72CSi Fuel Pump Issues

[Magnet]

I'm having a few issues. The car will start and run but has stalls when I give it gas. I just realized the fuel pump is NO LONGER PRIMING when I turn the key (no combo relay click under the passenger rear seat near the ECU).....The pump DOES RUN when cranks and when the the car is on (the combo relay clicks when cranking).

I bypassed the under seat combo relay and the pump runs louder/faster than before but the car still runs the same. How many amps should the fuel pump be pulling? I think it was pulling less than 1 amp which sounds low (but like I said it was running fast according to the buzz sound).

I think I may need a new relay in any case. Where can I purchase a new combo relay??

Also I read there is some other fuel related relay near the brake booster; is this true?

I'm going to check the pressure tonight, so any other tips would be appreciated.

I'm located in San Francisco.

Thanks

 

[pamp]

Relays

For sure...there are two relays bolted to the backside of the booster. The one you are after is the lower of the two...hard to see. Judging by your symptoms, this is a likely culprit. I had similar issues years ago and found the relay had been jumpered by the PO and the jumper wire had come loose. I replaced the relay with a VW bit, gently turning one spade 90 degrees as to fit the BMW plug. One other thing I did when I had later issues, was to run an additional ground wire, light gauge, from the battery ground back to the fuel pump ground point near the ECU under the back seat. This cured other ills as well, such as intermitant rear lights. Not intuitive...old cars.

 

[adawil2002]

May need a fuel pump

If you are running the original fuel pump, it's time to replace it.

Get a new pump for a mid 80s 528e, has the same flow rate, will have to re-route the hoses a little. Have done this on both my '73 BMWs. Solved stuttering and stalling on both Vern & Athena.

 

[Magnet]

Anyone know where I can get a new fuel pump relay (the large metal one under the passenger seat near the ECU)??

 

[weasel51]

fuel relay

Walloth & Nesch has this part. #A61311353361. $26.13

 

[sfdon]

Fuel relay is controlled by the ecu and main relay which is triggered
By the white wire at the dropping resister by coil.
You did the smart thing by jumping pin 30 to 87- now check fuel pressure.
The two relays at the booster are cold start and main.
Cold start is triggered by starter wire.

 

[Magnet]

32psi solid which is a little high but ok I think so pump is OK. My multimeter is acting wonky so I dont know the true current draw on the pump but i assume it is OK (the less than 1 amp value stated ealier was a bad measurement).

After shutdown the pressure drops to under 5 psi in less than minute!

If the check valve on the pump was not working that should not matter when running am I am guessing, right?

I must have a leak somewhere. I clamped the line to the cold start injector and the problem persists, so that is not the root cause.

Could bad trigger points cause a leaky injector?

Also I found a loose wire on the loom that also goes to the starter. It is a brown wire with a green line and some sort of block connector at the end. The wire that goes to the stsrter is black with red dots. There are other wires in the loom but these are the two that exit the loom by the starter. I think this must have been like this before so I dont think it is the root cause either but I wan to know where it goes.

 

[sfdon]

The block connector takes the double black wires that should go to the starter and instead allows them to signal the ecu and cold start system to operate.
Double black in and red out to starter and the other two wires as I said to ecu and cold start system.
Pinch off fuel supply, return and cold start injector hoses to find a leaky injector.
Your fuels sounds fine- did you listen to your injectors?

 

[sfdon]

Black/red at 12:00 of starter
Red at 6:00 of starter
Alternator and battery at 3:00
Green brown is oil pressure

 

[sfdon]

What you are describing is classic manifold pressure sensor (aka the grenade) failure.
You can come by my shop and borrow one if you need to for testing.
In oakland

 

[Magnet]

So only injectors 1,2&5 are working. Swapped in a new set of trigger points and same condition.

Any ideas besides checking the whole harness?

 

[sfdon]

There are 4 connections for the injectors at the ecu-
1 & 3 are a set, connected to the ecu at pin# 3
2 & 4 are a set, connected to the ecu at pin # 5
# 5 injector goes to pin # 5
# 6 injector goes to pin # 6
Measure circuit for exact ohms and tap each injector with a small hammer and screwdriver while running

 

[12doplumbing]

