VATS, rust or mice?
Thread Starter
Heel & Toe
Joined: Oct 2018
Posts: 19
Likes: 1
VATS, rust or mice?
Ok, I have read dozens of threads on 1990 c4 not starting and I an still a bit confused.
Here are the symptoms:
Car turns over no start. (Starter good)
Spray fuel in TB, runs for a few moments till fuel runs out. (Ignition parts good)
Replaced fuel pump and filter. (Pressure at rails Good)
Injectors Checked, 17.5 ohms on 6 of them and 2 were low, removed the plugs from them (Still no start)
No injector pulse.
Now here is the confusion.
How Do I determine what is killing the pulse. Vats, mice ate the wires somewhere, bad injector ground, bad distributor module sending signal to ECM, etc?
What would be your first course of action?
Thanks in advance.
Here are the symptoms:
Car turns over no start. (Starter good)
Spray fuel in TB, runs for a few moments till fuel runs out. (Ignition parts good)
Replaced fuel pump and filter. (Pressure at rails Good)
Injectors Checked, 17.5 ohms on 6 of them and 2 were low, removed the plugs from them (Still no start)
No injector pulse.
Now here is the confusion.
How Do I determine what is killing the pulse. Vats, mice ate the wires somewhere, bad injector ground, bad distributor module sending signal to ECM, etc?
What would be your first course of action?
Thanks in advance.
Team Owner
Joined: Jul 2004
Posts: 28,475
Likes: 3,291
From: Hartford WI
Car turns over means the VATS can't be blamed and made the whipping boy for every problem
Runs with fuel means that the car works but doesn't get fuel by itself.
If the ohm reading is bad on 2, dump all 8. If you have Multec injectors, dump all 8 even if they are good since they will not allow you to fill up with ethanol laced gas. Give our friend Jon a call at FIC.
After you fix it, check the injector fuses and go from there.
While you are there, replace the Fuel Pressure Regulator since it is a bit of a pain to fix in the future. Test for fuel pressure. It should spike up to 42 and hold for a while before bleeding down. Do this AFTER you replace it so we have some baseline to know if the fuel is holding or returning. Run a WOT test under load and see if the pump keeps up.
https://fuelinjectorconnection.com/c...d-rail-o-rings
I believe FIC has the regulator. Autozone will have the TB gaskets. Excellent time to do the coolant bypass mod, take off the TB and IAC and IAC housing to clean the TB passages and reseal it.
Runs with fuel means that the car works but doesn't get fuel by itself.
If the ohm reading is bad on 2, dump all 8. If you have Multec injectors, dump all 8 even if they are good since they will not allow you to fill up with ethanol laced gas. Give our friend Jon a call at FIC.
After you fix it, check the injector fuses and go from there.
While you are there, replace the Fuel Pressure Regulator since it is a bit of a pain to fix in the future. Test for fuel pressure. It should spike up to 42 and hold for a while before bleeding down. Do this AFTER you replace it so we have some baseline to know if the fuel is holding or returning. Run a WOT test under load and see if the pump keeps up.
https://fuelinjectorconnection.com/c...d-rail-o-rings
I believe FIC has the regulator. Autozone will have the TB gaskets. Excellent time to do the coolant bypass mod, take off the TB and IAC and IAC housing to clean the TB passages and reseal it.
Thread Starter
Heel & Toe
Joined: Oct 2018
Posts: 19
Likes: 1
Car turns over means the VATS can't be blamed and made the whipping boy for every problem. There has been lots of battles over the VAT system whether to remove or to fix. That is not a battle I want to fight in this thread. I will remove anything that keeps me from enjoying my ride.
Runs with fuel means that the car works but doesn't get fuel by itself. No injector pulse.
If the ohm reading is bad on 2, dump all 8. If you have Multec injectors, dump all 8 even if they are good since they will not allow you to fill up with ethanol laced gas. Give our friend Jon a call at FIC. I have 8 new injectors on the way. Still does not explain why I cant get it to run on 6.
After you fix it, check the injector fuses and go from there. Fuses good, and have 12v on each injector plug.
While you are there, replace the Fuel Pressure Regulator since it is a bit of a pain to fix in the future. Test for fuel pressure. It should spike up to 42 and hold for a while before bleeding down. Do this AFTER you replace it so we have some baseline to know if the fuel is holding or returning. Run a WOT test under load and see if the pump keeps up. Have schrader gauge on the way.
https://fuelinjectorconnection.com/c...d-rail-o-rings
I believe FIC has the regulator. Autozone will have the TB gaskets. Excellent time to do the coolant bypass mod, take off the TB and IAC and IAC housing to clean the TB passages and reseal it.
Runs with fuel means that the car works but doesn't get fuel by itself. No injector pulse.
If the ohm reading is bad on 2, dump all 8. If you have Multec injectors, dump all 8 even if they are good since they will not allow you to fill up with ethanol laced gas. Give our friend Jon a call at FIC. I have 8 new injectors on the way. Still does not explain why I cant get it to run on 6.
