Cranks but no start after head gasket replacement

suprasick

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#1
First off, as a long time member of this forum, I respect your time and always post as a last resort. I have about 20 hours diagnosing this and I can't figure it out. Its driving me mad!

After 4 years of the car sitting I finally got the motivation to replace the head gasket on my trusty 7m. The car ran great before the head gasket blew.
I have ran out of things to try hopefully somebody has some ideas. I have never had a car problem I couldn't fix until now.

PROBLEM: Car cranks over fine. It tries to start as I can hear it sputtering and gaining up to 550rpm but never stays running. Smells of gas afterwards. Here is a video:

DIAGNOSING BASICS:

SPARK: I was able to verify spark visually by pulling a plug and grounding it to see spark when cranking.
FUEL: I have an adjustable fuel pressure with the gauge reading at 40psi when cranking I have also pulled the return line to verify fuel was coming out. There is also 35psi of rest pressure after 1 hour.
COMPRESSION: On cold engine was 125psi with a 2psi maximum difference across all cylinders
TIMING: TDC 0 degree crank position verified by pulling number 1 spark plug and inserting a chop stick. Cam timing mark align with the back cover and metal dowel pin is in the center position. CPS position was tried in multiple ways. I tried the TSRM way, a guide on SM, and for shits flipped it 180. Here is a video of timing:
ENGINE CODES: none

DIGGING DEEPER:

Verified continuity from the ECU to NE, G1, G2
Checked resistance of CPS to TSRM spec
Coil Packs are within TSRM spec
Checked ECU voltages via TSRM with only IDL to E2 when throttle open out of spec @ 4.6v to a TSRM=10-14v
Fuel injectors pulled. Resistance verified and hooked up to pressure to verify spray pattern and no leaks.

OBSERVATIONS:
When cranking it smells extremely rich.
Spark plugs were fouled with gas. Looking inside cylinder shows wet top on piston
Only tries to fire if throttle open

All of these signify a rich condition.

I have tried lowering fuel pressure. Also tried unplugging the CSI time switch. All had no effect.

NEW PARTS:

Spark Plugs
Spark plug wires
Timing Belt



I have a DET3 hooked up running speed density and it ran fine before the headgasket change. I pulled the logs and attached them. I also took the DET3 out and returned car back to stock with the AFM attached. No change


Any help would be appreciated. I am at a loss of what to do next. Any ideas?
 

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Piratetip

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#2
I wanted to say excellent job with your current diagnosis/attempts at resolving the issue.
Unfortunately I don't have much experience with the DET3, so won't be of much help.

My general thoughts are that the cold start enrichment settings are way off.
Or the spark is weak (doubtful), or the spark timing is off.
If you have to floor it that usually is the universal method to clear a flooded engine. (cuts fuel)
Have you verified the injectors are working correctly? What CC ratings are they?
There isn't one sticking open?

I know others here are experienced with that system so hopefully they will chime in.
 

suprasick

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#3
Thanks for your feedback!

Yes I have verified they are working correctly by resistance and also attaching them to a syringe full of alcohol under pressure and turning the injector on. All hold pressure and shoot a fine mist. They are rx7 550cc but test out at 570cc. My fuel pressure after an hour is around 35psi. So that leads me to believe nothing is leaking.
 

plaaya69

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#4
On your piggyback do you have to set it up so the timing is synced? I am running the ECU Masters standalone and I had that issue at first with the Supra not starting. Also I would check to see if you need to update the tuning software and firmware on the DET3?
 

suprasick

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#5
On your piggyback do you have to set it up so the timing is synced? I am running the ECU Masters standalone and I had that issue at first with the Supra not starting. Also I would check to see if you need to update the tuning software and firmware on the DET3?
I noticed on the logs under ign status is says "No Sync". I also pulled up a log from 4 years ago when it was running and it also says "No Sync". Would you happen to know how to sync it?
 

plaaya69

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#6
That was the issue I had and it would remain blank but once my tuner synced it for me in the software, that ignition status box turns green when cranking. We also had it verified with a timing light. I would check out their facebook group and you might get a good answer over there:

https://www.facebook.com/groups/ECUMaster/
 

Piratetip

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#7
I was going to point out the no sync in the log, but you said it ran before :cool:.
Anyway plaaya69 is the guy that can help you with this.
 

suprasick

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#8
To rule out the DET3 I also wired everything back to stock and put the AFM back on and I had the same result.
 

