantly runs .
Once ecu has right signal and fault codes cleared it should switch off fan & hopefully start better .
It easy send a fake 3.2-3.4v (10-15degC) signal to pin 18 to do cold start test if needed/desired .
You want check harness and plug at sensor for supply voltage and signal line continuity.
If that all good sensor needs checking preferably off vehicle hot water range test .
Link below to FSM data on coolant sensor >
https://drive.google.com/file/d/0B7Ub2apq5-pfMDRwZHhuRktnLVk/view?usp=sharing

also got another issue which may relate to this.

My oil temperature gauge doesnt seem to work. So my investiagation has shown the following. Gauge works and needle moves to upright position when connected to a 12 power supply and 30 ohm decade box across the input.

There is good continuity between grey wire (sender wire) on gauge connector and engine bay sender loom.

the following measurements were at the engine bay connector and using body frame as earth/0V with the gauges disconnected.

With engine fully warm and ignition turned off sender value = 60ish ohms
With engine fully warm and ignition turned on sender value = 30ish ohms
with engine fully warm, ignition turned on and lights turned on = -6.5kohms (i know this value doesnt seem correct)

why would the resistance value changed to incorrect value when the lights are turned on. Would this be an earthing issue.

Annoying thing is with the lights off the value is correct. However even with the lights off and engine on gauge still does not work.

I am going to repeat the above tests but measuring at the gauge connector

What the voltage signal to gauge at varying temps and does voltage drop massively with lights etc on.
it quite easy test dial by feeding a variable voltage signal to it, i'll try pull out some more data on it but working in laos until friday and no free time .

just took some more measurements as i believe the earthing issue is causing problems.
ignition off - 0V on battery to Chassis = 0.2ohm
ignition off - 0V on battery to engine = 0.2ohm

ignition on and side lights on - 0V on battery to Chassis = 12ohms
ignition on and side lights on - 0V on battery to engine = 12ohms

ignition on and dip beam on - 0V on battery to Chassis = 24ohms
ignition on and dip beam on - 0V on battery to engine = 24ohms


Engine on - 0V on battery to Chassis = between -6 and -10ohms
Engine on - 0V on battery to engine = between -55 and -70ohms

I would of thought even with the engine on, between 0V terminal and engine bay chassis would be 0.2ohms or so. direct conection, its as if the earth is being pulled up.

also checked the engine light its code 55.