MS3 8v on Fuel Pump Enable

Raymond_B · Post by **Raymond_B** » Fri Oct 20, 2017 10:12 pm

So tonight I went out to finish my wiring and mount my fuse/relay box. Got everything hooked up turned the key and nothing. So I thought maybe I had wired up something wrong, went over everything and could not find a problem. But my MS3/3X would not power up. While I was troubleshooting I found that the fuel pump enable wire (37 purple) has ~ 8v on it. Looking over a few other the injector power wire (disconnected from relay) has 5-6v and the VREF wire has around 8v as well. So obviously I hosed up the MS. What I discovered by accident is that if I put a test light on FP enable I get a dim light and the MS powers up and I can connect via TS.

Any ideas on what I have damaged and how? I am really worried about getting the MS fixed and then doing it again because I did not find the issue.

Here's how the relays are wired, I've tested this before with no problem. One master MS pin 37 ground triggered relay kicks off the others.

DaveEFI · Post by **DaveEFI** » Sat Oct 21, 2017 1:45 am

According to that circuit, you have multiple relays sharing the same coil switching feed.

Raymond_B · Post by **Raymond_B** » Sat Oct 21, 2017 1:48 am

Right, the main relay output is the positive trigger for all except the MS. This all worked when I tested previously, that’s what has me baffled.

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DaveEFI · Post by **DaveEFI** » Sat Oct 21, 2017 4:01 am

Ah - for some reason I'm not seeing all that pic. But I'm not quite sure why you're not feeding the fuel pump relay from the MS driver?

It's very odd to have multiple relays all doing the same. Better to have just one suitable current one with fuses as needed on its output.

LAV1000 · Post by **LAV1000** » Sat Oct 21, 2017 4:15 am

What type of meter did you use and were did you put the meter wires to measure ?

Because if you measure the side of a relay coil which normally gets grounded I expect something like 12Vdc.
For a non activated coil of course.

Raymond_B · Post by **Raymond_B** » Sat Oct 21, 2017 6:25 am

DaveEFI wrote:Ah - for some reason I'm not seeing all that pic. But I'm not quite sure why you're not feeding the fuel pump relay from the MS driver?

It's very odd to have multiple relays all doing the same. Better to have just one suitable current one with fuses as needed on its output.

Dave, I simply added another relay doing the same thing, it triggers fuel pump, coils, O2, 12v sensors and accessories, and cooling fans. A lot of those items draw big current so I did not want to run it all off one relay hence splitting them out. Does that make sense?

LAV1000 wrote:What type of meter did you use and were did you put the meter wires to measure ?

Because if you measure the side of a relay coil which normally gets grounded I expect something like 12Vdc.
For a non activated coil of course.

I used a digital multi-meter, neg lead to my power distribution ground and the pos lead to the FP Enable wire. I had removed the wire completely from the relay. Same with the other wires I removed them completely from their relay outputs and triggers and measured voltage. Also like I mentioned if I hook a 12v test light to FP Enable and ground it the light comes on (dimly) and the MS will connect to TS.

Peter6000 · Post by **Peter6000** » Sat Oct 21, 2017 6:58 am

Raymond_B wrote:So tonight I went out to finish my wiring and mount my fuse/relay box. Got everything hooked up turned the key and nothing. So I thought maybe I had wired up something wrong, went over everything and could not find a problem. But my MS3/3X would not power up. While I was troubleshooting I found that the fuel pump enable wire (37 purple) has ~ 8v on it. Looking over a few other the injector power wire (disconnected from relay) has 5-6v and the VREF wire has around 8v as well. So obviously I hosed up the MS. What I discovered by accident is that if I put a test light on FP enable I get a dim light and the MS powers up and I can connect via TS.

Any ideas on what I have damaged and how? I am really worried about getting the MS fixed and then doing it again because I did not find the issue.

Here's how the relays are wired, I've tested this before with no problem. One master MS pin 37 ground triggered relay kicks off the others.

These voltages look strange could be a ground issue. I would measure the voltage going to the MS 3 first (7 blk and 28 red) you have to have 12V here. If you do and your MS 3 still does not start up disconnect everything else. If it still does not start the MS3 is damaged otherwise you have a problem with one of the outputs. Connect them one by one to find the one causing the problem.
Peter

DaveEFI · Post by **DaveEFI** » Sat Oct 21, 2017 9:35 am

IMHO best to stick to the MS external wiring diagram, for MS, injectors and ignition, with its own feed direct from the battery and its own grounds. For things that take a lot of current - like cooling fans - run them on an entirely separate circuit both 12v and ground, but control the relay from MS.

Raymond_B · Post by **Raymond_B** » Sat Oct 21, 2017 10:30 am

Went out and started testing again today. I have pretty close to battery voltage on all my MS and Sensor grounds, along with battery voltage on FP Enable and all the injectors. I disconnected all sensors, coils, and injectors and it's still the same.

I do think I know what happened though, somehow it looks like I reversed the polarity on my IGN-1A coil power circuits (I have 2, one for each bank). Those relays never fired that I know of, but maybe they did for an instant the first time that I hit the key??

I really, really, really hope I didn't kill 8 IGN-1As

@DaveEFI, I'll look at the circuit again thanks.

Raymond_B · Post by **Raymond_B** » Sun Oct 22, 2017 9:02 am

Going to pull the MS today and contact DIY to see how much to fix it.

billr · Post by **billr** » Sun Oct 22, 2017 9:27 am

I assume you are going to bench-test it, away from the vehicle wiring, correct?

Raymond_B · Post by **Raymond_B** » Sun Oct 22, 2017 9:30 am

billr wrote:I assume you are going to bench-test it, away from the vehicle wiring, correct?

Yes, I was going to hook it up to the Jimstim here in a bit, hopefully it does not damage that!

Raymond_B · Post by **Raymond_B** » Sun Oct 22, 2017 12:43 pm

Alrighty, possibly good but confusing findings. On the JimStim (1.5) the MS powers up and sensor inputs look OK. I set the wheel to 36-1 and I get RPM sync. Not sure how to simulate the cam sensor, but I do not think that's a big deal. But because it's a regular Jim stim I am not sure how to test the sequential coils and injectors. I did change the main fuel outputs to "Std fuel" and sequential off and tested Inj1 and 2. Those pulsed the LED as I tested. I also tested FIDLE with good results. So it sounds like the MS3 card is good right?

I just need to test the 3X expansion card? Sounds like I need a JimStimX.

Raymond_B · Post by **Raymond_B** » Sun Oct 22, 2017 4:48 pm

OK, for those still following this, I finally found out what it was. Apparently I made a bad crimp on the large ground wire I had running from the engine block to all my MS ground wires which terminate at a junction block. I'm not sure how it made it past my testing a while back, maybe I bumped or pulled it since, but it was definitely loose. After reassembling it all is good. I guess when I was testing and used the test light it was providing a ground and that's why the MS would come online.

Many thanks to Peter6000 for initially pointing out that it looked like a ground issue. I was really stumped especially after the MS appeared OK on the stim.

Now to put my harness back together

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