Hello, I have a automatic 1985 Volvo 260 it has a 2.8l PRV v6 with 208,000 miles on it. The car runs perfectly when the cars tank is full, however when the fuel is half way it starts to stutter in a jerking motion really badly even under a low level of acceleration. The car has had a new fuel pump however I believe it also has a pre pump which has not been replaced, I'm wondering if you could help me diagnose the issue.
Thanks,
Richard
COuld be clogged fuel filter or bad pump. check the sending unit too.
Thanks for your response, I will test the sending unit
I think a replacement pre-pump is in your near future....While at it, it probably wouldn't hurt to change the fuel filter as well.
I found this in a Volvo service site.
Fuel System Pre Pump 1978-1993 240/260 Models
The pre pump is a low-pressure, high-volume pump that sits inside the gas tank and supplies fuel to the main high pressure pump under the car. When it fails, symptoms include poor idle quality, hesitation when accelerating, reduced fuel economy, loud humming noises emanating from the main pump and accelerated wear of the main pump.
Sounds like it could be the problem, thanks for your response.
I concur. (Toyotagirl beat me to it.) Saabs of that vintage use the same setup with a pre-pump feeding the main fuel pump. I've experienced those very symptoms when the pre-pump fails.
Could be a bad gas cap starting to compromise the EVAP system. When the tank is full, it's not a problem. Get a new OEM gas cap and see if that takes care of it. It's the cheapest and easiest thing to try.
Thanks for the information, I will try to find a OEM petrol cap to see if it will correct the issue