Z06gette

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#9
sounds like maybe you washed the cylinder with fuel dropping compression. Shouldn't compression be 140 and up? Maybe try a splash of oil in each cylinder to reseal the rings.
 

Piratetip

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#10
I would check the CPS pinout.
Did you change anything with the wiring on that?

Check for bad wires / insulation / pins / connectors ect...

Are you able to log the NE and G1 / G2 CPS pickups (waveform) with the DET3 while cranking / partially running?
Preferably at a high sampling rate.
 

Enraged

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#11
+1 on the CPS wiring. Check both sides of the CPS connector, on my car it was the sensor side that was broken/intermittent connection. Made for some wonderful random no-start situations.
 

3p141592654

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#12
I would also look at anything you could have messed up during the HG repair. For example, are you sure the cam pulleys are properly aligned to the cams. There are multiple dowel holes that could put you off a decent amount. You show the pulleys properly aligned, but that is not sufficient if you removed the pulleys from the cams at any point in the repair.

I think you say you reverted to the stock ECU. Check that the tach responds during cranking. That confirms the CPS signals are ok.
 

suprasick

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#13
I would check the CPS pinout.
Did you change anything with the wiring on that?

Check for bad wires / insulation / pins / connectors ect...

Are you able to log the NE and G1 / G2 CPS pickups (waveform) with the DET3 while cranking / partially running?
Preferably at a high sampling rate.
I had to cut back and add wire to the CPS about 5 or so years ago but the car ran fine after that.

I have bench tested the CPS per TSRM and it tested good. I also probed the back of the ECU to the connector for the CPS in the engine bay. All show continuity.

After reading more about the DET3, it does show I can scope the NE signal to show the waveform. I will do that tomorrow and post the results.


I would also look at anything you could have messed up during the HG repair. For example, are you sure the cam pulleys are properly aligned to the cams. There are multiple dowel holes that could put you off a decent amount. You show the pulleys properly aligned, but that is not sufficient if you removed the pulleys from the cams at any point in the repair.

I think you say you reverted to the stock ECU. Check that the tach responds during cranking. That confirms the CPS signals are ok.

Thanks for your response! I have done 3 head gaskets on the 7M in my life but its been 4 years since I touched one so I have been picking my brain constantly to see if I have messed anything up during the HG repair. I had a buddy of mine who has a lot of experience with Supras come over yesterday to check my work and he came to the same conclusion I did unfortunately. It sounds weird, I know, but this is all I can think about for the last week its driving me crazy!

The cam pulleys are aligned with the dowel in the middle hole. Is this the correct way? I will get pictures tomorrow to verify.

The tachometer does respond during cranking and does rise with the half second or so when it tries to fire.

Is there anything else you can think off that I could of messed up that would cause this problem?
 

suprasick

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#14
sounds like maybe you washed the cylinder with fuel dropping compression. Shouldn't compression be 140 and up? Maybe try a splash of oil in each cylinder to reseal the rings.
I thought it was odd too but just blamed it on the engine being cold and the ring gap being larger?
 

plaaya69

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#15
Do you have all your grounds coming off of the engine wiring harness on the lower intake manifold connected? I believe there is two grounds with multiple wires on each one on the factory harness in that spot.
 

3p141592654

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#17
dowel pin in the middle is correct. I would double check that. Might explain the low compression. strictly speaking 128 to 156 psi pressure is ok but 142psi is the norm.

Given the tach is responding I would say you have good signals from the CPS. I would check for any big air leaks in the manifold. Brake booster hose disconnected, that sort of thing.
 

suprasick

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#18
I was able to get the waveform from NE off of the DET3. See attached. Also is a picture of the cam alignment.

