Hello all,

This is my first post on brickboard, so be gentle. I'm not very familiar with the maintenance/upkeep of my Volvo. However, at willing to give it a shot.

Recently, my 1990 760 Turbo has been stalling randomly while I'm driving it. At first it would happen occasionally when driving. I would stop and start it and it would run fine. Over a weeks time it starting getting progressively worse, to the point that it died at a friends house and would not start up after sitting for a few hours. The next day it started up and I drove it home.

I have been searching the website the last week or so. I bought and replaced the fuel pump relay. The car drove fine for about 10 or 15 minutes, but as soon as I pulled in the driveway and let it sit for about a minute, it died. I started it 2 or 3 times after that with the same results. One concern I have is that when I was using the toothpicks to pry out the clips for the fi relay, one fell back flush against the board the relay attaches to. I can't tell though if it is getting in the way of the relay, preventing it from connecting all the way. If the relay wasn't connected all the way the car would probably not run right? I should have removed the toothpick, but it was in a very tough spot, and I was already rather frustrated with how hard it was to get the relay and the one next to it out in the first place.

I next thought I would try to take out the radio suppression relay based on suggestions from the sight. I have it in front of me, but I do not notice any cracking anywhere. Should I try to solder all the large and small connections just in case? I have never soldered and I'll probably have to learn or get someone to help me. It seems like it's worth it regardless based on what I've read. But do all the connections need soldering?

If this still doesn't work I'll probably move on to the rpm sensor...if I can find it.

Any help would be greatly appreciated.

A big thanks in advance,
-Mark

PS - With the fuel pump relay I may have knocked something loose. My stereo had a short in it and banging the paneling right above the relay board (I didn't know there was anything there) would sometimes kick it back on. Needless to say it took quite a beating for a while...now I just accept my stereoless car. Darn.

As a quick check you can bypass the suppression relay.

Simply unplug the relay. Take a section of wire and "jumper" between the two female connections on the two heaviest wires in the plug.

If the car behaves normally without stalling then the suppression relay is probably the culprit.

Do not leave the jumper in place with the car just sitting as it will drain the battery. Good luck.

Randy

If you have a voltmeter you can easily check if the rsr is working. Unplug all of the injector connectors and turn the ignition on. If the rsr is working you should have twelve volts to ground on one of the injector plug pins and zero on the other. If taping the rsr gets the voltage back then it's bad.

If I tried this would the car have to start up? Would it not start up with the rsr in place? Or should I just turn the ignition to the point just before it would fire up the engine? Again, I'm a novice here, sorry for the the rudimentary questions.

Thanks again,
-Mark

Your injector test brings to mind a couple of simple procedures that can isolate a no start problem quickly and without getting too dirty. Takes a couple of minutes, and a test light.

1. Check the fuses. Swap out the appropriate ones and try to start.

2. Check for ground break at the coil. Ground off the light, then, with the key on, probe with the light for power on the ground side of the coil, pole #1 on the Bosch. The light should light. Then have someone crank the engine for a few seconds. The light should blink consistently. If it does, you've most likely eliminated half the ignition system from the mix - including the ICU, the crank sensor and the power stage. No blink, and you do't have to futz around with the cap and rotor and wires, at least not until you've fixed the downstream problem.

3. Check for power at an injector, as you suggest. If no power, replace the RSR.

If everything works to that point, then move on to test for fuel delivery or lack thereof. Spray some starter fluid into a vacuum port on the throttle body and crank it over - a couple of firings from the engine burning off the susbtitute fuel tells me that fuel delivery is the issue. If I can't get even a cough, then I move to the distributor to check for spark.

And I always repack the muffler bearings during months with a "R" :)

Are you sure those bearings can hold up with greasing only every "R" month?

I just noticed that one of the 4 prongs the rsr to the wires had some sort of brown markings on it. I scratched at it with my finger and it rubbery. It is too late and dark to run out and check the wires in the car, but do you think this holds any significance? Thanks again, -Mark

Sounds like it may have gotten hot. Did it smell like burnt electrical when you had the cover off? If not, that may be some kind of protective goo applied by a previous owner. Normally, those terminals should be clean dry bare metal.

Another thing to check in that area is to make sure all the wires to the relay are firmly seated in the connector block. Sometimes they can come loose and get pushed down out of position, so they don't make good contact when you plug the relay in.

A faulty relay will not always be immediately obvious to casual inspection. Look closely at the places where the pins protrude through the bakelite (or whatever it is made of) circuit board and are encased in solder. Use a magnifying glass if necessary. You are looking for tiny cracks between the pin, which may still have some of the solder adhering to it, and the remainder of the solder. It's not like there will be a large piece missing (though I have seen that too, once or twice) All it takes is enough of a gap to interrupt a small current.

The point about checking (or just replacing, as preventitive maintenance) the crankshaft position sensor (RPM sensor) is a good one, as that can also cause intermittent stalling. It is located at the top of the bellhousing, below the distributor. It can be hard to see, and even harder to remove, especially if you have large hands. A long 1/4" drive extension and a universal joint can be a big help here. Another problem you may encounter is that the sensor can become stuck in its mounting bracket. If this is the case, be careful, the bracket is somewhat fragile, and if it breaks, you have to drop the transmission to replace it. Also, while the sensor is out, be careful not to drop anything (like a bolt) down the hole.

Is your crank position sensor original? If not, it probably needs replacing.
http://www.brickboard.com/FAQ/700-900/ElectricalIgnition.htm#FailuretoStartFlywheelSensorBad

I took out the radio suppression relay and inspected closely and did not see any signs of damage. So I went ahead and ordered the crank sensor. I was able to get the old one out without any trouble. When I looked at it close to where it attaches at the bell housing, the wire had a cut that went around half-way, with the wires inside exposed. So I put in the replacement figuring this was surely what was causing my intermittent stalling. I started the car and it ran for about 30 seconds then died. Now it will not start. Does anybody have any suggestions? Would I be correct in guessing that the initial stalling was caused by the crank sensor? Is the no-start a new problem? I thought I had it!! Hopefully, I can get this thing running. Oh, and the fuel filter hasn't been replaced in a while and the car has been sitting for about a week/week and a half. Think maybe this is the problem? Thanks again.
-Mark

Today the car started up fine for me and ran for a few minutes. Unfortunately, I'm on my lunch break and I can't look to closely at it. I did notice that there was a sort of sputtering sound coming from underneath the car. I looked and the pipe that leads to the muffler (novice, I know) had exhaust leaking out near the front of the car, and there was a ring that seemed to be the cause of the sputtering. Might this contribute to any stalling/no-start problems? Thanks.

Its actually easier to solve a no start engine rather than intermittent.

Spray some ether in the intake bellow, a 5 second blast, reconnect and see if it starts and runs the ether out.
If yes then its either fuel pressure/pump (or relay)

or its still the injector relay.

If it doesn't fire up its time to look at the ignition spark problem.