Electrical help... please :-/

[SchnellSchweitz]

Ok... I've finally run into a major snag with my electrical setup. I'm in the process of upgrading to an IMI High-Torque Starter and switching over to a standard (NC modified) relay. However, I'm not seeing the desired results.

My issue is with fuel pump relay pin 87. I'm not sure where to hook the wire to this relay pin up. I'm assuming it goes to the yellow T-Plug connector wire shown at the bottom of the left image. When I hook this up to 87, the starter cranks in both run and start and the fuel pump does not engage. If I remove this wire, and leave it unplugged, the starter turns over correctly in start and not run, but no fuel pump.

Any ideas how to solve this? Appreciate the help in advance...

My system is running an MSD 6A and megasquirt, but I don't believe the wiring should be different than OEM in the trunk and starter areas since megasquirt is substituting the ground for the air sensor.

[SchnellSchweitz]

[redridge]

Originally Posted by SchnellSchweitz

Ok... I've finally run into a major snag with my electrical setup. I'm in the process of upgrading to an IMI High-Torque Starter and switching over to a standard (NC modified) relay. However, I'm not seeing the desired results.

My issue is with fuel pump relay pin 87. I'm not sure where to hook the wire to this relay pin up. I'm assuming it goes to the yellow T-Plug connector wire shown at the bottom of the left image. When I hook this up to 87, the starter cranks in both run and start and the fuel pump does not engage. If I remove this wire, and leave it unplugged, the starter turns over correctly in start and not run, but no fuel pump.

Any ideas how to solve this? Appreciate the help in advance...

huh???

Seems like you may need another relay to isolate the the pump and starter....

[SchnellSchweitz]

I'm unsure why I would need an additional relay since the car only had one relay for this job when it was new. Perhaps there is something I am missing and my new setup is different in someway.

I'm all ears... How would I do this?

[SchnellSchweitz]

Joe,

I thought I was creating an exact copy (function) of the original OEM red relay. Apparently, I may be mistaken. How does the OEM red relay vary from mine above. Perhaps there is something I missed?

[steely]

I may be way off base, but I'm not sure your relay schematic is drawn correctly for these symptoms.
Is that un-switched power there at 87a (and 86)? if so, the relay is always ON (leaving 30 switched to 87 for what that is worth).

[timmy2]

Please draw a schematic with the coil and the contacts drawn in the relay.
The terminal designation does not tell us anything.
(Unless you happen to have a bosch relay schematic imprinted on your brain)

[steely]

85 and 86 are the coil - 87a is NC, 87 is NO, 30 is the wiper (common).


on edit - corrected

[SchnellSchweitz]

This is what I believe this configuration of a standard 5 pole Bosch relay does. Let me know if I am wrong. I am definitely in learning mode...

[steely]

The schematic for the relay itself is correct.
But in your post #10 above, and as stated on post #7, your relay is always, as in forever, ON (your first figure in post 10).
This can drain the Batt.
Also, there isn't anything in the circuit to break the coil connection, so you never get to the state shown in your second figure.

I really am personally ignorant of what the yellow wire does in the car, and what your intentions are with respect to the megasquirt and the hi-torgue starter - so I can't comment on your goal here.

I do think that you want some sort of control from the ignition key, and maybe this should be in the coil path somehow.

Can you say what you want to do when the key is in each of the OFF/START/RUN positions? (for MS and FP)
And how much current is in that yellow wire and what does it do?
That way you'll get some help from me or someone else for sure.

Not trying to be smart alecky here, and if disregard me if I missed the boat on this.

[SchnellSchweitz]

Steely,

Don't worry about sounding smart alecky. I appreciate your help. I'm definitely wanting to get this solved as soon as possible. I'm just now finishing up a major project on my car and would like to be driving it.

My goal is to control the fuel pump with this relay so the key functions like this:

KEY = RESULT

OFF = OFF

ON = Megasquirt ground for 5 Seconds to activate fuel pump and then OFF (This has the same function as the OEM air sensor grounding)

CRANK = Starter ON CORRECTION: In the second figure in my diagram I use the term "CRANK" for the key direction. That should have been "RUN"

RUN = Fuel pump ON

[timmy2]

I'm installing a megasquirt soon.
Here's a good drawing for you.
The air sensor wire pink for this drawing (fuel cutout) is terminal 37 on the MS unit.
Hope that helps you figure out the circuit better.

[SchnellSchweitz]

Hi Timmy,

Thank you so much for the image. This is exactly what I am attempting to duplicate with a standard Bosch relay, but have been unable to do so. I wonder if the diagram above is only for the OEM red fuel pump relay only???

Perhaps I do need to go with a dual relay system since I changed to a standard Bosch relay. Anybody successfully create a dual relay combination and would be willing to share the diagram?

Thanks again everyone!

Eric J.

[timmy2]

Is your megasquirt set up for the reverse relay logic that Porsche has used here? You may need an interposing relay after all. (or go in and set the logic in your MS unit)
There are discussions about this at the yahoo Bitz racing groups when people upgrade to newer versions of megasquirt. Gsmith660 or some other more experienced MS users may be able to offer some more info here.

From the BITZ installation guide where I copied the diagram (63)
The Figure 63 shows how the fuel pump and relay is wired on the Porsche 911. The logic is such that when the
pink wire is GROUNDED the fuel pump stops. When the pink wire is un-connected (or HIGH
IMPEDANCE), the fuel pump runs. The standard MegaSquirt software expects the fuel pump to operate
opposite to this. No worry, the ECU software supplied from BitzRacing has been modified to operate with
Porsche fuel pump wiring. If you are installing your own relay for the fuel pump on a very early 911 which did
not have a relay, please ensure it is connected as shown in Figure 63.

Hope that helps.

[gsmith660]

Dennis is right Tony wrote into his firmware a logic to account for the reverse logic Porsche used for the fuel pump. If you have a standard Megasquirt ECU then you need to setup another relay and use the the pink wire to ground the relay which closes the relay and completes the ground that would normally be the air switch on CIS. It has been a long time and somebody check me on this you would want power to 86 and the pink wire on 85 and the wire to fuel pump relay from air switch on 87a and 30 to ground. And if that doesn't work then move the wire from 87a to 87 because I got it backwards. Doing this electrically does what Tony did in his firmware to duplicate the reverse logic. I mounted my relay on the relay board in the engine bay and took power from switched power for the MS ECU.

[SchnellSchweitz]

Just a quick update that I got everything running fine now... However, the issue was actually related to corrupt software in my megasquirt box.

I reflashed my box with MSextra following this video: Megasquirt1 firmware upgrade Part 1/2 - YouTube

I then switch to a standard Bosch Relay setup (NO) and I'm done.

Thanks again for all your advice!

Eric J.

[gsmith660]

Good glad to hear, it is always satisfying to fix a perplexing problem and get the car running again. If you haven't already save a copy of the firmware you flashed and your base MSQ that you got the car running reasonably well on to a safe location.

[timmy2]

I'm glad you were able to get it fgured out.
Thanks for posting your solution.