Developed a Starting Issue

[cableguy]

yea, im going to try and go back to basics. I have already ran every scenario in my head and it just doesnt make sense.

Fuel pump is good, as its brand new, i installed it two days ago.

ECUs i think are ok, as it didnt make any difference between the two. One was refurbished by the ECU doctor in kent, and the other one, I replaced the caps myself (Id say my electronics skills are above average) but unless i can find a brand new ECU, i wont be able to tell.

IAC, gave correct readings on the multimeter, how ever that doesnt mean its operating correctly, so perhaps I could change that and they are not that expensive.

I dont think its the PTU, as once the car is running, its running fine, there is no misfire and it looks like all cylinders are firing. but yes there could be a possiblity that it is the PTU.

Now the Vapor lock issue is another thing that i havent looked into properly, im planning to come up with a method of insulating the fuel lines in the engine bay to see if it make a difference as that seems like a common fault. I was also thinking of trying a tank of super high octane fuel, as your general 95 unleaded fuel contains 5% ethanol, which evaporates much easier. Esso’s super range and Shells V power contain no ethanol. Perhaps that would make a difference.

You are right about heat and electronics as heat increases resistance. High heat areas are in the engine bay, and i really cant think of anything that sensitive in the engine bay that could get effected by it

If its not Vapor lock, im down to changing the IAC, Fuel regulator, PTU and getting the injectors refurbished.

[spiros]

@cableguy Have You tried checking if You get fuel to the fuel rails by disconnecting the hose when the car is cranking but no starting ?

[cableguy]

I haven’t tried that, hoping to do that as last resort, scared of petrol going everywhere.

But

The mystery deepens…

Today the car stalled while hitting a road bump. It happens to me once before and I didn’t think much of it untill it happened again today.
And it would not start again.

Had to push the car to the side, waited around 10mins and it started fine.

[Vince_GTO]

Au contraire my friend, this is a big massive key to your mistery. So that points out to an electrical issue. a lot to check tho.

Badly plugged/corroded connectors?

Fuses… the box under the hood - all good in there? Worth checking wiring attachements to fuses sockets under it as well.

And probs most painfull - the wiring itself. Broken inside isolation wire is a pain to find.

But again, first order of business is to find out which of the building blocks - fuel/spark/injectors are at fault when it stalls and refuses to start. And then it’ll be more clear which connctors/wiring to track down.

[cableguy]

I checked every connection in the engine bay yesterday, none were broken, all wires looked good, fuse box looks like its brand new, no rust or loose connections, which would make sense as most of the time the car runs fine.

What makes it really difficult to check is that this problem usually occurs when im alone, and the window of checking for fuel flow and spark is like 10 minutes maximum, as after that the car starts fine as if nothing happened. By the time i disconnect the fuel rail, check spark (not possible alone) the window has closed.

I have come up with the following theories:

Theory 01:

If i hit a bump hard enough, its having an impact on an electrical component through shock, its cutting the power to coils/ PTU the engine floods and it stalls. Then i would wait 10mins or so, the fuel would evaporate/ disappear and the car starts fine. this would probably mean a faulty PTU.

Theory 02:
Theory two is same as 01, but it includes a leaking injector/ injectors.
Car is running fine, after a long drive, you switch it off, how ever, some of the injectors could be still leaking into the piston(s), flooding it as it still has pressure from the pump. as the engine is warm most of it will evaporate, but as the engine cools further, the remaining fuel floods and stays, hence it struggles to start after a few hours of cooling down. It will start the next day, because the fuel is thinner than oil, will pass the piston and go in the oil pan.

[Vince_GTO]

Good theories! Defo worth checking

So basically when it stalls you crank a few times and remove one of the spark plugs straight away - should be all wet to prove the the theory right? Taking out a sparkplug can be done fairly quickly just have your spark wrench ready.

And when removed you can actually spark test it. What I did when chasing my ghosts - I positioned my spark plug (apparently attached to its HT lead) so that it gets ground and positioned the phone so it records it when cranking. Video will be a bit shaky but if is not too bright outside the spark will be visible on the record.

Also a suggestion, coming back to the fact that bumps lead to some sort of electrical interruption - why not when the car is running try to manually wiggle connectors, wires, fuses under the hood. With a bit of luck the culprit can reveal itself.

And also, I was wathing the other day on youtube a dude was chasing an intermittent stalling issue on his eclipse, and eventually it was tracked down to a seemingly looking good TPS connector. One of the wires inside its insulation just near to where it connects in the socket, was broken, but not complerely, was held on jusy by one strand, so just buzzing the wire thru connector by a multimeter was showing continuity, but under the load was unable to conduct propely. And bumps were leading the wire to re-attach itself and the car was fine or get to just one strand connectivity and it was stalling then. That all was not visible to a naked eye. Not saying that this is the case in your situation, but you get the idea.

good luck bud. Doan’t give up and be persistent. You’ll find it.