Some good news (I think) is that I am now getting a repeatable code 14. If I pull the efi fuse I am able to get the code after cranking. Here's a video:


To me it seems like it tries to fire at first then when IGF is not detected it cuts fuel. It also doesn't smell like gas anymore after cranking.


I did try to test the ignitor on Sunday but I had the plug upside down when I applied 3 volts did I toast it?

The only way to test IGF is with a scope right?

I was looking in the TSRM for the pinout for the igniter so I could test continuity between IGF on the ECU to the Igniter plug but I couldn't find which pin IGF is on the Igniter plug.

EDIT: I couldn't remember if I have the throttle open when I was testing compression so I did it again I got a repeatable 134 | 142 |144 | 142 | 143 | 143
 

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figgie

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#20
SupraSick

Triple check the wiring at the CPS connector. Even 4 years, the heat cycles in that region are pretty high and unless you are using... oh something like a PTFE/Tefzel sheethed wire, the automotive GXP wire will melt and expose bare copper which usually shorts out in that area.
 

suprasick

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#21
SupraSick

Triple check the wiring at the CPS connector. Even 4 years, the heat cycles in that region are pretty high and unless you are using... oh something like a PTFE/Tefzel sheethed wire, the automotive GXP wire will melt and expose bare copper which usually shorts out in that area.
I have continuity from the ECU to NE, G1, G2 and CPS was in spec per TSRM. According to 3p, if the tachometer moves (mine does) the CPS is operable.

I was able to fix the code 14. It was due to the harness side coilpack connector wires breaking. I fixed that by wiring in a new connector. It must of broke when I was testing coilpacks last Sunday. So I'm back to square one. No codes and engine cranks and doesn't start.

I did just get an oscilloscope what can I check?
 

Piratetip

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#22
I did just get an oscilloscope what can I check?
Each Ignition Coil
-Secondary kV output
-Output Waveform Shape
-Ignition timing

-Also do you have the ground wire on the coil pack assembly connected to a good solid ground?
-Same goes for the igniter.

CPS
-It appears you have a signal from Ne.
-Did you check if there is also a signal from G1 / G2?

AFM
-Check the output signal from the AFM - KS

Does not sound like a fueling issue, sounds like an ignition issue.

Its either this or the signal from the CPS is not reaching where it needs to be.

As Pi mentioned before, there could also be a massive air leak somewhere still.
Check all the hoses, make sure nothing is disconnected.
 

suprasick

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#23
I used NE on the positive side of scope and G- as the ground with a positive trigger and got a square wave. What about G1 and G2? Do I hook them up on the positive side of the scope with G- being the ground? Should I get a square wave aswell? I sincerely appreciate your help.
 

Piratetip

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#24
Yes G- is the common ground for all 3 sensors.

http://www.cygnusx1.net/supra/Library/TEWD/MK3/manual.aspx?S=Main&P=040
http://www.cygnusx1.net/supra/Library/TSRM/MK3/manual.aspx?S=IG&P=9
http://www.cygnusx1.net/supra/Library/TSRM/MK3/manual.aspx?S=IG&P=16


Did you already perform all the igniter checks as well?
http://www.cygnusx1.net/supra/Library/TSRM/MK3/manual.aspx?S=IG&P=15


Also have you checked the output signal on the TPS sensor?
Just to verify it is telling the ECU the correct opening angle.

What else...
-Check the coolant temp sensor is in spec & wiring is good (the one the ECU reads) (THW)
-Check intake air temp sensor is in spec & wiring is good. (THA)
 

3p141592654

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#25
Just for education, the tach moving confirms NE and at least one Gx signal is active. You will not get any spark unless the ECU synchs on a Gx pulse. That is why you will usually see the tach jump up only after at least half a crank revolution. It only needs one of the two to run.

With the scope confirm good spark voltage. You should also confirm a square wave out of the AFM KS signal. Then I would look at the injector pulses.