After you fix it, check the injector fuses and go from there. Fuses good, and have 12v on each injector plug.
While you are there, replace the Fuel Pressure Regulator since it is a bit of a pain to fix in the future. Test for fuel pressure. It should spike up to 42 and hold for a while before bleeding down. Do this AFTER you replace it so we have some baseline to know if the fuel is holding or returning. Run a WOT test under load and see if the pump keeps up. Have schrader gauge on the way.
https://fuelinjectorconnection.com/c...d-rail-o-rings
I believe FIC has the regulator. Autozone will have the TB gaskets. Excellent time to do the coolant bypass mod, take off the TB and IAC and IAC housing to clean the TB passages and reseal it.
Thread Starter
Heel & Toe
Joined: Oct 2018
Posts: 19
Likes: 1
To pull the ECM codes by jumping ALDL A&B and look for code 46. If 46 is there, you have a VATS issue.
I assume you have a Service Engine Soon light with key=ON. If not, this is actually the first thing to fix. (NO codes, just getting 12 code over and over.)
90's have a starter interrupt relay that is controlled by the CCM based on VATS. Because your car cranks, this relay may have been bypassed which seems fairly common. An un-molested 90 with a VATS issue shouldn't crank or allow fuel injection. Look for Code 46. If there, that's your problem: The ECM is not receiving the fuel-enable signal from the CCM.
EDIT/ADD: I just read the FSM Code 46 DTC to confirm that I had the code correct. they make an interesting point. If the starter relay is intact, and it cranks but does not send the fuel enable signal, the CCM is processing the key pellet correctly to allow cranking, but the signal is not reaching the ECM. Maybe mice ate that wire. Unlikely. Check for Code 46 in the ECM, and go from there.
I assume you have a Service Engine Soon light with key=ON. If not, this is actually the first thing to fix. (NO codes, just getting 12 code over and over.)
90's have a starter interrupt relay that is controlled by the CCM based on VATS. Because your car cranks, this relay may have been bypassed which seems fairly common. An un-molested 90 with a VATS issue shouldn't crank or allow fuel injection. Look for Code 46. If there, that's your problem: The ECM is not receiving the fuel-enable signal from the CCM.
EDIT/ADD: I just read the FSM Code 46 DTC to confirm that I had the code correct. they make an interesting point. If the starter relay is intact, and it cranks but does not send the fuel enable signal, the CCM is processing the key pellet correctly to allow cranking, but the signal is not reaching the ECM. Maybe mice ate that wire. Unlikely. Check for Code 46 in the ECM, and go from there.
Team Owner
Joined: Jul 2004
Posts: 28,475
Likes: 3,291
From: Hartford WI
There has been lots of battles over the VAT system whether to remove or to fix. That is not a battle I want to fight in this thread. I will remove anything that keeps me from enjoying my ride.
No injector pulse.
I have 8 new injectors on the way. Still does not explain why I cant get it to run on 6.
Fuses good, and have 12v on each injector plug.
Have schrader gauge on the way.
No injector pulse.
I have 8 new injectors on the way. Still does not explain why I cant get it to run on 6.
Fuses good, and have 12v on each injector plug.
Have schrader gauge on the way.
Is there 12 volts with the key on?
I thought it batch fires (fires one entire side of 4) by the ECM grounding it and completing the circuit? Does it have 12 volts?
I do hope I am wrong but the last time I encountered that situation, my ECM was bad.
I think it is available for sale and rent at Autozone.
Team Owner
Joined: Jul 2004
Posts: 28,475
Likes: 3,291
From: Hartford WI
Another good possibility. IDK what to say except I would take that out and call around. I checked mine out at Autozone. Other parts shops might also have a tester. That should help you "try before you buy".
Race Director
Joined: Oct 2012
Posts: 17,386
Likes: 6,527
From: Melbourne, FL
For what it's worth,after cars (not sure on years) Vats disables injectors AND starter motor. My 92 was one of those. A previous owner had "disabled vats", but only the starter portion. My intermittent starting issues were due to the injector side. A tune to remove it later, and it's been fixed.
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Team Owner
Joined: Jul 2004
Posts: 28,475
Likes: 3,291
From: Hartford WI
For what it's worth,after cars (not sure on years) Vats disables injectors AND starter motor. My 92 was one of those. A previous owner had "disabled vats", but only the starter portion. My intermittent starting issues were due to the injector side. A tune to remove it later, and it's been fixed.
What I do not see is why it would intermittently disable the injectors.
Race Director
Joined: Oct 2012
Posts: 17,386
Likes: 6,527
From: Melbourne, FL
It only triggered vats intermittently. I suspect the issue was with the piece in the key cylinder. It would usually be fine after waiting the 5 minute cooldown from a vats trigger.
Team Owner
Joined: Jul 2004
Posts: 28,475
Likes: 3,291
From: Hartford WI
Ah, that explains it. A bad cylinder that requires CONSISTENT physical contact but you had INTERMITTENT failures to authenticate. After the failure, it would time out ASSUMING that it doesn't re-trigger on the next attempt.
