Dear ThridGen Members,

I am new to this site, so please let me introduce myself and my porject real quick:
I am owner of two 1966 Nova Coupés living in Germany.
One Nova is for drag only, the other is a cruizer that got engine/trans/tank transplant from a 1991 Camaro. I will post some pics as soon as I will remeber to take the camera to the garage...

Here is the problem that I am seeking help from you TPI-experienced guys for:

The engine cranks over, but does not start UNLESS I spray some starting fluid - then it starts right up and just runs fine like a normal TPI car. The situation is the same cold or warm.

I have been reading all posts that I found on this board with a no-start issue, but none of them seems to have the solution for me. Here are some more details:

Hardware
1991 Camaro 350 Z28 engine
TH700R4 transmission w 2400 stall converter w/lock-up
Tank from Camaro incl. new pump grafted into Nova
New fuel lines with -6AN Adapters
New fuel filter
Painless MAP TPI harness

ECM numbers
01227730
860571 M020625114
16150571

What I did check so far:
Chip did get VATS deleted
I do have 42PSI at the rail
Ohmed injectors - all are 16.8 +/- 0.2
Coil gets 12V in RUN
Coil gets 9.6V in START (I guess that is normal)
TPS adjusted to 0.5V
Initial spark advance to 6° (disconnected adv)
Idle RPM adjusted to 550rpm
Car did not start with TPS unplugged

So it seems like the injectors just do not fire while the starter is engaged - in RUN everything is fine.

Any ideas highly appreciated.

Regards,

Boris

 

im havin the same damn problem

 

fuel pump relay maybe.

 

You need to make 100% sure that your ECM is hooked to a power wire that is hot when the key is in both the "ON" AND "START" positions. ECM has 12V supplied through two wires, one is hot at all times (usually under the hood and hooked to the starter battery post) and one from the ignition switch or other switched power source. The ECM power MUST stay on and remain as close to 12V (or battery voltage) as possible when running AND when cranking!

If the ECM switched power is cut off during cranking, this is exactly the scenario you would encounter. Your distributor has power and therefore spark, so when you shoot the starting fluid to it it will start right up, soon as it starts, you let off the key, power goes back on to the ECM and the everything functions normally. There you are,scratching your head! Am I making any sense?

MANY early GM cars had circuits that were hot in the ON or RUN key positions and went OFF when you cranked the engine. That is why ALL GM cars in the 60's had cranking bypass wire from the "I" post of the solenoid to the coil post. That way the coil got full 12V when cranking and swapped over to a ballast resistor when running.
I assume you are running the correct HEI distributor for TPI? HEI runs at full 12 V all the time, there should not be a lot of voltage drop while cranking. How big are your distributor supply wires? OEM GM HEI requires at least #12 or larger wire for proper current capacity to the distributor. Is the engine properly grounded to the chassis? If the distributor voltage drops below a certain threshold the injectors and the fuel pump will not function, even though you may have spark. The distributor also supplies the reference pulse to make the injectors pulse and the fuel pump run. Low voltage will interrupt that reference pulse on Circuit 430 Purple/white from distributor to the ECM. I had a weak battery on my 305 TPI conversion in my 85 El Camino and it did exactly the same thing! Low voltage and the distributor would fire but no injectors and no fuel pump. Put a hot battery and solid cables, connections and ground straps and it fires off like a new car!

 

mlynch001:
Thanks for your suggestions.
Since I am using a Painless Muscle Car Harness for the rest of the car can it possibly be that scenario with no voltage to the ECM during cranking?
I hooked up the constant +12V for the ECM from the radio constant hot, and the other wire directly off the +side of the coil (I have the seperate coil distributor).
So if I understand you right, your suggestion for this would be to check if both have a proper 12V during cranking? I do have 9.6V at the coil while cranking, 12V when in IGN on.
I do have seperate grounds to the frame from the engine block, and the tranny.

Fuel pump relay works OK by the way.

Regards,

Boris

 

Has car ever started or is this a new install ?
The ECM has a 12 V input from the oil pressure switch that runs the fuel pump that it must see ( along with the ref pulse from dist ) in order to pulse the injectors when cranking .This input is only used while cranking

http://www.corvettebuyers.com/c4vettes/l98.htm

For the earlier '165 ECM but same setup

 

Nova66 - I do not know about the Painless Wire harness. My experience is with the OEM GM Harness. I would think that they would make sure that this could not happen. Have you checked the radio wire to make 100% sure that it is hot with 12V or more all the time. Why is the ECM hooked to the radio wire? Does the Painless harness NOT have a dedicated 12V+ "Constant" wire for the ECM?

The Constant 12V power from the 7730 ECM is not supplied from the oil pressure switch. This is a parallel circuit to 340 but it is not the supply for the ECM. The 12V flows from the starter relay fuseable link to circuit 340 AND to the Oil pressure switch then out to the fuel pump as well as to circuit 120 on B2. The oil pressure switch is a "Fail safe" for the fuel pump relay in the event that the relay fails. The ECM MUST see 12V power from the Pump relay OR the Oil pressure switch or it will not allow the engine to start. Circuit 120 is also a voltage reference line for the ECM that allows the ECM to compensate for system voltage fluctuations which affect fuel pressure and therefore the fuel mixture. If the ECM senses low voltage Under 2.0V over 1.5 second from the last reference pulse at circuit 120 and pin B2 it will set a code 54. this usually means that the fuel pump relay has failed.

ECM Ignition switched 12V+ power is fed through the ignition switch and to circuit 439 and into the ECM at Pin A6 which is a Pink/Black wire. This circuit MUST BE hot ONLY when the key is on AND in both the Start and Run positions.

ECM Constant hot is fed direct from the battery through a fusible link or fuse through circuit 340 and enters the ECM at pins B1 and C16 which is an Orange wire. This Circuit is HOT all the time.

Is there voltage drop at the ECM? I go back to my car with a low battery, it was turning over, but had such low voltage at the distributor that it would not trigger the injectors.

Have you had a Noid Light on the injectors harness and confirmed that they are not pulsing when cranking?

As a final "last ditch" effort to test, I would use an isolated and independent 12 V power source for the ECM, completely separate from the car 12V system and see if this made a difference. Power the ECM independent from the vehicle battery and harness.

Hope this helps. Good Luck!

 

OK, issue is solved!

mlynch001, I probably owe you a couple of beers for this one...

I spliced the +12V wire for the ECM required to be HOT in IGN and START into the fused radio circuit from the Painless harness. Turned out that it was HOT with IGN on, but dropped to near zero when in START (see your first suggestion in your first post).
Now, I used one of the accessory pins on the fuse box that delivers +12V in IGN on and during START - voilà!

Thanks again for saving me countless hours of clueless research!

Regards,

Boris

 

Cool! Glad I could help! If I ever get to Germany, I will look you up!

 

This single thing helped me out today. After nearly a decade chasing electrical leads in my spare time, and replaced parts that seemed to act bad but I couldn't verify, the power on while cranking eluded me for all this time. I spent countless hours searching forums for ideas and reading what problems and solutions other people had. This solves the big mystery for my TPI project that has been bugging me since 2003. Thank you