Your cam pulleys look fine, assuming the dowel is in the center hole on the cam. I'm sure you checked.
 
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suprasick

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#26
While waiting for the attenuation probes to arrive in the mail I checked out a few things. I tested the igniter to TSRM spec and it tested good. I also hooked up the scope the to CPS and NE, G1, and G2 all have great signal. I probed them on the bench and the ECU so that means signal to ECU is good.

I also get a square wave from KS.

The car was left uncovered for a year or so and turns out that the lower hatch trim was leaking and caused water to pool up in the spare tire area. Of course in the summer is when I noticed it (when the windows formed condensation) and when I looked under that dash it was horrible. There was corrosion everywhere. Especially on the front support bar. The wire terminals were corroded too.


To clean up the corrosion a bit I took out the fuse block and the integration relay 1. Damn that was a pain!

I was able to clean the corrosion and apply acf-50 to the terminals to hopefully beat anymore corrosion.
I got everything back together and plugged in and still the same problem of no starting.





Tomorrow I should have time to check the injector pulses.
 

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suprasick

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#31
I haven't had a lot of time to work on it but here are some of my findings.

Spark voltage is around 4.5kV when cranking. The secondary ignition waveforms look good if I unplug the fuel injectors. If I keep them hooked up the plugs get fouled and the waveform oscillates until is dissipates.

Injector pulse when cranking is 10ms (see picture). Correct me if I'm wrong but 10ms seems to be a long time when just cranking?

To test my over fuel theory I disconnected the fuel injectors and only used starting fluid when cranking. That resulted in me loosing some hair on my arm as it back fired through the intake. This screams timing but as you have seen in the previous posts my timing is spot on.

I also added and removed Hz to KS and the injector pulse stayed the same when cranking is this normal?

In the 15 years being involved in the Supra world, I don't think I have ever heard of a 7m ECU going bad have you?
 

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suprasick

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#32
Success! The Supra has risen (on Easter too coincidence?). In order to get it to run I disconnected the fuel pump relay and sprayed starting fluid into the throttle body and she ran on her own power!

So my next question is why are my plugs drowning in fuel? Bad injectors? I have put everything back to stock well kind of (550 cc injectors and lexus afm).

 

Piratetip

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#33
What type of injectors? Hi Z, low Z?
Running with or without resistor box?

Are you running with a cold start injector still?
If so have you checked the cold start injector and injector time switch is working properly?

Is the ECU Coolant Temp sensor reporting out normal values?

I wouldn't think all injectors are sticking open, but maybe possible.
 

suprasick

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#34
The injectors are RX7 550cc high impedance. I'm running them with the resistor box.

Still running the cold start injector. I haven't tested it by the book yet but when I open the throttle and look through it while cranking I see it spray for like a second.

I will test the ECU coolant sensor.

I don't believe any of them are stuck open because I have 30psi of rest pressure after an hour.
 

figgie

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#37
The injectors are RX7 550cc high impedance. I'm running them with the resistor box.
Regardless of what everone says,

if you are running High Imp injectors then remove the resistor box.

That would be #1.

#2. You mentioned this happened after an HG job,

did you triple check to make sure that the White-black ground (2 wire) and brown ground wire are grounded to stock (below intake manifold) or other good clean grounding point? This is what physically gives the EMS power to work correctly.

as for the coils, I recall the math put it at around up to 40kv but without anything impeding the spark event (ie fuel and compressed air) it will be lower for a longer period.
 

suprasick

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#38
I was able to test the coolant sensor today which is functioning within spec.

I bypassed the resistor box and same issue.

I quadruple checked the grounds on the intake manifold again the white/black and the brown wires on the intake manifold.

Here is the fuel injector pulse from the scope. It shows its width around 11ms. And this is just cranking. fuel injector.jpg
 
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3p141592654

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#39
your injector pulse looks completely normal . The injector is firing and the duration is reasonable. 11ms is about what I would expect at 30C.