Race Director
Joined: Oct 2012
Posts: 17,386
Likes: 6,527
From: Melbourne, FL
Yeah, nothing like 5 minutes to sit and think about how to turn a key right to get it done, haha.
Thread Starter
Heel & Toe
Joined: Oct 2018
Posts: 19
Likes: 1
Seems unlikely that the module or pick-up coil ("pick-up" coil is INTERNAL inside the base of the distributor. Do not confuse the "pick-up" coil with the one in the cap that makes the sparks). would allow ignition, but not send the pulses. Do this little test:
Turn Key to RUN, but do not start.
Did fuel pump run for 2 seconds and stop? (It should. If=NO, there are other issues than reference pulses).
Without turning key off, bump the starter enough to get about 1/2 turn of the crankshaft.
Listen for fuel pump after starter stops.
Did fuel pump run for 2 seconds and stop? If = Yes, the ECM received reference pulses from the distributor. If = NO, there were no reference pulses received.
The reference pulse wire is purple/wht. There is a 3 or 4 cavity weather-pac connector between the distributor and engine harness that contains this wire. I've never tried to measure voltage on the reference wire, but it may be possible to do so. Try the A.C. scale on your VOM to ground. Fire the engine by priming it, and watch the meter. If you see voltage while it runs, there are pulses.
Turn Key to RUN, but do not start.
Did fuel pump run for 2 seconds and stop? (It should. If=NO, there are other issues than reference pulses).
Without turning key off, bump the starter enough to get about 1/2 turn of the crankshaft.
Listen for fuel pump after starter stops.
Did fuel pump run for 2 seconds and stop? If = Yes, the ECM received reference pulses from the distributor. If = NO, there were no reference pulses received.
The reference pulse wire is purple/wht. There is a 3 or 4 cavity weather-pac connector between the distributor and engine harness that contains this wire. I've never tried to measure voltage on the reference wire, but it may be possible to do so. Try the A.C. scale on your VOM to ground. Fire the engine by priming it, and watch the meter. If you see voltage while it runs, there are pulses.
OK, Back at it today.
Have Fuel pump running for 2-3 sec. when the key is initially turned and when I bump the engine. Pressure is good @ 40-43psi.
Also I rechecked the codes and I have NONE. I just get the 12-12-12...12-12-12. SO nothing there...
Now what? Any ideas? If I cant get this going soon I may be posting parts in the classifieds.
Thank you to all who assisted so far.
Thread Starter
Heel & Toe
Joined: Oct 2018
Posts: 19
Likes: 1
Lets add new info. After MANY attempts and rechecking the troubleshooting steps, the fuel pressure drops from 43 to 0 within 2 seconds of pump stopping or when I stop cranking. It is immediate! Like someone released the line from the schrader. It was a slow bleed all day but now it drops instantly. Still no injector pulse.
Team Owner
Joined: Jul 2004
Posts: 28,475
Likes: 3,291
From: Hartford WI
Lets add new info. After MANY attempts and rechecking the troubleshooting steps, the fuel pressure drops from 43 to 0 within 2 seconds of pump stopping or when I stop cranking. It is immediate! Like someone released the line from the schrader. It was a slow bleed all day but now it drops instantly. Still no injector pulse.
So no injector pulse when you crank? Does it have 12V at all when you test the connector?
Thread Starter
Heel & Toe
Joined: Oct 2018
Posts: 19
Likes: 1
It isn't the injectors dripping fuel. I don't get a drop from them. The engine runs like a top with fuel dumped into the TB.
I have 12v at all 8 plugs.
I have 12v at all 8 plugs.
Last edited by Yeah dat me; Oct 12, 2019 at 07:05 PM.
Thread Starter
Heel & Toe
Joined: Oct 2018
Posts: 19
Likes: 1
Just to recap:
The injectors are not getting pulse.
If I spray fuel in TB the engine runs well.
I have disconnected 3 bad injectors (waiting on new ones).
I Have 12v at injector plugs.
No VATS codes.
Good NEW fuel pump.
Good pressure at rail.(Now all of a sudden it drops fast)
The injectors are not getting pulse.
If I spray fuel in TB the engine runs well.
I have disconnected 3 bad injectors (waiting on new ones).
I Have 12v at injector plugs.
No VATS codes.
Good NEW fuel pump.
Good pressure at rail.(Now all of a sudden it drops fast)
Team Owner
Joined: Jul 2004
Posts: 28,475
Likes: 3,291
From: Hartford WI
Doesn't mean much
OK. That is something. So for some reason, they are not grounding out when necessary. When the engine is running with fuel sprayed into the TB, I'm guessing you have ignition but no fuel to continue it. I wonder if the ECM is at fault.
Team Owner
Joined: Jul 2004
Posts: 28,475
Likes: 3,291
From: Hartford WI