TheSamba.com :: View topic - No power to injectors!! new relay, injectors, and resistor

Mon Aug 16, 2010 11:05 am

Hey guys, I have replaced the injectors, double relay, and series resistance block, and I am still not getting power to the injectors.

I tested everything before that with a test light, the double relay is getting circuit and functioning properly. The relay is sending power to the series resistance block, but the injector plugs are not getting any signal. I thought for sure it was the series resistors, but I just installed it and I have the same problem. What is left??? Please help I'm supremely frustrated.

Thanks

Mon Aug 16, 2010 11:17 am

Did you test for power coming out of the resistor block? Any of the pins pushed back in the plug or wires broken internally where they meet the terminal crimps?

Mon Aug 16, 2010 12:11 pm

I did test that to my knowledge by testing the plugs that go into the injectors. I tested it with a test light and my volt tester. I will test the wires at the crimp, It would have to be on the side of the harness because I just replaced the resistors. I'll check that out though.

Mon Aug 16, 2010 12:14 pm

Are the FI grounds clean and well attached? They look sort of like this...

Are you getting a good signal out of the green points wire? (test it with the dwell meter)

Are you getting right about 12 volts out of the battery?

Mon Aug 16, 2010 1:38 pm

Well I just checked the grounds, I cleaned them and still no power to the injectors. I did find something interesting though. When I tested the injector wires for circuit I tried grounding one of the probes on an outside source, and I got current! So does this mean the wires are faulty?? Any Ideas on what could cause this?

Mon Aug 16, 2010 1:43 pm

Tell us about your 1) dwell angle (and just how close to 47º +/- 3º it is), and 2) also the "big white wire" (actually tan) that goes from the "1" or "-" side of the coil to the ECU.

Mon Aug 16, 2010 3:44 pm

KMO wrote: Well I just checked the grounds, I cleaned them and still no power to the injectors. I did find something interesting though. When I tested the injector wires for circuit I tried grounding one of the probes on an outside source, and I got current! So does this mean the wires are faulty?? Any Ideas on what could cause this?
So all this time you've been testing for power between injector terminals in a plug? you aren't going to get a reading like that, the power is constant in one terminal and pulsed ground from the ECU in the other. If the terminals in the ECU plug are dirty or pushed back out of contact position or you've missed a ground you can get the result you're experiencing.

Keep at it, you'll kick yourself for missing something so simple when you do discover the problem.

Mon Aug 16, 2010 5:34 pm

I just had the same exact problem with the same exact year bus, after much trial and error I finally discovered I didn't have the wires connected correctly to the coil. There should be the main power feed and a black wire on the positive terminal and a white wire and a green one on the negetive.

Mon Aug 16, 2010 9:07 pm

please re-read what BusDaddy said until you competely understand it. The injetctors always have voltage to them when the bus is on. The series resistors limit the current flow so the injectors don't burn up inside. The ECU turns them on and off by grounding one side of them.

Mon Aug 16, 2010 11:14 pm

Thank you for all the replies! I unfortunately had to move back to school today, I thought the series resistor was the problem, but it wasn't so I was trying some quick trouble shooting today. I wish I could stay and put all this help into action.
Update: before I left I rechecked the grounds for the third time and this time it seemed like the engine was trying to start right when the battery was getting low, but before I was able to try while jumping it I noticed gas was leaking out of an exhaust gasket underneath, and when we turned it over again it spit out a ball of flame! Is this gas just a result of trying to start it and having no gas go through the injectors? It was just an awful time to call it quits and head out, but we are taking it to a guy in town and i will let you all know what the problem is when I do.
Sorry I couldn't follow through on all your suggestions but I do appreciate the help, I am still working on it (in my head) while I hand it over to a more knowledgeable vw mechanic.

Sun Dec 12, 2010 1:27 pm

busdaddy wrote: KMO wrote: Well I just checked the grounds, I cleaned them and still no power to the injectors. I did find something interesting though. When I tested the injector wires for circuit I tried grounding one of the probes on an outside source, and I got current! So does this mean the wires are faulty?? Any Ideas on what could cause this?
So all this time you've been testing for power between injector terminals in a plug? you aren't going to get a reading like that, the power is constant in one terminal and pulsed ground from the ECU in the other. If the terminals in the ECU plug are dirty or pushed back out of contact position or you've missed a ground you can get the result you're experiencing.

