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T2 cranking but wont start

Old 10-18-18, 07:26 PM
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T2 cranking but wont start

Hi, Ive got a 1987 gxl with a 1990~ t2 motor.
i rebuilt the motor and when i went to start it up it would just crank over and over and not start.
It has good compression, spark, it has fuel pressure, the injectors are firing, the timing has been set. And it wouldnt start. I then jumpered the f/p check connector and tried starting it and it started right up really easily and ran smoothly other than some idle issues.
It would idle at 1100 rpm but if i touched the gas pedal even slightly it would jump up to 2000 and stay there. If i hit the gas at all it would just rev up then fall back to 2000 rpm. Then if i put it in gear with the clutch pedal fully compressed it would bog down slowly until it eventually would stall. It would do all this until i turn it off and then start it up again in which the idle would stay at 1000 until i touch the pedal.
I saw some oil coming from the turbo area so i turned it off and wanted to see where the oil was coming from, so i removed the bac, air pump, and acv. I figured out it was just residual oil from when i poured it into the spark plug holes, leaking through the wastegate housing via small exhaust leak (theres no gasket? Not sure if thats normal)
so i cleaned it up and put it all back together, jumpered the f/p connector, and now it wont start at all just like it was doing initially. Its been a month now and i cant figure out what it is. Ive searched and searched but cant find a solution..
1990 t2 engine
Stock ports
Stock turbo freshly rebuilt
87gxl body
Engines pretty much all stock
T2 ecu
Has fuel pump regulator
Has all emissions equipment besides no cats
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Old 10-20-18, 07:18 PM
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You mentioned everything being fine (compression, spark, injectors, etc.) before you got it started the first time, did you confirm that that was still the case when you tried to start it after you pulled it all apart? No fouled plugs? No leaky injectors?

Also, can you confirm which T2 ECU you're using and also which injectors?
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Old 10-20-18, 09:21 PM
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I haven't checked compression again but ill do that as soon as i can. I have performed the deflood procedure time and time again and it hasnt made any difference. It has the stock 550cc injectors and the s5 ecu, (it says stage one on it in marker, maybe the guy before me modified it)
also i forgot to mention the omp is deleted so im running premix.
Would a vacuum leak cause this issue? I tried blowing into the intake and i couldnt hear any air leaks
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Old 10-23-18, 08:39 PM
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Originally Posted by Jake87fc View Post
I have performed the deflood procedure time and time again and it hasnt made any difference.
with new plugs?

It has the stock 550cc injectors and the s5 ecu,
Are you using the original '87 harness with the resistor between the two?

Would a vacuum leak cause this issue? I tried blowing into the intake and i couldnt hear any air leaks
If it's big enough, yes. However, it should also be trying to fire, or firing and dying right afterwards - maybe even a couple pops here and there.
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Old 10-23-18, 09:13 PM
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Originally Posted by diabolical1 View Post
with new plugs?
The plugs have been brand new throughout the whole process of it not starting then starting and then not starting again. Just like the first time it didnt start it sounds the exact same. It turns and turns and a little smoke comes out of the tailpipes.
also i just checked the plugs today and they are oil free and just smell like gas.

Originally Posted by diabolical1 View Post
Are you using the original '87 harness with the resistor between the two?
The resistor has been put in the trunk next to the gas tank. im not the one who did the t2 swap but im pretty sure it has the s4 body harness as well as the s5 engine harness considering there are so many unused plugs in the engine bay

Originally Posted by diabolical1 View Post
If it's big enough, yes. However, it should also be trying to fire, or firing and dying right afterwards - maybe even a couple pops here and there.
it just turns and doesnt even sound close to starting.

