My mom’s 1995 940 has developed a habit of misfiring under load. My first guess was that it is a fuel delivery problem because this is what the car will do if we run it out of gas. I began by simply changing the plugs, air filter and fuel filter but I NEVER get off that easy. Sooo, after checking every connection that I could find and finding none bad, I decided that I should check the injectors, fuel pump and so forth.

This is when I found that the Haynes manual for the 940 is basically a waste of paper. I have the Bentley manual for my 240 but I am unable to find an equivalent for the 940. Is there a manual somewhere for the 940 that just rocks?

This 940 has only one fuel pump in the tank. Volvo wants my left nut and even FCP Euro wants some $250 for a new one. I hate to take guesses at several hundred dollars per guess.

I wanted to test the voltage at the pump but I can find no connector where I can put the volt meter probes. I did at least check the voltage at the injectors. Across the terminals of my battery, I get 12.8 volts and at the injectors I get 11.8v. This doesn’t seem right to me. It seems to me that, if the battery is showing 12.8v, the injectors should at least be 12.6v...right? Can anyone tell me:

1. What the voltage at the injector should be?
2. If the voltage is too low, where should I go from there?
3. Really, how does one go about correctly tracing this type of problem down?

 

Ok, everyone!! It's been ten minutes now, WHERE'S MY ANSWER?

ROTFLOL!! I couldn't resist that. I've always wanted to do that on one of the forums that I log in to and so I did this time. Haha.

 

There is no great 940 Manual... A 240 Bentley applies in many areas to the 940 but still. The 1995 is a little odd as opposed to previous years, fuel system wise. Try https://www.brickboard.com/FAQ/700-900/, seriously good info there.
I seriously doubt that your problem is low injector voltage. A "high speed miss" is not necessarily fuel related, could be as likely ignition. Because it "feels like when you are running out of gas" is not a great diagnosis. How do you diagnose these problems? There is no sure fire way--it's hit and miss, experience, a little luck, and sometimes a lot of trial and error, aka throwing parts on a problem, which is what a lot of shops do, while you are footing the bill.

 

EXACTLY!! LOL, I just don't have anything else to go on. But I followed your link and now I've got a lot to try. Thank you very much for the link and I'll keep you apprised.

 

Ok, here is an update to this problem.

We should all remember to cover the basics when troubleshooting. Since this is my mother's car, she was out in the garage handing me tools and doing whatever she could to help me stay encouraged. She's a GREAT mom.

We both realized that it had been some time since we had just done a basic tune-up on the car and so, while we were troubleshooting, we thought that we should just replace the plugs, distributor cap, rotor and spark plug wires. We never did actually find the exact source of the problem, but when we replaced all those aforementioned goodies, the car ran like a top. It hasn't missed a beat since.

Lesson learned!!