Will I have some kind of fuel problem because of changed flow, if the previous owner changed the OEM Bosch for a walbro?

And another question.
Is it even possible to have the engine run smooth with WUR from an Audi, instead of the original 086 WUR?
I've been trying to adjust the pressure so the AFR on idle is about right...


Thanks in advance

 

Re flow, as long as its up to 928 spec or higher, should be ok. As long as your system pressure regulator delivers correct pressure, that should be ok, and it can be adjusted . I work on the principle that as long as the pump is designed for injection, and fits in place, it will probably work - except if it cant make CIS/K-jet system pressure of ~75psi - L and LH pressures are down around 45psi. My CIS car had an S4 LH pump on it when I got it, and it ran fine, in high temps (120F).
WUR.....you may have trouble getting cold and hot control to match 928 specs. If you get hot control on spec so it drives well, starting may be an issue...See if you can find the Audi pressure graph vs temperature, and compare with the 086.
jp 83 Euro S AT 55k

 

Thanks. But what IS the 928 specs?
I belive I saw 200lph @5bar/73,5 psi somewhere. I dont think the Walbro would give that much at that high pressure.

 

928 delivery is 1360cc/30 secs, tested at the return line over the RHS cam cover, at 75 psi/5bar system pressure. The pressure is set by the regulator in the fuel distributor. Low delivery may only affect power at upper levels, it should not stop it running unless it is VERY low.
jp 83 Euro S AT 55k

 

So 1360x2x60= approx 163 lph?

I think I need to find out the exact number on my Walbro.
I'm having a hell of a lot of trouble with my fuel CIS-system... Then again, I got the car really cheap.

 

Tell us what the real problems are , otherwise you may get correct but useless advice. If you ask based on your own diagnosis, without all the information provided, it will colour the responses.
Also useful if you can provide all the measurements you have done - preferably including delivery rate, system pressure, cold and hot control, rest pressure. If you dont understand all these terms, you need to do some reading so you understand their importance.
jp 83 euro S AT 55k

 

I'm used to build and tune stand alone ecu engines in dynos, so I do understand the terms..
However, I have not meassured the pump, but on todays afr-run everything seems fine to begin with. But the engine is weak, and above 4000 rpm the afr is crawling down from 12,2 and slowly down to about 10,8-10,9 on the thickest. So obviosly its not lean! Some times it could suddenly lean out under normal driving and give 16-something afr and the engine missfires. And the car is always a hell of a lot quicker if the plugs are brand new!
Tomorrow I think I'm going to try and change/meassure the coil. Should it have 12volts? What about recistors?

 

And sometimes its smoking black, and sometimes white on the top

 

Not sure exactly what volts the coil should see - hopefully another will come in with the figure. I know the resistors are quite low values (1 or less Ohms).
Do you know the condition of the injectors - correct spray pattern, and correct opening pressure? If the spray is bad you can get large drops of fuel, which may cause apparent leanness. I have seen users here fit the shorter brass MB version of the injectors with success, and they are cheap (~$20 ea) and readily available. It might also be useful to check that all injectors are getting full delivery, by fitting them firing into glass jars, jumpering the pump relay, and hand opening the air plate.
jp 83 Euro S AT 55k

 

You won't have a flow problem with any brand pump that's right for the application unless the pump is bad. It may be worth looking at though. The Bosch pump in my 80 euro (K-Jet) developed a loose impeller and the flow rate changed during operation. I chased fuel delivery problems for more than a year before I found it. And, like you, I started looking into the electrical side as well. I only found it by accident when I started to "shotgun" parts at the problem. When I replaced the fuel pump with a "cheap" Walbro pump all the problems magically went away. I cut open the Bosch pump and found the impeller was loose. I'm not saying you have the same problem but, yes, unstable flow can be an issue.

 

I allready have a Walbro actually.
I'm thinking of maby driving the car on ethanol for a period, to clean up the system.