Fuel Pressure Issues

[Nova Shark]

I have a 1983 633csi stock engine. I am almost done with my 2 year + restoration and I am having problems with the vehicle starting when cold. If I squirt starting fluid into the AFM and choke it with my hand (air filter off) after 3-4 times of doing this, it will start and run pretty good. I bought a fuel pressure gauge kit and checked the pressure, it was only 30 psi. I do have a new filter. So my thinking was not enough pressure to squirt the normal amount of gas via the CSV, (it is new and it works) and also not enough for the injectors to start it up cold. So I doubled checked my purchased pressure kit and rented one from AutoZone and it read the same, 30 psi. When I had it all apart I squirted brake cleaner in the lines and then air at 120 psi to clean it out more. I then purchased a new Bosch fuel pump y-day, got it hooked up and the pressure reads the same 30 psi ??? It acts the same so I need to give it a drink of starting fluid then it starts. I did clean the injectors when I had them removed from the engine. I am stumped as to why it will not start when cold? any suggestions as to what it might be or what else to check? I did remove the pre-pump from the tank and it works as in I can hear it and feel it working. Don't know if there is a certain pressure I should be looking for from that ? Any help would be appreciated.

[wattsmonkey]

Cold start valve/thermotime switch seems a likely place to look. It's a pain to get to, but easy to check once dragged out. The E28 Bentley manual is fantastic on this.

[plip1953]

Have you got the correct fuel pressure regulator?

[Nova Shark]

Cold start valve/thermotime switch seems a likely place to look. It's a pain to get to, but easy to check once dragged out. The E28 Bentley manual is fantastic on this.

Watts, the CSV is brand new from Fcp euro. I have not taken it out yet but I did confirm that it has power and it is getting fuel

[Nova Shark]

Have you got the correct fuel pressure regulator?

Plip,

I believe I do, it it is a 2.5 bar, it was on the car when I purchased it. Here is a pic along with something else further down the line? another regulator? the part# stamped on the top regulator piece in the photo is: 0 280 160 225 with 2.5 bar and 419 also stamped on the side. The regulator at the bottom of the pic has BMW 1.284.337.3 BISHOFF stamped on the bottom. Is there a way to test/confirm that the top regulator is working with or without the car running?

[hornhospital]

To test the regulator with the engine running, pull and plug the vacuum line going to the regulator while testing fuel pressure. The pressure should go to maximum with no vacuum feed. You can delete the bottom "regulator". It is actually a device to smooth out fuel pump pulses, not a pressure regulator. And 30 psi is very low. You should be seeing ~36psi at idle with the regulator working correctly.

[Nova Shark]

Update......I double checked the pre-pump today, It had 12 volts at the connection going into the pre-pump but I could not hear it working when plugged in inside the tank. I had it out y-day and it was working. I checked the Bentley manual and it said 0.3 bars or 4.3 psi should show on the pressure tester when hooked up to the pre-pump discharge line, ha ha there was none. With the switch on or the fuel pressure relay jumped, if I stick my finger over the rubber tube that goes to the main pump I can feel it trying to draw fuel. So I ordered a new pre-pump today and I'll get that hooked up and see what that does. Holy smokes, you have to check and double check every little thing. if it ain't one thing with these bimmer's its 5 !!! I will update when installed.

[Nova Shark]

Update #2.... Got the pre-pump delivered and installed, tested it before hooking up to main fuel pump and it has 4 to 4.5 psi out of the tank. That's where it should be. Hooked the rest of the lines up and got the vehicle running and still only has 30 psi !!!. So I backed it out of the garage and tried to take it down the street and it would barely stay running when giving it hardly any gas!!! Brought it back in the garage hooked up the pressure gauge again, still only 30 psi so I pinched off the small vacuum line going to the top of the fuel pressure regulator coming from the bottom of the air plenum. No change in pressure. Pinched off the bottom fuel line sized line (see previous photo) from the bottom of the FPR and after about 10 seconds the fuel pressure went up to over 50 psi. Would this indicate that I have a bad fuel pressure regulator? and is that causing the low fuel pressure? Checked on FCPeuro for FPR and its $315.00 !!!! there's got to be a cheaper one out there.

[plip1953]

I'd expect you to be able to pick up a regulator for a lot less than that.

[Nova Shark]

I ordered a new adjustable fuel pressure regulator thru Ireland Engineering for $165.00. That way I can adjust my fuel pressure the I want it.

[streifen]

Adjustable regulator is a smart move. Keep it at the OEM design setting for your engine. 36 to 38 psi is good for your engine. 43 psi or 3 bar is too much
When summer rolls around in Southern Cal, I readjust the pressure to accommodate the heat and the "summer blend" gasoline specs.
I have a collection of stock style fuel pressure regulators from Bosch and others and can attest that they just do not retain their design pressure/design spec.
Also, looking closely at your ultra clean engine, do I spy a frayed ground wire at your cold start sensor valve?