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Discussion Starter · #1 ·
Running Rich

Have a 75 manta 1900 with the bosch AFC fuel injection, I've changed the air mass sensor on it. I had an oil and decieded to order a new motor well after having it installed the thing just pours out black smoke as soon as you start it. I'm a lil lost with this particular FI system. Any help would be greatly apreciated. :)
 

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I moved this to the Factory Fuel Injection Forum.

I am still a newbie on L-Jetronic tuning. But there are a number of experts on this site that should be able to help you out. And there are several excellent manuals out there as well. I would recommend the '75 Opel Factory Service Manual (which is a condensed version with just the '75 upgrades, to be used as a companion to the '74 FSM), a MotorBooks manual on "How to Tune & Modify Bosch Fuel Injection", a Carbooks Inc. book "Bosch Fuel Injection Systems, 1970 - 1977", and a Robert Bosch book "Workshop Manual, Opel L-Jetronic".

HTH
 

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basic 101 on L-jet FI

the fuel injectors supply fuel to the motor instead of a Carb

but the FI system needs to know when and how much fuel to inject

they get the "when" from the RPM signal from the motor

they get the How much from the sensors

the AFM (air flow meter) or Flapper valve measures the amount of air then sends a voltage back to the ECU this is used to adj. how long the injectors stay open or how much fuel is delivered to the motor
the other sensors will modify the injector signal to give the motor more or less fuel

Now if you have black smoke coming out of the tail pipe you have way more fuel then air.

But before you start jacking with anything look for the easy fix first.

Make sure every thing is hooked up right.

like some Air is bypassed by the Auxiliary Air valve even when the motor is warm

Just give every thing a real close look and don't start adj. stuff until its the last resort.


HTH
Davegt27
 

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There is a 75 service manual supplement here http://www.books4cars.com/result1.htm?findmake=Opel&imageField.x=111&imageField.y=49
I have one and it contains on 6-10 of the engine section The EFI. I also have the workshop manual by Robert Bosh (14 pages, front and back) for the L-Jetronic, if that helps. It contains a very good troubleshooting chart. Since it seems so many are going into FI, I could try to scan it and upload it, and if that fails, I could copy it and send it out for the price of scaning and mailing. I have to go by the Post office today and will find out how much shipping would be. Jarrell
 

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FI problems

Your FI system is way rich. You're either over pressure on fuel, the cold start valve may be stuck open or you have a sensor that's connected incorrectly.

Test the cold start valve for leaking by clamping off the line when the car is running. If the idle drops or you black smoke problem disappears, the cold start valve has a leak.

This could be the connector from the auxiliary air valve connected to the coolant temperature sensor and vs. versa. The connectors are color coded. Blue to blue, brown to brown, white to white, etc.

Check the fuel pressure with a fuel pressure gauge on the cold start valve fuel feed. Make certain that these are correct and that the fuel pressure is between 32-45 psi at idle and under throttle. Lower or higher and you have a fuel delivery problem lending to your condition.

Good luck.
 

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Discussion Starter · #11 ·
Fuel Pressure check

I noticed that some said earlier that if I have to low/high fuel pressure, it may cause the problem I'm having with the car running rich. My question is how do I check the fuel pressure. I have a multiport fuel pressure gauge but its the kind that screws on a valve somewhere on the fuel rail. I'm pretty sure that this bosch system isnt set up like that so what I needed to know is how to make my pressure gauge work on this car. 75 Opel Manta 1900
 

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fristim said:
I noticed that some said earlier that if I have to low/high fuel pressure, it may cause the problem I'm having with the car running rich. My question is how do I check the fuel pressure. I have a multiport fuel pressure gauge but its the kind that screws on a valve somewhere on the fuel rail. I'm pretty sure that this bosch system isnt set up like that so what I needed to know is how to make my pressure gauge work on this car. 75 Opel Manta 1900
I'm with Dave on the possibility of it being the cold start valve.

In his post, he mentions hooking up the fuel pressure gauge to the cold start valve hose to test the system. You will need a barbed hose adapter (or a double barbed fitting and cut a hose) for the multiport gauge.
 
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