No Power, Running Super Rich

[bigfeller]

I bought a 1978 633 CSi in the summer. It’s a one owner car that was parked in 1993 and hadn’t run since.

Towed it home, drained the tank, changed all of the fluids, filters, belts, hoses, etc. It runs, but very badly. No power at all. Feels like it has about 30 hp. Running super rich.

We have replaced most of the fuel system hose, the fuel filter, the fuel pump, cleaned and checked the fuel rail, pulled, cleaned and tested the injectors. I installed new spark plugs, plug leads, distributor cap, rotor, and ignition coil.

Still runs terribly. Doesn’t want to start, finally does, runs for a bit, fouls the plugs with excess gas, stalls, and then dies.

Compression is good in all cylinders (150-155 psi). We have checked the cam timing, the ignition timing. I replace the coolant temperature sender, bought and tried another ECU, bought a rebuilt Bluestreak AFM. Still nothing.

I have taken it to two different mechanics shops, and we still have not been able to source the problem.

At this point, my only remaining guess is the crank position sensor, or the spark control unit. Am I missing something obvious?

[Ralph in Socal]

Coolant Temperature Sensor. It's blue or white/tan inserted into the thermostat housing. Sensor may be bad or signal is not getting to the ecu. Check signal to at the ecu connector to make sure sensor output is getting there

There are 2 different coolant sensors on the thermostat housing. One is for the ecu the other is for the gauge reading on the dash

Ralph

[bigfeller]

I replaced the temp sender (the long one that plugs into the blue and white wires to the ECU) with a brand new OEM BMW part. There's another one with a red plastic cap on it but it's not actually connected to anything.

This is it:
https://www.flickr.com/photos/29157481@N07/53203828740/

[Ralph in Socal]

Not sure which one that is with a red cap. There are 3 sensors I'm familar with- thermotime sensor/switch, Coolant Temp x2 as described before. Thermotime has a 7 second ON status if the engine is cold and that triggers the cold start valve. Unplug the cold start injector valve (csv) to see if the Thermotime switch has failed. You can also disconnect the CSV fuel line to see if that is feeding too much fuel when it's not supposed to.

Your car doesn't (shouldn't) have a crank position sensor except for the BMW Inspection Connector. I'm not well versed on that spark control unit. A friend had issues with one and I provided a known good replacement. Years ago so memory is spotty on his specific symptoms. I do have several used ones if you want to try swapping it out. Pic below is from E12 Repair Manual

You should have the stand up disrributor the has advance and retard function and maybe also centrifugal advance. Make sure you're getting proper timing advance when running

Ralph

20230917_224829.jpg (1.19 MiB) Viewed 738 times

[emac]

Fuel pressure regulator on fuel rail? I had one go bad causing too much pressure and very poor running except with wide open throttle.

[zinnocoupe]

I replaced the temp sender (the long one that plugs into the blue and white wires to the ECU) with a brand new OEM BMW part. There's another one with a red plastic cap on it but it's not actually connected to anything.

This is it:
https://www.flickr.com/photos/29157481@N07/53203828740/

I'm pretty sure that red capped plug is the unused dealer crank sensor, doesn't do anything anymore

[zinnocoupe]

Fuel pressure regulator on fuel rail? I had one go bad causing too much pressure and very poor running except with wide open throttle.

This is a good point, I don't see anywhere in the OPs posts where he has checked fuel pressure. I usually install a semi permanent gauge on my cars so I can always check its OK.

[zinnocoupe]

Fuel pressure regulator on fuel rail? I had one go bad causing too much pressure and very poor running except with wide open throttle.

This is a good point, I don't see anywhere in the OPs posts where he has checked fuel pressure. I usually install a semi permanent gauge on my cars so I can always check its OK. There is also a fuel delivery rate test you can preform to measure how much fuel is getting to the injectors. The test is described in the Bentley . The Bentley isn't actually for the e12 based cars but its full of good info

[bigfeller]

Just installed a brand new fuel pressure regulator. Sadly, no change.

Well, it looks like I am not out of options. Time for Megasquirt.

[Steve M6]

Since this car was sitting for a long time, it might be possible that one or more of the injectors are stuck open. That could certainly cause the symptoms you are experiencing. I know you said you tested the injectors.

[duracel79]

Could also be a blocked return line to the tank, would increase the pressure at the injectors.

[hornhospital]

As has been suggested many replies back, check the fuel pressure at the rail. You are playing "throw new parts at it" while ignoring that basic test (if it hasn't been done). Just replacing the FPR doesn't guarantee that the fuel pressure is now correct. Is the vacuum line to the FPR intact? If it isn't getting vacuum from the intake, the regulator will default to full pressure.

Two things that can cause serious over fuelling are excessive fuel pressure or open injectors. When you cleaned and tested the injectors, did you pulse them to see if they fire correctly, or did you just blow through them to see that they would pass fuel? They are closed against the fuel pressure more time per cycle than they are open. If they aren't actually closing completely they are flooding the intake with fuel.

[bigfeller]

My mechanic did test the pressure at the rail. I don't remember what the pressure was, but I do recall him putting a guage on it and being happy with the result. We pulled all of the injectors, checked to make sure none were stuck open, and looked for spray pattern.