Hello all,

Problem: Engine cranks but won't start

Facts:
Spark is confirmed
Fuel pressure is confirmed
Air restriction is non-issue
Starter fluid in throttle body allows car to start for a second

ECU codes:
13 Cylinder Head Temperature Sensor
23 Idle Switch circuit
31 Air conditioning
41 Fuel Temperature Sensor

Background: I was driving along one day and the fuel pump died on me, I had been experiencing fuel pump failure symptoms for a little while (low power, backfiring at highway speeds). I got the car home and disconnected the hose at the fuel filter to check for fuel pressure, I was getting hardly any fuel flow so that confirmed the fuel pump was bad (new fuel filter). I ordered the new fuel pump, got it installed, and confirmed fuel pressure up at the engine. Now the engine cranks but will not start, but the starter fluid in the throttle body gets it to fire for a second. My understanding is this means I'm not getting any fuel in the combustion chamber, and dry spark plugs confirm that suspicion. I decided to check the fuel pressure regulator, and did so by removing the fuel return line. The regulator seems to be working because it was sending fuel back to the tank, as it should with a functioning fuel pump. That pretty much leaves me with injectors as far as I know, I have not yet tested the crank angle position sensor to see if the injectors are working properly. I am skeptical that all my injectors would fail at once, so before I spend much more time digging in that direction I wanted to get your input.

P.S
The codes were all present before this new problem, so they may or may not be relevant.

 

Well I stumbled on the solution, and thought I would share with you all. I plugged my extra ECU (don't all cars come with exta ECU's?) and it fires right up. It seems that something about this last failure caused my old ECU to fail. I'm not sure if this will reoccur or if the issue was a fluke.

 

Hello all

I seem to have developed a new problem with my Z non-turbo. Or maybe its an old problem that just decided to kick me in the ars.

Current symptom:
Car starts and stalls out almost immediately. This started when I was driving down the road (right about when it got to operating temp) and the car just died, then it persisted to do the start/stall thing. I have not checked it again since its cooled down yet.

My last issue was similar, except the car would not get combustion at all, and it ended up being faulty wiring to my injectors. I soldered the wires and made sure I had continuity back at the computer end of the harness. When I took my injectors off to test/clean them one of my injectors died on me, so I've been running around on five injectors for a few days. Not a big deal since before I was only running on three because of the wiring fiasco. I digress.

While I was troubleshooting the car last time I identified some problems.

Known Problems:
MAF meter harness is bad, sensor tested good
Power Transistor is faulty
Fuel Temp Sensor is faulty
One injector is dead
These are problems I had while the car was running, not sure if they are connected to this new failure mode.

Codes:
21 Ignition signal missing in primary coil
23 Throttle valve switch circuit
31 Load signal circuit (power steering oil pressur switch, headlamp switch, radiator fan switch, rear defogger switch, heater/air conditioner switch)
41 Fuel temperature sensor circuit
13 Cylinder head temperature circuit

These are old codes, I need to get the car home to run the diagnostic mode and confirm these are the same codes.

Once I get it home I will go through the basics to hopefully come to a quick fix. I plan to confirm the fuel system is working, I'll even take the bloody injectors off again if I have to. Once I do that much I'll go through the electrical parts of ignition. I'll also go through all my vacuum lines to make sure nothing is clogged. If any of you have any ideas I'd be glad to hear them.

 

Merged threads.

This wasn't the last issue then?:


A 6 cylinder engine running on 5 cylinders IS a big deal. My car was running on 5 cyl due to a dead injector and as soon as I stepped on the throttle it would fall flat on it's face.

Fix these.

You seem to know what the problems are, but it sounds like you are downplaying them or trying to talk yourself out of these problems affecting how the car runs...

 

Thanks for the reply, from what I can tell the issue last time was I had a whole side that was not getting injector pulse from the ECU, and on my other side I had two good injectors (the third was nearly clogged). So that is what I meant by "its not a big deal." It is possible (probable) the issue I'm having now was also present the last time. But fixing the injector wiring caused the car to run, and it did have noticeably more power (but still not as much as it should) I hoped I could drive as-is for a while. I drove it for roughly a week and it seemed steady, except for two or three times when my fuel would cut out for a second (sort of like a single stutter). Usually happened just as I was changing gears and stepping on the accelerator. My RPMs were high, which I eventually traced to a vacuum line that was loose. The next day after I fixed the vacuum hose I took off for work and the car stalled out after about 3 miles in much the same way it had before. The similarity is in how the car died, but the difference this time is I can get it to fire.

I am aware of several issues with the car, and do intend to fix them, but as money is tight right now I'm most interested fixing the issue that's keeping me off the road while throwing minimal parts at it.

