PhantomUSA

I'm stumped, about a month ago the vette would not start....so I've been going thru everthing tryin to get it running this is what I've done so far
1) replaced the ECM with a rebuilt (twice) and Prom with a Hypertech Prom
2) ohmed all injectors they all ohmed 16 plus or minus .02
3) I have 40 psi at the fuel rail
4) I have spark at the plugs
5) it will start with gas squirted into the engine
6) Noid light no pulse to any injector
7) the VATS is bypassed
8) ECM, Inj1, inj2 fuse are ok
9) bellhousing ground and head ground are clean
10) 12 volts at every injector plug
11) when a scan tool is hooked up it says ECM not responding ???

I'm ready to beat my head on the floor can it still be a bad Ecm after putting on 2 rebuilt ecms ???

I have a buddy thats sending me another take off OEM ECM Service # 1227165 to try but I feel I'm still over looking something besides a bad ECM.....any input why my injectors are not pulsing will help

I'm ready to pull the injector system off and install a Holly 750 carb setup on but since this vette is all original and complete I hate to do that

RocketSled

Is there continuity between the plugs going to the ECU and the injectors? You seem to have looked at all the bits and pieces on the ends of the wires, but not the wires themselves.

WW7

Same thing I was thinking , bad wires somewere. If the scanner says the ECM is not responding, I would check the wires going to the ECM first....WW

PhantomUSA

I dont have a wiring diagram so I would be shooting in the dark which pin or wire to check from the ECM I do have power to the ECM

AGENT 86

Does the "Service Engine Soon" light up with ignition on ?
With ignition on, will jumping terminals "A" and "B" on the ALDL, cause the "SES" light to flash ?
ECM will not fire injectors without reference signal from distributor. The ignition module sends the signal to ECM. It may be your problem. Before digging into it, check the 4 way connector at base of dist, to see if it's clean and tight.

RocketSled

Knowledge is power!



http://www.oddfiddlythings.com/2010/...e-ecu-pin-out/

(Now, the next 8 pages or so are an electrical troubleshooting for a non-start condition...I don't have time right now to scan them in.)

The Service manual is worth it's weight in gold!

PhantomUSA

Ok found my service manual.....guess I'll start with the distributor wires to the ecm ...."after the rain stops"

jaa1992

Please replace the fuses anyway. Make sure you are replacing the correct ones. I know because my 92 had a problem with one bank not pulsing. I thought I checked both INJ fuses, after many hours of looking and playiong around with things I replaced the correct INJ1 fuse and she runs right again!

The key is the no pulse to any injector. You'll need to walk through the troubleshooting steps in the FSM.

Good luck

engle1147

The origional source for the pulses for the ECM comes from the ignition module/pickup coil......if you can crank the engine (5- 15 seconds) and see the the RPM gauge working then your problem is more than likely at the ECM or on the fuel injector's side of the circuit. Perhaps just the "fuel injector enable" circuit is not closing.....this is done by the ECM recieving a signal from the VATs module.

How long has the VATS "bypass" been installed?
Did the car run with it installed prior to the "no start" condition?
Are the OEM "Multech" fuel injectors still inplace?

I know you said you checked the resistance on the injectors but if they are the stock Multech version they could still be your problem regardles of what a resistance check shows. On the '89 all the injectors fire at once (one grounding point/switch in the ECM that pulses all 8 of the injectors in unison).....so it doesn't take much to drag down the injector pulse signal if one or more injectors has an issue. With this in mind - I recommend that you unplug all 8 of the injector's from the wiring harness all at once then check for the injector pulses from the ECM while cranking the engine again and see if you get anything. If still no pulses look to the ECM or your VATS bypass setup.

PhantomUSA

engle1147 The VATS is not the problem because the VATS disable the starter and the fuel pump I have fuel pressure and the starter rotates.....I need to find out why there is no pulse first even if the injectors where replaced without the pulse signal they will not fire

I have not been able to work on it today because of heavy rain all day tomorrow I'll check the wires at the distributor to the ECM ????? I just am not sure which wire sends the pulse is it the TACK wire ??

I donot know anything about the injectors my guess is they are OEM the car only has 38000 miles on it I replaced the engine (engine was knocking) when I got the car with a roller L98 and only put 4000 miles on since then

PhantomUSA

jaa1992 I'll recheck the fuses tomorrow and clean the fuse holders

AGENT 86

rodj

VATS does not disable the fuel pump; it disables the injector pulse.

Courtesy of Redrose
"86 and up ecm puts out a 5v signal that must be go to "sink" (ground) at 30 Hz before fuel (injectors) is enabled and starter relay is tripped... if the ecm 5v signal is open/grounded/ sink at other than 30 Hz, NO GO...the starter relay can simply be bypassed but the ecm MUST either get that 30 Hz sink OR be re-programmed to eliminate VATS to pulse the injectors."

PhantomUSA

I have the bypass module That gives the ECM the 30 Hz signal and the Key resistor installed to bypass the VATS That was my first thought too so I called the Vendor that sells these and he walked me thru a test to be sure it still worked and it tested OK.....I have tryed it without the VATS bypass and still no go

Does anyone know which wire from the disturber send the pulse to the ECM is it the EST, Reference, Bypass or ground wire ?? these are whats showing on the wiring diagram ???

The tests I plan to recheck today are all the Injector with a noid light recheck the fuses recheck all the grounds, Ohm test the disturber wires to the ECM and recheck fuel pressure at the rail.....the scan tool still says ECM not responding and no codes


If that checks OK I mite pull all the injectors and have them tested we have a disel shop that tests and rebuilds injectors close by

AGENT 86

You don't want to answer my questions, so I will do the same.
Good Luck !!

PhantomUSA

I'll answer y'all after I get back on it need to wait for the rain to stop

RocketSled

I'd follow the procedures in the manual, they're written for a mechanic that's on the clock.

PhantomUSA

To answer all I get is the 12 flash.....no other codes

50ithSILVERz06

remember there is an ECM fuse, it might not be labeled "ECM" however it might be tied in with another circuit, but if my memmory serves me you will have a labeled "ECM" fust that must not be overlooked, frankly check EVERY FUSE! from cig lighter to acc EVERYFUSE.......also id take a stab in the dark with that ignition control module.....

also on the bypass did all you do was install the key bypass and leave the VATS box hooked up? If so the box can still malfunction reguardless if the system is getting the correct resistance off the key or a bypass....

and as a side not the on some earlier VATS systems the pump will turn on and the car will crank till the cows come home jsut wont start.....

PhantomUSA

The fuses have been checked and rechecked they are all OK......The key pill and the Vats have been bypassed (Disabled) in the ECM Prom was burned disabling the VATS along with other mods programed into the Prom like cooler operating Temp (180*) The plugs are firing and new plugs are installed so the ignition control module must be good