What is this?

[raygreenwood]

[Pepperbilly]

Glad you got it running by fixing the fuel pump relay. Good work!

As Ray said make sure you have the proper fuel pressure and that is easy to check because you have the engine running. You will need a pressure gauge and it hooks up to a 8mm screw fitting you remove to slide the hose on. Located on the fuel line between #3 and #4 fuel injectors. Running, it needs to be at about 28 psi. Careful of fuel leaks!

I suspect the MPS has been tampered with or it does not function properly because the vac hose was disconnected and plugged. I would first check to see if the MPS can hold any vacuum...this is a first basic check that is important. I would start here. Photos included...

Mityvac gauge is nice to have. Slip the hose on the vacuum port and draw it down to between 12-15 inches Hg. Should hold that vacuum for 3 to 5 minutes. This indicates the seal between the halves of the MPS is good.

This shows the black seal that I am talking about.

The copper diaphragm is part of what is inside the MPS. The black seal and this thin diaphragm is part of a kit one can order from Tangerine Racing if needed.

Your MPS if not previously tampered with should look like this with an epoxy filler over the the adjustment screw on the back side. There are 2 MPS's in the photo here.

Bill

[Alaninin]

More pictures of the relay added to the starter. Not sure what this relay is doing but it looks like one red wire going to the relay is original and might go to the starter where the added red wire is going to on the starter. Yellow wire has fuse and going to starter looks like added. Black on relay goes to ground. Thoughts??

[Pepperbilly]

[raygreenwood]

I agree with Pepperbilly.

Due to its location and configuration, it's most likely a hard start relay.

However, still.....before just removing it, carefully follow the power lines. I want to know exactly where the large red power wire is coming from, meaning, where is it pulling power FROM.

My worry goes back to one of my first line of questions here. I have seen A LOT of these cars over the years.
Back in the day....call it the late 70s, 80s and maybe into the early 90s when a lot of the surviving 411 and 412 cars had been sitting in back yards and garages for a while not running because of a whole slew of problems mostly to do with higher complexity and virtually no one outside of dealer care able or willing to work on them.....a lot of first owner cars......the 2nd owner was usually some young kid like I was when I got mine in 1979.

Back in the late 70s into the early 80s, cars had tons of emissions vacuum lines and widgets. On American cars, owners could spend all day unplugging and bypassing vacuum lines and wires from the emissions system and they seemed to make no difference....on basic running.....if all you needed it to do was make it "run".

When American car owners got their hands on a 411 or 412 and looked under the hood at D-jet and the gasoline furnace system....they largely thought the same hack rules applied. Plug emissions stuff....and if you need power for something....pull it from wherever seems to supply it that does not seem to be using it right now.

The 411 and 412 did NOT have vacuum lines and wires that were not KEY. The first place that usually got robbed for power back in the rear of the car was the gasoline furnace.

So we need to carefully trace where everything came from and where it's going so we can put the power supply back where it belongs.

Ray

[Pepperbilly]

Good advice from Ray. Each wire from the relay has to be traced so we know exactly where the wires go. No power should be taken off of the gas furnace circuit.

Bill

[Alaninin]

Thank you all for your help and support. I will be on travel the next few months and will have little time to work on the car. I will trace this hot wire back to see where it originates from once I get back.
I replaced all the vacuum line last week. Fuel lines have all been replaced from previous owner and don’t seem to be very old.

Thanks again,
Alan

[Alaninin]

All,
My MPS is not holding a vacuum as Pepperbilly mentioned. Not sure if I should buy the rebuild kit. The diaphragm looks good but again not sure how to test. I really don’t want to buy a $195 rebuild kit if it’s not needed. Can you just buy the gasket/o-ring?
Any help would be appreciated.
Thank you,
Alan

[raygreenwood]

In the pictures of the MPS that peperbilly posted, on the back end where the epoxy plug is...notice the two oval slot shaped holes at about 7 and 8 o'clock position.

Cover those two holes with a double layer of scotch tape to seal them up.

Pull vacuum again. If it stops the leak it means your copper diaphragm is cracked and you need a kit. If it does not seal the unit then your o-ijg between the unit halves is leaking.

Ray

[Alaninin]

Thank you Ray. Got back in the garage today and tested the MPS with vacuum and taped up holes. Good news it still leaked. Next I will try to find a o-ring that will work. If you know what is being used as a replacement let me know.

[raygreenwood]

[Alaninin]

Again thank you for all the information. I have another question about the MPS. Could it be losing vacuum from another areas like the plug? I put silicone around the seam and it still lost vacuum.

[raygreenwood]