Lost engine power

740 4ever · Post by **740 4ever** » 24 May 2004, 14:49

Hi! I have a Volvo 740 from 1985 with a B230 carburator engine and automatic transmission. The engine has lost a lot of power and will not run in a clean way when I press the trottel to max. The engine goes better if I decrease the trottel a bit but is still very slow. When I turn it off after the drive there is a very strong smell of petrol in the front of the car.
Any idea of what is wrong?

A.Baker · Post by **A.Baker** » 25 May 2004, 03:58

It sounds like the carb. is over fueling.The flot may be sticking,if it has been a wile since the last rebuild you might start there. Before you do that check other things like timming, plugs, plug wires, cap, rotor, air cleaner,fuel filter. Is it huffing black smoke?. good luck. let us Know if we can help further.
A.Baker

LaRy · Post by **LaRy** » 25 May 2004, 10:04

It is probably the rubber diaphragm in the trottle that is broken. Loosen the big upper part ( fastened by 4 screws)of the trottle and take out the diaphragm. Check it carefully that it has no small cracks or holes. It is easy to change and it is a typical aging problem. If you have a hole in this diaphram the vacuum can not open the throttle and the engine is slow.

Normally this will not cause a smell of fuel so it could also be the floater needle that is bad or dirty.

740 4ever · Post by **740 4ever** » 25 May 2004, 13:07

Thanx for your tips so far. There is no black smoke from the engine. More a white steamy smoke when the engine is cold. No oil in the cooling water. I have checked the rubber diaphragm but could not see any faults in it. Maybe it is old and hard so I will try to change it. The exhaust is OK according to the yearly car control. (Maybe a little bit low CO) The trottle needle looks OK as well.
Will this create any more tips so please let me know. (Alla other cars are passing me on the highway)

Guest · Post by **Guest** » 26 May 2004, 12:59

The steam from the exhaust is most likely condensation in the pipe burning off. if it continues then there may be cause for concern. Im not sure if your car has a fuel presure regulator. I had a customer that had one fail and was pushing fuel past the carb. I also had one that the vapor return to the tank was pluged and he did not have a vented fuel cap and caused the same thing. I know these are just hail marys. And thay were also on diferant maks of cars. I still think the problem is in the carb. It can't hurt to rebuild it. Just take your time and make sure all parts are sano! befor reassy. And use factory parts. Hope this helps.
A.Baker

Volvo740 4ever · Post by **Volvo740 4ever** » 26 May 2004, 14:43

Hi all and thanx for your helpful hints. I have now rebuilt the carburator and adjusted the CO and the engine is as new. Now I could pass some cars

. When I removed the carburator I found a damaged yellow green cable going to a magnetic valve on a "ventilator" from the carburator. Tha valve was full of petrol and I think that was the problem with the petrol smell. I replaced the wire and the smell is gone.

LaRy · Post by **LaRy** » 27 May 2004, 11:43

It's good that it is running again. Some explanation of the valves. You have one valve in front of the carburator. The valve is connected to a rubber hose going down under the car. That valve is closed electrically when driving. When stopping the engine it is just a ventilation to free air under the car. If it was a lot of petrol in this tube it is a sign that the carburator you had has been overfueling with a sticking flot. I have met this problem with my B230A.
Then you have one more valve at the carburator outlet side. This valve is shutting off the petrol when switching off the engine, in order to avoid ignition by incandescence. If that one is out of order, the engine should not run normally.