Its weird because it was doing this exact thing before and i took off the uim and everything around it and inspected everything then unplugged pretty much everything testing resistances and such, then i put it all back together and by chance i forgot the jumper wire in the F/P check connector and when i turned the key it fired up after a second of cranking. It sounded super healthy and whenever i turned it off it woukd start up again just fine. But when i tried starting it without the jumper it wouldnt start. Since i saw oil and smoke coming from the turbo area i removed the bac, the acv, and the air pump and unplugged all associated plugs and hoses. I removed the down pipe and the wastegate cover and re installed everything. No start just like before. I tried it with and without the F/P jumper with no luck. Is there anyway i left something unplugged before that would allow it to start? And why would it start only with it jumpered?
All injectors are working and all spark plugs are clean and firing. Im going to buy a new battery on payday so i can test the compression since this one cant keep a charge anymore
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Old 10-23-18, 09:35 PM
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recently had this kind of issue. Mine sounded like it wanted to start but wouldn't. make sure you have correct ecu, boost sensor, and Air fuel meter that match your year.
here is a link to my post and issues. idk maybe it will help. https://www.rx7club.com/2nd-generati...start-1130377/
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Old 10-23-18, 10:30 PM
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It has the correct ecu and afm and ill check the boost sensor tomorrow. However wouldnt the fact that it ran fine before with all the current equipment rule all that out?
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Old 10-23-18, 10:50 PM
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no not really. I Did get mine to start a hand full of times with a s5 boost sensor and s5 AFM even tho mine is a s4.
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Old 10-24-18, 08:17 AM
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Originally Posted by Jake87fc View Post
also i forgot to mention the omp is deleted so im running premix.
Sorry if this has already been addressed, but I'm fresh out of ideas. I can't say I'm well-versed when it comes to S5 OEM troubleshooting. However, I'm going through your posts line-by-line and this just jumped out, so I figured I would ask. I know S5 cars go into limp mode when the MOP fails, but is still connected. Do you know how they behave when the MOP is missing altogether?
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Old 10-24-18, 11:05 AM
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I was going to mention the same thing. If you're running S5 ECU without OMP then you will be in limp mode. If you fetch for codes you will probably be flashing 20,27, and 37.
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Old 10-25-18, 09:57 PM
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I had no idea about a limp mode. The Omp is capped off but still connected! Ill unplug that tomorrow and see what happens.

Today i tried checking the TPS but was getting unclear readings, i think im supposed to see 1000 ohms or something? I dont really know if im doing it right. I also did a test to see how well my fuel pressure holds, it dropped to zero in about 30seconds.

not gonna lie my car is a wiring nightmare and as soon as its running healthy im gonna clean it all up.
But i do know it started fine until i messed with the wires and hoses and things to get to the turbo, so ill try unhooking the omp!

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Old 10-26-18, 01:16 PM
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Originally Posted by Jake87fc View Post
I had no idea about a limp mode. The Omp is capped off but still connected! Ill unplug that tomorrow and see what happens.
Well, just to be clear, I was under the impression that you had it disconnected when I mentioned it. I'm not sure disconnecting it now will serve you any purpose. As far as I know, limp mode will allow the engine to fire and run, it just doesn't allow you to make any power with it. As I said, I don't know how the computer would react to not "seeing" it at all, but that's not the scenario you have here.

I also did a test to see how well my fuel pressure holds, it dropped to zero in about 30seconds.
This may or may not be significant. Maybe you have a leaky injector. With the return line in place, I don't know how long the pressure should stay in the line, but I don't think it should go to zero. I've pulled those lines before and had significant spray. Maybe cap off the return and retest it and see how long it holds pressure then?

But i do know it started fine until i messed with the wires and hoses and things to get to the turbo, so ill try unhooking the omp!
It is certainly worth retracing your steps and double-checking everything you touched, because you are correct in thinking the car should still be able to start, with all else being equal. Your intervention was the only difference, and I've been there enough times to know we can make simple mistakes and/or oversights when trying to put these things together.
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Old 10-28-18, 11:40 PM
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Originally Posted by Jake87fc View Post
I also did a test to see how well my fuel pressure holds, it dropped to zero in about 30seconds.