 

if it runs fairly well until it gets hot unplug the O2 sensor. driver side towards the rear and down. do it cold you don't get burned. If that fixes things you know the cause. the other cause of issues with engine heat is the CHTS. yours sounds more like O2 but could be both. I'd just replace the CHTS anyway had to do it on three I've owned.

 

got the car home tonight, it did start and I was able to drive it onto the car dolly. In the garage I ran it for a while and it idled fine. I decided to do the ol' screwdriver-stethoscope test on my injectors and I'm pretty sure now I am only running on my passenger side injectors. The two toward the front of the car sound solid and the back one sounds lighter. I double-checked the other side to listen for a pulse... and nothing. Funny because before my front two injectors on the driver side were the only ones working.. so it switched. Tomorrow I'll test the injectors for continuity to get a headcount.

I will look into the cylinder head temp sensor and O2 sensor tomorrow as well, but i'm less inclined to think its a heat related issue after tonight. If I had to guess I'd say I'm running on two-and-a-half intermittent injectors driving down the road at normal load and if they sputter or anything at all the car stalls since there are only two (or three) of them. I'll take the injectors out of the engine tomorrow and turn the engine over to see what the injectors are doing... should be able to get to the bottom of it.

 

An update, I have confirmed that the three injectors on passenger side are operational via an ohm test, there is only one on the driver side that shows the correct resistance now so that is the only one I'd expect to see function when the car is running. I ran the car for a while this morning and confirmed I am only getting injector pulse to the passenger side injectors. This led to a complete rundown on the wiring harness, to which I confirmed the wiring harness is good. I've got battery voltage at the red wire and the green wire tested good at the ECU side of the harness.

So the wiring harness is fine, and the injectors are good (the ones that aren't bad anyways). So that leaves me with an ECU problem. Now the question is, there are six injector wires going out of the ECU and only two are being used. Can I check the other ECU terminals to see if they pulse and switch wires to get my injectors running. I'm going to open up my ECU to see if there is anything obviously wrong.

 

well my first ECU is a mess, looks like the transistors anchored to the wall of the interior on the ECU are pretty well corroded. My guess is those are the transistors that switch the injector green wire low to pulse them. My second ECU (the only one the car runs with now) looks better, but I still only get the passenger side of injectors. I know I need to get a new computer, but I would still like to mess around with this one some more.

Fun note, the plastic pieces that anchor the transistors to the wall of the ECU has a metal strip on its back. I had the metal part facing the transistors thus tying them together, and the metal case was electronically live enough to arc on the car body when it touched. That may be why the car randomly cut out as I was going down a bumpy road. Anyways I put the plastic insulator clamp thing in right and no more arcing, so that's always good.

I'm going to take the car outside and run it at 2-3K RPM for 5-10 minutes to see if I can get it to replicate the failure I experienced this last time. I'm getting tired of having it towed home.

Added a new computer to my "grocery" list

 

Took the wiring harness out to visually inspect and ohm it out with a mulitimeter. I now have a better understanding of how the wiring harness works. I also changed my injectors back to pre-service campaign while I had it out. I put the harness back in the car and am confident it is good. Started the car up, still not getting injector pulse on the driver side. The car does run, but it sputters intermittently. It has not stalled out on me like it did before, but I've only been reving it in neutral, I've yet to take it on the road.

I'm getting to the point where I'm confident the computer is faulty, and I feel pretty good about putting another one in since I checked the wiring harness.

My next step is to order a computer and an injector, since I can't think of anything else to try. I'll update with the results.

 

The saga continues, I purchased a new (used) ECU and installed it, which had a drastic effect on how the car runs. It now seems that both sides of my engine are getting injector pulse, which is good. However, the car now idles at 1500 RPM when cold and 1200 RPM when warm. When I press the accelerator I now get a hesitation until about 2000 RPMs then the car revs normal.

I took the car for a 10 mile drive and the power is where I'd expect it to be, climbing hills in second gear I was only able to crawl up in first before. I'm thrilled to have all my cylinders working but now I need to deal with this fast idle and throttle hesitation.

I have adjusted and confirmed the TPS sensor, and know the wiring harness is functional, but I'm still getting a code.

I have adjusted the MAF screw next to the connector with no noticeable influence on the RPMs

I have adjusted the Idle-up solenoid screw with no noticeable influence on the RPMs, but if I disconnect the solenoid the idle goes down to 1100 RPMs.

I have checked for vacuum leaks, and cannot find any. The car idled right around 700 RPMs with the previous faulty computer, and the only thing I changed was putting a new computer in.