Volvo 940 random non-start and stall.
 

Over the last 2 months I will be driving my 94 940, pull into a gas station and when I go to start the car again, it fails. I will mess around with relays, and bang on the pump and filter and suddenly it will start and be fine for weeks or will have spasms of non starts for a day or two. The thing is, I a not sure what gets it started again. The first time It happened I thought it was the relay because I was jiggling it just as it started. A couple of non-starts later, it started as soon as I banged on the pump/filter.

When I'm trying to start it, and it fails, it almost seems like its firing slightly as i'm turning it over and when I let off it continues for a moment before dieing. If I try immediately after, oftentimes it will just crank and I hear no firing.

Just today for the first time it stalled out while driving. I couldn't get it started up for more than 2 hours. The last thing I did (after doing it multiple times before) before it started was bank on the pump and jiggle the connectors to the pump. I don't want to drive it unless I'm sure its not going to happen again. I don't want to pay an arm and a leg to get it towed off of a freeway.

I was browsing through some other threads and one person had a similar problem and solved it by lining up the timing properly.

My car needs a new belt. Its about 15k overdue. A new fuel filter is due about now too.

I cant really replace either easily as I am living at college and can only replace stuff that doesn't require getting things messy. I would really like to be able to diagnose the problem so I don't have to replace multiple messy things. I could maybe get away with one.

Now that you have the back story, here are a couple questions I love the answers to help diagnose the problem.

1. should the pump buzz every time I turn the key? Even after just waiting 1-10 seconds?

My pump will buzz intermittently. Maybe the pump only turns on after pressure drops after a couple minutes?

2. which relay is for the fuel pump and/or injection system? there is a little square blue one on the front right that seems to click on and off for the duration of the fuel pump buzz. However, I was looking to buy a new one and online it seems to look like one of the 2 relays in the far right corner. Are there 2 relays for the fuel system?

I have a friend who owns a 94 turbo 940 and I could probably bum a relay off of him for testing, but I would like to know which one(s) to borrow.

3. how off does the timing need to be to have problems with the timing cap having to arc? just 1 tooth on the belt? Since its getting late, I'll be checking the timing tomorrow morning.

4. What are some other things I can do to diagnose?

EDIT: Also, its getting pretty ****ty mileage. Around 20-22. Previously I never got worse than 26 and usually 27+. These numbers are for freeways. It may or may not be relevant.

Man, you are all over the place. Sounds to me like you have a fuel pump going out. If you have a friend that has a relay you can test, I would suggest putting your relay in his car. The fuel system should hold pressure for several hours. You should hear your pump buzz every time you try to start it.

Tested his just a moment ago. His buzzes every time like you said. I think I might just get this over with and replace everything.

From the symptoms you mention, it sounds to me that your fuel pump relay is bad. I would swap it out first. Or if you have a soldering iron, pull it apart and touch up the solder points on the circuit board that hold the relay coil. They tend to crack from vibration over time.

Hmm.... Are the cracks usually visible? I popped it apart (what I think is the right relay) and I couldn't see any micro cracks in the solder material on the back of the board.

Well, after much research, I figured out which relay is actually for the fuel pump I just yanked each and checked the part # of the one the pump wouldn't buzz on. the fuel pump relay is a little blue one first row far right marked 4rd 003 520-52 http://heathholden.com/relay.jpg from http://www.volvo-forums.com/t21325-1...pump-relay.htm
There isn't really anything I can re solder . Its a little 3 sided copper box with an eletro magnet inside that opens and closes a switch.
Previously I was looking at a fuel inject relay maybe?

EDIT: On top of that I'm pretty sure the relay clicked on and off each time I tried starting the car on my last no-start episode. I do remember it being pretty warm though. I'm starting to lean towards just fuel pump.

EDIT2: In that above link someone mentioned that the high-beam relay is identical to the fuel pump relay and can be swapped for testing. Could anyone else confirm this?

So I changed the fuel pump and have been driving it for the last 8 days or so. It hasn't failed yet. It still has ****ty mileage though :( and has low power at higher RPMs. I tested it against another 94 940 non turbo (same color too) that my brother has.

pump only and not filter?
 

I learned the hard way (on a previous vehicle) that the filter gets changed at least as often as the manufacture says [60K on a 1994 940]. If you are running elcheapo gas ... much sooner than 60K.
At least the bolts are loosened on the plate and you are familiar with relieving the fuel pressure.