My Tii drops fuel pressure back to 0 just seconds after turning the car off. Its done it with two different OEM fuel pumps and still does it with the TT Supra pump(new in box), its done it with the OEM fuel rail with built in regulator and does it with RisingRPM rails and a Aeromotive regulator, its done it with both OEM 550s and the current ID 850/1000 combo. But its never caused a drivability or starting issue on either the stock N370 ecu or with the Megasquirt 3X the car has had for a few years now. So i would venture a guess that that isnt cause your starting issues.
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Old 10-28-18, 11:53 PM
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Originally Posted by Jake87fc View Post
I saw some oil coming from the turbo area so i turned it off and wanted to see where the oil was coming from, so i removed the bac, air pump, and acv.
From what you describe i would venture a vaccum leak exists somewhere. I assume you ended up reinstalled the BACV and ACV with new gaskets. Have you checked for vacuum leaks around the ACV? Ive found it quite a pain over the years to get them to seal well. Also you made sure the check valve disc between the LIM and AVC was reinstalled and seated correctly right? When you rebuilt the engine did you install new orings on the primary and secondary fuel injectors air bleed sockets? Ive definitely seen those orings be rock hard and a massive vacuum leak in the past.
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Old 11-14-18, 06:24 PM
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Originally Posted by SpikeDerailed View Post
From what you describe i would venture a vaccum leak exists somewhere. I assume you ended up reinstalled the BACV and ACV with new gaskets. Have you checked for vacuum leaks around the ACV? Ive found it quite a pain over the years to get them to seal well. Also you made sure the check valve disc between the LIM and AVC was reinstalled and seated correctly right? When you rebuilt the engine did you install new orings on the primary and secondary fuel injectors air bleed sockets? Ive definitely seen those orings be rock hard and a massive vacuum leak in the past.
Everything has new gaskets. i searched for vacuum leaks but everything is plumbed up and where it needs to be. I also suspect a vacuum leak, So How can i check for a vac leak if it wont start? I didnt make sure the check valve disk was seated properly so ill check that. And i did put new O rings on the bleed sockets.
The only thing that isnt there since it was working is the air silencer for the acv.

Last edited by Jake87fc; 11-14-18 at 06:28 PM.
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Old 11-15-18, 10:14 AM
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I feel like it isn't a vacuum leak. It should start even with let's say, the brake booster line off, which is a massive leak. Is the brake booster line connected to intake?

Maybe it's time to step back and start over.

Compression, fuel, spark, timing. Check all of these again. One or more of these things is guaranteed to be the problem. Whether it's mechanical or electrical is the question. Prove to yourself that all of these items are acceptable.

Have you fetched for codes? Very easy, very useful.

If you're running stock ECU you NEED the OMP connected.

The car will start with the boost sensor disconnected.

Have you tested resistance of the water thermosensor? Have you tried starting it with the water thermosensor disconnected?

When you try to start it does it catch at all? I've had success with a low compression engine where I would crank it for about 5-6 seconds. Then I would wait for about 30 seconds, then I would crank again with the peddle to the floor and she would start every time.

Last edited by Rotary Alkymist; 11-15-18 at 10:35 AM. Reason: bad english
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Old 11-15-18, 10:33 AM
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I'm not sure if waiting played any part in it but felt like it did haha.
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Old 11-15-18, 09:18 PM
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Originally Posted by Rotary Alkymist View Post
Is the brake booster line connected to intake?
I just checked its good and tight. Is there a method of checking for a leak?
Originally Posted by Rotary Alkymist View Post
Compression, fuel, spark, timing. Check all of these again. One or more of these things is guaranteed to be the problem. Whether it's mechanical or electrical is the question. Prove to yourself that all of these items are acceptable.
Ive been thinking the same thing, to start over with the basics. ill see what i can do on the weekend, ill need to borrow a timing light.
H
Originally Posted by Rotary Alkymist View Post
Have you fetched for codes? Very easy, very useful.
I cant find the single pin connector by the battery, i think the car has the s4 body harness cause it has a green 2 pin connector. Ill post a pic.