My coupe is stuttering; I accellerate and it doesn't respond that well, then all of a sudden it acts like it gets full fuel and jumps, then drops-off again -- as if I let off the accelerator. It's different than the original stuttering problem at higher rpm. This feels like a similar problem in this thread.
I removed the ballast due to the blue coil swap, then took it for a first test drive with rebuilt injectors, etc. It may've been fully warmed up during that first test drive. Yesterday, I started her up and allowed her to run and idle for a few minutes, not sure about full temp, then drove about three miles. It acted as I've described. I parked for a half hour, started her up and drove another five miles - same symptoms throughout; would be cruising at thirty in second or forty in third, and it'd jump like it woke up with a blast of full fuel and immediately return or fall back to where it was. I parked and went into a store, came back and saw that my two taillights were dimly lit... What the heck -- unlocked car and checked switches: nothing on. Started her up, idled fine (was my blinker on? I can't recall) drove home another five miles with same acceleration issues. Feels solid otherwise; somewhat smooth idle (a little lopey), solid acceleration until I stop depressing pedal and hold (that's when it acts like it can't find consistency) no backfiring, and it doesn't diesel when I turn off ignition. Fuel pressure is steady 29lbs, I pinch the return line and it'll act no different when idling, and when I shut her down the fuel pressure drops as fast as the needle can fall - ? Good or bad?
Order a new relay? How to check the ohms at injectors? A thread on that? While running, etc?
I think I just found a loose connection... The black and spotted red wire on the outlet side of blue coil was pretty much disconnected... Could this have caused these symptoms? This wire used to jump from the top of the ballast to this outlet side of the old coil, now it is disconnected on the old ballast end and I just connected to the outlet side of coil.

 

[pamp]

Try this...run a 12 gauge wire from battery ground back to the fuel pump grounding point next to the ECU. This cured quite a few "intermittent" ghosts on my car. Not intuitive, but it seems these cars want a good ground reference at the stern.

 

[12doplumbing]

Sunday's chore. Thank you!

 

[pamp]

Fuel pump...

When you pull out the right rear seat, you should be able to see the brown fuel pump ground wire attached next to the ECU to the body work with a sheet metal screw. Attach your helper ground here. Worked for me, similar symptoms you describe, and has cured other CSi's as well. Let me know if it works...

 

[12doplumbing]

Ok Pamp, I did my chore:

Had difficulty figuring out the best way from ECU to engine compartment, so decided to temporarily go through to the trunk

And while there, double up on ground:

Then I zip-tied to my brake lines underneath and came up through fuel line opening, finally ending up here:

Still consider it temporary...
So then I tried to start her up; just kept trying to fire. Had fuel pressure, battery, so I checked the coil wires again. My black and red-dotted wire that used to connect to my ballast then jump to the negative side was plugged in only to the negative side, so I tried to study my new laminated diagram:

And got confused... Made an idiot mistake and plugged the old ballast feed into the positive, tried to start up, saw smoke, came back to the coil:


And quickly unplugged both -- black and red-spotted #16 insulation melting in my fingers...
****. Looked at the diagram, tried to figure out what I need the #16 plugged in for? Not understanding why; goes to starter on one feed and used to goto ballast and feed speed relay 1 (?) and 2... I don't get it. I went back and tried to start it -- fired right up! That is with the unplugged #16. What am I supposed to do, leave it unplugged? The old ballast (or "resister") connections I guess are plugged into the positive side of the coil now but #16 is just flopping in the wind... Should I have left my resister in for these "Speed Relay 1 & 2"? Do these speed relays need #16 connected to them to communicate with the ECU? Hmm...
I have my new ground wire, so I guess I will take her for a test drive.

 

[12doplumbing]

Test drove it... New ground in, but it still has delay/hesitation -- not as bad as my drive a few days ago, so I believe the ground may've helped.
Going to post in D-Jetronic Rebuild to keep the thread whole.
Thanks again for your help, Pamp

 

[pamp]

Oh man...I am out on a boat way north in Alaska, on a slooow sat feed for internet so cannot see your pics without taking 5 mins per shot. If I was home I could look at how mine is set up! That won't be for a few more weeks. Mine never had a ballast resistor. That extra wire rings a bell. You say you changed injectors? Make sure all those connections are good and tell me what spec. you used. I have tried a few different coils and forget the one I settled on. Also use Pertronix...no points. Wish I could be more help, stuck at the moment! Sounds to me like the ground wire (I ran it under the carpet) helped your fuel pump issue. Now you need to check the rail pressure, make sure that is OK (28-30 if I recall) Then that the MAP sensor is holding vacuum. Hopefully your ECU is OK. Talk to you again in three weeks if you haven't solved all by then. I have been so busy with work that I haven't turned a wrench on my car in almost two years, I have her perfect performance -wise. Just drive her when I get the chance...

 

[pamp]

****...that wire. Speed relay(s) That is for the A/C fan!