New Problem...No power to injectors 944S
12-11-2017, 10:03 AM
#1
New Problem...No power to injectors 944S - Power restored, now just sputters - FIXED!
**EDITED 1/20
Problem fixed. Although I had a reading from the DME temp sensor it was failing and finally died completely. Replaced and car fired right up.
Thanks to all for the suggestions down the road.
After putting a new head gasket into the S and resealing the oil pump I have been trying to start with no luck.
In my other threads I mentioned other issues but those have been solved.
Everything checks out other than no power to injectors.
1) My DME Relay is solid state with pump prime
2) I have good tach bounce
3) Engine will fire with starter fluid
4) Used Noid light to test for injector pulse, no pulse
5) Checked for 12v across both terminals (testing for harness short) and got zero volts
6) Checked for 12v on either terminal, no voltage
Could this be:
A) Sudden defective ballast resistor bank?
B) I see the tank venting valve is on the ballast too. Would a faulty one cause the system to fail?
C) Failed DME? I an not leaning towards this as the DEM sends a ground pulse to fire the injector, not 12v.
The electrical of this car is always the trickiest. I don't think apart from the DME Relay that power could get to the injectors so if I have a fault in the harness post relay that would do it.
I'm about to put over the wiring diagrams but is there something I am overlooking?
Thanks
Chris
Problem fixed. Although I had a reading from the DME temp sensor it was failing and finally died completely. Replaced and car fired right up.
Thanks to all for the suggestions down the road.
After putting a new head gasket into the S and resealing the oil pump I have been trying to start with no luck.
In my other threads I mentioned other issues but those have been solved.
Everything checks out other than no power to injectors.
1) My DME Relay is solid state with pump prime
2) I have good tach bounce
3) Engine will fire with starter fluid
4) Used Noid light to test for injector pulse, no pulse
5) Checked for 12v across both terminals (testing for harness short) and got zero volts
6) Checked for 12v on either terminal, no voltage
Could this be:
A) Sudden defective ballast resistor bank?
B) I see the tank venting valve is on the ballast too. Would a faulty one cause the system to fail?
C) Failed DME? I an not leaning towards this as the DEM sends a ground pulse to fire the injector, not 12v.
The electrical of this car is always the trickiest. I don't think apart from the DME Relay that power could get to the injectors so if I have a fault in the harness post relay that would do it.
I'm about to put over the wiring diagrams but is there something I am overlooking?
Thanks
Chris
Last edited by CVR_Rally; 01-20-2018 at 01:16 PM. Reason: Solved
12-11-2017, 02:38 PM
#2
Rennlist Member
My understanding is that the injectors get their power through the DME relay, same pin/stage that powers the DME. Since that's getting power, that would imply a fault in the wiring or ballast resistor system.
12-11-2017, 03:41 PM
#4
12-11-2017, 04:33 PM
#7
When I tested my injectors, I gave one side pulses of 12V from the postive terminal of a battery charger, and the other side connected to the negative terminal, aka ground. So I would think you'd want one of the terminals to be grounded. You've got continuity from pin 17 to both terminals of every injector plug?
Edit: If you don't already have this, it was very helpful to me.
Edit: If you don't already have this, it was very helpful to me.
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12-11-2017, 05:49 PM
#8
When I tested my injectors, I gave one side pulses of 12V from the postive terminal of a battery charger, and the other side connected to the negative terminal, aka ground. So I would think you'd want one of the terminals to be grounded. You've got continuity from pin 17 to both terminals of every injector plug?
Edit: If you don't already have this, it was very helpful to me.
Edit: If you don't already have this, it was very helpful to me.
12-11-2017, 05:54 PM
#9
Rennlist Member
The DME provides a ground to each channel. Do you see 12v between every injector's hot pin and a chassis ground? Try both pins because I don't remember if they're marked +\- . The power should be present as long as the key is in the run position.
12-11-2017, 06:02 PM
#10
no I don’t have any voltage on either pin thus the problem.
12-13-2017, 12:40 PM
#12
Turns out I had a dislodged connector from the harness underneath the fuseblock. Re-seated it and I have power to the injectors now.
However, my joy was short lived as it catches a couple times but still isn't starting. It acts like the fuel still isn't going in so I'll be checking with a Noid light again.
Ugh...
However, my joy was short lived as it catches a couple times but still isn't starting. It acts like the fuel still isn't going in so I'll be checking with a Noid light again.
Ugh...
12-14-2017, 11:19 AM
#13
In documenting my progress:
a) Checked injector pulse signal with Noid light: Checks OKAY
b) Checked for Spark: Checks good
c)Tried my spare injectors: Still no start, just a little stumble
I can hear the fuel pump prime up (I have the Solid State Relay with Pump Prime)
This morning I had enough time to attached the fuel pressure gauge but not enough time to bypass. With the priming I immediately got pressure to the appropriate 3.8 bar for 16v.
I won't have time to dig further till Friday but my next test is to bypass the relay and see if it starts. If it does then I either have a bad solid state relay (I have spares to test) or possible as I was having a little wonkyness with the ignition switch that it isn't powering the fuel pump in start position.
a) Checked injector pulse signal with Noid light: Checks OKAY
b) Checked for Spark: Checks good
c)Tried my spare injectors: Still no start, just a little stumble
I can hear the fuel pump prime up (I have the Solid State Relay with Pump Prime)
This morning I had enough time to attached the fuel pressure gauge but not enough time to bypass. With the priming I immediately got pressure to the appropriate 3.8 bar for 16v.
I won't have time to dig further till Friday but my next test is to bypass the relay and see if it starts. If it does then I either have a bad solid state relay (I have spares to test) or possible as I was having a little wonkyness with the ignition switch that it isn't powering the fuel pump in start position.
12-14-2017, 12:43 PM
#14
Rennlist Member
In documenting my progress:
a) Checked injector pulse signal with Noid light: Checks OKAY
b) Checked for Spark: Checks good
c)Tried my spare injectors: Still no start, just a little stumble
I can hear the fuel pump prime up (I have the Solid State Relay with Pump Prime)
This morning I had enough time to attached the fuel pressure gauge but not enough time to bypass. With the priming I immediately got pressure to the appropriate 3.8 bar for 16v.
I won't have time to dig further till Friday but my next test is to bypass the relay and see if it starts. If it does then I either have a bad solid state relay (I have spares to test) or possible as I was having a little wonkyness with the ignition switch that it isn't powering the fuel pump in start position.
a) Checked injector pulse signal with Noid light: Checks OKAY
b) Checked for Spark: Checks good
c)Tried my spare injectors: Still no start, just a little stumble
I can hear the fuel pump prime up (I have the Solid State Relay with Pump Prime)
This morning I had enough time to attached the fuel pressure gauge but not enough time to bypass. With the priming I immediately got pressure to the appropriate 3.8 bar for 16v.
I won't have time to dig further till Friday but my next test is to bypass the relay and see if it starts. If it does then I either have a bad solid state relay (I have spares to test) or possible as I was having a little wonkyness with the ignition switch that it isn't powering the fuel pump in start position.