[vtecgrin]

A friend of mine had a similar problem with his 944. Great at starting cold … but trying to restart when warm was a problem. Turned out it was one of the wiring harnesses in the engine bay breaking down due to heat and old age. Your issues sound similar to his. Wear gloves and wiggle harnesses whilst engine warming up and use extreme caution whilst doing so. good luck

[cableguy]

Hey all, I thought id keep you guys updated on my battle with this car…

It looks like i came out of a pothole and fell into a well…

… after checking everywire everywhere, pulling it, yanking it, wacking all electronic bits with screw driver, it all seemed to be ok. didnt make a difference while the car was running.

So i decided to take out the injectors and have them refurbished.

I got the injectors back, the guy told me they are all balanced and he refitted new seals and what not.

Fitted them back in the car, and now the car keeps stalling. before it stalled once in 6 months, now it stalls when i give it gas. When driving, if you floor it, it will cut out.

While stationary, it will stall sometimes .

To also mention, I also replaced the IAC motor with a brandnew one. didnt make a difference.

So its either too much fuel or not enough fuel?

[Titch2000]

Hi there,

Going by what you are saying I would be looking to check the spark by removing the HT leads one at a time from the coil pack and see how strong the spark / arc is from it. Maybe you have had one of them go or something that controls them could be wrong. Just to confirm do you have all of the HT leads going to the correct plugs? Spark order matters

I am by no means knowledgeable like some here but given you have new spark plugs, HT leads and have confirmed there to be fuel this would lead me to one of two other options. Air or Spark. Given these are cable throttle controlled then I would not expect it to be Air related in which case my next place to look would be the spark.

Hope this helps.

[spiros]

Here is a good how to diagnose coil packs tip !

Larry McCoy

[cableguy]

Damn thats a good idea, but unfortunately I don’t have spare vacuum hoses.

However an update.

This morning started the car to try and create the same nonstart issue, which I managed to do. Then took out a spark plug, grounded it while I got a mate to crank.

Guess what, no spark! Across the front 3 and didn’t check the back, if the front don’t work I can only assume the back don’t either.

I know if I leave it for a bit and go back, after an hour or so it’s going to start.

Are we back to the original ECU issue?

[Vince_GTO]

You’re neraly there bud! Simply put the origin of spark goes ECU → PTU → Coil → HT leads ->spark plug

Given that all three do not spark doubtfully it’s the leads, Coils - also doubtgully but worth checking (at least check resistace if it is within the normal range), then PTU - this defo needs to be tested carefully, there are transistors that work hard, transistors breaking in the way that they work ok when cooled and misbehave when warm - not unheard of.

And lastly - our notorious ECUs. But let’s keep in mind that the ECU as such might not be at fault as it produces signals to PTU based on the inputs of other sensors…

[Titch2000]

Yeah I would go with Vince’s reply above next to look at either testing or replacing the PTU if you have no spark for all 3 of the front from what I know of it is extremely unlikly for all 3 coils to fail.

Take a look at Vince’s message above this sums up the next steps of where I would be looking.

[cableguy]

Thanks, yes we are going to get to the bottom of this.

Sparks plugs, HT leads are new so I know those are fine.

I think coils are good too, as once its running, it’s running. There is no misfire or any indication to bad coils.

I bought an aftermarket PTU, made by blue print, but I don’t think the car likes it, as when I connected it, it makes the revs jump, so that’s going back.
I have bought a genuine PTU, just waiting for that to arrive, hopefully there should be some improvements.

[cableguy]

Update,

Installed a new PTU. doesnt make a difference. Starts runs, but when you switch off, it wont start again.
before it was when it was hot, now its if you switch it off, and try to start again after 30 seconds, it wont start.

Checked again, there is no spark.

I am going to check the signals with a probe and multi meter, Does anyone know what the voltage should be coming out from the ECU to the PTU?

Using the wiring diagram (that i forgot i had) i have made an easy to understand diagram:

[vtecgrin]

This site goes into great detail. The PTU is about 2 thirds down the page

ignition system

[vtecgrin]

You’ve probably already checked engine earth straps and continuity when hot or cold ?

[cableguy]

Thanks great find, going to read through it.

In regards to the ground straps, I could only find two, one connected to the gearbox and the other from intake manifold to the main body. Both had ground but I only checked them while cold.

Are there other earth straps?

The thing that really bugs me is why it starts when I leave it for a few hours🤬

[vtecgrin]

Maybe this checklist might help ? Is there any way for yoy to test or check your ECU or swap it out with A known good one, or get hold of a decent scanner ?

service manual 92-96 vol1 link https://drive.google.com/file/d/19iA1-24vz9AlXrIPVRmNiNF2-6pzaryU/view?usp=sharing

click link to view of preferably download

[vtecgrin]

Ok, last crack at this. When the engine stalls or won’t restart and you crank the engine … is your tacho reading zero ? if so it’s your CPS (crankshaft/camshaft position sensor/ harness) you mention it runs worse since the injectors were changed. I’m thinking the harness for the CPS is very close to the injector harness ? Checking these sensors along with trouble shooting is from around page 103 in the above file.
copied from elsewhere

“The problem that happens alot is with crank position sensors. Once they heat up to operating temperature they stop work intermittently like a faulty oil pressure sensor does.(only when the sensor is failing). You will have to let your engine cool off before your crank position sensor will begin to work again. This is often misdiagnosed as ignition problems but when this sensor fails, pcm cant time spark ignition so there will be no spark.”