Rich Mixture

[Hallaian42]

Does anyone know how to test the fuel pressure regulator? I am still having a problem with a rich mixture because im getting black smoke and black spark plugs. I have a fuel injected 75-78 L28 in my 240z. Any other idea's as too why i might be getting a rich mixture? FYI...I got the car in a salvage yard so im trying to piece it back together. I was just wondering what things i should test and how. THanks guys for info.

[2ManyZs]

First thing is you really ought to get yourself a Factory Service Manual for the year of your 280 engine. There are just so many tests described in there to troubleshoot your fuel injection it is worth it's weight in gold (well almost) and it will make your job so much simpler.

One thing I'm thinking about is that your water temp switch or air temp switch may be bad and is causing the cold start injector to enrichen the mixture as if it is trying to choke for a cold start. That's one idea, as far as any others, I don't have my 280 anymore and therefore don't have an FSM to go by.

As far as the pressure regulator goes, I don't think that will cause a flooding condition as it is before the injectors, the injectors will only flow so much fuel unless something is tricking the FI to think it needs more. It could be in the air flow meter, one of the temp switches, cold start valve ( injector),possibly the throttle body itself. There are a lot of things that need to be checked and without an FSM I'm just grasping ideas out of thin air.

[dohc]

What have you checked already?

My EFi car was doing that and it was a combination of a blocked air filter and a faulty MAF sensor in the air intake. Combined the engine wasn't getting enough air (filter) but thought it was getting heaps (sensor).

As a result the ECU piled the fuel in and I got plumes of black smoke and a tendancy to flood!

Hope this helps a bit?

R.

[Hallaian42]

Alot of things on this car seem to be aftermarket. It has a performance intake (looks much like the end filter of a K&N Cold air system). The filter is connected to a boot that goes to the air flow meter. The MAF appers to be aftermarket. But the connecter fits. How do i go about finding out if it is the right one or not? The throttle body is stock. I was thinking about getting the performance throttle body from motorsport. Do you think it's worth it? Here's another thing... I recently took off the fuel rail w/ injectors. I noticed that none of the o-rings for the injectors were present, yet before it sealed OK. Now...they leak air which i think is causeing an uncontrolable idle. The ECU wiring harness looks pretty brittle. Where can you buy another wiring harness. Im also beginning to wonder if the ecu i have could be for a different year and maybe it requires an O2 sensor. Can i call bosch and ask for a wiring schematic or something like that for that specific computer. There alot of loose wires and it would be nice to know what they are for. All in all...im wondering if it would just be a good idea to replace all the sensors for good measure. Sorry to go on and on...but im having a hell of a time trying to figure this car out. Thanks again guys

PS.. who makes the best service manual...i have the one from Chilton...But it seems to tell me crap about testing any of this stuff. The wiring schematics are very hard to follow and the wire colors dont match

[smg1404]

You could easily spend a lot of time and money finding all of the problems. Especially if someone has modified the Injection system. A couple of Ideas come to mind as to how to approach this problem. You could try to find a complete replacement for the intake manifold/ injection system. Or you could ditch the injection and go to carburators. I had a failing injection system on my old 280 years ago. I decided to go for carburators for a couple of reasons. First I knew very little about fuel injection, and was comfortable with carbs. The second was when I found out was wrong with my injection system the cost was very close to the purchase price of a set of carbs.

This just how it worked for me My 2cents

Good luck

[dohc]

Hmmmmmm...... No O2 Sensor makes it a bit harder. Does anyone know if these ECU's have limp home mode where a predefined set of values replace a sensors input if it is a) disconnected or giving readings of the scale?....

Firstly though I'd consider getting the injectors cleaned and sonic tested to make sure they are alright (its cheap and can't hurt anyway) and get them sealing properly as you'll never fix the big problem if little probs start occuring and making it worse.....

Next? Hell, It's been ages since I've tinkered with EFi..... If it had limp home mode (or similar) you could disconnect the MAF and see what difference it makes and work from there. Without Limp Mode I really don't know what it will do.

Let us know how you go or anything else that may help us help you:ermm:

R.

[Sleeper78Z]

You mentioned the fuel pressure regulator, and yes, it can cause what you are seeing. There is a spring inside that can stick or break, giving full pump pressure to your injectors. You can have it tested by any reputable mechanic, or buy yourself a pressure gauge ($20 for a 0-60 psi from Summit or Jegs) and plumb it into your rubber fuel line after the filter. To check the pressure, start the engine, disconnect and plug the vacuum line to the regulator. The pressure should be about 37-38 psi, and drop to 32 psi when you reconnect the vacuum line.