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740 No Pulse to Injectors, Has Spark

PromiseRing said:
Pretty sure without the grounds being clean and tight the car won?t run. Are they the grounds for the ecu?
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From what I understand they are the grounds for the ECU, and they are all clean and tight.

I tested the ballast resistor, about 12.6 ohms between each of the terminals. Proper spec from what I understand.
As I've said before, RSR clicks on as it's supposed to. Whatever this issue is is coming from the ground side of the injectors, not the power side. They have sufficient power.
 
:uh: if those grounds aren?t clean, the ecu isn?t grounded, which means the injectors can?t be grounded. My statement remains then, they are also injector grounds.

Did you try starting fluid yet?

And just because the RSR clicks doesn?t mean 100% forsure that the injectors are receiving full current. You could bypass the relay just for safe measure. Run 12v directly from the battery to the output wire of the relay (look at a diagram).
 
Good enough!
Haven't tried the starting fluid, been on and off raining all day and never got the chance to do that. But I still see no reason why it wouldn't run on it.
I will try the bypass tomorrow.
 
Pull the fuel injector relay, then jump power to the output. If it starts and runs, the ecu has failed to provide a ground, a common failure. Replace it.
 
ZVOLV said:
Why would bypassing a relay when there is already power do anything for you?
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Just because some voltage is getting to the relay doesn’t mean sufficient current is being supplied to the injectors
MikeSr. said:
Pull the fuel injector relay, then jump power to the output. If it starts and runs, the ecu has failed to provide a ground, a common failure. Replace it.
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Jumping the fuel pump relay doesn’t work on a 7/9 because it also provides power to the RSR. So your pumps will cycle but injectors won’t fire. At least on the ones I’ve driven.
 
ZVOLV said:
WTF. Looking at a diagram shows it's a standard 4 prong relay. What the heck is this Y crap?
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Dang image quality got killed so you might have to google it. Pin 1 from the fuel pump relay runs up to fuse 9 (blue and yellow wire). Pin 2 from the RSR is also blue and yellow and runs to fuse 9. I think if the FPR does not energize, neither will the RSR. Just in my experience at least. On a 240 (where the RSR is absent), jumping the FPR works great as a temporary solution.
nPXxExX_d.jpg
 
ZVOLV said:
WTF. Looking at a diagram shows it's a standard 4 prong relay. What the heck is this Y crap?
Click to expand...

You’re looking only at the RSR I think. The RSR is a standard style 4 post relay. It gets a constant 12v, constant ground, then when the FPR is energized, the blue/yellow wire on the RSR is as well. This closes the contacts on the RSR and allows current to flow to the injectors. Someone please correct me if I’m wrong, this is how I’ve inderstood it in the past when I was dealing with wonky RSR stuff.
 
PromiseRing said:
You?re looking only at the RSR I think. The RSR is a standard style 4 post relay. It gets a constant 12v, constant ground, then when the FPR is energized, the blue/yellow wire on the RSR is as well. This closes the contacts on the RSR and allows current to flow to the injectors. Someone please correct me if I?m wrong, this is how I?ve inderstood it in the past when I was dealing with wonky RSR stuff.
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That?s how I understand it as well. From what I previously tested, that?s exactly how it works.
The RSR, as has been mentioned, sends power to the injectors. My problem is not getting power to the injectors, it?s grounding them.
 
What needs to happen in order for the injectors to be grounded? ECU must be good, it must receive a signal from the CPS/hall sensor, grounds on intake must be clean and tight, resistor pack spades must be clean and tight, what else? You ohm checked resistance between the connectors on the resistor side, but did you check to see if the male spades were clean? I filed mine down until they were shiny and then the vehicle started
 
I don't recommend using a file to clean terminals, but it sure will destroy any fretting.

Another way to test the ground side is to connect a test light to a positive source and to the injector control side of the circuit.

I would make sure your ECU is powered up.
 
I used a flat head screw driver and a harbor freight pick on site to clean them. Got it running, drove it home, then used file. At this point in my 940s life it doesn’t matter what I use. Maybe something a bit less abrasive is recommended but I didn’t really care. It worked.
 
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