Vehicle: 1995 960 wagon

Background: Exhibits intermittent no-start behavior in both warm and cold weather, wet and dry weather, having sat overnight, or only sitting a few minutes. Turns over fine, but won't start. Sunday, it started fine several times, went to Home Depot, wouldn't start. Called a friend to pick me up. When he was almost there, I tried it again and it started back fine. Been in shop a few times, they played around with a few electrical connections, battery cables and grounds to injectors. Also replaced fuel pump. I have not verified if it is a fuel or spark problem, I just bought a FI fuel pressure gauge last night.

Once started, it does fine. It never stalls or cuts out. That is why I am leaning toward a CPS (that's what jeep people call it.) Sometimes, under the slow cranking speed (relative to idle) the signal is too weak to be useful. However, during idle and normal operation, the flywheel is moving fast enough that the signal is much stronger (being a magnetic pickup). Thus, the reason it only happens during starting, not during running.

Here's my current working theory: Bad crank position sensor (is that Volvo people call it?)

This is the only part I can think of that would cause this. A fuel pump problem would probably show up during running. I think the pump also receives a signal from the cam sensor, so if that sensor were the problem, it would happen during running too, not just starting. It the cam sensor an optical sensor? AMM shouldn't cause it to not start, although it might cause a difficult start.

Reasonable?

I have a 2000 C70 that just this week started doing the same thing. It turns over fine, but won't start. After trying it a couple of times, it finally starts. How did you solve the problem....I'm sure they are the same issue. THanks!!!!!!

It very well could be the crank position sensor, but I would also check the fuel pump relay. They can get over come with resistance and heat and develop cracked solder joints, which I've read are very repairable. You might need a magnifying glass to inspect them though.

If you choose to replace the sensor, be sure to use a quality torx head, not one from an assortment kit. Because of the aluminum bell housing, there is sure to be some corrosion and you will only get one chance to get that out before it rounds out. Use some no seize after replacement.

Has it ever thrown a code? I believe there is a code for intermittent sensing. While your check engine light is not illuminated, it might be worth seeing if anything has been stored, not all codes will light the dash light.

DanR '94 964 333,000 miles (99,000 on the new engine)

It hasn't thrown any codes, which surprises me. As for the relay, I tried swapping it out with an identical one in the box (for the horn or something like that) with no change in luck. I've seen a lot of posts about corrosion being a problem, but mine looks fairly clean. Of course, its been in the South most of its life, and that may help.

I'm going to go ahead and replace the sensor, because its cheaper than having it in the shop for another hour. Hopefully once I have the old one out, I can stress test it and make it fail on the bench. Otherwise, it will be difficult for me to assess the efficacy of the repair. Maybe I'll pile the wife and kid and dog in it, leave the cell phones at home, and drive to the middle of nowhere and shut it off. If its going to fail, that will be the time.

An update: I haven't changed anything since the last post. It seemed to be doing ok, so I left it alone. It gave me a couple of no-starts recently, but after sitting a few minutes it would be ok. Today it wouldn't start after going to the store (Home Depot, again) and it is still sitting there. I'm going to go check it out again in a few minutes.

As I was starting it, I noticed that the RPM needle was moving some. I take that as an indication that I was getting a signal from the cam sensor. Now I'm leaning toward a fuel related problem. I'm keeping a fuel pressure gauge in the vehicle so I can check it when it happens.

I'll throw this out in case somebody can make a connection: the length of cranking time needed to start the car is inversely proportional to the amount of fuel remaining in the tank. When the tank is full, it starts right up (when it starts, of course), but when the tank is near empty on the gauge, it requires a significantly longer cranking time. Also, when the gauge shows near empty, it only takes 8.5 gallons to fill it up.

How many miles do you drive before doing your usual fill up? Wonder if someone has messed with the in tank fuel pump?

DanR

We drive about 150-160 miles between fillups. The pump was replaced by the mechanics in an attempt to resolve the starting issue. However, the fuel-level problem existed before. I don't think there are any dents in the tank, but I'll check again.

Ok, went to pick it up, started fine. Got home, hooked up the fuel pressure gauge. I'm reading about 85psi, about twice what it should be. The pressure leaked off withing a couple of minutes. I checked the return line for blockage. I could blow through the hose, but with some difficulty. It feels like it was in the fuel, so by blowing I was having to overcome the weight of the fluid. When I stopped blowing, I could feel the air coming back through the line, where the fuel in the line was returning to equilibrium.

So I don't think there is a blockage, but most fuel return lines I'm familiar with empty above the fuel line, not below it. I can't find a diagram for this tank, so I can't be for sure. I'll try to replace the pressure regulator. Could this be causing my intermittent starting problem?

Another idea?

Have you ever replaced the fuel pressure regulator? It could be leaking internally and causing a flooding condition. Or you have a vacuum leak, that won't allow the regulator to work as it should.

DanR

That's a good suggestion. I'm going to try using my hand vacuum pump in the morning to see if I can get any modulation of the fuel pressure.

Check the Idle Air control valve. I had the exact same problem and that was it. Its a motor that cotrolls the amount of air into the intake for startup and additional electrical load. It will hang shut and make it virtually impossible to start if at all. And is notorious for causing stalls while driving. Follow the line from the air cleaner to the valve and feel it to se if its running or remove the lines to check for blockage. I'll bet the farm thats the Prob.

I'll check it out, but it hasn't had any drivablity problems at all.

Update:

I replaced the fuel pressure regulator and everything has worked fine since then. Fuel pressure has been normal and starting has not been a problem. I'm going to give it a couple of more weeks before declaring it "fixed".

been doing fine. problem considered fixed.

I have a 940 1995 Turbo Volvo with the EXACT same symptoms as you....so I replaced the Fuel pump regulator and the CPS as well....with no success! Now I'm at the point where about the only other thing that I personally can replace is the Air Flow Meter and if that doesn't fix it, I'll have to tow it in and have them run a code check on it. I'm about as frustrated as I can be! I had it towed in once and it STARTED right up for them! So I brought the car back home thinking it might have just been some blockage in the fuel line or something. Hasn't started since. Had no hesitation problems or power problems....but just like you....it just stopped cranking. I'm getting spark. What would you do next?

I would buy a fuel pressure gauge and place it on the rail to watch the fuel pressure as you are cranking. If you have good spark, then I'd expect the fuel pressure to be abnormal.

...funny thing is right after I had it towed in.....it started right up for the auto place! I'm just wondering if all that bouncing around on the tow truck may have reactivated a wire or connection, thus allowing the car to start when it got dropped off at the auto repair shop? Maybe it's just a loose connection to the fuel pump. By the way, when we turn the ignition key on we don't "hear" the fuel pump sound. I've checked the fuses of course. How many fuel pumps on my model and where are they found? Are they difficult to get to? Any help would be appreciated!