81 528i B34 Conversion - No Power

porschelou · Post by **porschelou** » Sun Dec 07, 2014 8:03 pm

Hello,
I just finished installing a very low mile m30/b34 ( 60k) to replace a seized 2.8L. The car has changed hands a few times before I got it so I had never driven it or have any history. I did the long block conversion - re-installed all of the 2.8L injection/exhaust system on the 3.5L block. Now that I have started it I need some help.

History of parts that were replaced:
- Rebuilt injectors ( Rock Auto)
- All new gaskets
- New Fuel Pressure Reg
- PO installed a new high pressure fuel pump
- PO replaced the ECU with a rebuilt unit
- PO replace cap/ rotor/ wires ( wires test good - cap / rotor look new)

Starting / Idle:
- It starts great - few seconds and it fires right up idles at 1k
- Idle is a little rough ( almost like it's missing)

Driving:
- Is has no power - I race an e30 with a built b34 so i know how the torque should feel - This one can barely get up a hill
- Feels like one cylinder is dead

Diagnostics:
- Fuel pressure - Key on / Engine off - 36lbs
- Fuel Pressure - Engine running - 30lbs
- Fuel Pressure while accelerating - 30lbs
- If I pinch the return line the pressure goes way up - 70lbs +
- 10V at the positive coil terminal - should be correct since it goes through the resistor
- Idle / WOT switch adjusted / tested with a Fluke DVM
- Put a Noid light on one of the injector connectors - flashing - looks normal
- Tested injectors impedance - 2-3ohms
- The ignition module ( box below the washer fluid tank) looks brand new
- Checked all of the grounds
- All questionable hoses were replaced
- Pulled the new plugs - they all look the same

So - I'm not sure where I should head next. I feel like someone was chasing the same issue with the number of new parts ( ecu, fuel pump, ignition module) all look new.

All I can think of is that the "rebuilt" ecu is messed up, Distributor is bad, MAF???

Any suggestions? Thanks

wkohler · Post by **wkohler** » Sun Dec 07, 2014 11:22 pm

I will bet that the issue lies in using the injection from the 528i. I cannot see how it would give that motor enough fuel.

CabbageFumes · Post by **CabbageFumes** » Mon Dec 08, 2014 12:28 am

It's definitely starving (what Chris said). In a perfect world, you could use the throttle body, AFM, ECU and engine harness from a same year Euro 635i to solve your problems and maintain a stock look. If that's not a factor, consider MAF conversion, Megasquirt, or b34 intake & injectors paired with a Motronic conversion. Any of these should provide fuel enrichment, none of these being that simple.

porschelou · Post by **porschelou** » Mon Dec 08, 2014 10:22 pm

The fuel system can handle the 3.5. This conversion has been done many times. But I'm with you - could still have a fueling issue. Need to test the low pressure pump next - it looks original.

Question for anyone who has done this conversion - is there any special timing / installation sequence for the distributor nut? This is the special one that allowed me to reuse the e12 geared distributor. I don't think so since once I had the balancer at TDC I set the distributor so the rotor is at #1.

Thanks

porschelou · Post by **porschelou** » Mon Dec 08, 2014 10:26 pm

Think it's funny you said if you had a Euro 635csi the parts could be used. I just bought a 81 Euro last week. Don't really want to strip the parts out.

Mike W. · Post by **Mike W.** » Tue Dec 09, 2014 10:54 pm

You guys ought to do some research before suggesting the massive 20% increase in displacement and 8% increase in rated HP overwhelms the stock system. On US cars 2.8 and 3.3 used the same parts, I took this sampling from Realoem on euro stuff, it looks about the same on AFM.

Part 13621359641 (Volume air flow sensor) was found on the following vehicles:

E12: Details on E12
E12 528i Sedan, Europe
E12 535i Sedan, Europe

E23: Details on E23
E23 728i Sedan, Europe
E23 733i Sedan, Europe
E23 735i Sedan, Europe

E24: Details on E24
E24 628CSi Coupe, Europe
E24 633CSi Coupe, Europe
E24 635CSi Coupe, Europe

E3: Details on E3
E3 3.0Si Sedan, Europe
E3 3.3Li Sedan, Europe

wkohler · Post by **wkohler** » Tue Dec 09, 2014 11:10 pm

I didn't figure any research was needed given my M535i acted like a dying squirrel on a 122 ECU and just fine on the stock one. It idled fine but don't ask it to do anything. Of course no one is asking it to do anything now.

porschelou · Post by **porschelou** » Tue Dec 09, 2014 11:12 pm

Tonight - I removed the transfer pump from the tank. It was the original one and it was bad. The ground strap on the side of the pump was broken. I'm not 100% convinced that this would cause the poor running condition but have one on order. Going to replace the filter as well. The high pressure looks new. I can also tell someone recently coated the inside of the tank - it's pink.

Has anyone used the special slotted nut ( big 40mm) that must be used when converting a b34 to the old style distributor drive? Need to make sure there was no special alignment process for that.

Thanks

porschelou · Post by **porschelou** » Wed Dec 17, 2014 9:55 pm

Figured I would close this out and let you know what the root cause was.
I started pulling plug wires to verify each one would drop RPM's ( wanted to verify all cylinders were working). I found out that two had no change. I connected a noid light and each injector was getting a pulse. Next I verified spark - all good. Then pulled the rail loose (leaving it connected and aimed the injectors towards shop towels. Turned over the motor and found no gas spray out of 2 of the new rock auto injectors..

I put two of the old ones in and bingo car runs great.. Tons of power and smooth idle - all fixed.
Thanks for the inputs..