Keep at it, you'll kick yourself for missing something so simple when you do discover the problem.

My 1980 air cooled van won't start and I've been through a whole bunch of checks. In the end the injectors aren't firing. The double relay is functioning properly.

When I test the connections to the injectors (from the ECU) I'm getting power at both terminals. To test this I've plugged in one lead of my test light to one terminal and the other to the engine block. Then I do the same to the other terminal and the engine block. I the light turns on in both cases.

My understanding is that only one side should turn the light on while the other should be an intermittent ground connection controlled by the ECU. Or, does it supply both terminals power until it connects one side to ground?

Thanks

Sun Dec 12, 2010 2:35 pm

The ECU supplies the ground. The ECU side will have power intermittently when the ECU is not in the ground part of the cycle. Were you cranking the engine at the time you were measuring? The ECU isn't going to turn the injectors on while the car sits or the cylinders would fill up with gasoline.

Sun Dec 12, 2010 2:58 pm

Thanks Merlin, that's exactly what I was wondering: if "The ECU side will have power intermittently when the ECU is not in the ground part of the cycle".

Sun Dec 12, 2010 3:20 pm

Both circuits and all four injectors fire at the same time. As Merlin said the EDU supplies the ground so any time the key is "ON" and the engine is not running you should have 12+V at both terminals. Clean the grounds on the upper front of the engine block well and coat with dielectric grease, and make sure you have the trigger wire to the fuel injection hooked to the #1 (-) terminal on the coil.

Mon Dec 13, 2010 9:41 am

Sorry KMO, I'm not meaning to thread jack, but I must have done something wrong when I checked the last time because the double relay seems to be working now and so do my injectors. I have spark, all other connections/sensors are working. I have good grounds. It still won't start.

The only thing I've noticed is when I was checking my ecu connections and watched the voltage from the "starter signal" during starting. It is supposed to go from 0V to 12V during starting but it only goes to about 5.5V. I hooked up my meter to the battery directly and turned the key and it only goes down to 9.5V while cranking. I don't really know what the ECU does with this 12V signal but maybe 5.5V isn't enough to make it do what it's gotta do.

I have another thread going here if you have an answer: http://www.thesamba.com/vw/forum/viewtopic.php?t=443550&highlight=drod

Thanks for the replies.

Mon Dec 13, 2010 9:48 am

Not sure where you are doing your measuring, but the resister pack is there to lower the voltage across the injectors. 5.5 volts seems about right. 9.5V at the battery during cranking is at the low end of what is acceptable. You might go through and remove and clean all you cable and ground connections. A 0.2 V drop here and a 0.4 drop there add up to a engine that won't start easily.

Mon Dec 13, 2010 12:03 pm

I'm just going off the Bentley. I'm checking for voltage between pin 4 on the the ECU wires and ground. I believe pin 4 is connected to terminal 86 on the dual relay which should be directly connected to the starter. I'll confirm this tonight.

Mon Dec 13, 2010 2:11 pm

If you only have 5.5 volts on pin #4 you have a serious problem somewhere, if you have 9.5 Volts at the battery then you are getting a 4 volt drop through your wiring. This is pretty severe and must be corrected. You may well need a new battery and new cables. Your starter may well be drawing way more amps than it should as well. You may want buy or borrow an ammeter that will read your starter draw.

Mon Dec 13, 2010 2:39 pm

5.5 V at the injectors would seem reasonable if they are firing. It would not be reasonable if the ignition is on and the engine is not being cranked. With zero current the voltage drop would be zero drop and the voltage therefore the same as the battery side of the ballasts. Check the voltage at the pin on the coil the ECU is attached to. It should be about the same as the battery.

Mon Dec 13, 2010 3:55 pm

SGKent wrote: 5.5 V at the injectors would seem reasonable if they are firing. It would not be reasonable if the ignition is on and the engine is not being cranked. With zero current the voltage drop would be the same and the battery side of the ballasts. Check the voltage at the pin on the coil the ECU is attached to. It should be about the same as the battery.

Merlin, I thought at first he was talking injector voltage as well, but pin 4 is either going to be voltage for the #50 circuit off the ignition switch or more likely the voltage of the high amperage #30 circuit at the starter. The drawings always show the #50 circuit, but most systems actually use the "extra" spade on the solenoid which is for all intents and purposes the $30 circuit.