1994 940 Turbo-won't accelerate,popping,backfiring

pwhatley · Post by **pwhatley** » 04 Oct 2007, 11:12

I came across this forum awhile back,but this is my first post. Lots of valuable info here. My 1994 940 Turbo haas recently developed a intermittent problem that causes a lack of acceleration and there are popping and backfire sounds coming from under the hood.

In the last few months,I have replaced both fuel pumps,the catalytic converter and added new wires,plugs,cap and rotor. The cars drives normally when its cold and it idles fine. It appears once the car has been driven for awhile and is warmed up,the problem occurs.

Pressing the gas pedal causes the car to hesistate,the rpms won't go past 4K and boost gauge goes into the white. If I try to push the pedal to the floor, the popping and backfiring occurs.

Any help or assistance with the problem will be greatly appreciated.

Thanks

Post by **billofdurham** » 04 Oct 2007, 11:44

Welcome to Matthew's Volvo Site.

A couple of questions to assist with a diagnosis.

What mileage on the car?

Are there any fault codes?

Bill.

pwhatley · Post by **pwhatley** » 04 Oct 2007, 14:25

The mileage is 166k and there are no fault codes at the present time.

sullihood · Post by **sullihood** » 14 Oct 2007, 10:26

Just one question - did the lack of power and sputtering happen after changing the fuel pumps? Is it possible that you reversed the intank pump wires? To test this idea remove fuse #11 start the vehicle and let me know what happens.

John Sullivan

pwhatley · Post by **pwhatley** » 14 Oct 2007, 16:27

The problem started occuring after the new pumps were installed. The pumps were installed by a shop,so I don't know if the wires were reversed.
I'll give your suggestion a try and let you know what happens. Another forum suggested that I might have a bad fuel injection resistor. The one on the car now came from a salvage yard. The original one was damaged when my car was hit. I ordered a new one. I'll let you know if it makes a difference.

pwhatley · Post by **pwhatley** » 20 Oct 2007, 13:20

I pulled the #11 fuse(in tank pump) and the problem seems to be solved. I didn't think the car would run without the in tank pump. How do I fix this ?

Thanks

sullihood · Post by **sullihood** » 04 Nov 2007, 22:03

pwhatley,

The car will definitely run without the intank pump operational but I have experienced that the car periodically will not start when the engine is hot. Especially after some highway driving in this hot TX climate with the AC running. The car is absolutely dead but wait for it to cool down and it fires right up.

I am in the same situation as you with my '94 940. I changed the intank fuel pump, fuel filter and check valve to cure the problem that I mentioned above and I suspect that I have the two wires on the pump reversed. I plan to remove the pump and switch the wires around and reinstall the pump.

JS

pwhatley · Post by **pwhatley** » 05 Nov 2007, 22:51

I haven't experienced any starting problems with my current situation. The car was exhibiting the same symptoms even while it was running on one pump. I will pull the in tank pump and reverse the electrical leads and see if that solves the problem. Thanks for the suggestion