Originally Posted by Rotary Alkymist View Post
Have you tested resistance of the water thermosensor? Have you tried starting it with the water thermosensor disconnected?
no i havent, where abouts is it located?

Originally Posted by Rotary Alkymist View Post
When you try to start it does it catch at all? I've had success with a low compression engine where I would crank it for about 5-6 seconds. Then I would wait for about 30 seconds, then I would crank again with the peddle to the floor and she would start every time.
Today i got it up to500 rpm but it was shaking and didnt really sound like it was going to start. When it was working before i removed those things it cranked for maybe a second before firing right up.

Last edited by Jake87fc; 11-15-18 at 09:23 PM.
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Old 11-16-18, 02:26 PM
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If you ground the orange wire on the two pin then you could grab the codes from the 6 pin. There are writeups on how to fetch for zenki(s4) error codes.

Do you have a compression tester? It would be nice to know you're getting three even pulses on both rotors.
Does the the rhythm of the engine sound very nice and consistent? Is it an even locomotive sounding ch ch ch ch ch? Or does is have a different rhythm? Are some pulses more pronounced than others(hopefully not)?

The water thermosensor is located behind the alternator.

Could you take a photo of the position of your CAS, with blind cap off, with your yellow mark lined up on main pulley?
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Old 11-17-18, 10:03 AM
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I forgot to mention i fixed the fuel hold pressure issue (or just bandaided it) it had just under a 1/4 tank of fuel and i could hear air in the fuel lines. So i dumped another 20L in and now i cant hear any air and it holds at 20 after 5 mins. Its not the stock fuel pump and it has no branding on it. Im worried its chinese ebay crap.. but the fuel pressure is strong at 40 psi when cranking so i doubt thats the issue. Why would it be able to suck in air though? Ill get a picture of it today. Heres a picture of my cas


I did move the cas back and forth a little since it was timed so it might not be 100%

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Old 11-17-18, 05:13 PM
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I tried with the water thermo sensor disconnected, but it made no difference.

i tested spark on both rotors and both are strong
I tested compression on the front and it has 90 psi but strong even pulses, the rear has 120 psi and strong even pulses.

the engine has a new front rotor and both new rotor housings all new goopy performance apex seals, all new atkins side seals and solid corner seals + springs, new oil control rings + and all new rubbers and gaskets. The irons and rear rotor didnt get replaced but were well within spec
The exhaust smells like gas and makes smoke when cranking but doesnt want to catch at all.

the stock turbo inlet duct has many sections that are capable of leaking, but they all look and feel good. If i blew into the intake or something would that be enough to find an air leak?

Last edited by Jake87fc; 11-17-18 at 05:20 PM.
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Old 11-22-18, 04:13 AM
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hi,

how did you route your fuel lines to the engine?
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Old 11-22-18, 07:22 AM
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Ill look at the fuel lines today.

but last night i got it "started" for about 30 seconds. I was screwing with the timing and advanced it so the marks on the CAS were lined up when the timing peg was slightly to the left of the red mark. I had to give a little gas to keep it going but it sounded funny with it being advanced and all so i let it die.
ill check the fuel lines and maybe the injectors today to see if its all routed properly and to make sure the injectors are opening and closing properly.
any other ideas why it would be hart to start butt still start when advanced?
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Old 11-22-18, 04:46 PM
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The CAS photo is not any help. Take another photo straight on and centered with mark at yellow.

Last edited by Rotary Alkymist; 11-22-18 at 04:55 PM.
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Old 11-22-18, 04:52 PM
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You spark, fuel(spark plug looks wet to me), compression; it should start in a reasonable temp.

One thing left.
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